15 files changed, 7945 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/walk/assign.go b/src/cmd/compile/internal/walk/assign.go
new file mode 100644
index 0000000..9350c38
--- /dev/null
+++ b/src/cmd/compile/internal/walk/assign.go
@@ -0,0 +1,719 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// walkAssign walks an OAS (AssignExpr) or OASOP (AssignOpExpr) node.
+func walkAssign(init *ir.Nodes, n ir.Node) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+
+	var left, right ir.Node
+	switch n.Op() {
+	case ir.OAS:
+		n := n.(*ir.AssignStmt)
+		left, right = n.X, n.Y
+	case ir.OASOP:
+		n := n.(*ir.AssignOpStmt)
+		left, right = n.X, n.Y
+	}
+
+	// Recognize m[k] = append(m[k], ...) so we can reuse
+	// the mapassign call.
+	var mapAppend *ir.CallExpr
+	if left.Op() == ir.OINDEXMAP && right.Op() == ir.OAPPEND {
+		left := left.(*ir.IndexExpr)
+		mapAppend = right.(*ir.CallExpr)
+		if !ir.SameSafeExpr(left, mapAppend.Args[0]) {
+			base.Fatalf("not same expressions: %v != %v", left, mapAppend.Args[0])
+		}
+	}
+
+	left = walkExpr(left, init)
+	left = safeExpr(left, init)
+	if mapAppend != nil {
+		mapAppend.Args[0] = left
+	}
+
+	if n.Op() == ir.OASOP {
+		// Rewrite x op= y into x = x op y.
+		n = ir.NewAssignStmt(base.Pos, left, typecheck.Expr(ir.NewBinaryExpr(base.Pos, n.(*ir.AssignOpStmt).AsOp, left, right)))
+	} else {
+		n.(*ir.AssignStmt).X = left
+	}
+	as := n.(*ir.AssignStmt)
+
+	if oaslit(as, init) {
+		return ir.NewBlockStmt(as.Pos(), nil)
+	}
+
+	if as.Y == nil {
+		// TODO(austin): Check all "implicit zeroing"
+		return as
+	}
+
+	if !base.Flag.Cfg.Instrumenting && ir.IsZero(as.Y) {
+		return as
+	}
+
+	switch as.Y.Op() {
+	default:
+		as.Y = walkExpr(as.Y, init)
+
+	case ir.ORECV:
+		// x = <-c; as.Left is x, as.Right.Left is c.
+		// order.stmt made sure x is addressable.
+		recv := as.Y.(*ir.UnaryExpr)
+		recv.X = walkExpr(recv.X, init)
+
+		n1 := typecheck.NodAddr(as.X)
+		r := recv.X // the channel
+		return mkcall1(chanfn("chanrecv1", 2, r.Type()), nil, init, r, n1)
+
+	case ir.OAPPEND:
+		// x = append(...)
+		call := as.Y.(*ir.CallExpr)
+		if call.Type().Elem().NotInHeap() {
+			base.Errorf("%v can't be allocated in Go; it is incomplete (or unallocatable)", call.Type().Elem())
+		}
+		var r ir.Node
+		switch {
+		case isAppendOfMake(call):
+			// x = append(y, make([]T, y)...)
+			r = extendSlice(call, init)
+		case call.IsDDD:
+			r = appendSlice(call, init) // also works for append(slice, string).
+		default:
+			r = walkAppend(call, init, as)
+		}
+		as.Y = r
+		if r.Op() == ir.OAPPEND {
+			// Left in place for back end.
+			// Do not add a new write barrier.
+			// Set up address of type for back end.
+			r.(*ir.CallExpr).X = reflectdata.TypePtr(r.Type().Elem())
+			return as
+		}
+		// Otherwise, lowered for race detector.
+		// Treat as ordinary assignment.
+	}
+
+	if as.X != nil && as.Y != nil {
+		return convas(as, init)
+	}
+	return as
+}
+
+// walkAssignDotType walks an OAS2DOTTYPE node.
+func walkAssignDotType(n *ir.AssignListStmt, init *ir.Nodes) ir.Node {
+	walkExprListSafe(n.Lhs, init)
+	n.Rhs[0] = walkExpr(n.Rhs[0], init)
+	return n
+}
+
+// walkAssignFunc walks an OAS2FUNC node.
+func walkAssignFunc(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+
+	r := n.Rhs[0]
+	walkExprListSafe(n.Lhs, init)
+	r = walkExpr(r, init)
+
+	if ir.IsIntrinsicCall(r.(*ir.CallExpr)) {
+		n.Rhs = []ir.Node{r}
+		return n
+	}
+	init.Append(r)
+
+	ll := ascompatet(n.Lhs, r.Type())
+	return ir.NewBlockStmt(src.NoXPos, ll)
+}
+
+// walkAssignList walks an OAS2 node.
+func walkAssignList(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+	return ir.NewBlockStmt(src.NoXPos, ascompatee(ir.OAS, n.Lhs, n.Rhs))
+}
+
+// walkAssignMapRead walks an OAS2MAPR node.
+func walkAssignMapRead(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+
+	r := n.Rhs[0].(*ir.IndexExpr)
+	walkExprListSafe(n.Lhs, init)
+	r.X = walkExpr(r.X, init)
+	r.Index = walkExpr(r.Index, init)
+	t := r.X.Type()
+
+	fast := mapfast(t)
+	key := mapKeyArg(fast, r, r.Index)
+
+	// from:
+	//   a,b = m[i]
+	// to:
+	//   var,b = mapaccess2*(t, m, i)
+	//   a = *var
+	a := n.Lhs[0]
+
+	var call *ir.CallExpr
+	if w := t.Elem().Size(); w <= zeroValSize {
+		fn := mapfn(mapaccess2[fast], t, false)
+		call = mkcall1(fn, fn.Type().Results(), init, reflectdata.TypePtr(t), r.X, key)
+	} else {
+		fn := mapfn("mapaccess2_fat", t, true)
+		z := reflectdata.ZeroAddr(w)
+		call = mkcall1(fn, fn.Type().Results(), init, reflectdata.TypePtr(t), r.X, key, z)
+	}
+
+	// mapaccess2* returns a typed bool, but due to spec changes,
+	// the boolean result of i.(T) is now untyped so we make it the
+	// same type as the variable on the lhs.
+	if ok := n.Lhs[1]; !ir.IsBlank(ok) && ok.Type().IsBoolean() {
+		call.Type().Field(1).Type = ok.Type()
+	}
+	n.Rhs = []ir.Node{call}
+	n.SetOp(ir.OAS2FUNC)
+
+	// don't generate a = *var if a is _
+	if ir.IsBlank(a) {
+		return walkExpr(typecheck.Stmt(n), init)
+	}
+
+	var_ := typecheck.Temp(types.NewPtr(t.Elem()))
+	var_.SetTypecheck(1)
+	var_.MarkNonNil() // mapaccess always returns a non-nil pointer
+
+	n.Lhs[0] = var_
+	init.Append(walkExpr(n, init))
+
+	as := ir.NewAssignStmt(base.Pos, a, ir.NewStarExpr(base.Pos, var_))
+	return walkExpr(typecheck.Stmt(as), init)
+}
+
+// walkAssignRecv walks an OAS2RECV node.
+func walkAssignRecv(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+
+	r := n.Rhs[0].(*ir.UnaryExpr) // recv
+	walkExprListSafe(n.Lhs, init)
+	r.X = walkExpr(r.X, init)
+	var n1 ir.Node
+	if ir.IsBlank(n.Lhs[0]) {
+		n1 = typecheck.NodNil()
+	} else {
+		n1 = typecheck.NodAddr(n.Lhs[0])
+	}
+	fn := chanfn("chanrecv2", 2, r.X.Type())
+	ok := n.Lhs[1]
+	call := mkcall1(fn, types.Types[types.TBOOL], init, r.X, n1)
+	return typecheck.Stmt(ir.NewAssignStmt(base.Pos, ok, call))
+}
+
+// walkReturn walks an ORETURN node.
+func walkReturn(n *ir.ReturnStmt) ir.Node {
+	fn := ir.CurFunc
+
+	fn.NumReturns++
+	if len(n.Results) == 0 {
+		return n
+	}
+
+	results := fn.Type().Results().FieldSlice()
+	dsts := make([]ir.Node, len(results))
+	for i, v := range results {
+		// TODO(mdempsky): typecheck should have already checked the result variables.
+		dsts[i] = typecheck.AssignExpr(v.Nname.(*ir.Name))
+	}
+
+	n.Results = ascompatee(n.Op(), dsts, n.Results)
+	return n
+}
+
+// check assign type list to
+// an expression list. called in
+//	expr-list = func()
+func ascompatet(nl ir.Nodes, nr *types.Type) []ir.Node {
+	if len(nl) != nr.NumFields() {
+		base.Fatalf("ascompatet: assignment count mismatch: %d = %d", len(nl), nr.NumFields())
+	}
+
+	var nn ir.Nodes
+	for i, l := range nl {
+		if ir.IsBlank(l) {
+			continue
+		}
+		r := nr.Field(i)
+
+		// Order should have created autotemps of the appropriate type for
+		// us to store results into.
+		if tmp, ok := l.(*ir.Name); !ok || !tmp.AutoTemp() || !types.Identical(tmp.Type(), r.Type) {
+			base.FatalfAt(l.Pos(), "assigning %v to %+v", r.Type, l)
+		}
+
+		res := ir.NewResultExpr(base.Pos, nil, types.BADWIDTH)
+		res.Index = int64(i)
+		res.SetType(r.Type)
+		res.SetTypecheck(1)
+
+		nn.Append(ir.NewAssignStmt(base.Pos, l, res))
+	}
+	return nn
+}
+
+// check assign expression list to
+// an expression list. called in
+//	expr-list = expr-list
+func ascompatee(op ir.Op, nl, nr []ir.Node) []ir.Node {
+	// cannot happen: should have been rejected during type checking
+	if len(nl) != len(nr) {
+		base.Fatalf("assignment operands mismatch: %+v / %+v", ir.Nodes(nl), ir.Nodes(nr))
+	}
+
+	var assigned ir.NameSet
+	var memWrite, deferResultWrite bool
+
+	// affected reports whether expression n could be affected by
+	// the assignments applied so far.
+	affected := func(n ir.Node) bool {
+		if deferResultWrite {
+			return true
+		}
+		return ir.Any(n, func(n ir.Node) bool {
+			if n.Op() == ir.ONAME && assigned.Has(n.(*ir.Name)) {
+				return true
+			}
+			if memWrite && readsMemory(n) {
+				return true
+			}
+			return false
+		})
+	}
+
+	// If a needed expression may be affected by an
+	// earlier assignment, make an early copy of that
+	// expression and use the copy instead.
+	var early ir.Nodes
+	save := func(np *ir.Node) {
+		if n := *np; affected(n) {
+			*np = copyExpr(n, n.Type(), &early)
+		}
+	}
+
+	var late ir.Nodes
+	for i, lorig := range nl {
+		l, r := lorig, nr[i]
+
+		// Do not generate 'x = x' during return. See issue 4014.
+		if op == ir.ORETURN && ir.SameSafeExpr(l, r) {
+			continue
+		}
+
+		// Save subexpressions needed on left side.
+		// Drill through non-dereferences.
+		for {
+			// If an expression has init statements, they must be evaluated
+			// before any of its saved sub-operands (#45706).
+			// TODO(mdempsky): Disallow init statements on lvalues.
+			init := ir.TakeInit(l)
+			walkStmtList(init)
+			early.Append(init...)
+
+			switch ll := l.(type) {
+			case *ir.IndexExpr:
+				if ll.X.Type().IsArray() {
+					save(&ll.Index)
+					l = ll.X
+					continue
+				}
+			case *ir.ParenExpr:
+				l = ll.X
+				continue
+			case *ir.SelectorExpr:
+				if ll.Op() == ir.ODOT {
+					l = ll.X
+					continue
+				}
+			}
+			break
+		}
+
+		var name *ir.Name
+		switch l.Op() {
+		default:
+			base.Fatalf("unexpected lvalue %v", l.Op())
+		case ir.ONAME:
+			name = l.(*ir.Name)
+		case ir.OINDEX, ir.OINDEXMAP:
+			l := l.(*ir.IndexExpr)
+			save(&l.X)
+			save(&l.Index)
+		case ir.ODEREF:
+			l := l.(*ir.StarExpr)
+			save(&l.X)
+		case ir.ODOTPTR:
+			l := l.(*ir.SelectorExpr)
+			save(&l.X)
+		}
+
+		// Save expression on right side.
+		save(&r)
+
+		appendWalkStmt(&late, convas(ir.NewAssignStmt(base.Pos, lorig, r), &late))
+
+		// Check for reasons why we may need to compute later expressions
+		// before this assignment happens.
+
+		if name == nil {
+			// Not a direct assignment to a declared variable.
+			// Conservatively assume any memory access might alias.
+			memWrite = true
+			continue
+		}
+
+		if name.Class == ir.PPARAMOUT && ir.CurFunc.HasDefer() {
+			// Assignments to a result parameter in a function with defers
+			// becomes visible early if evaluation of any later expression
+			// panics (#43835).
+			deferResultWrite = true
+			continue
+		}
+
+		if sym := types.OrigSym(name.Sym()); sym == nil || sym.IsBlank() {
+			// We can ignore assignments to blank or anonymous result parameters.
+			// These can't appear in expressions anyway.
+			continue
+		}
+
+		if name.Addrtaken() || !name.OnStack() {
+			// Global variable, heap escaped, or just addrtaken.
+			// Conservatively assume any memory access might alias.
+			memWrite = true
+			continue
+		}
+
+		// Local, non-addrtaken variable.
+		// Assignments can only alias with direct uses of this variable.
+		assigned.Add(name)
+	}
+
+	early.Append(late.Take()...)
+	return early
+}
+
+// readsMemory reports whether the evaluation n directly reads from
+// memory that might be written to indirectly.
+func readsMemory(n ir.Node) bool {
+	switch n.Op() {
+	case ir.ONAME:
+		n := n.(*ir.Name)
+		if n.Class == ir.PFUNC {
+			return false
+		}
+		return n.Addrtaken() || !n.OnStack()
+
+	case ir.OADD,
+		ir.OAND,
+		ir.OANDAND,
+		ir.OANDNOT,
+		ir.OBITNOT,
+		ir.OCONV,
+		ir.OCONVIFACE,
+		ir.OCONVIDATA,
+		ir.OCONVNOP,
+		ir.ODIV,
+		ir.ODOT,
+		ir.ODOTTYPE,
+		ir.OLITERAL,
+		ir.OLSH,
+		ir.OMOD,
+		ir.OMUL,
+		ir.ONEG,
+		ir.ONIL,
+		ir.OOR,
+		ir.OOROR,
+		ir.OPAREN,
+		ir.OPLUS,
+		ir.ORSH,
+		ir.OSUB,
+		ir.OXOR:
+		return false
+	}
+
+	// Be conservative.
+	return true
+}
+
+// expand append(l1, l2...) to
+//   init {
+//     s := l1
+//     n := len(s) + len(l2)
+//     // Compare as uint so growslice can panic on overflow.
+//     if uint(n) > uint(cap(s)) {
+//       s = growslice(s, n)
+//     }
+//     s = s[:n]
+//     memmove(&s[len(l1)], &l2[0], len(l2)*sizeof(T))
+//   }
+//   s
+//
+// l2 is allowed to be a string.
+func appendSlice(n *ir.CallExpr, init *ir.Nodes) ir.Node {
+	walkAppendArgs(n, init)
+
+	l1 := n.Args[0]
+	l2 := n.Args[1]
+	l2 = cheapExpr(l2, init)
+	n.Args[1] = l2
+
+	var nodes ir.Nodes
+
+	// var s []T
+	s := typecheck.Temp(l1.Type())
+	nodes.Append(ir.NewAssignStmt(base.Pos, s, l1)) // s = l1
+
+	elemtype := s.Type().Elem()
+
+	// n := len(s) + len(l2)
+	nn := typecheck.Temp(types.Types[types.TINT])
+	nodes.Append(ir.NewAssignStmt(base.Pos, nn, ir.NewBinaryExpr(base.Pos, ir.OADD, ir.NewUnaryExpr(base.Pos, ir.OLEN, s), ir.NewUnaryExpr(base.Pos, ir.OLEN, l2))))
+
+	// if uint(n) > uint(cap(s))
+	nif := ir.NewIfStmt(base.Pos, nil, nil, nil)
+	nuint := typecheck.Conv(nn, types.Types[types.TUINT])
+	scapuint := typecheck.Conv(ir.NewUnaryExpr(base.Pos, ir.OCAP, s), types.Types[types.TUINT])
+	nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OGT, nuint, scapuint)
+
+	// instantiate growslice(typ *type, []any, int) []any
+	fn := typecheck.LookupRuntime("growslice")
+	fn = typecheck.SubstArgTypes(fn, elemtype, elemtype)
+
+	// s = growslice(T, s, n)
+	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, s, mkcall1(fn, s.Type(), nif.PtrInit(), reflectdata.TypePtr(elemtype), s, nn))}
+	nodes.Append(nif)
+
+	// s = s[:n]
+	nt := ir.NewSliceExpr(base.Pos, ir.OSLICE, s, nil, nn, nil)
+	nt.SetBounded(true)
+	nodes.Append(ir.NewAssignStmt(base.Pos, s, nt))
+
+	var ncopy ir.Node
+	if elemtype.HasPointers() {
+		// copy(s[len(l1):], l2)
+		slice := ir.NewSliceExpr(base.Pos, ir.OSLICE, s, ir.NewUnaryExpr(base.Pos, ir.OLEN, l1), nil, nil)
+		slice.SetType(s.Type())
+
+		ir.CurFunc.SetWBPos(n.Pos())
+
+		// instantiate typedslicecopy(typ *type, dstPtr *any, dstLen int, srcPtr *any, srcLen int) int
+		fn := typecheck.LookupRuntime("typedslicecopy")
+		fn = typecheck.SubstArgTypes(fn, l1.Type().Elem(), l2.Type().Elem())
+		ptr1, len1 := backingArrayPtrLen(cheapExpr(slice, &nodes))
+		ptr2, len2 := backingArrayPtrLen(l2)
+		ncopy = mkcall1(fn, types.Types[types.TINT], &nodes, reflectdata.TypePtr(elemtype), ptr1, len1, ptr2, len2)
+	} else if base.Flag.Cfg.Instrumenting && !base.Flag.CompilingRuntime {
+		// rely on runtime to instrument:
+		//  copy(s[len(l1):], l2)
+		// l2 can be a slice or string.
+		slice := ir.NewSliceExpr(base.Pos, ir.OSLICE, s, ir.NewUnaryExpr(base.Pos, ir.OLEN, l1), nil, nil)
+		slice.SetType(s.Type())
+
+		ptr1, len1 := backingArrayPtrLen(cheapExpr(slice, &nodes))
+		ptr2, len2 := backingArrayPtrLen(l2)
+
+		fn := typecheck.LookupRuntime("slicecopy")
+		fn = typecheck.SubstArgTypes(fn, ptr1.Type().Elem(), ptr2.Type().Elem())
+		ncopy = mkcall1(fn, types.Types[types.TINT], &nodes, ptr1, len1, ptr2, len2, ir.NewInt(elemtype.Size()))
+	} else {
+		// memmove(&s[len(l1)], &l2[0], len(l2)*sizeof(T))
+		ix := ir.NewIndexExpr(base.Pos, s, ir.NewUnaryExpr(base.Pos, ir.OLEN, l1))
+		ix.SetBounded(true)
+		addr := typecheck.NodAddr(ix)
+
+		sptr := ir.NewUnaryExpr(base.Pos, ir.OSPTR, l2)
+
+		nwid := cheapExpr(typecheck.Conv(ir.NewUnaryExpr(base.Pos, ir.OLEN, l2), types.Types[types.TUINTPTR]), &nodes)
+		nwid = ir.NewBinaryExpr(base.Pos, ir.OMUL, nwid, ir.NewInt(elemtype.Size()))
+
+		// instantiate func memmove(to *any, frm *any, length uintptr)
+		fn := typecheck.LookupRuntime("memmove")
+		fn = typecheck.SubstArgTypes(fn, elemtype, elemtype)
+		ncopy = mkcall1(fn, nil, &nodes, addr, sptr, nwid)
+	}
+	ln := append(nodes, ncopy)
+
+	typecheck.Stmts(ln)
+	walkStmtList(ln)
+	init.Append(ln...)
+	return s
+}
+
+// isAppendOfMake reports whether n is of the form append(x, make([]T, y)...).
+// isAppendOfMake assumes n has already been typechecked.
+func isAppendOfMake(n ir.Node) bool {
+	if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
+		return false
+	}
+
+	if n.Typecheck() == 0 {
+		base.Fatalf("missing typecheck: %+v", n)
+	}
+
+	if n.Op() != ir.OAPPEND {
+		return false
+	}
+	call := n.(*ir.CallExpr)
+	if !call.IsDDD || len(call.Args) != 2 || call.Args[1].Op() != ir.OMAKESLICE {
+		return false
+	}
+
+	mk := call.Args[1].(*ir.MakeExpr)
+	if mk.Cap != nil {
+		return false
+	}
+
+	// y must be either an integer constant or the largest possible positive value
+	// of variable y needs to fit into an uint.
+
+	// typecheck made sure that constant arguments to make are not negative and fit into an int.
+
+	// The care of overflow of the len argument to make will be handled by an explicit check of int(len) < 0 during runtime.
+	y := mk.Len
+	if !ir.IsConst(y, constant.Int) && y.Type().Size() > types.Types[types.TUINT].Size() {
+		return false
+	}
+
+	return true
+}
+
+// extendSlice rewrites append(l1, make([]T, l2)...) to
+//   init {
+//     if l2 >= 0 { // Empty if block here for more meaningful node.SetLikely(true)
+//     } else {
+//       panicmakeslicelen()
+//     }
+//     s := l1
+//     n := len(s) + l2
+//     // Compare n and s as uint so growslice can panic on overflow of len(s) + l2.
+//     // cap is a positive int and n can become negative when len(s) + l2
+//     // overflows int. Interpreting n when negative as uint makes it larger
+//     // than cap(s). growslice will check the int n arg and panic if n is
+//     // negative. This prevents the overflow from being undetected.
+//     if uint(n) > uint(cap(s)) {
+//       s = growslice(T, s, n)
+//     }
+//     s = s[:n]
+//     lptr := &l1[0]
+//     sptr := &s[0]
+//     if lptr == sptr || !T.HasPointers() {
+//       // growslice did not clear the whole underlying array (or did not get called)
+//       hp := &s[len(l1)]
+//       hn := l2 * sizeof(T)
+//       memclr(hp, hn)
+//     }
+//   }
+//   s
+func extendSlice(n *ir.CallExpr, init *ir.Nodes) ir.Node {
+	// isAppendOfMake made sure all possible positive values of l2 fit into an uint.
+	// The case of l2 overflow when converting from e.g. uint to int is handled by an explicit
+	// check of l2 < 0 at runtime which is generated below.
+	l2 := typecheck.Conv(n.Args[1].(*ir.MakeExpr).Len, types.Types[types.TINT])
+	l2 = typecheck.Expr(l2)
+	n.Args[1] = l2 // walkAppendArgs expects l2 in n.List.Second().
+
+	walkAppendArgs(n, init)
+
+	l1 := n.Args[0]
+	l2 = n.Args[1] // re-read l2, as it may have been updated by walkAppendArgs
+
+	var nodes []ir.Node
+
+	// if l2 >= 0 (likely happens), do nothing
+	nifneg := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OGE, l2, ir.NewInt(0)), nil, nil)
+	nifneg.Likely = true
+
+	// else panicmakeslicelen()
+	nifneg.Else = []ir.Node{mkcall("panicmakeslicelen", nil, init)}
+	nodes = append(nodes, nifneg)
+
+	// s := l1
+	s := typecheck.Temp(l1.Type())
+	nodes = append(nodes, ir.NewAssignStmt(base.Pos, s, l1))
+
+	elemtype := s.Type().Elem()
+
+	// n := len(s) + l2
+	nn := typecheck.Temp(types.Types[types.TINT])
+	nodes = append(nodes, ir.NewAssignStmt(base.Pos, nn, ir.NewBinaryExpr(base.Pos, ir.OADD, ir.NewUnaryExpr(base.Pos, ir.OLEN, s), l2)))
+
+	// if uint(n) > uint(cap(s))
+	nuint := typecheck.Conv(nn, types.Types[types.TUINT])
+	capuint := typecheck.Conv(ir.NewUnaryExpr(base.Pos, ir.OCAP, s), types.Types[types.TUINT])
+	nif := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OGT, nuint, capuint), nil, nil)
+
+	// instantiate growslice(typ *type, old []any, newcap int) []any
+	fn := typecheck.LookupRuntime("growslice")
+	fn = typecheck.SubstArgTypes(fn, elemtype, elemtype)
+
+	// s = growslice(T, s, n)
+	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, s, mkcall1(fn, s.Type(), nif.PtrInit(), reflectdata.TypePtr(elemtype), s, nn))}
+	nodes = append(nodes, nif)
+
+	// s = s[:n]
+	nt := ir.NewSliceExpr(base.Pos, ir.OSLICE, s, nil, nn, nil)
+	nt.SetBounded(true)
+	nodes = append(nodes, ir.NewAssignStmt(base.Pos, s, nt))
+
+	// lptr := &l1[0]
+	l1ptr := typecheck.Temp(l1.Type().Elem().PtrTo())
+	tmp := ir.NewUnaryExpr(base.Pos, ir.OSPTR, l1)
+	nodes = append(nodes, ir.NewAssignStmt(base.Pos, l1ptr, tmp))
+
+	// sptr := &s[0]
+	sptr := typecheck.Temp(elemtype.PtrTo())
+	tmp = ir.NewUnaryExpr(base.Pos, ir.OSPTR, s)
+	nodes = append(nodes, ir.NewAssignStmt(base.Pos, sptr, tmp))
+
+	// hp := &s[len(l1)]
+	ix := ir.NewIndexExpr(base.Pos, s, ir.NewUnaryExpr(base.Pos, ir.OLEN, l1))
+	ix.SetBounded(true)
+	hp := typecheck.ConvNop(typecheck.NodAddr(ix), types.Types[types.TUNSAFEPTR])
+
+	// hn := l2 * sizeof(elem(s))
+	hn := typecheck.Conv(ir.NewBinaryExpr(base.Pos, ir.OMUL, l2, ir.NewInt(elemtype.Size())), types.Types[types.TUINTPTR])
+
+	clrname := "memclrNoHeapPointers"
+	hasPointers := elemtype.HasPointers()
+	if hasPointers {
+		clrname = "memclrHasPointers"
+		ir.CurFunc.SetWBPos(n.Pos())
+	}
+
+	var clr ir.Nodes
+	clrfn := mkcall(clrname, nil, &clr, hp, hn)
+	clr.Append(clrfn)
+
+	if hasPointers {
+		// if l1ptr == sptr
+		nifclr := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OEQ, l1ptr, sptr), nil, nil)
+		nifclr.Body = clr
+		nodes = append(nodes, nifclr)
+	} else {
+		nodes = append(nodes, clr...)
+	}
+
+	typecheck.Stmts(nodes)
+	walkStmtList(nodes)
+	init.Append(nodes...)
+	return s
+}
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
new file mode 100644
index 0000000..d0aaee0
--- /dev/null
+++ b/src/cmd/compile/internal/walk/builtin.go
@@ -0,0 +1,708 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"fmt"
+	"go/constant"
+	"go/token"
+	"strings"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/escape"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+)
+
+// Rewrite append(src, x, y, z) so that any side effects in
+// x, y, z (including runtime panics) are evaluated in
+// initialization statements before the append.
+// For normal code generation, stop there and leave the
+// rest to cgen_append.
+//
+// For race detector, expand append(src, a [, b]* ) to
+//
+//   init {
+//     s := src
+//     const argc = len(args) - 1
+//     if cap(s) - len(s) < argc {
+//	    s = growslice(s, len(s)+argc)
+//     }
+//     n := len(s)
+//     s = s[:n+argc]
+//     s[n] = a
+//     s[n+1] = b
+//     ...
+//   }
+//   s
+func walkAppend(n *ir.CallExpr, init *ir.Nodes, dst ir.Node) ir.Node {
+	if !ir.SameSafeExpr(dst, n.Args[0]) {
+		n.Args[0] = safeExpr(n.Args[0], init)
+		n.Args[0] = walkExpr(n.Args[0], init)
+	}
+	walkExprListSafe(n.Args[1:], init)
+
+	nsrc := n.Args[0]
+
+	// walkExprListSafe will leave OINDEX (s[n]) alone if both s
+	// and n are name or literal, but those may index the slice we're
+	// modifying here. Fix explicitly.
+	// Using cheapExpr also makes sure that the evaluation
+	// of all arguments (and especially any panics) happen
+	// before we begin to modify the slice in a visible way.
+	ls := n.Args[1:]
+	for i, n := range ls {
+		n = cheapExpr(n, init)
+		if !types.Identical(n.Type(), nsrc.Type().Elem()) {
+			n = typecheck.AssignConv(n, nsrc.Type().Elem(), "append")
+			n = walkExpr(n, init)
+		}
+		ls[i] = n
+	}
+
+	argc := len(n.Args) - 1
+	if argc < 1 {
+		return nsrc
+	}
+
+	// General case, with no function calls left as arguments.
+	// Leave for gen, except that instrumentation requires old form.
+	if !base.Flag.Cfg.Instrumenting || base.Flag.CompilingRuntime {
+		return n
+	}
+
+	var l []ir.Node
+
+	ns := typecheck.Temp(nsrc.Type())
+	l = append(l, ir.NewAssignStmt(base.Pos, ns, nsrc)) // s = src
+
+	na := ir.NewInt(int64(argc))                 // const argc
+	nif := ir.NewIfStmt(base.Pos, nil, nil, nil) // if cap(s) - len(s) < argc
+	nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OLT, ir.NewBinaryExpr(base.Pos, ir.OSUB, ir.NewUnaryExpr(base.Pos, ir.OCAP, ns), ir.NewUnaryExpr(base.Pos, ir.OLEN, ns)), na)
+
+	fn := typecheck.LookupRuntime("growslice") //   growslice(<type>, old []T, mincap int) (ret []T)
+	fn = typecheck.SubstArgTypes(fn, ns.Type().Elem(), ns.Type().Elem())
+
+	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, ns, mkcall1(fn, ns.Type(), nif.PtrInit(), reflectdata.TypePtr(ns.Type().Elem()), ns,
+		ir.NewBinaryExpr(base.Pos, ir.OADD, ir.NewUnaryExpr(base.Pos, ir.OLEN, ns), na)))}
+
+	l = append(l, nif)
+
+	nn := typecheck.Temp(types.Types[types.TINT])
+	l = append(l, ir.NewAssignStmt(base.Pos, nn, ir.NewUnaryExpr(base.Pos, ir.OLEN, ns))) // n = len(s)
+
+	slice := ir.NewSliceExpr(base.Pos, ir.OSLICE, ns, nil, ir.NewBinaryExpr(base.Pos, ir.OADD, nn, na), nil) // ...s[:n+argc]
+	slice.SetBounded(true)
+	l = append(l, ir.NewAssignStmt(base.Pos, ns, slice)) // s = s[:n+argc]
+
+	ls = n.Args[1:]
+	for i, n := range ls {
+		ix := ir.NewIndexExpr(base.Pos, ns, nn) // s[n] ...
+		ix.SetBounded(true)
+		l = append(l, ir.NewAssignStmt(base.Pos, ix, n)) // s[n] = arg
+		if i+1 < len(ls) {
+			l = append(l, ir.NewAssignStmt(base.Pos, nn, ir.NewBinaryExpr(base.Pos, ir.OADD, nn, ir.NewInt(1)))) // n = n + 1
+		}
+	}
+
+	typecheck.Stmts(l)
+	walkStmtList(l)
+	init.Append(l...)
+	return ns
+}
+
+// walkClose walks an OCLOSE node.
+func walkClose(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
+	// cannot use chanfn - closechan takes any, not chan any
+	fn := typecheck.LookupRuntime("closechan")
+	fn = typecheck.SubstArgTypes(fn, n.X.Type())
+	return mkcall1(fn, nil, init, n.X)
+}
+
+// Lower copy(a, b) to a memmove call or a runtime call.
+//
+// init {
+//   n := len(a)
+//   if n > len(b) { n = len(b) }
+//   if a.ptr != b.ptr { memmove(a.ptr, b.ptr, n*sizeof(elem(a))) }
+// }
+// n;
+//
+// Also works if b is a string.
+//
+func walkCopy(n *ir.BinaryExpr, init *ir.Nodes, runtimecall bool) ir.Node {
+	if n.X.Type().Elem().HasPointers() {
+		ir.CurFunc.SetWBPos(n.Pos())
+		fn := writebarrierfn("typedslicecopy", n.X.Type().Elem(), n.Y.Type().Elem())
+		n.X = cheapExpr(n.X, init)
+		ptrL, lenL := backingArrayPtrLen(n.X)
+		n.Y = cheapExpr(n.Y, init)
+		ptrR, lenR := backingArrayPtrLen(n.Y)
+		return mkcall1(fn, n.Type(), init, reflectdata.TypePtr(n.X.Type().Elem()), ptrL, lenL, ptrR, lenR)
+	}
+
+	if runtimecall {
+		// rely on runtime to instrument:
+		//  copy(n.Left, n.Right)
+		// n.Right can be a slice or string.
+
+		n.X = cheapExpr(n.X, init)
+		ptrL, lenL := backingArrayPtrLen(n.X)
+		n.Y = cheapExpr(n.Y, init)
+		ptrR, lenR := backingArrayPtrLen(n.Y)
+
+		fn := typecheck.LookupRuntime("slicecopy")
+		fn = typecheck.SubstArgTypes(fn, ptrL.Type().Elem(), ptrR.Type().Elem())
+
+		return mkcall1(fn, n.Type(), init, ptrL, lenL, ptrR, lenR, ir.NewInt(n.X.Type().Elem().Size()))
+	}
+
+	n.X = walkExpr(n.X, init)
+	n.Y = walkExpr(n.Y, init)
+	nl := typecheck.Temp(n.X.Type())
+	nr := typecheck.Temp(n.Y.Type())
+	var l []ir.Node
+	l = append(l, ir.NewAssignStmt(base.Pos, nl, n.X))
+	l = append(l, ir.NewAssignStmt(base.Pos, nr, n.Y))
+
+	nfrm := ir.NewUnaryExpr(base.Pos, ir.OSPTR, nr)
+	nto := ir.NewUnaryExpr(base.Pos, ir.OSPTR, nl)
+
+	nlen := typecheck.Temp(types.Types[types.TINT])
+
+	// n = len(to)
+	l = append(l, ir.NewAssignStmt(base.Pos, nlen, ir.NewUnaryExpr(base.Pos, ir.OLEN, nl)))
+
+	// if n > len(frm) { n = len(frm) }
+	nif := ir.NewIfStmt(base.Pos, nil, nil, nil)
+
+	nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OGT, nlen, ir.NewUnaryExpr(base.Pos, ir.OLEN, nr))
+	nif.Body.Append(ir.NewAssignStmt(base.Pos, nlen, ir.NewUnaryExpr(base.Pos, ir.OLEN, nr)))
+	l = append(l, nif)
+
+	// if to.ptr != frm.ptr { memmove( ... ) }
+	ne := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.ONE, nto, nfrm), nil, nil)
+	ne.Likely = true
+	l = append(l, ne)
+
+	fn := typecheck.LookupRuntime("memmove")
+	fn = typecheck.SubstArgTypes(fn, nl.Type().Elem(), nl.Type().Elem())
+	nwid := ir.Node(typecheck.Temp(types.Types[types.TUINTPTR]))
+	setwid := ir.NewAssignStmt(base.Pos, nwid, typecheck.Conv(nlen, types.Types[types.TUINTPTR]))
+	ne.Body.Append(setwid)
+	nwid = ir.NewBinaryExpr(base.Pos, ir.OMUL, nwid, ir.NewInt(nl.Type().Elem().Size()))
+	call := mkcall1(fn, nil, init, nto, nfrm, nwid)
+	ne.Body.Append(call)
+
+	typecheck.Stmts(l)
+	walkStmtList(l)
+	init.Append(l...)
+	return nlen
+}
+
+// walkDelete walks an ODELETE node.
+func walkDelete(init *ir.Nodes, n *ir.CallExpr) ir.Node {
+	init.Append(ir.TakeInit(n)...)
+	map_ := n.Args[0]
+	key := n.Args[1]
+	map_ = walkExpr(map_, init)
+	key = walkExpr(key, init)
+
+	t := map_.Type()
+	fast := mapfast(t)
+	key = mapKeyArg(fast, n, key)
+	return mkcall1(mapfndel(mapdelete[fast], t), nil, init, reflectdata.TypePtr(t), map_, key)
+}
+
+// walkLenCap walks an OLEN or OCAP node.
+func walkLenCap(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
+	if isRuneCount(n) {
+		// Replace len([]rune(string)) with runtime.countrunes(string).
+		return mkcall("countrunes", n.Type(), init, typecheck.Conv(n.X.(*ir.ConvExpr).X, types.Types[types.TSTRING]))
+	}
+
+	n.X = walkExpr(n.X, init)
+
+	// replace len(*[10]int) with 10.
+	// delayed until now to preserve side effects.
+	t := n.X.Type()
+
+	if t.IsPtr() {
+		t = t.Elem()
+	}
+	if t.IsArray() {
+		safeExpr(n.X, init)
+		con := typecheck.OrigInt(n, t.NumElem())
+		con.SetTypecheck(1)
+		return con
+	}
+	return n
+}
+
+// walkMakeChan walks an OMAKECHAN node.
+func walkMakeChan(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
+	// When size fits into int, use makechan instead of
+	// makechan64, which is faster and shorter on 32 bit platforms.
+	size := n.Len
+	fnname := "makechan64"
+	argtype := types.Types[types.TINT64]
+
+	// Type checking guarantees that TIDEAL size is positive and fits in an int.
+	// The case of size overflow when converting TUINT or TUINTPTR to TINT
+	// will be handled by the negative range checks in makechan during runtime.
+	if size.Type().IsKind(types.TIDEAL) || size.Type().Size() <= types.Types[types.TUINT].Size() {
+		fnname = "makechan"
+		argtype = types.Types[types.TINT]
+	}
+
+	return mkcall1(chanfn(fnname, 1, n.Type()), n.Type(), init, reflectdata.TypePtr(n.Type()), typecheck.Conv(size, argtype))
+}
+
+// walkMakeMap walks an OMAKEMAP node.
+func walkMakeMap(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
+	t := n.Type()
+	hmapType := reflectdata.MapType(t)
+	hint := n.Len
+
+	// var h *hmap
+	var h ir.Node
+	if n.Esc() == ir.EscNone {
+		// Allocate hmap on stack.
+
+		// var hv hmap
+		// h = &hv
+		h = stackTempAddr(init, hmapType)
+
+		// Allocate one bucket pointed to by hmap.buckets on stack if hint
+		// is not larger than BUCKETSIZE. In case hint is larger than
+		// BUCKETSIZE runtime.makemap will allocate the buckets on the heap.
+		// Maximum key and elem size is 128 bytes, larger objects
+		// are stored with an indirection. So max bucket size is 2048+eps.
+		if !ir.IsConst(hint, constant.Int) ||
+			constant.Compare(hint.Val(), token.LEQ, constant.MakeInt64(reflectdata.BUCKETSIZE)) {
+
+			// In case hint is larger than BUCKETSIZE runtime.makemap
+			// will allocate the buckets on the heap, see #20184
+			//
+			// if hint <= BUCKETSIZE {
+			//     var bv bmap
+			//     b = &bv
+			//     h.buckets = b
+			// }
+
+			nif := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OLE, hint, ir.NewInt(reflectdata.BUCKETSIZE)), nil, nil)
+			nif.Likely = true
+
+			// var bv bmap
+			// b = &bv
+			b := stackTempAddr(&nif.Body, reflectdata.MapBucketType(t))
+
+			// h.buckets = b
+			bsym := hmapType.Field(5).Sym // hmap.buckets see reflect.go:hmap
+			na := ir.NewAssignStmt(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, h, bsym), b)
+			nif.Body.Append(na)
+			appendWalkStmt(init, nif)
+		}
+	}
+
+	if ir.IsConst(hint, constant.Int) && constant.Compare(hint.Val(), token.LEQ, constant.MakeInt64(reflectdata.BUCKETSIZE)) {
+		// Handling make(map[any]any) and
+		// make(map[any]any, hint) where hint <= BUCKETSIZE
+		// special allows for faster map initialization and
+		// improves binary size by using calls with fewer arguments.
+		// For hint <= BUCKETSIZE overLoadFactor(hint, 0) is false
+		// and no buckets will be allocated by makemap. Therefore,
+		// no buckets need to be allocated in this code path.
+		if n.Esc() == ir.EscNone {
+			// Only need to initialize h.hash0 since
+			// hmap h has been allocated on the stack already.
+			// h.hash0 = fastrand()
+			rand := mkcall("fastrand", types.Types[types.TUINT32], init)
+			hashsym := hmapType.Field(4).Sym // hmap.hash0 see reflect.go:hmap
+			appendWalkStmt(init, ir.NewAssignStmt(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, h, hashsym), rand))
+			return typecheck.ConvNop(h, t)
+		}
+		// Call runtime.makehmap to allocate an
+		// hmap on the heap and initialize hmap's hash0 field.
+		fn := typecheck.LookupRuntime("makemap_small")
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem())
+		return mkcall1(fn, n.Type(), init)
+	}
+
+	if n.Esc() != ir.EscNone {
+		h = typecheck.NodNil()
+	}
+	// Map initialization with a variable or large hint is
+	// more complicated. We therefore generate a call to
+	// runtime.makemap to initialize hmap and allocate the
+	// map buckets.
+
+	// When hint fits into int, use makemap instead of
+	// makemap64, which is faster and shorter on 32 bit platforms.
+	fnname := "makemap64"
+	argtype := types.Types[types.TINT64]
+
+	// Type checking guarantees that TIDEAL hint is positive and fits in an int.
+	// See checkmake call in TMAP case of OMAKE case in OpSwitch in typecheck1 function.
+	// The case of hint overflow when converting TUINT or TUINTPTR to TINT
+	// will be handled by the negative range checks in makemap during runtime.
+	if hint.Type().IsKind(types.TIDEAL) || hint.Type().Size() <= types.Types[types.TUINT].Size() {
+		fnname = "makemap"
+		argtype = types.Types[types.TINT]
+	}
+
+	fn := typecheck.LookupRuntime(fnname)
+	fn = typecheck.SubstArgTypes(fn, hmapType, t.Key(), t.Elem())
+	return mkcall1(fn, n.Type(), init, reflectdata.TypePtr(n.Type()), typecheck.Conv(hint, argtype), h)
+}
+
+// walkMakeSlice walks an OMAKESLICE node.
+func walkMakeSlice(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
+	l := n.Len
+	r := n.Cap
+	if r == nil {
+		r = safeExpr(l, init)
+		l = r
+	}
+	t := n.Type()
+	if t.Elem().NotInHeap() {
+		base.Errorf("%v can't be allocated in Go; it is incomplete (or unallocatable)", t.Elem())
+	}
+	if n.Esc() == ir.EscNone {
+		if why := escape.HeapAllocReason(n); why != "" {
+			base.Fatalf("%v has EscNone, but %v", n, why)
+		}
+		// var arr [r]T
+		// n = arr[:l]
+		i := typecheck.IndexConst(r)
+		if i < 0 {
+			base.Fatalf("walkExpr: invalid index %v", r)
+		}
+
+		// cap is constrained to [0,2^31) or [0,2^63) depending on whether
+		// we're in 32-bit or 64-bit systems. So it's safe to do:
+		//
+		// if uint64(len) > cap {
+		//     if len < 0 { panicmakeslicelen() }
+		//     panicmakeslicecap()
+		// }
+		nif := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OGT, typecheck.Conv(l, types.Types[types.TUINT64]), ir.NewInt(i)), nil, nil)
+		niflen := ir.NewIfStmt(base.Pos, ir.NewBinaryExpr(base.Pos, ir.OLT, l, ir.NewInt(0)), nil, nil)
+		niflen.Body = []ir.Node{mkcall("panicmakeslicelen", nil, init)}
+		nif.Body.Append(niflen, mkcall("panicmakeslicecap", nil, init))
+		init.Append(typecheck.Stmt(nif))
+
+		t = types.NewArray(t.Elem(), i) // [r]T
+		var_ := typecheck.Temp(t)
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, nil))  // zero temp
+		r := ir.NewSliceExpr(base.Pos, ir.OSLICE, var_, nil, l, nil) // arr[:l]
+		// The conv is necessary in case n.Type is named.
+		return walkExpr(typecheck.Expr(typecheck.Conv(r, n.Type())), init)
+	}
+
+	// n escapes; set up a call to makeslice.
+	// When len and cap can fit into int, use makeslice instead of
+	// makeslice64, which is faster and shorter on 32 bit platforms.
+
+	len, cap := l, r
+
+	fnname := "makeslice64"
+	argtype := types.Types[types.TINT64]
+
+	// Type checking guarantees that TIDEAL len/cap are positive and fit in an int.
+	// The case of len or cap overflow when converting TUINT or TUINTPTR to TINT
+	// will be handled by the negative range checks in makeslice during runtime.
+	if (len.Type().IsKind(types.TIDEAL) || len.Type().Size() <= types.Types[types.TUINT].Size()) &&
+		(cap.Type().IsKind(types.TIDEAL) || cap.Type().Size() <= types.Types[types.TUINT].Size()) {
+		fnname = "makeslice"
+		argtype = types.Types[types.TINT]
+	}
+	fn := typecheck.LookupRuntime(fnname)
+	ptr := mkcall1(fn, types.Types[types.TUNSAFEPTR], init, reflectdata.TypePtr(t.Elem()), typecheck.Conv(len, argtype), typecheck.Conv(cap, argtype))
+	ptr.MarkNonNil()
+	len = typecheck.Conv(len, types.Types[types.TINT])
+	cap = typecheck.Conv(cap, types.Types[types.TINT])
+	sh := ir.NewSliceHeaderExpr(base.Pos, t, ptr, len, cap)
+	return walkExpr(typecheck.Expr(sh), init)
+}
+
+// walkMakeSliceCopy walks an OMAKESLICECOPY node.
+func walkMakeSliceCopy(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
+	if n.Esc() == ir.EscNone {
+		base.Fatalf("OMAKESLICECOPY with EscNone: %v", n)
+	}
+
+	t := n.Type()
+	if t.Elem().NotInHeap() {
+		base.Errorf("%v can't be allocated in Go; it is incomplete (or unallocatable)", t.Elem())
+	}
+
+	length := typecheck.Conv(n.Len, types.Types[types.TINT])
+	copylen := ir.NewUnaryExpr(base.Pos, ir.OLEN, n.Cap)
+	copyptr := ir.NewUnaryExpr(base.Pos, ir.OSPTR, n.Cap)
+
+	if !t.Elem().HasPointers() && n.Bounded() {
+		// When len(to)==len(from) and elements have no pointers:
+		// replace make+copy with runtime.mallocgc+runtime.memmove.
+
+		// We do not check for overflow of len(to)*elem.Width here
+		// since len(from) is an existing checked slice capacity
+		// with same elem.Width for the from slice.
+		size := ir.NewBinaryExpr(base.Pos, ir.OMUL, typecheck.Conv(length, types.Types[types.TUINTPTR]), typecheck.Conv(ir.NewInt(t.Elem().Size()), types.Types[types.TUINTPTR]))
+
+		// instantiate mallocgc(size uintptr, typ *byte, needszero bool) unsafe.Pointer
+		fn := typecheck.LookupRuntime("mallocgc")
+		ptr := mkcall1(fn, types.Types[types.TUNSAFEPTR], init, size, typecheck.NodNil(), ir.NewBool(false))
+		ptr.MarkNonNil()
+		sh := ir.NewSliceHeaderExpr(base.Pos, t, ptr, length, length)
+
+		s := typecheck.Temp(t)
+		r := typecheck.Stmt(ir.NewAssignStmt(base.Pos, s, sh))
+		r = walkExpr(r, init)
+		init.Append(r)
+
+		// instantiate memmove(to *any, frm *any, size uintptr)
+		fn = typecheck.LookupRuntime("memmove")
+		fn = typecheck.SubstArgTypes(fn, t.Elem(), t.Elem())
+		ncopy := mkcall1(fn, nil, init, ir.NewUnaryExpr(base.Pos, ir.OSPTR, s), copyptr, size)
+		init.Append(walkExpr(typecheck.Stmt(ncopy), init))
+
+		return s
+	}
+	// Replace make+copy with runtime.makeslicecopy.
+	// instantiate makeslicecopy(typ *byte, tolen int, fromlen int, from unsafe.Pointer) unsafe.Pointer
+	fn := typecheck.LookupRuntime("makeslicecopy")
+	ptr := mkcall1(fn, types.Types[types.TUNSAFEPTR], init, reflectdata.TypePtr(t.Elem()), length, copylen, typecheck.Conv(copyptr, types.Types[types.TUNSAFEPTR]))
+	ptr.MarkNonNil()
+	sh := ir.NewSliceHeaderExpr(base.Pos, t, ptr, length, length)
+	return walkExpr(typecheck.Expr(sh), init)
+}
+
+// walkNew walks an ONEW node.
+func walkNew(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
+	t := n.Type().Elem()
+	if t.NotInHeap() {
+		base.Errorf("%v can't be allocated in Go; it is incomplete (or unallocatable)", n.Type().Elem())
+	}
+	if n.Esc() == ir.EscNone {
+		if t.Size() > ir.MaxImplicitStackVarSize {
+			base.Fatalf("large ONEW with EscNone: %v", n)
+		}
+		return stackTempAddr(init, t)
+	}
+	types.CalcSize(t)
+	n.MarkNonNil()
+	return n
+}
+
+// generate code for print
+func walkPrint(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
+	// Hoist all the argument evaluation up before the lock.
+	walkExprListCheap(nn.Args, init)
+
+	// For println, add " " between elements and "\n" at the end.
+	if nn.Op() == ir.OPRINTN {
+		s := nn.Args
+		t := make([]ir.Node, 0, len(s)*2)
+		for i, n := range s {
+			if i != 0 {
+				t = append(t, ir.NewString(" "))
+			}
+			t = append(t, n)
+		}
+		t = append(t, ir.NewString("\n"))
+		nn.Args = t
+	}
+
+	// Collapse runs of constant strings.
+	s := nn.Args
+	t := make([]ir.Node, 0, len(s))
+	for i := 0; i < len(s); {
+		var strs []string
+		for i < len(s) && ir.IsConst(s[i], constant.String) {
+			strs = append(strs, ir.StringVal(s[i]))
+			i++
+		}
+		if len(strs) > 0 {
+			t = append(t, ir.NewString(strings.Join(strs, "")))
+		}
+		if i < len(s) {
+			t = append(t, s[i])
+			i++
+		}
+	}
+	nn.Args = t
+
+	calls := []ir.Node{mkcall("printlock", nil, init)}
+	for i, n := range nn.Args {
+		if n.Op() == ir.OLITERAL {
+			if n.Type() == types.UntypedRune {
+				n = typecheck.DefaultLit(n, types.RuneType)
+			}
+
+			switch n.Val().Kind() {
+			case constant.Int:
+				n = typecheck.DefaultLit(n, types.Types[types.TINT64])
+
+			case constant.Float:
+				n = typecheck.DefaultLit(n, types.Types[types.TFLOAT64])
+			}
+		}
+
+		if n.Op() != ir.OLITERAL && n.Type() != nil && n.Type().Kind() == types.TIDEAL {
+			n = typecheck.DefaultLit(n, types.Types[types.TINT64])
+		}
+		n = typecheck.DefaultLit(n, nil)
+		nn.Args[i] = n
+		if n.Type() == nil || n.Type().Kind() == types.TFORW {
+			continue
+		}
+
+		var on *ir.Name
+		switch n.Type().Kind() {
+		case types.TINTER:
+			if n.Type().IsEmptyInterface() {
+				on = typecheck.LookupRuntime("printeface")
+			} else {
+				on = typecheck.LookupRuntime("printiface")
+			}
+			on = typecheck.SubstArgTypes(on, n.Type()) // any-1
+		case types.TPTR:
+			if n.Type().Elem().NotInHeap() {
+				on = typecheck.LookupRuntime("printuintptr")
+				n = ir.NewConvExpr(base.Pos, ir.OCONV, nil, n)
+				n.SetType(types.Types[types.TUNSAFEPTR])
+				n = ir.NewConvExpr(base.Pos, ir.OCONV, nil, n)
+				n.SetType(types.Types[types.TUINTPTR])
+				break
+			}
+			fallthrough
+		case types.TCHAN, types.TMAP, types.TFUNC, types.TUNSAFEPTR:
+			on = typecheck.LookupRuntime("printpointer")
+			on = typecheck.SubstArgTypes(on, n.Type()) // any-1
+		case types.TSLICE:
+			on = typecheck.LookupRuntime("printslice")
+			on = typecheck.SubstArgTypes(on, n.Type()) // any-1
+		case types.TUINT, types.TUINT8, types.TUINT16, types.TUINT32, types.TUINT64, types.TUINTPTR:
+			if types.IsRuntimePkg(n.Type().Sym().Pkg) && n.Type().Sym().Name == "hex" {
+				on = typecheck.LookupRuntime("printhex")
+			} else {
+				on = typecheck.LookupRuntime("printuint")
+			}
+		case types.TINT, types.TINT8, types.TINT16, types.TINT32, types.TINT64:
+			on = typecheck.LookupRuntime("printint")
+		case types.TFLOAT32, types.TFLOAT64:
+			on = typecheck.LookupRuntime("printfloat")
+		case types.TCOMPLEX64, types.TCOMPLEX128:
+			on = typecheck.LookupRuntime("printcomplex")
+		case types.TBOOL:
+			on = typecheck.LookupRuntime("printbool")
+		case types.TSTRING:
+			cs := ""
+			if ir.IsConst(n, constant.String) {
+				cs = ir.StringVal(n)
+			}
+			switch cs {
+			case " ":
+				on = typecheck.LookupRuntime("printsp")
+			case "\n":
+				on = typecheck.LookupRuntime("printnl")
+			default:
+				on = typecheck.LookupRuntime("printstring")
+			}
+		default:
+			badtype(ir.OPRINT, n.Type(), nil)
+			continue
+		}
+
+		r := ir.NewCallExpr(base.Pos, ir.OCALL, on, nil)
+		if params := on.Type().Params().FieldSlice(); len(params) > 0 {
+			t := params[0].Type
+			n = typecheck.Conv(n, t)
+			r.Args.Append(n)
+		}
+		calls = append(calls, r)
+	}
+
+	calls = append(calls, mkcall("printunlock", nil, init))
+
+	typecheck.Stmts(calls)
+	walkExprList(calls, init)
+
+	r := ir.NewBlockStmt(base.Pos, nil)
+	r.List = calls
+	return walkStmt(typecheck.Stmt(r))
+}
+
+// walkRecover walks an ORECOVERFP node.
+func walkRecoverFP(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
+	return mkcall("gorecover", nn.Type(), init, walkExpr(nn.Args[0], init))
+}
+
+func walkUnsafeSlice(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
+	ptr := safeExpr(n.X, init)
+	len := safeExpr(n.Y, init)
+
+	fnname := "unsafeslice64"
+	lenType := types.Types[types.TINT64]
+
+	// Type checking guarantees that TIDEAL len/cap are positive and fit in an int.
+	// The case of len or cap overflow when converting TUINT or TUINTPTR to TINT
+	// will be handled by the negative range checks in unsafeslice during runtime.
+	if ir.ShouldCheckPtr(ir.CurFunc, 1) {
+		fnname = "unsafeslicecheckptr"
+		// for simplicity, unsafeslicecheckptr always uses int64
+	} else if len.Type().IsKind(types.TIDEAL) || len.Type().Size() <= types.Types[types.TUINT].Size() {
+		fnname = "unsafeslice"
+		lenType = types.Types[types.TINT]
+	}
+
+	t := n.Type()
+
+	// Call runtime.unsafeslice{,64,checkptr} to check ptr and len.
+	fn := typecheck.LookupRuntime(fnname)
+	init.Append(mkcall1(fn, nil, init, reflectdata.TypePtr(t.Elem()), typecheck.Conv(ptr, types.Types[types.TUNSAFEPTR]), typecheck.Conv(len, lenType)))
+
+	h := ir.NewSliceHeaderExpr(n.Pos(), t,
+		typecheck.Conv(ptr, types.Types[types.TUNSAFEPTR]),
+		typecheck.Conv(len, types.Types[types.TINT]),
+		typecheck.Conv(len, types.Types[types.TINT]))
+	return walkExpr(typecheck.Expr(h), init)
+}
+
+func badtype(op ir.Op, tl, tr *types.Type) {
+	var s string
+	if tl != nil {
+		s += fmt.Sprintf("\n\t%v", tl)
+	}
+	if tr != nil {
+		s += fmt.Sprintf("\n\t%v", tr)
+	}
+
+	// common mistake: *struct and *interface.
+	if tl != nil && tr != nil && tl.IsPtr() && tr.IsPtr() {
+		if tl.Elem().IsStruct() && tr.Elem().IsInterface() {
+			s += "\n\t(*struct vs *interface)"
+		} else if tl.Elem().IsInterface() && tr.Elem().IsStruct() {
+			s += "\n\t(*interface vs *struct)"
+		}
+	}
+
+	base.Errorf("illegal types for operand: %v%s", op, s)
+}
+
+func writebarrierfn(name string, l *types.Type, r *types.Type) ir.Node {
+	fn := typecheck.LookupRuntime(name)
+	fn = typecheck.SubstArgTypes(fn, l, r)
+	return fn
+}
+
+// isRuneCount reports whether n is of the form len([]rune(string)).
+// These are optimized into a call to runtime.countrunes.
+func isRuneCount(n ir.Node) bool {
+	return base.Flag.N == 0 && !base.Flag.Cfg.Instrumenting && n.Op() == ir.OLEN && n.(*ir.UnaryExpr).X.Op() == ir.OSTR2RUNES
+}
diff --git a/src/cmd/compile/internal/walk/closure.go b/src/cmd/compile/internal/walk/closure.go
new file mode 100644
index 0000000..cd922c9
--- /dev/null
+++ b/src/cmd/compile/internal/walk/closure.go
@@ -0,0 +1,276 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// directClosureCall rewrites a direct call of a function literal into
+// a normal function call with closure variables passed as arguments.
+// This avoids allocation of a closure object.
+//
+// For illustration, the following call:
+//
+//	func(a int) {
+//		println(byval)
+//		byref++
+//	}(42)
+//
+// becomes:
+//
+//	func(byval int, &byref *int, a int) {
+//		println(byval)
+//		(*&byref)++
+//	}(byval, &byref, 42)
+func directClosureCall(n *ir.CallExpr) {
+	clo := n.X.(*ir.ClosureExpr)
+	clofn := clo.Func
+
+	if ir.IsTrivialClosure(clo) {
+		return // leave for walkClosure to handle
+	}
+
+	// We are going to insert captured variables before input args.
+	var params []*types.Field
+	var decls []*ir.Name
+	for _, v := range clofn.ClosureVars {
+		if !v.Byval() {
+			// If v of type T is captured by reference,
+			// we introduce function param &v *T
+			// and v remains PAUTOHEAP with &v heapaddr
+			// (accesses will implicitly deref &v).
+
+			addr := ir.NewNameAt(clofn.Pos(), typecheck.Lookup("&"+v.Sym().Name))
+			addr.Curfn = clofn
+			addr.SetType(types.NewPtr(v.Type()))
+			v.Heapaddr = addr
+			v = addr
+		}
+
+		v.Class = ir.PPARAM
+		decls = append(decls, v)
+
+		fld := types.NewField(src.NoXPos, v.Sym(), v.Type())
+		fld.Nname = v
+		params = append(params, fld)
+	}
+
+	// f is ONAME of the actual function.
+	f := clofn.Nname
+	typ := f.Type()
+
+	// Create new function type with parameters prepended, and
+	// then update type and declarations.
+	typ = types.NewSignature(typ.Pkg(), nil, nil, append(params, typ.Params().FieldSlice()...), typ.Results().FieldSlice())
+	f.SetType(typ)
+	clofn.Dcl = append(decls, clofn.Dcl...)
+
+	// Rewrite call.
+	n.X = f
+	n.Args.Prepend(closureArgs(clo)...)
+
+	// Update the call expression's type. We need to do this
+	// because typecheck gave it the result type of the OCLOSURE
+	// node, but we only rewrote the ONAME node's type. Logically,
+	// they're the same, but the stack offsets probably changed.
+	if typ.NumResults() == 1 {
+		n.SetType(typ.Results().Field(0).Type)
+	} else {
+		n.SetType(typ.Results())
+	}
+
+	// Add to Closures for enqueueFunc. It's no longer a proper
+	// closure, but we may have already skipped over it in the
+	// functions list as a non-trivial closure, so this just
+	// ensures it's compiled.
+	ir.CurFunc.Closures = append(ir.CurFunc.Closures, clofn)
+}
+
+func walkClosure(clo *ir.ClosureExpr, init *ir.Nodes) ir.Node {
+	clofn := clo.Func
+
+	// If no closure vars, don't bother wrapping.
+	if ir.IsTrivialClosure(clo) {
+		if base.Debug.Closure > 0 {
+			base.WarnfAt(clo.Pos(), "closure converted to global")
+		}
+		return clofn.Nname
+	}
+
+	// The closure is not trivial or directly called, so it's going to stay a closure.
+	ir.ClosureDebugRuntimeCheck(clo)
+	clofn.SetNeedctxt(true)
+
+	// The closure expression may be walked more than once if it appeared in composite
+	// literal initialization (e.g, see issue #49029).
+	//
+	// Don't add the closure function to compilation queue more than once, since when
+	// compiling a function twice would lead to an ICE.
+	if !clofn.Walked() {
+		clofn.SetWalked(true)
+		ir.CurFunc.Closures = append(ir.CurFunc.Closures, clofn)
+	}
+
+	typ := typecheck.ClosureType(clo)
+
+	clos := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, ir.TypeNode(typ), nil)
+	clos.SetEsc(clo.Esc())
+	clos.List = append([]ir.Node{ir.NewUnaryExpr(base.Pos, ir.OCFUNC, clofn.Nname)}, closureArgs(clo)...)
+	for i, value := range clos.List {
+		clos.List[i] = ir.NewStructKeyExpr(base.Pos, typ.Field(i), value)
+	}
+
+	addr := typecheck.NodAddr(clos)
+	addr.SetEsc(clo.Esc())
+
+	// Force type conversion from *struct to the func type.
+	cfn := typecheck.ConvNop(addr, clo.Type())
+
+	// non-escaping temp to use, if any.
+	if x := clo.Prealloc; x != nil {
+		if !types.Identical(typ, x.Type()) {
+			panic("closure type does not match order's assigned type")
+		}
+		addr.Prealloc = x
+		clo.Prealloc = nil
+	}
+
+	return walkExpr(cfn, init)
+}
+
+// closureArgs returns a slice of expressions that an be used to
+// initialize the given closure's free variables. These correspond
+// one-to-one with the variables in clo.Func.ClosureVars, and will be
+// either an ONAME node (if the variable is captured by value) or an
+// OADDR-of-ONAME node (if not).
+func closureArgs(clo *ir.ClosureExpr) []ir.Node {
+	fn := clo.Func
+
+	args := make([]ir.Node, len(fn.ClosureVars))
+	for i, v := range fn.ClosureVars {
+		var outer ir.Node
+		outer = v.Outer
+		if !v.Byval() {
+			outer = typecheck.NodAddrAt(fn.Pos(), outer)
+		}
+		args[i] = typecheck.Expr(outer)
+	}
+	return args
+}
+
+func walkMethodValue(n *ir.SelectorExpr, init *ir.Nodes) ir.Node {
+	// Create closure in the form of a composite literal.
+	// For x.M with receiver (x) type T, the generated code looks like:
+	//
+	//	clos = &struct{F uintptr; R T}{T.M·f, x}
+	//
+	// Like walkClosure above.
+
+	if n.X.Type().IsInterface() {
+		// Trigger panic for method on nil interface now.
+		// Otherwise it happens in the wrapper and is confusing.
+		n.X = cheapExpr(n.X, init)
+		n.X = walkExpr(n.X, nil)
+
+		tab := ir.NewUnaryExpr(base.Pos, ir.OITAB, n.X)
+		check := ir.NewUnaryExpr(base.Pos, ir.OCHECKNIL, tab)
+		init.Append(typecheck.Stmt(check))
+	}
+
+	typ := typecheck.MethodValueType(n)
+
+	clos := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, ir.TypeNode(typ), nil)
+	clos.SetEsc(n.Esc())
+	clos.List = []ir.Node{ir.NewUnaryExpr(base.Pos, ir.OCFUNC, methodValueWrapper(n)), n.X}
+
+	addr := typecheck.NodAddr(clos)
+	addr.SetEsc(n.Esc())
+
+	// Force type conversion from *struct to the func type.
+	cfn := typecheck.ConvNop(addr, n.Type())
+
+	// non-escaping temp to use, if any.
+	if x := n.Prealloc; x != nil {
+		if !types.Identical(typ, x.Type()) {
+			panic("partial call type does not match order's assigned type")
+		}
+		addr.Prealloc = x
+		n.Prealloc = nil
+	}
+
+	return walkExpr(cfn, init)
+}
+
+// methodValueWrapper returns the ONAME node representing the
+// wrapper function (*-fm) needed for the given method value. If the
+// wrapper function hasn't already been created yet, it's created and
+// added to typecheck.Target.Decls.
+func methodValueWrapper(dot *ir.SelectorExpr) *ir.Name {
+	if dot.Op() != ir.OMETHVALUE {
+		base.Fatalf("methodValueWrapper: unexpected %v (%v)", dot, dot.Op())
+	}
+
+	t0 := dot.Type()
+	meth := dot.Sel
+	rcvrtype := dot.X.Type()
+	sym := ir.MethodSymSuffix(rcvrtype, meth, "-fm")
+
+	if sym.Uniq() {
+		return sym.Def.(*ir.Name)
+	}
+	sym.SetUniq(true)
+
+	if base.Debug.Unified != 0 && base.Debug.UnifiedQuirks == 0 {
+		base.FatalfAt(dot.Pos(), "missing wrapper for %v", meth)
+	}
+
+	savecurfn := ir.CurFunc
+	saveLineNo := base.Pos
+	ir.CurFunc = nil
+
+	base.Pos = base.AutogeneratedPos
+
+	tfn := ir.NewFuncType(base.Pos, nil,
+		typecheck.NewFuncParams(t0.Params(), true),
+		typecheck.NewFuncParams(t0.Results(), false))
+
+	fn := typecheck.DeclFunc(sym, tfn)
+	fn.SetDupok(true)
+	fn.SetWrapper(true)
+
+	// Declare and initialize variable holding receiver.
+	ptr := ir.NewHiddenParam(base.Pos, fn, typecheck.Lookup(".this"), rcvrtype)
+
+	call := ir.NewCallExpr(base.Pos, ir.OCALL, ir.NewSelectorExpr(base.Pos, ir.OXDOT, ptr, meth), nil)
+	call.Args = ir.ParamNames(tfn.Type())
+	call.IsDDD = tfn.Type().IsVariadic()
+
+	var body ir.Node = call
+	if t0.NumResults() != 0 {
+		ret := ir.NewReturnStmt(base.Pos, nil)
+		ret.Results = []ir.Node{call}
+		body = ret
+	}
+
+	fn.Body = []ir.Node{body}
+	typecheck.FinishFuncBody()
+
+	typecheck.Func(fn)
+	// Need to typecheck the body of the just-generated wrapper.
+	// typecheckslice() requires that Curfn is set when processing an ORETURN.
+	ir.CurFunc = fn
+	typecheck.Stmts(fn.Body)
+	sym.Def = fn.Nname
+	typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
+	ir.CurFunc = savecurfn
+	base.Pos = saveLineNo
+
+	return fn.Nname
+}
diff --git a/src/cmd/compile/internal/walk/compare.go b/src/cmd/compile/internal/walk/compare.go
new file mode 100644
index 0000000..625e216
--- /dev/null
+++ b/src/cmd/compile/internal/walk/compare.go
@@ -0,0 +1,491 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/ssagen"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+)
+
+// The result of walkCompare MUST be assigned back to n, e.g.
+// 	n.Left = walkCompare(n.Left, init)
+func walkCompare(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
+	if n.X.Type().IsInterface() && n.Y.Type().IsInterface() && n.X.Op() != ir.ONIL && n.Y.Op() != ir.ONIL {
+		return walkCompareInterface(n, init)
+	}
+
+	if n.X.Type().IsString() && n.Y.Type().IsString() {
+		return walkCompareString(n, init)
+	}
+
+	n.X = walkExpr(n.X, init)
+	n.Y = walkExpr(n.Y, init)
+
+	// Given mixed interface/concrete comparison,
+	// rewrite into types-equal && data-equal.
+	// This is efficient, avoids allocations, and avoids runtime calls.
+	if n.X.Type().IsInterface() != n.Y.Type().IsInterface() {
+		// Preserve side-effects in case of short-circuiting; see #32187.
+		l := cheapExpr(n.X, init)
+		r := cheapExpr(n.Y, init)
+		// Swap so that l is the interface value and r is the concrete value.
+		if n.Y.Type().IsInterface() {
+			l, r = r, l
+		}
+
+		// Handle both == and !=.
+		eq := n.Op()
+		andor := ir.OOROR
+		if eq == ir.OEQ {
+			andor = ir.OANDAND
+		}
+		// Check for types equal.
+		// For empty interface, this is:
+		//   l.tab == type(r)
+		// For non-empty interface, this is:
+		//   l.tab != nil && l.tab._type == type(r)
+		var eqtype ir.Node
+		tab := ir.NewUnaryExpr(base.Pos, ir.OITAB, l)
+		rtyp := reflectdata.TypePtr(r.Type())
+		if l.Type().IsEmptyInterface() {
+			tab.SetType(types.NewPtr(types.Types[types.TUINT8]))
+			tab.SetTypecheck(1)
+			eqtype = ir.NewBinaryExpr(base.Pos, eq, tab, rtyp)
+		} else {
+			nonnil := ir.NewBinaryExpr(base.Pos, brcom(eq), typecheck.NodNil(), tab)
+			match := ir.NewBinaryExpr(base.Pos, eq, itabType(tab), rtyp)
+			eqtype = ir.NewLogicalExpr(base.Pos, andor, nonnil, match)
+		}
+		// Check for data equal.
+		eqdata := ir.NewBinaryExpr(base.Pos, eq, ifaceData(n.Pos(), l, r.Type()), r)
+		// Put it all together.
+		expr := ir.NewLogicalExpr(base.Pos, andor, eqtype, eqdata)
+		return finishCompare(n, expr, init)
+	}
+
+	// Must be comparison of array or struct.
+	// Otherwise back end handles it.
+	// While we're here, decide whether to
+	// inline or call an eq alg.
+	t := n.X.Type()
+	var inline bool
+
+	maxcmpsize := int64(4)
+	unalignedLoad := ssagen.Arch.LinkArch.CanMergeLoads
+	if unalignedLoad {
+		// Keep this low enough to generate less code than a function call.
+		maxcmpsize = 2 * int64(ssagen.Arch.LinkArch.RegSize)
+	}
+
+	switch t.Kind() {
+	default:
+		if base.Debug.Libfuzzer != 0 && t.IsInteger() {
+			n.X = cheapExpr(n.X, init)
+			n.Y = cheapExpr(n.Y, init)
+
+			// If exactly one comparison operand is
+			// constant, invoke the constcmp functions
+			// instead, and arrange for the constant
+			// operand to be the first argument.
+			l, r := n.X, n.Y
+			if r.Op() == ir.OLITERAL {
+				l, r = r, l
+			}
+			constcmp := l.Op() == ir.OLITERAL && r.Op() != ir.OLITERAL
+
+			var fn string
+			var paramType *types.Type
+			switch t.Size() {
+			case 1:
+				fn = "libfuzzerTraceCmp1"
+				if constcmp {
+					fn = "libfuzzerTraceConstCmp1"
+				}
+				paramType = types.Types[types.TUINT8]
+			case 2:
+				fn = "libfuzzerTraceCmp2"
+				if constcmp {
+					fn = "libfuzzerTraceConstCmp2"
+				}
+				paramType = types.Types[types.TUINT16]
+			case 4:
+				fn = "libfuzzerTraceCmp4"
+				if constcmp {
+					fn = "libfuzzerTraceConstCmp4"
+				}
+				paramType = types.Types[types.TUINT32]
+			case 8:
+				fn = "libfuzzerTraceCmp8"
+				if constcmp {
+					fn = "libfuzzerTraceConstCmp8"
+				}
+				paramType = types.Types[types.TUINT64]
+			default:
+				base.Fatalf("unexpected integer size %d for %v", t.Size(), t)
+			}
+			init.Append(mkcall(fn, nil, init, tracecmpArg(l, paramType, init), tracecmpArg(r, paramType, init)))
+		}
+		return n
+	case types.TARRAY:
+		// We can compare several elements at once with 2/4/8 byte integer compares
+		inline = t.NumElem() <= 1 || (types.IsSimple[t.Elem().Kind()] && (t.NumElem() <= 4 || t.Elem().Size()*t.NumElem() <= maxcmpsize))
+	case types.TSTRUCT:
+		inline = t.NumComponents(types.IgnoreBlankFields) <= 4
+	}
+
+	cmpl := n.X
+	for cmpl != nil && cmpl.Op() == ir.OCONVNOP {
+		cmpl = cmpl.(*ir.ConvExpr).X
+	}
+	cmpr := n.Y
+	for cmpr != nil && cmpr.Op() == ir.OCONVNOP {
+		cmpr = cmpr.(*ir.ConvExpr).X
+	}
+
+	// Chose not to inline. Call equality function directly.
+	if !inline {
+		// eq algs take pointers; cmpl and cmpr must be addressable
+		if !ir.IsAddressable(cmpl) || !ir.IsAddressable(cmpr) {
+			base.Fatalf("arguments of comparison must be lvalues - %v %v", cmpl, cmpr)
+		}
+
+		fn, needsize := eqFor(t)
+		call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, nil)
+		call.Args.Append(typecheck.NodAddr(cmpl))
+		call.Args.Append(typecheck.NodAddr(cmpr))
+		if needsize {
+			call.Args.Append(ir.NewInt(t.Size()))
+		}
+		res := ir.Node(call)
+		if n.Op() != ir.OEQ {
+			res = ir.NewUnaryExpr(base.Pos, ir.ONOT, res)
+		}
+		return finishCompare(n, res, init)
+	}
+
+	// inline: build boolean expression comparing element by element
+	andor := ir.OANDAND
+	if n.Op() == ir.ONE {
+		andor = ir.OOROR
+	}
+	var expr ir.Node
+	compare := func(el, er ir.Node) {
+		a := ir.NewBinaryExpr(base.Pos, n.Op(), el, er)
+		if expr == nil {
+			expr = a
+		} else {
+			expr = ir.NewLogicalExpr(base.Pos, andor, expr, a)
+		}
+	}
+	cmpl = safeExpr(cmpl, init)
+	cmpr = safeExpr(cmpr, init)
+	if t.IsStruct() {
+		for _, f := range t.Fields().Slice() {
+			sym := f.Sym
+			if sym.IsBlank() {
+				continue
+			}
+			compare(
+				ir.NewSelectorExpr(base.Pos, ir.OXDOT, cmpl, sym),
+				ir.NewSelectorExpr(base.Pos, ir.OXDOT, cmpr, sym),
+			)
+		}
+	} else {
+		step := int64(1)
+		remains := t.NumElem() * t.Elem().Size()
+		combine64bit := unalignedLoad && types.RegSize == 8 && t.Elem().Size() <= 4 && t.Elem().IsInteger()
+		combine32bit := unalignedLoad && t.Elem().Size() <= 2 && t.Elem().IsInteger()
+		combine16bit := unalignedLoad && t.Elem().Size() == 1 && t.Elem().IsInteger()
+		for i := int64(0); remains > 0; {
+			var convType *types.Type
+			switch {
+			case remains >= 8 && combine64bit:
+				convType = types.Types[types.TINT64]
+				step = 8 / t.Elem().Size()
+			case remains >= 4 && combine32bit:
+				convType = types.Types[types.TUINT32]
+				step = 4 / t.Elem().Size()
+			case remains >= 2 && combine16bit:
+				convType = types.Types[types.TUINT16]
+				step = 2 / t.Elem().Size()
+			default:
+				step = 1
+			}
+			if step == 1 {
+				compare(
+					ir.NewIndexExpr(base.Pos, cmpl, ir.NewInt(i)),
+					ir.NewIndexExpr(base.Pos, cmpr, ir.NewInt(i)),
+				)
+				i++
+				remains -= t.Elem().Size()
+			} else {
+				elemType := t.Elem().ToUnsigned()
+				cmplw := ir.Node(ir.NewIndexExpr(base.Pos, cmpl, ir.NewInt(i)))
+				cmplw = typecheck.Conv(cmplw, elemType) // convert to unsigned
+				cmplw = typecheck.Conv(cmplw, convType) // widen
+				cmprw := ir.Node(ir.NewIndexExpr(base.Pos, cmpr, ir.NewInt(i)))
+				cmprw = typecheck.Conv(cmprw, elemType)
+				cmprw = typecheck.Conv(cmprw, convType)
+				// For code like this:  uint32(s[0]) | uint32(s[1])<<8 | uint32(s[2])<<16 ...
+				// ssa will generate a single large load.
+				for offset := int64(1); offset < step; offset++ {
+					lb := ir.Node(ir.NewIndexExpr(base.Pos, cmpl, ir.NewInt(i+offset)))
+					lb = typecheck.Conv(lb, elemType)
+					lb = typecheck.Conv(lb, convType)
+					lb = ir.NewBinaryExpr(base.Pos, ir.OLSH, lb, ir.NewInt(8*t.Elem().Size()*offset))
+					cmplw = ir.NewBinaryExpr(base.Pos, ir.OOR, cmplw, lb)
+					rb := ir.Node(ir.NewIndexExpr(base.Pos, cmpr, ir.NewInt(i+offset)))
+					rb = typecheck.Conv(rb, elemType)
+					rb = typecheck.Conv(rb, convType)
+					rb = ir.NewBinaryExpr(base.Pos, ir.OLSH, rb, ir.NewInt(8*t.Elem().Size()*offset))
+					cmprw = ir.NewBinaryExpr(base.Pos, ir.OOR, cmprw, rb)
+				}
+				compare(cmplw, cmprw)
+				i += step
+				remains -= step * t.Elem().Size()
+			}
+		}
+	}
+	if expr == nil {
+		expr = ir.NewBool(n.Op() == ir.OEQ)
+		// We still need to use cmpl and cmpr, in case they contain
+		// an expression which might panic. See issue 23837.
+		t := typecheck.Temp(cmpl.Type())
+		a1 := typecheck.Stmt(ir.NewAssignStmt(base.Pos, t, cmpl))
+		a2 := typecheck.Stmt(ir.NewAssignStmt(base.Pos, t, cmpr))
+		init.Append(a1, a2)
+	}
+	return finishCompare(n, expr, init)
+}
+
+func walkCompareInterface(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
+	n.Y = cheapExpr(n.Y, init)
+	n.X = cheapExpr(n.X, init)
+	eqtab, eqdata := reflectdata.EqInterface(n.X, n.Y)
+	var cmp ir.Node
+	if n.Op() == ir.OEQ {
+		cmp = ir.NewLogicalExpr(base.Pos, ir.OANDAND, eqtab, eqdata)
+	} else {
+		eqtab.SetOp(ir.ONE)
+		cmp = ir.NewLogicalExpr(base.Pos, ir.OOROR, eqtab, ir.NewUnaryExpr(base.Pos, ir.ONOT, eqdata))
+	}
+	return finishCompare(n, cmp, init)
+}
+
+func walkCompareString(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
+	// Rewrite comparisons to short constant strings as length+byte-wise comparisons.
+	var cs, ncs ir.Node // const string, non-const string
+	switch {
+	case ir.IsConst(n.X, constant.String) && ir.IsConst(n.Y, constant.String):
+		// ignore; will be constant evaluated
+	case ir.IsConst(n.X, constant.String):
+		cs = n.X
+		ncs = n.Y
+	case ir.IsConst(n.Y, constant.String):
+		cs = n.Y
+		ncs = n.X
+	}
+	if cs != nil {
+		cmp := n.Op()
+		// Our comparison below assumes that the non-constant string
+		// is on the left hand side, so rewrite "" cmp x to x cmp "".
+		// See issue 24817.
+		if ir.IsConst(n.X, constant.String) {
+			cmp = brrev(cmp)
+		}
+
+		// maxRewriteLen was chosen empirically.
+		// It is the value that minimizes cmd/go file size
+		// across most architectures.
+		// See the commit description for CL 26758 for details.
+		maxRewriteLen := 6
+		// Some architectures can load unaligned byte sequence as 1 word.
+		// So we can cover longer strings with the same amount of code.
+		canCombineLoads := ssagen.Arch.LinkArch.CanMergeLoads
+		combine64bit := false
+		if canCombineLoads {
+			// Keep this low enough to generate less code than a function call.
+			maxRewriteLen = 2 * ssagen.Arch.LinkArch.RegSize
+			combine64bit = ssagen.Arch.LinkArch.RegSize >= 8
+		}
+
+		var and ir.Op
+		switch cmp {
+		case ir.OEQ:
+			and = ir.OANDAND
+		case ir.ONE:
+			and = ir.OOROR
+		default:
+			// Don't do byte-wise comparisons for <, <=, etc.
+			// They're fairly complicated.
+			// Length-only checks are ok, though.
+			maxRewriteLen = 0
+		}
+		if s := ir.StringVal(cs); len(s) <= maxRewriteLen {
+			if len(s) > 0 {
+				ncs = safeExpr(ncs, init)
+			}
+			r := ir.Node(ir.NewBinaryExpr(base.Pos, cmp, ir.NewUnaryExpr(base.Pos, ir.OLEN, ncs), ir.NewInt(int64(len(s)))))
+			remains := len(s)
+			for i := 0; remains > 0; {
+				if remains == 1 || !canCombineLoads {
+					cb := ir.NewInt(int64(s[i]))
+					ncb := ir.NewIndexExpr(base.Pos, ncs, ir.NewInt(int64(i)))
+					r = ir.NewLogicalExpr(base.Pos, and, r, ir.NewBinaryExpr(base.Pos, cmp, ncb, cb))
+					remains--
+					i++
+					continue
+				}
+				var step int
+				var convType *types.Type
+				switch {
+				case remains >= 8 && combine64bit:
+					convType = types.Types[types.TINT64]
+					step = 8
+				case remains >= 4:
+					convType = types.Types[types.TUINT32]
+					step = 4
+				case remains >= 2:
+					convType = types.Types[types.TUINT16]
+					step = 2
+				}
+				ncsubstr := typecheck.Conv(ir.NewIndexExpr(base.Pos, ncs, ir.NewInt(int64(i))), convType)
+				csubstr := int64(s[i])
+				// Calculate large constant from bytes as sequence of shifts and ors.
+				// Like this:  uint32(s[0]) | uint32(s[1])<<8 | uint32(s[2])<<16 ...
+				// ssa will combine this into a single large load.
+				for offset := 1; offset < step; offset++ {
+					b := typecheck.Conv(ir.NewIndexExpr(base.Pos, ncs, ir.NewInt(int64(i+offset))), convType)
+					b = ir.NewBinaryExpr(base.Pos, ir.OLSH, b, ir.NewInt(int64(8*offset)))
+					ncsubstr = ir.NewBinaryExpr(base.Pos, ir.OOR, ncsubstr, b)
+					csubstr |= int64(s[i+offset]) << uint8(8*offset)
+				}
+				csubstrPart := ir.NewInt(csubstr)
+				// Compare "step" bytes as once
+				r = ir.NewLogicalExpr(base.Pos, and, r, ir.NewBinaryExpr(base.Pos, cmp, csubstrPart, ncsubstr))
+				remains -= step
+				i += step
+			}
+			return finishCompare(n, r, init)
+		}
+	}
+
+	var r ir.Node
+	if n.Op() == ir.OEQ || n.Op() == ir.ONE {
+		// prepare for rewrite below
+		n.X = cheapExpr(n.X, init)
+		n.Y = cheapExpr(n.Y, init)
+		eqlen, eqmem := reflectdata.EqString(n.X, n.Y)
+		// quick check of len before full compare for == or !=.
+		// memequal then tests equality up to length len.
+		if n.Op() == ir.OEQ {
+			// len(left) == len(right) && memequal(left, right, len)
+			r = ir.NewLogicalExpr(base.Pos, ir.OANDAND, eqlen, eqmem)
+		} else {
+			// len(left) != len(right) || !memequal(left, right, len)
+			eqlen.SetOp(ir.ONE)
+			r = ir.NewLogicalExpr(base.Pos, ir.OOROR, eqlen, ir.NewUnaryExpr(base.Pos, ir.ONOT, eqmem))
+		}
+	} else {
+		// sys_cmpstring(s1, s2) :: 0
+		r = mkcall("cmpstring", types.Types[types.TINT], init, typecheck.Conv(n.X, types.Types[types.TSTRING]), typecheck.Conv(n.Y, types.Types[types.TSTRING]))
+		r = ir.NewBinaryExpr(base.Pos, n.Op(), r, ir.NewInt(0))
+	}
+
+	return finishCompare(n, r, init)
+}
+
+// The result of finishCompare MUST be assigned back to n, e.g.
+// 	n.Left = finishCompare(n.Left, x, r, init)
+func finishCompare(n *ir.BinaryExpr, r ir.Node, init *ir.Nodes) ir.Node {
+	r = typecheck.Expr(r)
+	r = typecheck.Conv(r, n.Type())
+	r = walkExpr(r, init)
+	return r
+}
+
+func eqFor(t *types.Type) (n ir.Node, needsize bool) {
+	// Should only arrive here with large memory or
+	// a struct/array containing a non-memory field/element.
+	// Small memory is handled inline, and single non-memory
+	// is handled by walkCompare.
+	switch a, _ := types.AlgType(t); a {
+	case types.AMEM:
+		n := typecheck.LookupRuntime("memequal")
+		n = typecheck.SubstArgTypes(n, t, t)
+		return n, true
+	case types.ASPECIAL:
+		sym := reflectdata.TypeSymPrefix(".eq", t)
+		// TODO(austin): This creates an ir.Name with a nil Func.
+		n := typecheck.NewName(sym)
+		ir.MarkFunc(n)
+		n.SetType(types.NewSignature(types.NoPkg, nil, nil, []*types.Field{
+			types.NewField(base.Pos, nil, types.NewPtr(t)),
+			types.NewField(base.Pos, nil, types.NewPtr(t)),
+		}, []*types.Field{
+			types.NewField(base.Pos, nil, types.Types[types.TBOOL]),
+		}))
+		return n, false
+	}
+	base.Fatalf("eqFor %v", t)
+	return nil, false
+}
+
+// brcom returns !(op).
+// For example, brcom(==) is !=.
+func brcom(op ir.Op) ir.Op {
+	switch op {
+	case ir.OEQ:
+		return ir.ONE
+	case ir.ONE:
+		return ir.OEQ
+	case ir.OLT:
+		return ir.OGE
+	case ir.OGT:
+		return ir.OLE
+	case ir.OLE:
+		return ir.OGT
+	case ir.OGE:
+		return ir.OLT
+	}
+	base.Fatalf("brcom: no com for %v\n", op)
+	return op
+}
+
+// brrev returns reverse(op).
+// For example, Brrev(<) is >.
+func brrev(op ir.Op) ir.Op {
+	switch op {
+	case ir.OEQ:
+		return ir.OEQ
+	case ir.ONE:
+		return ir.ONE
+	case ir.OLT:
+		return ir.OGT
+	case ir.OGT:
+		return ir.OLT
+	case ir.OLE:
+		return ir.OGE
+	case ir.OGE:
+		return ir.OLE
+	}
+	base.Fatalf("brrev: no rev for %v\n", op)
+	return op
+}
+
+func tracecmpArg(n ir.Node, t *types.Type, init *ir.Nodes) ir.Node {
+	// Ugly hack to avoid "constant -1 overflows uintptr" errors, etc.
+	if n.Op() == ir.OLITERAL && n.Type().IsSigned() && ir.Int64Val(n) < 0 {
+		n = copyExpr(n, n.Type(), init)
+	}
+
+	return typecheck.Conv(n, t)
+}
diff --git a/src/cmd/compile/internal/walk/complit.go b/src/cmd/compile/internal/walk/complit.go
new file mode 100644
index 0000000..e957580
--- /dev/null
+++ b/src/cmd/compile/internal/walk/complit.go
@@ -0,0 +1,676 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/ssagen"
+	"cmd/compile/internal/staticdata"
+	"cmd/compile/internal/staticinit"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+)
+
+// walkCompLit walks a composite literal node:
+// OARRAYLIT, OSLICELIT, OMAPLIT, OSTRUCTLIT (all CompLitExpr), or OPTRLIT (AddrExpr).
+func walkCompLit(n ir.Node, init *ir.Nodes) ir.Node {
+	if isStaticCompositeLiteral(n) && !ssagen.TypeOK(n.Type()) {
+		n := n.(*ir.CompLitExpr) // not OPTRLIT
+		// n can be directly represented in the read-only data section.
+		// Make direct reference to the static data. See issue 12841.
+		vstat := readonlystaticname(n.Type())
+		fixedlit(inInitFunction, initKindStatic, n, vstat, init)
+		return typecheck.Expr(vstat)
+	}
+	var_ := typecheck.Temp(n.Type())
+	anylit(n, var_, init)
+	return var_
+}
+
+// initContext is the context in which static data is populated.
+// It is either in an init function or in any other function.
+// Static data populated in an init function will be written either
+// zero times (as a readonly, static data symbol) or
+// one time (during init function execution).
+// Either way, there is no opportunity for races or further modification,
+// so the data can be written to a (possibly readonly) data symbol.
+// Static data populated in any other function needs to be local to
+// that function to allow multiple instances of that function
+// to execute concurrently without clobbering each others' data.
+type initContext uint8
+
+const (
+	inInitFunction initContext = iota
+	inNonInitFunction
+)
+
+func (c initContext) String() string {
+	if c == inInitFunction {
+		return "inInitFunction"
+	}
+	return "inNonInitFunction"
+}
+
+// readonlystaticname returns a name backed by a read-only static data symbol.
+func readonlystaticname(t *types.Type) *ir.Name {
+	n := staticinit.StaticName(t)
+	n.MarkReadonly()
+	n.Linksym().Set(obj.AttrContentAddressable, true)
+	n.Linksym().Set(obj.AttrLocal, true)
+	return n
+}
+
+func isSimpleName(nn ir.Node) bool {
+	if nn.Op() != ir.ONAME || ir.IsBlank(nn) {
+		return false
+	}
+	n := nn.(*ir.Name)
+	return n.OnStack()
+}
+
+func litas(l ir.Node, r ir.Node, init *ir.Nodes) {
+	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, l, r))
+}
+
+// initGenType is a bitmap indicating the types of generation that will occur for a static value.
+type initGenType uint8
+
+const (
+	initDynamic initGenType = 1 << iota // contains some dynamic values, for which init code will be generated
+	initConst                           // contains some constant values, which may be written into data symbols
+)
+
+// getdyn calculates the initGenType for n.
+// If top is false, getdyn is recursing.
+func getdyn(n ir.Node, top bool) initGenType {
+	switch n.Op() {
+	default:
+		if ir.IsConstNode(n) {
+			return initConst
+		}
+		return initDynamic
+
+	case ir.OSLICELIT:
+		n := n.(*ir.CompLitExpr)
+		if !top {
+			return initDynamic
+		}
+		if n.Len/4 > int64(len(n.List)) {
+			// <25% of entries have explicit values.
+			// Very rough estimation, it takes 4 bytes of instructions
+			// to initialize 1 byte of result. So don't use a static
+			// initializer if the dynamic initialization code would be
+			// smaller than the static value.
+			// See issue 23780.
+			return initDynamic
+		}
+
+	case ir.OARRAYLIT, ir.OSTRUCTLIT:
+	}
+	lit := n.(*ir.CompLitExpr)
+
+	var mode initGenType
+	for _, n1 := range lit.List {
+		switch n1.Op() {
+		case ir.OKEY:
+			n1 = n1.(*ir.KeyExpr).Value
+		case ir.OSTRUCTKEY:
+			n1 = n1.(*ir.StructKeyExpr).Value
+		}
+		mode |= getdyn(n1, false)
+		if mode == initDynamic|initConst {
+			break
+		}
+	}
+	return mode
+}
+
+// isStaticCompositeLiteral reports whether n is a compile-time constant.
+func isStaticCompositeLiteral(n ir.Node) bool {
+	switch n.Op() {
+	case ir.OSLICELIT:
+		return false
+	case ir.OARRAYLIT:
+		n := n.(*ir.CompLitExpr)
+		for _, r := range n.List {
+			if r.Op() == ir.OKEY {
+				r = r.(*ir.KeyExpr).Value
+			}
+			if !isStaticCompositeLiteral(r) {
+				return false
+			}
+		}
+		return true
+	case ir.OSTRUCTLIT:
+		n := n.(*ir.CompLitExpr)
+		for _, r := range n.List {
+			r := r.(*ir.StructKeyExpr)
+			if !isStaticCompositeLiteral(r.Value) {
+				return false
+			}
+		}
+		return true
+	case ir.OLITERAL, ir.ONIL:
+		return true
+	case ir.OCONVIFACE:
+		// See staticassign's OCONVIFACE case for comments.
+		n := n.(*ir.ConvExpr)
+		val := ir.Node(n)
+		for val.Op() == ir.OCONVIFACE {
+			val = val.(*ir.ConvExpr).X
+		}
+		if val.Type().IsInterface() {
+			return val.Op() == ir.ONIL
+		}
+		if types.IsDirectIface(val.Type()) && val.Op() == ir.ONIL {
+			return true
+		}
+		return isStaticCompositeLiteral(val)
+	}
+	return false
+}
+
+// initKind is a kind of static initialization: static, dynamic, or local.
+// Static initialization represents literals and
+// literal components of composite literals.
+// Dynamic initialization represents non-literals and
+// non-literal components of composite literals.
+// LocalCode initialization represents initialization
+// that occurs purely in generated code local to the function of use.
+// Initialization code is sometimes generated in passes,
+// first static then dynamic.
+type initKind uint8
+
+const (
+	initKindStatic initKind = iota + 1
+	initKindDynamic
+	initKindLocalCode
+)
+
+// fixedlit handles struct, array, and slice literals.
+// TODO: expand documentation.
+func fixedlit(ctxt initContext, kind initKind, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes) {
+	isBlank := var_ == ir.BlankNode
+	var splitnode func(ir.Node) (a ir.Node, value ir.Node)
+	switch n.Op() {
+	case ir.OARRAYLIT, ir.OSLICELIT:
+		var k int64
+		splitnode = func(r ir.Node) (ir.Node, ir.Node) {
+			if r.Op() == ir.OKEY {
+				kv := r.(*ir.KeyExpr)
+				k = typecheck.IndexConst(kv.Key)
+				if k < 0 {
+					base.Fatalf("fixedlit: invalid index %v", kv.Key)
+				}
+				r = kv.Value
+			}
+			a := ir.NewIndexExpr(base.Pos, var_, ir.NewInt(k))
+			k++
+			if isBlank {
+				return ir.BlankNode, r
+			}
+			return a, r
+		}
+	case ir.OSTRUCTLIT:
+		splitnode = func(rn ir.Node) (ir.Node, ir.Node) {
+			r := rn.(*ir.StructKeyExpr)
+			if r.Sym().IsBlank() || isBlank {
+				return ir.BlankNode, r.Value
+			}
+			ir.SetPos(r)
+			return ir.NewSelectorExpr(base.Pos, ir.ODOT, var_, r.Sym()), r.Value
+		}
+	default:
+		base.Fatalf("fixedlit bad op: %v", n.Op())
+	}
+
+	for _, r := range n.List {
+		a, value := splitnode(r)
+		if a == ir.BlankNode && !staticinit.AnySideEffects(value) {
+			// Discard.
+			continue
+		}
+
+		switch value.Op() {
+		case ir.OSLICELIT:
+			value := value.(*ir.CompLitExpr)
+			if (kind == initKindStatic && ctxt == inNonInitFunction) || (kind == initKindDynamic && ctxt == inInitFunction) {
+				slicelit(ctxt, value, a, init)
+				continue
+			}
+
+		case ir.OARRAYLIT, ir.OSTRUCTLIT:
+			value := value.(*ir.CompLitExpr)
+			fixedlit(ctxt, kind, value, a, init)
+			continue
+		}
+
+		islit := ir.IsConstNode(value)
+		if (kind == initKindStatic && !islit) || (kind == initKindDynamic && islit) {
+			continue
+		}
+
+		// build list of assignments: var[index] = expr
+		ir.SetPos(a)
+		as := ir.NewAssignStmt(base.Pos, a, value)
+		as = typecheck.Stmt(as).(*ir.AssignStmt)
+		switch kind {
+		case initKindStatic:
+			genAsStatic(as)
+		case initKindDynamic, initKindLocalCode:
+			a = orderStmtInPlace(as, map[string][]*ir.Name{})
+			a = walkStmt(a)
+			init.Append(a)
+		default:
+			base.Fatalf("fixedlit: bad kind %d", kind)
+		}
+
+	}
+}
+
+func isSmallSliceLit(n *ir.CompLitExpr) bool {
+	if n.Op() != ir.OSLICELIT {
+		return false
+	}
+
+	return n.Type().Elem().Size() == 0 || n.Len <= ir.MaxSmallArraySize/n.Type().Elem().Size()
+}
+
+func slicelit(ctxt initContext, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes) {
+	// make an array type corresponding the number of elements we have
+	t := types.NewArray(n.Type().Elem(), n.Len)
+	types.CalcSize(t)
+
+	if ctxt == inNonInitFunction {
+		// put everything into static array
+		vstat := staticinit.StaticName(t)
+
+		fixedlit(ctxt, initKindStatic, n, vstat, init)
+		fixedlit(ctxt, initKindDynamic, n, vstat, init)
+
+		// copy static to slice
+		var_ = typecheck.AssignExpr(var_)
+		name, offset, ok := staticinit.StaticLoc(var_)
+		if !ok || name.Class != ir.PEXTERN {
+			base.Fatalf("slicelit: %v", var_)
+		}
+		staticdata.InitSlice(name, offset, vstat.Linksym(), t.NumElem())
+		return
+	}
+
+	// recipe for var = []t{...}
+	// 1. make a static array
+	//	var vstat [...]t
+	// 2. assign (data statements) the constant part
+	//	vstat = constpart{}
+	// 3. make an auto pointer to array and allocate heap to it
+	//	var vauto *[...]t = new([...]t)
+	// 4. copy the static array to the auto array
+	//	*vauto = vstat
+	// 5. for each dynamic part assign to the array
+	//	vauto[i] = dynamic part
+	// 6. assign slice of allocated heap to var
+	//	var = vauto[:]
+	//
+	// an optimization is done if there is no constant part
+	//	3. var vauto *[...]t = new([...]t)
+	//	5. vauto[i] = dynamic part
+	//	6. var = vauto[:]
+
+	// if the literal contains constants,
+	// make static initialized array (1),(2)
+	var vstat ir.Node
+
+	mode := getdyn(n, true)
+	if mode&initConst != 0 && !isSmallSliceLit(n) {
+		if ctxt == inInitFunction {
+			vstat = readonlystaticname(t)
+		} else {
+			vstat = staticinit.StaticName(t)
+		}
+		fixedlit(ctxt, initKindStatic, n, vstat, init)
+	}
+
+	// make new auto *array (3 declare)
+	vauto := typecheck.Temp(types.NewPtr(t))
+
+	// set auto to point at new temp or heap (3 assign)
+	var a ir.Node
+	if x := n.Prealloc; x != nil {
+		// temp allocated during order.go for dddarg
+		if !types.Identical(t, x.Type()) {
+			panic("dotdotdot base type does not match order's assigned type")
+		}
+		a = initStackTemp(init, x, vstat)
+	} else if n.Esc() == ir.EscNone {
+		a = initStackTemp(init, typecheck.Temp(t), vstat)
+	} else {
+		a = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(t))
+	}
+	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, vauto, a))
+
+	if vstat != nil && n.Prealloc == nil && n.Esc() != ir.EscNone {
+		// If we allocated on the heap with ONEW, copy the static to the
+		// heap (4). We skip this for stack temporaries, because
+		// initStackTemp already handled the copy.
+		a = ir.NewStarExpr(base.Pos, vauto)
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, a, vstat))
+	}
+
+	// put dynamics into array (5)
+	var index int64
+	for _, value := range n.List {
+		if value.Op() == ir.OKEY {
+			kv := value.(*ir.KeyExpr)
+			index = typecheck.IndexConst(kv.Key)
+			if index < 0 {
+				base.Fatalf("slicelit: invalid index %v", kv.Key)
+			}
+			value = kv.Value
+		}
+		a := ir.NewIndexExpr(base.Pos, vauto, ir.NewInt(index))
+		a.SetBounded(true)
+		index++
+
+		// TODO need to check bounds?
+
+		switch value.Op() {
+		case ir.OSLICELIT:
+			break
+
+		case ir.OARRAYLIT, ir.OSTRUCTLIT:
+			value := value.(*ir.CompLitExpr)
+			k := initKindDynamic
+			if vstat == nil {
+				// Generate both static and dynamic initializations.
+				// See issue #31987.
+				k = initKindLocalCode
+			}
+			fixedlit(ctxt, k, value, a, init)
+			continue
+		}
+
+		if vstat != nil && ir.IsConstNode(value) { // already set by copy from static value
+			continue
+		}
+
+		// build list of vauto[c] = expr
+		ir.SetPos(value)
+		as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, a, value))
+		as = orderStmtInPlace(as, map[string][]*ir.Name{})
+		as = walkStmt(as)
+		init.Append(as)
+	}
+
+	// make slice out of heap (6)
+	a = ir.NewAssignStmt(base.Pos, var_, ir.NewSliceExpr(base.Pos, ir.OSLICE, vauto, nil, nil, nil))
+
+	a = typecheck.Stmt(a)
+	a = orderStmtInPlace(a, map[string][]*ir.Name{})
+	a = walkStmt(a)
+	init.Append(a)
+}
+
+func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
+	// make the map var
+	a := ir.NewCallExpr(base.Pos, ir.OMAKE, nil, nil)
+	a.SetEsc(n.Esc())
+	a.Args = []ir.Node{ir.TypeNode(n.Type()), ir.NewInt(int64(len(n.List)))}
+	litas(m, a, init)
+
+	entries := n.List
+
+	// The order pass already removed any dynamic (runtime-computed) entries.
+	// All remaining entries are static. Double-check that.
+	for _, r := range entries {
+		r := r.(*ir.KeyExpr)
+		if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
+			base.Fatalf("maplit: entry is not a literal: %v", r)
+		}
+	}
+
+	if len(entries) > 25 {
+		// For a large number of entries, put them in an array and loop.
+
+		// build types [count]Tindex and [count]Tvalue
+		tk := types.NewArray(n.Type().Key(), int64(len(entries)))
+		te := types.NewArray(n.Type().Elem(), int64(len(entries)))
+
+		// TODO(#47904): mark tk and te NoAlg here once the
+		// compiler/linker can handle NoAlg types correctly.
+
+		types.CalcSize(tk)
+		types.CalcSize(te)
+
+		// make and initialize static arrays
+		vstatk := readonlystaticname(tk)
+		vstate := readonlystaticname(te)
+
+		datak := ir.NewCompLitExpr(base.Pos, ir.OARRAYLIT, nil, nil)
+		datae := ir.NewCompLitExpr(base.Pos, ir.OARRAYLIT, nil, nil)
+		for _, r := range entries {
+			r := r.(*ir.KeyExpr)
+			datak.List.Append(r.Key)
+			datae.List.Append(r.Value)
+		}
+		fixedlit(inInitFunction, initKindStatic, datak, vstatk, init)
+		fixedlit(inInitFunction, initKindStatic, datae, vstate, init)
+
+		// loop adding structure elements to map
+		// for i = 0; i < len(vstatk); i++ {
+		//	map[vstatk[i]] = vstate[i]
+		// }
+		i := typecheck.Temp(types.Types[types.TINT])
+		rhs := ir.NewIndexExpr(base.Pos, vstate, i)
+		rhs.SetBounded(true)
+
+		kidx := ir.NewIndexExpr(base.Pos, vstatk, i)
+		kidx.SetBounded(true)
+		lhs := ir.NewIndexExpr(base.Pos, m, kidx)
+
+		zero := ir.NewAssignStmt(base.Pos, i, ir.NewInt(0))
+		cond := ir.NewBinaryExpr(base.Pos, ir.OLT, i, ir.NewInt(tk.NumElem()))
+		incr := ir.NewAssignStmt(base.Pos, i, ir.NewBinaryExpr(base.Pos, ir.OADD, i, ir.NewInt(1)))
+
+		var body ir.Node = ir.NewAssignStmt(base.Pos, lhs, rhs)
+		body = typecheck.Stmt(body) // typechecker rewrites OINDEX to OINDEXMAP
+		body = orderStmtInPlace(body, map[string][]*ir.Name{})
+
+		loop := ir.NewForStmt(base.Pos, nil, cond, incr, nil)
+		loop.Body = []ir.Node{body}
+		loop.SetInit([]ir.Node{zero})
+
+		appendWalkStmt(init, loop)
+		return
+	}
+	// For a small number of entries, just add them directly.
+
+	// Build list of var[c] = expr.
+	// Use temporaries so that mapassign1 can have addressable key, elem.
+	// TODO(josharian): avoid map key temporaries for mapfast_* assignments with literal keys.
+	tmpkey := typecheck.Temp(m.Type().Key())
+	tmpelem := typecheck.Temp(m.Type().Elem())
+
+	for _, r := range entries {
+		r := r.(*ir.KeyExpr)
+		index, elem := r.Key, r.Value
+
+		ir.SetPos(index)
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmpkey, index))
+
+		ir.SetPos(elem)
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmpelem, elem))
+
+		ir.SetPos(tmpelem)
+		var a ir.Node = ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, tmpkey), tmpelem)
+		a = typecheck.Stmt(a) // typechecker rewrites OINDEX to OINDEXMAP
+		a = orderStmtInPlace(a, map[string][]*ir.Name{})
+		appendWalkStmt(init, a)
+	}
+
+	appendWalkStmt(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, tmpkey))
+	appendWalkStmt(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, tmpelem))
+}
+
+func anylit(n ir.Node, var_ ir.Node, init *ir.Nodes) {
+	t := n.Type()
+	switch n.Op() {
+	default:
+		base.Fatalf("anylit: not lit, op=%v node=%v", n.Op(), n)
+
+	case ir.ONAME:
+		n := n.(*ir.Name)
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, n))
+
+	case ir.OMETHEXPR:
+		n := n.(*ir.SelectorExpr)
+		anylit(n.FuncName(), var_, init)
+
+	case ir.OPTRLIT:
+		n := n.(*ir.AddrExpr)
+		if !t.IsPtr() {
+			base.Fatalf("anylit: not ptr")
+		}
+
+		var r ir.Node
+		if n.Prealloc != nil {
+			// n.Prealloc is stack temporary used as backing store.
+			r = initStackTemp(init, n.Prealloc, nil)
+		} else {
+			r = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(n.X.Type()))
+			r.SetEsc(n.Esc())
+		}
+		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, r))
+
+		var_ = ir.NewStarExpr(base.Pos, var_)
+		var_ = typecheck.AssignExpr(var_)
+		anylit(n.X, var_, init)
+
+	case ir.OSTRUCTLIT, ir.OARRAYLIT:
+		n := n.(*ir.CompLitExpr)
+		if !t.IsStruct() && !t.IsArray() {
+			base.Fatalf("anylit: not struct/array")
+		}
+
+		if isSimpleName(var_) && len(n.List) > 4 {
+			// lay out static data
+			vstat := readonlystaticname(t)
+
+			ctxt := inInitFunction
+			if n.Op() == ir.OARRAYLIT {
+				ctxt = inNonInitFunction
+			}
+			fixedlit(ctxt, initKindStatic, n, vstat, init)
+
+			// copy static to var
+			appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, vstat))
+
+			// add expressions to automatic
+			fixedlit(inInitFunction, initKindDynamic, n, var_, init)
+			break
+		}
+
+		var components int64
+		if n.Op() == ir.OARRAYLIT {
+			components = t.NumElem()
+		} else {
+			components = int64(t.NumFields())
+		}
+		// initialization of an array or struct with unspecified components (missing fields or arrays)
+		if isSimpleName(var_) || int64(len(n.List)) < components {
+			appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, nil))
+		}
+
+		fixedlit(inInitFunction, initKindLocalCode, n, var_, init)
+
+	case ir.OSLICELIT:
+		n := n.(*ir.CompLitExpr)
+		slicelit(inInitFunction, n, var_, init)
+
+	case ir.OMAPLIT:
+		n := n.(*ir.CompLitExpr)
+		if !t.IsMap() {
+			base.Fatalf("anylit: not map")
+		}
+		maplit(n, var_, init)
+	}
+}
+
+// oaslit handles special composite literal assignments.
+// It returns true if n's effects have been added to init,
+// in which case n should be dropped from the program by the caller.
+func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool {
+	if n.X == nil || n.Y == nil {
+		// not a special composite literal assignment
+		return false
+	}
+	if n.X.Type() == nil || n.Y.Type() == nil {
+		// not a special composite literal assignment
+		return false
+	}
+	if !isSimpleName(n.X) {
+		// not a special composite literal assignment
+		return false
+	}
+	x := n.X.(*ir.Name)
+	if !types.Identical(n.X.Type(), n.Y.Type()) {
+		// not a special composite literal assignment
+		return false
+	}
+	if x.Addrtaken() {
+		// If x is address-taken, the RHS may (implicitly) uses LHS.
+		// Not safe to do a special composite literal assignment
+		// (which may expand to multiple assignments).
+		return false
+	}
+
+	switch n.Y.Op() {
+	default:
+		// not a special composite literal assignment
+		return false
+
+	case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
+		if ir.Any(n.Y, func(y ir.Node) bool { return ir.Uses(y, x) }) {
+			// not safe to do a special composite literal assignment if RHS uses LHS.
+			return false
+		}
+		anylit(n.Y, n.X, init)
+	}
+
+	return true
+}
+
+func genAsStatic(as *ir.AssignStmt) {
+	if as.X.Type() == nil {
+		base.Fatalf("genAsStatic as.Left not typechecked")
+	}
+
+	name, offset, ok := staticinit.StaticLoc(as.X)
+	if !ok || (name.Class != ir.PEXTERN && as.X != ir.BlankNode) {
+		base.Fatalf("genAsStatic: lhs %v", as.X)
+	}
+
+	switch r := as.Y; r.Op() {
+	case ir.OLITERAL:
+		staticdata.InitConst(name, offset, r, int(r.Type().Size()))
+		return
+	case ir.OMETHEXPR:
+		r := r.(*ir.SelectorExpr)
+		staticdata.InitAddr(name, offset, staticdata.FuncLinksym(r.FuncName()))
+		return
+	case ir.ONAME:
+		r := r.(*ir.Name)
+		if r.Offset_ != 0 {
+			base.Fatalf("genAsStatic %+v", as)
+		}
+		if r.Class == ir.PFUNC {
+			staticdata.InitAddr(name, offset, staticdata.FuncLinksym(r))
+			return
+		}
+	}
+	base.Fatalf("genAsStatic: rhs %v", as.Y)
+}
diff --git a/src/cmd/compile/internal/walk/convert.go b/src/cmd/compile/internal/walk/convert.go
new file mode 100644
index 0000000..ffc5fd1
--- /dev/null
+++ b/src/cmd/compile/internal/walk/convert.go
@@ -0,0 +1,474 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"encoding/binary"
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/ssagen"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+	"cmd/internal/sys"
+)
+
+// walkConv walks an OCONV or OCONVNOP (but not OCONVIFACE) node.
+func walkConv(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	if n.Op() == ir.OCONVNOP && n.Type() == n.X.Type() {
+		return n.X
+	}
+	if n.Op() == ir.OCONVNOP && ir.ShouldCheckPtr(ir.CurFunc, 1) {
+		if n.Type().IsUnsafePtr() && n.X.Type().IsUintptr() { // uintptr to unsafe.Pointer
+			return walkCheckPtrArithmetic(n, init)
+		}
+	}
+	param, result := rtconvfn(n.X.Type(), n.Type())
+	if param == types.Txxx {
+		return n
+	}
+	fn := types.BasicTypeNames[param] + "to" + types.BasicTypeNames[result]
+	return typecheck.Conv(mkcall(fn, types.Types[result], init, typecheck.Conv(n.X, types.Types[param])), n.Type())
+}
+
+// walkConvInterface walks an OCONVIFACE node.
+func walkConvInterface(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+
+	n.X = walkExpr(n.X, init)
+
+	fromType := n.X.Type()
+	toType := n.Type()
+	if !fromType.IsInterface() && !ir.IsBlank(ir.CurFunc.Nname) {
+		// skip unnamed functions (func _())
+		reflectdata.MarkTypeUsedInInterface(fromType, ir.CurFunc.LSym)
+	}
+
+	if !fromType.IsInterface() {
+		var typeWord ir.Node
+		if toType.IsEmptyInterface() {
+			typeWord = reflectdata.TypePtr(fromType)
+		} else {
+			typeWord = reflectdata.ITabAddr(fromType, toType)
+		}
+		l := ir.NewBinaryExpr(base.Pos, ir.OEFACE, typeWord, dataWord(n.Pos(), n.X, init, n.Esc() != ir.EscNone))
+		l.SetType(toType)
+		l.SetTypecheck(n.Typecheck())
+		return l
+	}
+	if fromType.IsEmptyInterface() {
+		base.Fatalf("OCONVIFACE can't operate on an empty interface")
+	}
+
+	// Evaluate the input interface.
+	c := typecheck.Temp(fromType)
+	init.Append(ir.NewAssignStmt(base.Pos, c, n.X))
+
+	// Grab its parts.
+	itab := ir.NewUnaryExpr(base.Pos, ir.OITAB, c)
+	itab.SetType(types.Types[types.TUINTPTR].PtrTo())
+	itab.SetTypecheck(1)
+	data := ir.NewUnaryExpr(n.Pos(), ir.OIDATA, c)
+	data.SetType(types.Types[types.TUINT8].PtrTo()) // Type is generic pointer - we're just passing it through.
+	data.SetTypecheck(1)
+
+	var typeWord ir.Node
+	if toType.IsEmptyInterface() {
+		// Implement interface to empty interface conversion.
+		// res = itab
+		// if res != nil {
+		//    res = res.type
+		// }
+		typeWord = typecheck.Temp(types.NewPtr(types.Types[types.TUINT8]))
+		init.Append(ir.NewAssignStmt(base.Pos, typeWord, itab))
+		nif := ir.NewIfStmt(base.Pos, typecheck.Expr(ir.NewBinaryExpr(base.Pos, ir.ONE, typeWord, typecheck.NodNil())), nil, nil)
+		nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, typeWord, itabType(typeWord))}
+		init.Append(nif)
+	} else {
+		// Must be converting I2I (more specific to less specific interface).
+		// res = convI2I(toType, itab)
+		fn := typecheck.LookupRuntime("convI2I")
+		types.CalcSize(fn.Type())
+		call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, nil)
+		call.Args = []ir.Node{reflectdata.TypePtr(toType), itab}
+		typeWord = walkExpr(typecheck.Expr(call), init)
+	}
+
+	// Build the result.
+	// e = iface{typeWord, data}
+	e := ir.NewBinaryExpr(base.Pos, ir.OEFACE, typeWord, data)
+	e.SetType(toType) // assign type manually, typecheck doesn't understand OEFACE.
+	e.SetTypecheck(1)
+	return e
+}
+
+// Returns the data word (the second word) used to represent n in an interface.
+// n must not be of interface type.
+// esc describes whether the result escapes.
+func dataWord(pos src.XPos, n ir.Node, init *ir.Nodes, escapes bool) ir.Node {
+	fromType := n.Type()
+
+	// If it's a pointer, it is its own representation.
+	if types.IsDirectIface(fromType) {
+		return n
+	}
+
+	// Try a bunch of cases to avoid an allocation.
+	var value ir.Node
+	switch {
+	case fromType.Size() == 0:
+		// n is zero-sized. Use zerobase.
+		cheapExpr(n, init) // Evaluate n for side-effects. See issue 19246.
+		value = ir.NewLinksymExpr(base.Pos, ir.Syms.Zerobase, types.Types[types.TUINTPTR])
+	case fromType.IsBoolean() || (fromType.Size() == 1 && fromType.IsInteger()):
+		// n is a bool/byte. Use staticuint64s[n * 8] on little-endian
+		// and staticuint64s[n * 8 + 7] on big-endian.
+		n = cheapExpr(n, init)
+		// byteindex widens n so that the multiplication doesn't overflow.
+		index := ir.NewBinaryExpr(base.Pos, ir.OLSH, byteindex(n), ir.NewInt(3))
+		if ssagen.Arch.LinkArch.ByteOrder == binary.BigEndian {
+			index = ir.NewBinaryExpr(base.Pos, ir.OADD, index, ir.NewInt(7))
+		}
+		// The actual type is [256]uint64, but we use [256*8]uint8 so we can address
+		// individual bytes.
+		staticuint64s := ir.NewLinksymExpr(base.Pos, ir.Syms.Staticuint64s, types.NewArray(types.Types[types.TUINT8], 256*8))
+		xe := ir.NewIndexExpr(base.Pos, staticuint64s, index)
+		xe.SetBounded(true)
+		value = xe
+	case n.Op() == ir.ONAME && n.(*ir.Name).Class == ir.PEXTERN && n.(*ir.Name).Readonly():
+		// n is a readonly global; use it directly.
+		value = n
+	case !escapes && fromType.Size() <= 1024:
+		// n does not escape. Use a stack temporary initialized to n.
+		value = typecheck.Temp(fromType)
+		init.Append(typecheck.Stmt(ir.NewAssignStmt(base.Pos, value, n)))
+	}
+	if value != nil {
+		// The interface data word is &value.
+		return typecheck.Expr(typecheck.NodAddr(value))
+	}
+
+	// Time to do an allocation. We'll call into the runtime for that.
+	fnname, argType, needsaddr := dataWordFuncName(fromType)
+	fn := typecheck.LookupRuntime(fnname)
+
+	var args []ir.Node
+	if needsaddr {
+		// Types of large or unknown size are passed by reference.
+		// Orderexpr arranged for n to be a temporary for all
+		// the conversions it could see. Comparison of an interface
+		// with a non-interface, especially in a switch on interface value
+		// with non-interface cases, is not visible to order.stmt, so we
+		// have to fall back on allocating a temp here.
+		if !ir.IsAddressable(n) {
+			n = copyExpr(n, fromType, init)
+		}
+		fn = typecheck.SubstArgTypes(fn, fromType)
+		args = []ir.Node{reflectdata.TypePtr(fromType), typecheck.NodAddr(n)}
+	} else {
+		// Use a specialized conversion routine that takes the type being
+		// converted by value, not by pointer.
+		var arg ir.Node
+		switch {
+		case fromType == argType:
+			// already in the right type, nothing to do
+			arg = n
+		case fromType.Kind() == argType.Kind(),
+			fromType.IsPtrShaped() && argType.IsPtrShaped():
+			// can directly convert (e.g. named type to underlying type, or one pointer to another)
+			// TODO: never happens because pointers are directIface?
+			arg = ir.NewConvExpr(pos, ir.OCONVNOP, argType, n)
+		case fromType.IsInteger() && argType.IsInteger():
+			// can directly convert (e.g. int32 to uint32)
+			arg = ir.NewConvExpr(pos, ir.OCONV, argType, n)
+		default:
+			// unsafe cast through memory
+			arg = copyExpr(n, fromType, init)
+			var addr ir.Node = typecheck.NodAddr(arg)
+			addr = ir.NewConvExpr(pos, ir.OCONVNOP, argType.PtrTo(), addr)
+			arg = ir.NewStarExpr(pos, addr)
+			arg.SetType(argType)
+		}
+		args = []ir.Node{arg}
+	}
+	call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, nil)
+	call.Args = args
+	return safeExpr(walkExpr(typecheck.Expr(call), init), init)
+}
+
+// walkConvIData walks an OCONVIDATA node.
+func walkConvIData(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	return dataWord(n.Pos(), n.X, init, n.Esc() != ir.EscNone)
+}
+
+// walkBytesRunesToString walks an OBYTES2STR or ORUNES2STR node.
+func walkBytesRunesToString(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	a := typecheck.NodNil()
+	if n.Esc() == ir.EscNone {
+		// Create temporary buffer for string on stack.
+		a = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
+	}
+	if n.Op() == ir.ORUNES2STR {
+		// slicerunetostring(*[32]byte, []rune) string
+		return mkcall("slicerunetostring", n.Type(), init, a, n.X)
+	}
+	// slicebytetostring(*[32]byte, ptr *byte, n int) string
+	n.X = cheapExpr(n.X, init)
+	ptr, len := backingArrayPtrLen(n.X)
+	return mkcall("slicebytetostring", n.Type(), init, a, ptr, len)
+}
+
+// walkBytesToStringTemp walks an OBYTES2STRTMP node.
+func walkBytesToStringTemp(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	if !base.Flag.Cfg.Instrumenting {
+		// Let the backend handle OBYTES2STRTMP directly
+		// to avoid a function call to slicebytetostringtmp.
+		return n
+	}
+	// slicebytetostringtmp(ptr *byte, n int) string
+	n.X = cheapExpr(n.X, init)
+	ptr, len := backingArrayPtrLen(n.X)
+	return mkcall("slicebytetostringtmp", n.Type(), init, ptr, len)
+}
+
+// walkRuneToString walks an ORUNESTR node.
+func walkRuneToString(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	a := typecheck.NodNil()
+	if n.Esc() == ir.EscNone {
+		a = stackBufAddr(4, types.Types[types.TUINT8])
+	}
+	// intstring(*[4]byte, rune)
+	return mkcall("intstring", n.Type(), init, a, typecheck.Conv(n.X, types.Types[types.TINT64]))
+}
+
+// walkStringToBytes walks an OSTR2BYTES node.
+func walkStringToBytes(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	s := n.X
+	if ir.IsConst(s, constant.String) {
+		sc := ir.StringVal(s)
+
+		// Allocate a [n]byte of the right size.
+		t := types.NewArray(types.Types[types.TUINT8], int64(len(sc)))
+		var a ir.Node
+		if n.Esc() == ir.EscNone && len(sc) <= int(ir.MaxImplicitStackVarSize) {
+			a = stackBufAddr(t.NumElem(), t.Elem())
+		} else {
+			types.CalcSize(t)
+			a = ir.NewUnaryExpr(base.Pos, ir.ONEW, nil)
+			a.SetType(types.NewPtr(t))
+			a.SetTypecheck(1)
+			a.MarkNonNil()
+		}
+		p := typecheck.Temp(t.PtrTo()) // *[n]byte
+		init.Append(typecheck.Stmt(ir.NewAssignStmt(base.Pos, p, a)))
+
+		// Copy from the static string data to the [n]byte.
+		if len(sc) > 0 {
+			as := ir.NewAssignStmt(base.Pos, ir.NewStarExpr(base.Pos, p), ir.NewStarExpr(base.Pos, typecheck.ConvNop(ir.NewUnaryExpr(base.Pos, ir.OSPTR, s), t.PtrTo())))
+			appendWalkStmt(init, as)
+		}
+
+		// Slice the [n]byte to a []byte.
+		slice := ir.NewSliceExpr(n.Pos(), ir.OSLICEARR, p, nil, nil, nil)
+		slice.SetType(n.Type())
+		slice.SetTypecheck(1)
+		return walkExpr(slice, init)
+	}
+
+	a := typecheck.NodNil()
+	if n.Esc() == ir.EscNone {
+		// Create temporary buffer for slice on stack.
+		a = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
+	}
+	// stringtoslicebyte(*32[byte], string) []byte
+	return mkcall("stringtoslicebyte", n.Type(), init, a, typecheck.Conv(s, types.Types[types.TSTRING]))
+}
+
+// walkStringToBytesTemp walks an OSTR2BYTESTMP node.
+func walkStringToBytesTemp(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	// []byte(string) conversion that creates a slice
+	// referring to the actual string bytes.
+	// This conversion is handled later by the backend and
+	// is only for use by internal compiler optimizations
+	// that know that the slice won't be mutated.
+	// The only such case today is:
+	// for i, c := range []byte(string)
+	n.X = walkExpr(n.X, init)
+	return n
+}
+
+// walkStringToRunes walks an OSTR2RUNES node.
+func walkStringToRunes(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	a := typecheck.NodNil()
+	if n.Esc() == ir.EscNone {
+		// Create temporary buffer for slice on stack.
+		a = stackBufAddr(tmpstringbufsize, types.Types[types.TINT32])
+	}
+	// stringtoslicerune(*[32]rune, string) []rune
+	return mkcall("stringtoslicerune", n.Type(), init, a, typecheck.Conv(n.X, types.Types[types.TSTRING]))
+}
+
+// dataWordFuncName returns the name of the function used to convert a value of type "from"
+// to the data word of an interface.
+// argType is the type the argument needs to be coerced to.
+// needsaddr reports whether the value should be passed (needaddr==false) or its address (needsaddr==true).
+func dataWordFuncName(from *types.Type) (fnname string, argType *types.Type, needsaddr bool) {
+	if from.IsInterface() {
+		base.Fatalf("can only handle non-interfaces")
+	}
+	switch {
+	case from.Size() == 2 && uint8(from.Alignment()) == 2:
+		return "convT16", types.Types[types.TUINT16], false
+	case from.Size() == 4 && uint8(from.Alignment()) == 4 && !from.HasPointers():
+		return "convT32", types.Types[types.TUINT32], false
+	case from.Size() == 8 && uint8(from.Alignment()) == uint8(types.Types[types.TUINT64].Alignment()) && !from.HasPointers():
+		return "convT64", types.Types[types.TUINT64], false
+	}
+	if sc := from.SoleComponent(); sc != nil {
+		switch {
+		case sc.IsString():
+			return "convTstring", types.Types[types.TSTRING], false
+		case sc.IsSlice():
+			return "convTslice", types.NewSlice(types.Types[types.TUINT8]), false // the element type doesn't matter
+		}
+	}
+
+	if from.HasPointers() {
+		return "convT", types.Types[types.TUNSAFEPTR], true
+	}
+	return "convTnoptr", types.Types[types.TUNSAFEPTR], true
+}
+
+// rtconvfn returns the parameter and result types that will be used by a
+// runtime function to convert from type src to type dst. The runtime function
+// name can be derived from the names of the returned types.
+//
+// If no such function is necessary, it returns (Txxx, Txxx).
+func rtconvfn(src, dst *types.Type) (param, result types.Kind) {
+	if ssagen.Arch.SoftFloat {
+		return types.Txxx, types.Txxx
+	}
+
+	switch ssagen.Arch.LinkArch.Family {
+	case sys.ARM, sys.MIPS:
+		if src.IsFloat() {
+			switch dst.Kind() {
+			case types.TINT64, types.TUINT64:
+				return types.TFLOAT64, dst.Kind()
+			}
+		}
+		if dst.IsFloat() {
+			switch src.Kind() {
+			case types.TINT64, types.TUINT64:
+				return src.Kind(), dst.Kind()
+			}
+		}
+
+	case sys.I386:
+		if src.IsFloat() {
+			switch dst.Kind() {
+			case types.TINT64, types.TUINT64:
+				return types.TFLOAT64, dst.Kind()
+			case types.TUINT32, types.TUINT, types.TUINTPTR:
+				return types.TFLOAT64, types.TUINT32
+			}
+		}
+		if dst.IsFloat() {
+			switch src.Kind() {
+			case types.TINT64, types.TUINT64:
+				return src.Kind(), dst.Kind()
+			case types.TUINT32, types.TUINT, types.TUINTPTR:
+				return types.TUINT32, types.TFLOAT64
+			}
+		}
+	}
+	return types.Txxx, types.Txxx
+}
+
+// byteindex converts n, which is byte-sized, to an int used to index into an array.
+// We cannot use conv, because we allow converting bool to int here,
+// which is forbidden in user code.
+func byteindex(n ir.Node) ir.Node {
+	// We cannot convert from bool to int directly.
+	// While converting from int8 to int is possible, it would yield
+	// the wrong result for negative values.
+	// Reinterpreting the value as an unsigned byte solves both cases.
+	if !types.Identical(n.Type(), types.Types[types.TUINT8]) {
+		n = ir.NewConvExpr(base.Pos, ir.OCONV, nil, n)
+		n.SetType(types.Types[types.TUINT8])
+		n.SetTypecheck(1)
+	}
+	n = ir.NewConvExpr(base.Pos, ir.OCONV, nil, n)
+	n.SetType(types.Types[types.TINT])
+	n.SetTypecheck(1)
+	return n
+}
+
+func walkCheckPtrArithmetic(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
+	// Calling cheapExpr(n, init) below leads to a recursive call to
+	// walkExpr, which leads us back here again. Use n.Checkptr to
+	// prevent infinite loops.
+	if n.CheckPtr() {
+		return n
+	}
+	n.SetCheckPtr(true)
+	defer n.SetCheckPtr(false)
+
+	// TODO(mdempsky): Make stricter. We only need to exempt
+	// reflect.Value.Pointer and reflect.Value.UnsafeAddr.
+	switch n.X.Op() {
+	case ir.OCALLMETH:
+		base.FatalfAt(n.X.Pos(), "OCALLMETH missed by typecheck")
+	case ir.OCALLFUNC, ir.OCALLINTER:
+		return n
+	}
+
+	if n.X.Op() == ir.ODOTPTR && ir.IsReflectHeaderDataField(n.X) {
+		return n
+	}
+
+	// Find original unsafe.Pointer operands involved in this
+	// arithmetic expression.
+	//
+	// "It is valid both to add and to subtract offsets from a
+	// pointer in this way. It is also valid to use &^ to round
+	// pointers, usually for alignment."
+	var originals []ir.Node
+	var walk func(n ir.Node)
+	walk = func(n ir.Node) {
+		switch n.Op() {
+		case ir.OADD:
+			n := n.(*ir.BinaryExpr)
+			walk(n.X)
+			walk(n.Y)
+		case ir.OSUB, ir.OANDNOT:
+			n := n.(*ir.BinaryExpr)
+			walk(n.X)
+		case ir.OCONVNOP:
+			n := n.(*ir.ConvExpr)
+			if n.X.Type().IsUnsafePtr() {
+				n.X = cheapExpr(n.X, init)
+				originals = append(originals, typecheck.ConvNop(n.X, types.Types[types.TUNSAFEPTR]))
+			}
+		}
+	}
+	walk(n.X)
+
+	cheap := cheapExpr(n, init)
+
+	slice := typecheck.MakeDotArgs(base.Pos, types.NewSlice(types.Types[types.TUNSAFEPTR]), originals)
+	slice.SetEsc(ir.EscNone)
+
+	init.Append(mkcall("checkptrArithmetic", nil, init, typecheck.ConvNop(cheap, types.Types[types.TUNSAFEPTR]), slice))
+	// TODO(khr): Mark backing store of slice as dead. This will allow us to reuse
+	// the backing store for multiple calls to checkptrArithmetic.
+
+	return cheap
+}
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
new file mode 100644
index 0000000..e5bf6cf
--- /dev/null
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -0,0 +1,1024 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"fmt"
+	"go/constant"
+	"internal/buildcfg"
+	"strings"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/staticdata"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+)
+
+// The result of walkExpr MUST be assigned back to n, e.g.
+// 	n.Left = walkExpr(n.Left, init)
+func walkExpr(n ir.Node, init *ir.Nodes) ir.Node {
+	if n == nil {
+		return n
+	}
+
+	if n, ok := n.(ir.InitNode); ok && init == n.PtrInit() {
+		// not okay to use n->ninit when walking n,
+		// because we might replace n with some other node
+		// and would lose the init list.
+		base.Fatalf("walkExpr init == &n->ninit")
+	}
+
+	if len(n.Init()) != 0 {
+		walkStmtList(n.Init())
+		init.Append(ir.TakeInit(n)...)
+	}
+
+	lno := ir.SetPos(n)
+
+	if base.Flag.LowerW > 1 {
+		ir.Dump("before walk expr", n)
+	}
+
+	if n.Typecheck() != 1 {
+		base.Fatalf("missed typecheck: %+v", n)
+	}
+
+	if n.Type().IsUntyped() {
+		base.Fatalf("expression has untyped type: %+v", n)
+	}
+
+	n = walkExpr1(n, init)
+
+	// Eagerly compute sizes of all expressions for the back end.
+	if typ := n.Type(); typ != nil && typ.Kind() != types.TBLANK && !typ.IsFuncArgStruct() {
+		types.CheckSize(typ)
+	}
+	if n, ok := n.(*ir.Name); ok && n.Heapaddr != nil {
+		types.CheckSize(n.Heapaddr.Type())
+	}
+	if ir.IsConst(n, constant.String) {
+		// Emit string symbol now to avoid emitting
+		// any concurrently during the backend.
+		_ = staticdata.StringSym(n.Pos(), constant.StringVal(n.Val()))
+	}
+
+	if base.Flag.LowerW != 0 && n != nil {
+		ir.Dump("after walk expr", n)
+	}
+
+	base.Pos = lno
+	return n
+}
+
+func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
+	switch n.Op() {
+	default:
+		ir.Dump("walk", n)
+		base.Fatalf("walkExpr: switch 1 unknown op %+v", n.Op())
+		panic("unreachable")
+
+	case ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP:
+		return n
+
+	case ir.OTYPE, ir.ONAME, ir.OLITERAL, ir.ONIL, ir.OLINKSYMOFFSET:
+		// TODO(mdempsky): Just return n; see discussion on CL 38655.
+		// Perhaps refactor to use Node.mayBeShared for these instead.
+		// If these return early, make sure to still call
+		// StringSym for constant strings.
+		return n
+
+	case ir.OMETHEXPR:
+		// TODO(mdempsky): Do this right after type checking.
+		n := n.(*ir.SelectorExpr)
+		return n.FuncName()
+
+	case ir.ONOT, ir.ONEG, ir.OPLUS, ir.OBITNOT, ir.OREAL, ir.OIMAG, ir.OSPTR, ir.OITAB, ir.OIDATA:
+		n := n.(*ir.UnaryExpr)
+		n.X = walkExpr(n.X, init)
+		return n
+
+	case ir.ODOTMETH, ir.ODOTINTER:
+		n := n.(*ir.SelectorExpr)
+		n.X = walkExpr(n.X, init)
+		return n
+
+	case ir.OADDR:
+		n := n.(*ir.AddrExpr)
+		n.X = walkExpr(n.X, init)
+		return n
+
+	case ir.ODEREF:
+		n := n.(*ir.StarExpr)
+		n.X = walkExpr(n.X, init)
+		return n
+
+	case ir.OEFACE, ir.OAND, ir.OANDNOT, ir.OSUB, ir.OMUL, ir.OADD, ir.OOR, ir.OXOR, ir.OLSH, ir.ORSH,
+		ir.OUNSAFEADD:
+		n := n.(*ir.BinaryExpr)
+		n.X = walkExpr(n.X, init)
+		n.Y = walkExpr(n.Y, init)
+		return n
+
+	case ir.OUNSAFESLICE:
+		n := n.(*ir.BinaryExpr)
+		return walkUnsafeSlice(n, init)
+
+	case ir.ODOT, ir.ODOTPTR:
+		n := n.(*ir.SelectorExpr)
+		return walkDot(n, init)
+
+	case ir.ODOTTYPE, ir.ODOTTYPE2:
+		n := n.(*ir.TypeAssertExpr)
+		return walkDotType(n, init)
+
+	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
+		n := n.(*ir.DynamicTypeAssertExpr)
+		return walkDynamicDotType(n, init)
+
+	case ir.OLEN, ir.OCAP:
+		n := n.(*ir.UnaryExpr)
+		return walkLenCap(n, init)
+
+	case ir.OCOMPLEX:
+		n := n.(*ir.BinaryExpr)
+		n.X = walkExpr(n.X, init)
+		n.Y = walkExpr(n.Y, init)
+		return n
+
+	case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
+		n := n.(*ir.BinaryExpr)
+		return walkCompare(n, init)
+
+	case ir.OANDAND, ir.OOROR:
+		n := n.(*ir.LogicalExpr)
+		return walkLogical(n, init)
+
+	case ir.OPRINT, ir.OPRINTN:
+		return walkPrint(n.(*ir.CallExpr), init)
+
+	case ir.OPANIC:
+		n := n.(*ir.UnaryExpr)
+		return mkcall("gopanic", nil, init, n.X)
+
+	case ir.ORECOVERFP:
+		return walkRecoverFP(n.(*ir.CallExpr), init)
+
+	case ir.OCFUNC:
+		return n
+
+	case ir.OCALLINTER, ir.OCALLFUNC:
+		n := n.(*ir.CallExpr)
+		return walkCall(n, init)
+
+	case ir.OAS, ir.OASOP:
+		return walkAssign(init, n)
+
+	case ir.OAS2:
+		n := n.(*ir.AssignListStmt)
+		return walkAssignList(init, n)
+
+	// a,b,... = fn()
+	case ir.OAS2FUNC:
+		n := n.(*ir.AssignListStmt)
+		return walkAssignFunc(init, n)
+
+	// x, y = <-c
+	// order.stmt made sure x is addressable or blank.
+	case ir.OAS2RECV:
+		n := n.(*ir.AssignListStmt)
+		return walkAssignRecv(init, n)
+
+	// a,b = m[i]
+	case ir.OAS2MAPR:
+		n := n.(*ir.AssignListStmt)
+		return walkAssignMapRead(init, n)
+
+	case ir.ODELETE:
+		n := n.(*ir.CallExpr)
+		return walkDelete(init, n)
+
+	case ir.OAS2DOTTYPE:
+		n := n.(*ir.AssignListStmt)
+		return walkAssignDotType(n, init)
+
+	case ir.OCONVIFACE:
+		n := n.(*ir.ConvExpr)
+		return walkConvInterface(n, init)
+
+	case ir.OCONVIDATA:
+		n := n.(*ir.ConvExpr)
+		return walkConvIData(n, init)
+
+	case ir.OCONV, ir.OCONVNOP:
+		n := n.(*ir.ConvExpr)
+		return walkConv(n, init)
+
+	case ir.OSLICE2ARRPTR:
+		n := n.(*ir.ConvExpr)
+		n.X = walkExpr(n.X, init)
+		return n
+
+	case ir.ODIV, ir.OMOD:
+		n := n.(*ir.BinaryExpr)
+		return walkDivMod(n, init)
+
+	case ir.OINDEX:
+		n := n.(*ir.IndexExpr)
+		return walkIndex(n, init)
+
+	case ir.OINDEXMAP:
+		n := n.(*ir.IndexExpr)
+		return walkIndexMap(n, init)
+
+	case ir.ORECV:
+		base.Fatalf("walkExpr ORECV") // should see inside OAS only
+		panic("unreachable")
+
+	case ir.OSLICEHEADER:
+		n := n.(*ir.SliceHeaderExpr)
+		return walkSliceHeader(n, init)
+
+	case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
+		n := n.(*ir.SliceExpr)
+		return walkSlice(n, init)
+
+	case ir.ONEW:
+		n := n.(*ir.UnaryExpr)
+		return walkNew(n, init)
+
+	case ir.OADDSTR:
+		return walkAddString(n.(*ir.AddStringExpr), init)
+
+	case ir.OAPPEND:
+		// order should make sure we only see OAS(node, OAPPEND), which we handle above.
+		base.Fatalf("append outside assignment")
+		panic("unreachable")
+
+	case ir.OCOPY:
+		return walkCopy(n.(*ir.BinaryExpr), init, base.Flag.Cfg.Instrumenting && !base.Flag.CompilingRuntime)
+
+	case ir.OCLOSE:
+		n := n.(*ir.UnaryExpr)
+		return walkClose(n, init)
+
+	case ir.OMAKECHAN:
+		n := n.(*ir.MakeExpr)
+		return walkMakeChan(n, init)
+
+	case ir.OMAKEMAP:
+		n := n.(*ir.MakeExpr)
+		return walkMakeMap(n, init)
+
+	case ir.OMAKESLICE:
+		n := n.(*ir.MakeExpr)
+		return walkMakeSlice(n, init)
+
+	case ir.OMAKESLICECOPY:
+		n := n.(*ir.MakeExpr)
+		return walkMakeSliceCopy(n, init)
+
+	case ir.ORUNESTR:
+		n := n.(*ir.ConvExpr)
+		return walkRuneToString(n, init)
+
+	case ir.OBYTES2STR, ir.ORUNES2STR:
+		n := n.(*ir.ConvExpr)
+		return walkBytesRunesToString(n, init)
+
+	case ir.OBYTES2STRTMP:
+		n := n.(*ir.ConvExpr)
+		return walkBytesToStringTemp(n, init)
+
+	case ir.OSTR2BYTES:
+		n := n.(*ir.ConvExpr)
+		return walkStringToBytes(n, init)
+
+	case ir.OSTR2BYTESTMP:
+		n := n.(*ir.ConvExpr)
+		return walkStringToBytesTemp(n, init)
+
+	case ir.OSTR2RUNES:
+		n := n.(*ir.ConvExpr)
+		return walkStringToRunes(n, init)
+
+	case ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT, ir.OSTRUCTLIT, ir.OPTRLIT:
+		return walkCompLit(n, init)
+
+	case ir.OSEND:
+		n := n.(*ir.SendStmt)
+		return walkSend(n, init)
+
+	case ir.OCLOSURE:
+		return walkClosure(n.(*ir.ClosureExpr), init)
+
+	case ir.OMETHVALUE:
+		return walkMethodValue(n.(*ir.SelectorExpr), init)
+	}
+
+	// No return! Each case must return (or panic),
+	// to avoid confusion about what gets returned
+	// in the presence of type assertions.
+}
+
+// walk the whole tree of the body of an
+// expression or simple statement.
+// the types expressions are calculated.
+// compile-time constants are evaluated.
+// complex side effects like statements are appended to init
+func walkExprList(s []ir.Node, init *ir.Nodes) {
+	for i := range s {
+		s[i] = walkExpr(s[i], init)
+	}
+}
+
+func walkExprListCheap(s []ir.Node, init *ir.Nodes) {
+	for i, n := range s {
+		s[i] = cheapExpr(n, init)
+		s[i] = walkExpr(s[i], init)
+	}
+}
+
+func walkExprListSafe(s []ir.Node, init *ir.Nodes) {
+	for i, n := range s {
+		s[i] = safeExpr(n, init)
+		s[i] = walkExpr(s[i], init)
+	}
+}
+
+// return side-effect free and cheap n, appending side effects to init.
+// result may not be assignable.
+func cheapExpr(n ir.Node, init *ir.Nodes) ir.Node {
+	switch n.Op() {
+	case ir.ONAME, ir.OLITERAL, ir.ONIL:
+		return n
+	}
+
+	return copyExpr(n, n.Type(), init)
+}
+
+// return side effect-free n, appending side effects to init.
+// result is assignable if n is.
+func safeExpr(n ir.Node, init *ir.Nodes) ir.Node {
+	if n == nil {
+		return nil
+	}
+
+	if len(n.Init()) != 0 {
+		walkStmtList(n.Init())
+		init.Append(ir.TakeInit(n)...)
+	}
+
+	switch n.Op() {
+	case ir.ONAME, ir.OLITERAL, ir.ONIL, ir.OLINKSYMOFFSET:
+		return n
+
+	case ir.OLEN, ir.OCAP:
+		n := n.(*ir.UnaryExpr)
+		l := safeExpr(n.X, init)
+		if l == n.X {
+			return n
+		}
+		a := ir.Copy(n).(*ir.UnaryExpr)
+		a.X = l
+		return walkExpr(typecheck.Expr(a), init)
+
+	case ir.ODOT, ir.ODOTPTR:
+		n := n.(*ir.SelectorExpr)
+		l := safeExpr(n.X, init)
+		if l == n.X {
+			return n
+		}
+		a := ir.Copy(n).(*ir.SelectorExpr)
+		a.X = l
+		return walkExpr(typecheck.Expr(a), init)
+
+	case ir.ODEREF:
+		n := n.(*ir.StarExpr)
+		l := safeExpr(n.X, init)
+		if l == n.X {
+			return n
+		}
+		a := ir.Copy(n).(*ir.StarExpr)
+		a.X = l
+		return walkExpr(typecheck.Expr(a), init)
+
+	case ir.OINDEX, ir.OINDEXMAP:
+		n := n.(*ir.IndexExpr)
+		l := safeExpr(n.X, init)
+		r := safeExpr(n.Index, init)
+		if l == n.X && r == n.Index {
+			return n
+		}
+		a := ir.Copy(n).(*ir.IndexExpr)
+		a.X = l
+		a.Index = r
+		return walkExpr(typecheck.Expr(a), init)
+
+	case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT:
+		n := n.(*ir.CompLitExpr)
+		if isStaticCompositeLiteral(n) {
+			return n
+		}
+	}
+
+	// make a copy; must not be used as an lvalue
+	if ir.IsAddressable(n) {
+		base.Fatalf("missing lvalue case in safeExpr: %v", n)
+	}
+	return cheapExpr(n, init)
+}
+
+func copyExpr(n ir.Node, t *types.Type, init *ir.Nodes) ir.Node {
+	l := typecheck.Temp(t)
+	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, l, n))
+	return l
+}
+
+func walkAddString(n *ir.AddStringExpr, init *ir.Nodes) ir.Node {
+	c := len(n.List)
+
+	if c < 2 {
+		base.Fatalf("walkAddString count %d too small", c)
+	}
+
+	buf := typecheck.NodNil()
+	if n.Esc() == ir.EscNone {
+		sz := int64(0)
+		for _, n1 := range n.List {
+			if n1.Op() == ir.OLITERAL {
+				sz += int64(len(ir.StringVal(n1)))
+			}
+		}
+
+		// Don't allocate the buffer if the result won't fit.
+		if sz < tmpstringbufsize {
+			// Create temporary buffer for result string on stack.
+			buf = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
+		}
+	}
+
+	// build list of string arguments
+	args := []ir.Node{buf}
+	for _, n2 := range n.List {
+		args = append(args, typecheck.Conv(n2, types.Types[types.TSTRING]))
+	}
+
+	var fn string
+	if c <= 5 {
+		// small numbers of strings use direct runtime helpers.
+		// note: order.expr knows this cutoff too.
+		fn = fmt.Sprintf("concatstring%d", c)
+	} else {
+		// large numbers of strings are passed to the runtime as a slice.
+		fn = "concatstrings"
+
+		t := types.NewSlice(types.Types[types.TSTRING])
+		// args[1:] to skip buf arg
+		slice := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, ir.TypeNode(t), args[1:])
+		slice.Prealloc = n.Prealloc
+		args = []ir.Node{buf, slice}
+		slice.SetEsc(ir.EscNone)
+	}
+
+	cat := typecheck.LookupRuntime(fn)
+	r := ir.NewCallExpr(base.Pos, ir.OCALL, cat, nil)
+	r.Args = args
+	r1 := typecheck.Expr(r)
+	r1 = walkExpr(r1, init)
+	r1.SetType(n.Type())
+
+	return r1
+}
+
+// walkCall walks an OCALLFUNC or OCALLINTER node.
+func walkCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
+	if n.Op() == ir.OCALLMETH {
+		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
+	}
+	if n.Op() == ir.OCALLINTER || n.X.Op() == ir.OMETHEXPR {
+		// We expect both interface call reflect.Type.Method and concrete
+		// call reflect.(*rtype).Method.
+		usemethod(n)
+	}
+	if n.Op() == ir.OCALLINTER {
+		reflectdata.MarkUsedIfaceMethod(n)
+	}
+
+	if n.Op() == ir.OCALLFUNC && n.X.Op() == ir.OCLOSURE {
+		directClosureCall(n)
+	}
+
+	if isFuncPCIntrinsic(n) {
+		// For internal/abi.FuncPCABIxxx(fn), if fn is a defined function, rewrite
+		// it to the address of the function of the ABI fn is defined.
+		name := n.X.(*ir.Name).Sym().Name
+		arg := n.Args[0]
+		var wantABI obj.ABI
+		switch name {
+		case "FuncPCABI0":
+			wantABI = obj.ABI0
+		case "FuncPCABIInternal":
+			wantABI = obj.ABIInternal
+		}
+		if isIfaceOfFunc(arg) {
+			fn := arg.(*ir.ConvExpr).X.(*ir.Name)
+			abi := fn.Func.ABI
+			if abi != wantABI {
+				base.ErrorfAt(n.Pos(), "internal/abi.%s expects an %v function, %s is defined as %v", name, wantABI, fn.Sym().Name, abi)
+			}
+			var e ir.Node = ir.NewLinksymExpr(n.Pos(), fn.Sym().LinksymABI(abi), types.Types[types.TUINTPTR])
+			e = ir.NewAddrExpr(n.Pos(), e)
+			e.SetType(types.Types[types.TUINTPTR].PtrTo())
+			e = ir.NewConvExpr(n.Pos(), ir.OCONVNOP, n.Type(), e)
+			return e
+		}
+		// fn is not a defined function. It must be ABIInternal.
+		// Read the address from func value, i.e. *(*uintptr)(idata(fn)).
+		if wantABI != obj.ABIInternal {
+			base.ErrorfAt(n.Pos(), "internal/abi.%s does not accept func expression, which is ABIInternal", name)
+		}
+		arg = walkExpr(arg, init)
+		var e ir.Node = ir.NewUnaryExpr(n.Pos(), ir.OIDATA, arg)
+		e.SetType(n.Type().PtrTo())
+		e = ir.NewStarExpr(n.Pos(), e)
+		e.SetType(n.Type())
+		return e
+	}
+
+	walkCall1(n, init)
+	return n
+}
+
+func walkCall1(n *ir.CallExpr, init *ir.Nodes) {
+	if n.Walked() {
+		return // already walked
+	}
+	n.SetWalked(true)
+
+	if n.Op() == ir.OCALLMETH {
+		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
+	}
+
+	args := n.Args
+	params := n.X.Type().Params()
+
+	n.X = walkExpr(n.X, init)
+	walkExprList(args, init)
+
+	for i, arg := range args {
+		// Validate argument and parameter types match.
+		param := params.Field(i)
+		if !types.Identical(arg.Type(), param.Type) {
+			base.FatalfAt(n.Pos(), "assigning %L to parameter %v (type %v)", arg, param.Sym, param.Type)
+		}
+
+		// For any argument whose evaluation might require a function call,
+		// store that argument into a temporary variable,
+		// to prevent that calls from clobbering arguments already on the stack.
+		if mayCall(arg) {
+			// assignment of arg to Temp
+			tmp := typecheck.Temp(param.Type)
+			init.Append(convas(typecheck.Stmt(ir.NewAssignStmt(base.Pos, tmp, arg)).(*ir.AssignStmt), init))
+			// replace arg with temp
+			args[i] = tmp
+		}
+	}
+
+	n.Args = args
+}
+
+// walkDivMod walks an ODIV or OMOD node.
+func walkDivMod(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	n.Y = walkExpr(n.Y, init)
+
+	// rewrite complex div into function call.
+	et := n.X.Type().Kind()
+
+	if types.IsComplex[et] && n.Op() == ir.ODIV {
+		t := n.Type()
+		call := mkcall("complex128div", types.Types[types.TCOMPLEX128], init, typecheck.Conv(n.X, types.Types[types.TCOMPLEX128]), typecheck.Conv(n.Y, types.Types[types.TCOMPLEX128]))
+		return typecheck.Conv(call, t)
+	}
+
+	// Nothing to do for float divisions.
+	if types.IsFloat[et] {
+		return n
+	}
+
+	// rewrite 64-bit div and mod on 32-bit architectures.
+	// TODO: Remove this code once we can introduce
+	// runtime calls late in SSA processing.
+	if types.RegSize < 8 && (et == types.TINT64 || et == types.TUINT64) {
+		if n.Y.Op() == ir.OLITERAL {
+			// Leave div/mod by constant powers of 2 or small 16-bit constants.
+			// The SSA backend will handle those.
+			switch et {
+			case types.TINT64:
+				c := ir.Int64Val(n.Y)
+				if c < 0 {
+					c = -c
+				}
+				if c != 0 && c&(c-1) == 0 {
+					return n
+				}
+			case types.TUINT64:
+				c := ir.Uint64Val(n.Y)
+				if c < 1<<16 {
+					return n
+				}
+				if c != 0 && c&(c-1) == 0 {
+					return n
+				}
+			}
+		}
+		var fn string
+		if et == types.TINT64 {
+			fn = "int64"
+		} else {
+			fn = "uint64"
+		}
+		if n.Op() == ir.ODIV {
+			fn += "div"
+		} else {
+			fn += "mod"
+		}
+		return mkcall(fn, n.Type(), init, typecheck.Conv(n.X, types.Types[et]), typecheck.Conv(n.Y, types.Types[et]))
+	}
+	return n
+}
+
+// walkDot walks an ODOT or ODOTPTR node.
+func walkDot(n *ir.SelectorExpr, init *ir.Nodes) ir.Node {
+	usefield(n)
+	n.X = walkExpr(n.X, init)
+	return n
+}
+
+// walkDotType walks an ODOTTYPE or ODOTTYPE2 node.
+func walkDotType(n *ir.TypeAssertExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	// Set up interface type addresses for back end.
+	if !n.Type().IsInterface() && !n.X.Type().IsEmptyInterface() {
+		n.Itab = reflectdata.ITabAddr(n.Type(), n.X.Type())
+	}
+	return n
+}
+
+// walkDynamicdotType walks an ODYNAMICDOTTYPE or ODYNAMICDOTTYPE2 node.
+func walkDynamicDotType(n *ir.DynamicTypeAssertExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	n.T = walkExpr(n.T, init)
+	return n
+}
+
+// walkIndex walks an OINDEX node.
+func walkIndex(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+
+	// save the original node for bounds checking elision.
+	// If it was a ODIV/OMOD walk might rewrite it.
+	r := n.Index
+
+	n.Index = walkExpr(n.Index, init)
+
+	// if range of type cannot exceed static array bound,
+	// disable bounds check.
+	if n.Bounded() {
+		return n
+	}
+	t := n.X.Type()
+	if t != nil && t.IsPtr() {
+		t = t.Elem()
+	}
+	if t.IsArray() {
+		n.SetBounded(bounded(r, t.NumElem()))
+		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
+			base.Warn("index bounds check elided")
+		}
+		if ir.IsSmallIntConst(n.Index) && !n.Bounded() {
+			base.Errorf("index out of bounds")
+		}
+	} else if ir.IsConst(n.X, constant.String) {
+		n.SetBounded(bounded(r, int64(len(ir.StringVal(n.X)))))
+		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
+			base.Warn("index bounds check elided")
+		}
+		if ir.IsSmallIntConst(n.Index) && !n.Bounded() {
+			base.Errorf("index out of bounds")
+		}
+	}
+
+	if ir.IsConst(n.Index, constant.Int) {
+		if v := n.Index.Val(); constant.Sign(v) < 0 || ir.ConstOverflow(v, types.Types[types.TINT]) {
+			base.Errorf("index out of bounds")
+		}
+	}
+	return n
+}
+
+// mapKeyArg returns an expression for key that is suitable to be passed
+// as the key argument for mapaccess and mapdelete functions.
+// n is is the map indexing or delete Node (to provide Pos).
+// Note: this is not used for mapassign, which does distinguish pointer vs.
+// integer key.
+func mapKeyArg(fast int, n, key ir.Node) ir.Node {
+	switch fast {
+	case mapslow:
+		// standard version takes key by reference.
+		// order.expr made sure key is addressable.
+		return typecheck.NodAddr(key)
+	case mapfast32ptr:
+		// mapaccess and mapdelete don't distinguish pointer vs. integer key.
+		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT32], key)
+	case mapfast64ptr:
+		// mapaccess and mapdelete don't distinguish pointer vs. integer key.
+		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT64], key)
+	default:
+		// fast version takes key by value.
+		return key
+	}
+}
+
+// walkIndexMap walks an OINDEXMAP node.
+func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
+	// Replace m[k] with *map{access1,assign}(maptype, m, &k)
+	n.X = walkExpr(n.X, init)
+	n.Index = walkExpr(n.Index, init)
+	map_ := n.X
+	key := n.Index
+	t := map_.Type()
+	var call *ir.CallExpr
+	if n.Assigned {
+		// This m[k] expression is on the left-hand side of an assignment.
+		fast := mapfast(t)
+		if fast == mapslow {
+			// standard version takes key by reference.
+			// order.expr made sure key is addressable.
+			key = typecheck.NodAddr(key)
+		}
+		call = mkcall1(mapfn(mapassign[fast], t, false), nil, init, reflectdata.TypePtr(t), map_, key)
+	} else {
+		// m[k] is not the target of an assignment.
+		fast := mapfast(t)
+		key = mapKeyArg(fast, n, key)
+		if w := t.Elem().Size(); w <= zeroValSize {
+			call = mkcall1(mapfn(mapaccess1[fast], t, false), types.NewPtr(t.Elem()), init, reflectdata.TypePtr(t), map_, key)
+		} else {
+			z := reflectdata.ZeroAddr(w)
+			call = mkcall1(mapfn("mapaccess1_fat", t, true), types.NewPtr(t.Elem()), init, reflectdata.TypePtr(t), map_, key, z)
+		}
+	}
+	call.SetType(types.NewPtr(t.Elem()))
+	call.MarkNonNil() // mapaccess1* and mapassign always return non-nil pointers.
+	star := ir.NewStarExpr(base.Pos, call)
+	star.SetType(t.Elem())
+	star.SetTypecheck(1)
+	return star
+}
+
+// walkLogical walks an OANDAND or OOROR node.
+func walkLogical(n *ir.LogicalExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+
+	// cannot put side effects from n.Right on init,
+	// because they cannot run before n.Left is checked.
+	// save elsewhere and store on the eventual n.Right.
+	var ll ir.Nodes
+
+	n.Y = walkExpr(n.Y, &ll)
+	n.Y = ir.InitExpr(ll, n.Y)
+	return n
+}
+
+// walkSend walks an OSEND node.
+func walkSend(n *ir.SendStmt, init *ir.Nodes) ir.Node {
+	n1 := n.Value
+	n1 = typecheck.AssignConv(n1, n.Chan.Type().Elem(), "chan send")
+	n1 = walkExpr(n1, init)
+	n1 = typecheck.NodAddr(n1)
+	return mkcall1(chanfn("chansend1", 2, n.Chan.Type()), nil, init, n.Chan, n1)
+}
+
+// walkSlice walks an OSLICE, OSLICEARR, OSLICESTR, OSLICE3, or OSLICE3ARR node.
+func walkSlice(n *ir.SliceExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	n.Low = walkExpr(n.Low, init)
+	if n.Low != nil && ir.IsZero(n.Low) {
+		// Reduce x[0:j] to x[:j] and x[0:j:k] to x[:j:k].
+		n.Low = nil
+	}
+	n.High = walkExpr(n.High, init)
+	n.Max = walkExpr(n.Max, init)
+
+	if n.Op().IsSlice3() {
+		if n.Max != nil && n.Max.Op() == ir.OCAP && ir.SameSafeExpr(n.X, n.Max.(*ir.UnaryExpr).X) {
+			// Reduce x[i:j:cap(x)] to x[i:j].
+			if n.Op() == ir.OSLICE3 {
+				n.SetOp(ir.OSLICE)
+			} else {
+				n.SetOp(ir.OSLICEARR)
+			}
+			return reduceSlice(n)
+		}
+		return n
+	}
+	return reduceSlice(n)
+}
+
+// walkSliceHeader walks an OSLICEHEADER node.
+func walkSliceHeader(n *ir.SliceHeaderExpr, init *ir.Nodes) ir.Node {
+	n.Ptr = walkExpr(n.Ptr, init)
+	n.Len = walkExpr(n.Len, init)
+	n.Cap = walkExpr(n.Cap, init)
+	return n
+}
+
+// TODO(josharian): combine this with its caller and simplify
+func reduceSlice(n *ir.SliceExpr) ir.Node {
+	if n.High != nil && n.High.Op() == ir.OLEN && ir.SameSafeExpr(n.X, n.High.(*ir.UnaryExpr).X) {
+		// Reduce x[i:len(x)] to x[i:].
+		n.High = nil
+	}
+	if (n.Op() == ir.OSLICE || n.Op() == ir.OSLICESTR) && n.Low == nil && n.High == nil {
+		// Reduce x[:] to x.
+		if base.Debug.Slice > 0 {
+			base.Warn("slice: omit slice operation")
+		}
+		return n.X
+	}
+	return n
+}
+
+// return 1 if integer n must be in range [0, max), 0 otherwise
+func bounded(n ir.Node, max int64) bool {
+	if n.Type() == nil || !n.Type().IsInteger() {
+		return false
+	}
+
+	sign := n.Type().IsSigned()
+	bits := int32(8 * n.Type().Size())
+
+	if ir.IsSmallIntConst(n) {
+		v := ir.Int64Val(n)
+		return 0 <= v && v < max
+	}
+
+	switch n.Op() {
+	case ir.OAND, ir.OANDNOT:
+		n := n.(*ir.BinaryExpr)
+		v := int64(-1)
+		switch {
+		case ir.IsSmallIntConst(n.X):
+			v = ir.Int64Val(n.X)
+		case ir.IsSmallIntConst(n.Y):
+			v = ir.Int64Val(n.Y)
+			if n.Op() == ir.OANDNOT {
+				v = ^v
+				if !sign {
+					v &= 1<<uint(bits) - 1
+				}
+			}
+		}
+		if 0 <= v && v < max {
+			return true
+		}
+
+	case ir.OMOD:
+		n := n.(*ir.BinaryExpr)
+		if !sign && ir.IsSmallIntConst(n.Y) {
+			v := ir.Int64Val(n.Y)
+			if 0 <= v && v <= max {
+				return true
+			}
+		}
+
+	case ir.ODIV:
+		n := n.(*ir.BinaryExpr)
+		if !sign && ir.IsSmallIntConst(n.Y) {
+			v := ir.Int64Val(n.Y)
+			for bits > 0 && v >= 2 {
+				bits--
+				v >>= 1
+			}
+		}
+
+	case ir.ORSH:
+		n := n.(*ir.BinaryExpr)
+		if !sign && ir.IsSmallIntConst(n.Y) {
+			v := ir.Int64Val(n.Y)
+			if v > int64(bits) {
+				return true
+			}
+			bits -= int32(v)
+		}
+	}
+
+	if !sign && bits <= 62 && 1<<uint(bits) <= max {
+		return true
+	}
+
+	return false
+}
+
+// usemethod checks calls for uses of reflect.Type.{Method,MethodByName}.
+func usemethod(n *ir.CallExpr) {
+	// Don't mark reflect.(*rtype).Method, etc. themselves in the reflect package.
+	// Those functions may be alive via the itab, which should not cause all methods
+	// alive. We only want to mark their callers.
+	if base.Ctxt.Pkgpath == "reflect" {
+		switch ir.CurFunc.Nname.Sym().Name { // TODO: is there a better way than hardcoding the names?
+		case "(*rtype).Method", "(*rtype).MethodByName", "(*interfaceType).Method", "(*interfaceType).MethodByName":
+			return
+		}
+	}
+
+	dot, ok := n.X.(*ir.SelectorExpr)
+	if !ok {
+		return
+	}
+
+	// Looking for either direct method calls and interface method calls of:
+	//	reflect.Type.Method       - func(int) reflect.Method
+	//	reflect.Type.MethodByName - func(string) (reflect.Method, bool)
+	var pKind types.Kind
+
+	switch dot.Sel.Name {
+	case "Method":
+		pKind = types.TINT
+	case "MethodByName":
+		pKind = types.TSTRING
+	default:
+		return
+	}
+
+	t := dot.Selection.Type
+	if t.NumParams() != 1 || t.Params().Field(0).Type.Kind() != pKind {
+		return
+	}
+	switch t.NumResults() {
+	case 1:
+		// ok
+	case 2:
+		if t.Results().Field(1).Type.Kind() != types.TBOOL {
+			return
+		}
+	default:
+		return
+	}
+
+	// Check that first result type is "reflect.Method". Note that we have to check sym name and sym package
+	// separately, as we can't check for exact string "reflect.Method" reliably (e.g., see #19028 and #38515).
+	if s := t.Results().Field(0).Type.Sym(); s != nil && s.Name == "Method" && types.IsReflectPkg(s.Pkg) {
+		ir.CurFunc.SetReflectMethod(true)
+		// The LSym is initialized at this point. We need to set the attribute on the LSym.
+		ir.CurFunc.LSym.Set(obj.AttrReflectMethod, true)
+	}
+}
+
+func usefield(n *ir.SelectorExpr) {
+	if !buildcfg.Experiment.FieldTrack {
+		return
+	}
+
+	switch n.Op() {
+	default:
+		base.Fatalf("usefield %v", n.Op())
+
+	case ir.ODOT, ir.ODOTPTR:
+		break
+	}
+
+	field := n.Selection
+	if field == nil {
+		base.Fatalf("usefield %v %v without paramfld", n.X.Type(), n.Sel)
+	}
+	if field.Sym != n.Sel {
+		base.Fatalf("field inconsistency: %v != %v", field.Sym, n.Sel)
+	}
+	if !strings.Contains(field.Note, "go:\"track\"") {
+		return
+	}
+
+	outer := n.X.Type()
+	if outer.IsPtr() {
+		outer = outer.Elem()
+	}
+	if outer.Sym() == nil {
+		base.Errorf("tracked field must be in named struct type")
+	}
+	if !types.IsExported(field.Sym.Name) {
+		base.Errorf("tracked field must be exported (upper case)")
+	}
+
+	sym := reflectdata.TrackSym(outer, field)
+	if ir.CurFunc.FieldTrack == nil {
+		ir.CurFunc.FieldTrack = make(map[*obj.LSym]struct{})
+	}
+	ir.CurFunc.FieldTrack[sym] = struct{}{}
+}
diff --git a/src/cmd/compile/internal/walk/order.go b/src/cmd/compile/internal/walk/order.go
new file mode 100644
index 0000000..861c122
--- /dev/null
+++ b/src/cmd/compile/internal/walk/order.go
@@ -0,0 +1,1507 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"fmt"
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/staticinit"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/objabi"
+	"cmd/internal/src"
+)
+
+// Rewrite tree to use separate statements to enforce
+// order of evaluation. Makes walk easier, because it
+// can (after this runs) reorder at will within an expression.
+//
+// Rewrite m[k] op= r into m[k] = m[k] op r if op is / or %.
+//
+// Introduce temporaries as needed by runtime routines.
+// For example, the map runtime routines take the map key
+// by reference, so make sure all map keys are addressable
+// by copying them to temporaries as needed.
+// The same is true for channel operations.
+//
+// Arrange that map index expressions only appear in direct
+// assignments x = m[k] or m[k] = x, never in larger expressions.
+//
+// Arrange that receive expressions only appear in direct assignments
+// x = <-c or as standalone statements <-c, never in larger expressions.
+
+// TODO(rsc): The temporary introduction during multiple assignments
+// should be moved into this file, so that the temporaries can be cleaned
+// and so that conversions implicit in the OAS2FUNC and OAS2RECV
+// nodes can be made explicit and then have their temporaries cleaned.
+
+// TODO(rsc): Goto and multilevel break/continue can jump over
+// inserted VARKILL annotations. Work out a way to handle these.
+// The current implementation is safe, in that it will execute correctly.
+// But it won't reuse temporaries as aggressively as it might, and
+// it can result in unnecessary zeroing of those variables in the function
+// prologue.
+
+// orderState holds state during the ordering process.
+type orderState struct {
+	out  []ir.Node             // list of generated statements
+	temp []*ir.Name            // stack of temporary variables
+	free map[string][]*ir.Name // free list of unused temporaries, by type.LinkString().
+	edit func(ir.Node) ir.Node // cached closure of o.exprNoLHS
+}
+
+// Order rewrites fn.Nbody to apply the ordering constraints
+// described in the comment at the top of the file.
+func order(fn *ir.Func) {
+	if base.Flag.W > 1 {
+		s := fmt.Sprintf("\nbefore order %v", fn.Sym())
+		ir.DumpList(s, fn.Body)
+	}
+
+	orderBlock(&fn.Body, map[string][]*ir.Name{})
+}
+
+// append typechecks stmt and appends it to out.
+func (o *orderState) append(stmt ir.Node) {
+	o.out = append(o.out, typecheck.Stmt(stmt))
+}
+
+// newTemp allocates a new temporary with the given type,
+// pushes it onto the temp stack, and returns it.
+// If clear is true, newTemp emits code to zero the temporary.
+func (o *orderState) newTemp(t *types.Type, clear bool) *ir.Name {
+	var v *ir.Name
+	key := t.LinkString()
+	if a := o.free[key]; len(a) > 0 {
+		v = a[len(a)-1]
+		if !types.Identical(t, v.Type()) {
+			base.Fatalf("expected %L to have type %v", v, t)
+		}
+		o.free[key] = a[:len(a)-1]
+	} else {
+		v = typecheck.Temp(t)
+	}
+	if clear {
+		o.append(ir.NewAssignStmt(base.Pos, v, nil))
+	}
+
+	o.temp = append(o.temp, v)
+	return v
+}
+
+// copyExpr behaves like newTemp but also emits
+// code to initialize the temporary to the value n.
+func (o *orderState) copyExpr(n ir.Node) *ir.Name {
+	return o.copyExpr1(n, false)
+}
+
+// copyExprClear is like copyExpr but clears the temp before assignment.
+// It is provided for use when the evaluation of tmp = n turns into
+// a function call that is passed a pointer to the temporary as the output space.
+// If the call blocks before tmp has been written,
+// the garbage collector will still treat the temporary as live,
+// so we must zero it before entering that call.
+// Today, this only happens for channel receive operations.
+// (The other candidate would be map access, but map access
+// returns a pointer to the result data instead of taking a pointer
+// to be filled in.)
+func (o *orderState) copyExprClear(n ir.Node) *ir.Name {
+	return o.copyExpr1(n, true)
+}
+
+func (o *orderState) copyExpr1(n ir.Node, clear bool) *ir.Name {
+	t := n.Type()
+	v := o.newTemp(t, clear)
+	o.append(ir.NewAssignStmt(base.Pos, v, n))
+	return v
+}
+
+// cheapExpr returns a cheap version of n.
+// The definition of cheap is that n is a variable or constant.
+// If not, cheapExpr allocates a new tmp, emits tmp = n,
+// and then returns tmp.
+func (o *orderState) cheapExpr(n ir.Node) ir.Node {
+	if n == nil {
+		return nil
+	}
+
+	switch n.Op() {
+	case ir.ONAME, ir.OLITERAL, ir.ONIL:
+		return n
+	case ir.OLEN, ir.OCAP:
+		n := n.(*ir.UnaryExpr)
+		l := o.cheapExpr(n.X)
+		if l == n.X {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.UnaryExpr)
+		a.X = l
+		return typecheck.Expr(a)
+	}
+
+	return o.copyExpr(n)
+}
+
+// safeExpr returns a safe version of n.
+// The definition of safe is that n can appear multiple times
+// without violating the semantics of the original program,
+// and that assigning to the safe version has the same effect
+// as assigning to the original n.
+//
+// The intended use is to apply to x when rewriting x += y into x = x + y.
+func (o *orderState) safeExpr(n ir.Node) ir.Node {
+	switch n.Op() {
+	case ir.ONAME, ir.OLITERAL, ir.ONIL:
+		return n
+
+	case ir.OLEN, ir.OCAP:
+		n := n.(*ir.UnaryExpr)
+		l := o.safeExpr(n.X)
+		if l == n.X {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.UnaryExpr)
+		a.X = l
+		return typecheck.Expr(a)
+
+	case ir.ODOT:
+		n := n.(*ir.SelectorExpr)
+		l := o.safeExpr(n.X)
+		if l == n.X {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.SelectorExpr)
+		a.X = l
+		return typecheck.Expr(a)
+
+	case ir.ODOTPTR:
+		n := n.(*ir.SelectorExpr)
+		l := o.cheapExpr(n.X)
+		if l == n.X {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.SelectorExpr)
+		a.X = l
+		return typecheck.Expr(a)
+
+	case ir.ODEREF:
+		n := n.(*ir.StarExpr)
+		l := o.cheapExpr(n.X)
+		if l == n.X {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.StarExpr)
+		a.X = l
+		return typecheck.Expr(a)
+
+	case ir.OINDEX, ir.OINDEXMAP:
+		n := n.(*ir.IndexExpr)
+		var l ir.Node
+		if n.X.Type().IsArray() {
+			l = o.safeExpr(n.X)
+		} else {
+			l = o.cheapExpr(n.X)
+		}
+		r := o.cheapExpr(n.Index)
+		if l == n.X && r == n.Index {
+			return n
+		}
+		a := ir.SepCopy(n).(*ir.IndexExpr)
+		a.X = l
+		a.Index = r
+		return typecheck.Expr(a)
+
+	default:
+		base.Fatalf("order.safeExpr %v", n.Op())
+		return nil // not reached
+	}
+}
+
+// isaddrokay reports whether it is okay to pass n's address to runtime routines.
+// Taking the address of a variable makes the liveness and optimization analyses
+// lose track of where the variable's lifetime ends. To avoid hurting the analyses
+// of ordinary stack variables, those are not 'isaddrokay'. Temporaries are okay,
+// because we emit explicit VARKILL instructions marking the end of those
+// temporaries' lifetimes.
+func isaddrokay(n ir.Node) bool {
+	return ir.IsAddressable(n) && (n.Op() != ir.ONAME || n.(*ir.Name).Class == ir.PEXTERN || ir.IsAutoTmp(n))
+}
+
+// addrTemp ensures that n is okay to pass by address to runtime routines.
+// If the original argument n is not okay, addrTemp creates a tmp, emits
+// tmp = n, and then returns tmp.
+// The result of addrTemp MUST be assigned back to n, e.g.
+// 	n.Left = o.addrTemp(n.Left)
+func (o *orderState) addrTemp(n ir.Node) ir.Node {
+	if n.Op() == ir.OLITERAL || n.Op() == ir.ONIL {
+		// TODO: expand this to all static composite literal nodes?
+		n = typecheck.DefaultLit(n, nil)
+		types.CalcSize(n.Type())
+		vstat := readonlystaticname(n.Type())
+		var s staticinit.Schedule
+		s.StaticAssign(vstat, 0, n, n.Type())
+		if s.Out != nil {
+			base.Fatalf("staticassign of const generated code: %+v", n)
+		}
+		vstat = typecheck.Expr(vstat).(*ir.Name)
+		return vstat
+	}
+	if isaddrokay(n) {
+		return n
+	}
+	return o.copyExpr(n)
+}
+
+// mapKeyTemp prepares n to be a key in a map runtime call and returns n.
+// It should only be used for map runtime calls which have *_fast* versions.
+func (o *orderState) mapKeyTemp(t *types.Type, n ir.Node) ir.Node {
+	// Most map calls need to take the address of the key.
+	// Exception: map*_fast* calls. See golang.org/issue/19015.
+	alg := mapfast(t)
+	if alg == mapslow {
+		return o.addrTemp(n)
+	}
+	var kt *types.Type
+	switch alg {
+	case mapfast32:
+		kt = types.Types[types.TUINT32]
+	case mapfast64:
+		kt = types.Types[types.TUINT64]
+	case mapfast32ptr, mapfast64ptr:
+		kt = types.Types[types.TUNSAFEPTR]
+	case mapfaststr:
+		kt = types.Types[types.TSTRING]
+	}
+	nt := n.Type()
+	switch {
+	case nt == kt:
+		return n
+	case nt.Kind() == kt.Kind(), nt.IsPtrShaped() && kt.IsPtrShaped():
+		// can directly convert (e.g. named type to underlying type, or one pointer to another)
+		return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONVNOP, kt, n))
+	case nt.IsInteger() && kt.IsInteger():
+		// can directly convert (e.g. int32 to uint32)
+		if n.Op() == ir.OLITERAL && nt.IsSigned() {
+			// avoid constant overflow error
+			n = ir.NewConstExpr(constant.MakeUint64(uint64(ir.Int64Val(n))), n)
+			n.SetType(kt)
+			return n
+		}
+		return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONV, kt, n))
+	default:
+		// Unsafe cast through memory.
+		// We'll need to do a load with type kt. Create a temporary of type kt to
+		// ensure sufficient alignment. nt may be under-aligned.
+		if uint8(kt.Alignment()) < uint8(nt.Alignment()) {
+			base.Fatalf("mapKeyTemp: key type is not sufficiently aligned, kt=%v nt=%v", kt, nt)
+		}
+		tmp := o.newTemp(kt, true)
+		// *(*nt)(&tmp) = n
+		var e ir.Node = typecheck.NodAddr(tmp)
+		e = ir.NewConvExpr(n.Pos(), ir.OCONVNOP, nt.PtrTo(), e)
+		e = ir.NewStarExpr(n.Pos(), e)
+		o.append(ir.NewAssignStmt(base.Pos, e, n))
+		return tmp
+	}
+}
+
+// mapKeyReplaceStrConv replaces OBYTES2STR by OBYTES2STRTMP
+// in n to avoid string allocations for keys in map lookups.
+// Returns a bool that signals if a modification was made.
+//
+// For:
+//  x = m[string(k)]
+//  x = m[T1{... Tn{..., string(k), ...}]
+// where k is []byte, T1 to Tn is a nesting of struct and array literals,
+// the allocation of backing bytes for the string can be avoided
+// by reusing the []byte backing array. These are special cases
+// for avoiding allocations when converting byte slices to strings.
+// It would be nice to handle these generally, but because
+// []byte keys are not allowed in maps, the use of string(k)
+// comes up in important cases in practice. See issue 3512.
+func mapKeyReplaceStrConv(n ir.Node) bool {
+	var replaced bool
+	switch n.Op() {
+	case ir.OBYTES2STR:
+		n := n.(*ir.ConvExpr)
+		n.SetOp(ir.OBYTES2STRTMP)
+		replaced = true
+	case ir.OSTRUCTLIT:
+		n := n.(*ir.CompLitExpr)
+		for _, elem := range n.List {
+			elem := elem.(*ir.StructKeyExpr)
+			if mapKeyReplaceStrConv(elem.Value) {
+				replaced = true
+			}
+		}
+	case ir.OARRAYLIT:
+		n := n.(*ir.CompLitExpr)
+		for _, elem := range n.List {
+			if elem.Op() == ir.OKEY {
+				elem = elem.(*ir.KeyExpr).Value
+			}
+			if mapKeyReplaceStrConv(elem) {
+				replaced = true
+			}
+		}
+	}
+	return replaced
+}
+
+type ordermarker int
+
+// markTemp returns the top of the temporary variable stack.
+func (o *orderState) markTemp() ordermarker {
+	return ordermarker(len(o.temp))
+}
+
+// popTemp pops temporaries off the stack until reaching the mark,
+// which must have been returned by markTemp.
+func (o *orderState) popTemp(mark ordermarker) {
+	for _, n := range o.temp[mark:] {
+		key := n.Type().LinkString()
+		o.free[key] = append(o.free[key], n)
+	}
+	o.temp = o.temp[:mark]
+}
+
+// cleanTempNoPop emits VARKILL instructions to *out
+// for each temporary above the mark on the temporary stack.
+// It does not pop the temporaries from the stack.
+func (o *orderState) cleanTempNoPop(mark ordermarker) []ir.Node {
+	var out []ir.Node
+	for i := len(o.temp) - 1; i >= int(mark); i-- {
+		n := o.temp[i]
+		out = append(out, typecheck.Stmt(ir.NewUnaryExpr(base.Pos, ir.OVARKILL, n)))
+	}
+	return out
+}
+
+// cleanTemp emits VARKILL instructions for each temporary above the
+// mark on the temporary stack and removes them from the stack.
+func (o *orderState) cleanTemp(top ordermarker) {
+	o.out = append(o.out, o.cleanTempNoPop(top)...)
+	o.popTemp(top)
+}
+
+// stmtList orders each of the statements in the list.
+func (o *orderState) stmtList(l ir.Nodes) {
+	s := l
+	for i := range s {
+		orderMakeSliceCopy(s[i:])
+		o.stmt(s[i])
+	}
+}
+
+// orderMakeSliceCopy matches the pattern:
+//  m = OMAKESLICE([]T, x); OCOPY(m, s)
+// and rewrites it to:
+//  m = OMAKESLICECOPY([]T, x, s); nil
+func orderMakeSliceCopy(s []ir.Node) {
+	if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
+		return
+	}
+	if len(s) < 2 || s[0] == nil || s[0].Op() != ir.OAS || s[1] == nil || s[1].Op() != ir.OCOPY {
+		return
+	}
+
+	as := s[0].(*ir.AssignStmt)
+	cp := s[1].(*ir.BinaryExpr)
+	if as.Y == nil || as.Y.Op() != ir.OMAKESLICE || ir.IsBlank(as.X) ||
+		as.X.Op() != ir.ONAME || cp.X.Op() != ir.ONAME || cp.Y.Op() != ir.ONAME ||
+		as.X.Name() != cp.X.Name() || cp.X.Name() == cp.Y.Name() {
+		// The line above this one is correct with the differing equality operators:
+		// we want as.X and cp.X to be the same name,
+		// but we want the initial data to be coming from a different name.
+		return
+	}
+
+	mk := as.Y.(*ir.MakeExpr)
+	if mk.Esc() == ir.EscNone || mk.Len == nil || mk.Cap != nil {
+		return
+	}
+	mk.SetOp(ir.OMAKESLICECOPY)
+	mk.Cap = cp.Y
+	// Set bounded when m = OMAKESLICE([]T, len(s)); OCOPY(m, s)
+	mk.SetBounded(mk.Len.Op() == ir.OLEN && ir.SameSafeExpr(mk.Len.(*ir.UnaryExpr).X, cp.Y))
+	as.Y = typecheck.Expr(mk)
+	s[1] = nil // remove separate copy call
+}
+
+// edge inserts coverage instrumentation for libfuzzer.
+func (o *orderState) edge() {
+	if base.Debug.Libfuzzer == 0 {
+		return
+	}
+
+	// Create a new uint8 counter to be allocated in section
+	// __libfuzzer_extra_counters.
+	counter := staticinit.StaticName(types.Types[types.TUINT8])
+	counter.SetLibfuzzerExtraCounter(true)
+	// As well as setting SetLibfuzzerExtraCounter, we preemptively set the
+	// symbol type to SLIBFUZZER_EXTRA_COUNTER so that the race detector
+	// instrumentation pass (which does not have access to the flags set by
+	// SetLibfuzzerExtraCounter) knows to ignore them. This information is
+	// lost by the time it reaches the compile step, so SetLibfuzzerExtraCounter
+	// is still necessary.
+	counter.Linksym().Type = objabi.SLIBFUZZER_EXTRA_COUNTER
+
+	// counter += 1
+	incr := ir.NewAssignOpStmt(base.Pos, ir.OADD, counter, ir.NewInt(1))
+	o.append(incr)
+}
+
+// orderBlock orders the block of statements in n into a new slice,
+// and then replaces the old slice in n with the new slice.
+// free is a map that can be used to obtain temporary variables by type.
+func orderBlock(n *ir.Nodes, free map[string][]*ir.Name) {
+	var order orderState
+	order.free = free
+	mark := order.markTemp()
+	order.edge()
+	order.stmtList(*n)
+	order.cleanTemp(mark)
+	*n = order.out
+}
+
+// exprInPlace orders the side effects in *np and
+// leaves them as the init list of the final *np.
+// The result of exprInPlace MUST be assigned back to n, e.g.
+// 	n.Left = o.exprInPlace(n.Left)
+func (o *orderState) exprInPlace(n ir.Node) ir.Node {
+	var order orderState
+	order.free = o.free
+	n = order.expr(n, nil)
+	n = ir.InitExpr(order.out, n)
+
+	// insert new temporaries from order
+	// at head of outer list.
+	o.temp = append(o.temp, order.temp...)
+	return n
+}
+
+// orderStmtInPlace orders the side effects of the single statement *np
+// and replaces it with the resulting statement list.
+// The result of orderStmtInPlace MUST be assigned back to n, e.g.
+// 	n.Left = orderStmtInPlace(n.Left)
+// free is a map that can be used to obtain temporary variables by type.
+func orderStmtInPlace(n ir.Node, free map[string][]*ir.Name) ir.Node {
+	var order orderState
+	order.free = free
+	mark := order.markTemp()
+	order.stmt(n)
+	order.cleanTemp(mark)
+	return ir.NewBlockStmt(src.NoXPos, order.out)
+}
+
+// init moves n's init list to o.out.
+func (o *orderState) init(n ir.Node) {
+	if ir.MayBeShared(n) {
+		// For concurrency safety, don't mutate potentially shared nodes.
+		// First, ensure that no work is required here.
+		if len(n.Init()) > 0 {
+			base.Fatalf("order.init shared node with ninit")
+		}
+		return
+	}
+	o.stmtList(ir.TakeInit(n))
+}
+
+// call orders the call expression n.
+// n.Op is OCALLFUNC/OCALLINTER or a builtin like OCOPY.
+func (o *orderState) call(nn ir.Node) {
+	if len(nn.Init()) > 0 {
+		// Caller should have already called o.init(nn).
+		base.Fatalf("%v with unexpected ninit", nn.Op())
+	}
+	if nn.Op() == ir.OCALLMETH {
+		base.FatalfAt(nn.Pos(), "OCALLMETH missed by typecheck")
+	}
+
+	// Builtin functions.
+	if nn.Op() != ir.OCALLFUNC && nn.Op() != ir.OCALLINTER {
+		switch n := nn.(type) {
+		default:
+			base.Fatalf("unexpected call: %+v", n)
+		case *ir.UnaryExpr:
+			n.X = o.expr(n.X, nil)
+		case *ir.ConvExpr:
+			n.X = o.expr(n.X, nil)
+		case *ir.BinaryExpr:
+			n.X = o.expr(n.X, nil)
+			n.Y = o.expr(n.Y, nil)
+		case *ir.MakeExpr:
+			n.Len = o.expr(n.Len, nil)
+			n.Cap = o.expr(n.Cap, nil)
+		case *ir.CallExpr:
+			o.exprList(n.Args)
+		}
+		return
+	}
+
+	n := nn.(*ir.CallExpr)
+	typecheck.FixVariadicCall(n)
+
+	if isFuncPCIntrinsic(n) && isIfaceOfFunc(n.Args[0]) {
+		// For internal/abi.FuncPCABIxxx(fn), if fn is a defined function,
+		// do not introduce temporaries here, so it is easier to rewrite it
+		// to symbol address reference later in walk.
+		return
+	}
+
+	n.X = o.expr(n.X, nil)
+	o.exprList(n.Args)
+}
+
+// mapAssign appends n to o.out.
+func (o *orderState) mapAssign(n ir.Node) {
+	switch n.Op() {
+	default:
+		base.Fatalf("order.mapAssign %v", n.Op())
+
+	case ir.OAS:
+		n := n.(*ir.AssignStmt)
+		if n.X.Op() == ir.OINDEXMAP {
+			n.Y = o.safeMapRHS(n.Y)
+		}
+		o.out = append(o.out, n)
+	case ir.OASOP:
+		n := n.(*ir.AssignOpStmt)
+		if n.X.Op() == ir.OINDEXMAP {
+			n.Y = o.safeMapRHS(n.Y)
+		}
+		o.out = append(o.out, n)
+	}
+}
+
+func (o *orderState) safeMapRHS(r ir.Node) ir.Node {
+	// Make sure we evaluate the RHS before starting the map insert.
+	// We need to make sure the RHS won't panic.  See issue 22881.
+	if r.Op() == ir.OAPPEND {
+		r := r.(*ir.CallExpr)
+		s := r.Args[1:]
+		for i, n := range s {
+			s[i] = o.cheapExpr(n)
+		}
+		return r
+	}
+	return o.cheapExpr(r)
+}
+
+// stmt orders the statement n, appending to o.out.
+// Temporaries created during the statement are cleaned
+// up using VARKILL instructions as possible.
+func (o *orderState) stmt(n ir.Node) {
+	if n == nil {
+		return
+	}
+
+	lno := ir.SetPos(n)
+	o.init(n)
+
+	switch n.Op() {
+	default:
+		base.Fatalf("order.stmt %v", n.Op())
+
+	case ir.OVARKILL, ir.OVARLIVE, ir.OINLMARK:
+		o.out = append(o.out, n)
+
+	case ir.OAS:
+		n := n.(*ir.AssignStmt)
+		t := o.markTemp()
+		n.X = o.expr(n.X, nil)
+		n.Y = o.expr(n.Y, n.X)
+		o.mapAssign(n)
+		o.cleanTemp(t)
+
+	case ir.OASOP:
+		n := n.(*ir.AssignOpStmt)
+		t := o.markTemp()
+		n.X = o.expr(n.X, nil)
+		n.Y = o.expr(n.Y, nil)
+
+		if base.Flag.Cfg.Instrumenting || n.X.Op() == ir.OINDEXMAP && (n.AsOp == ir.ODIV || n.AsOp == ir.OMOD) {
+			// Rewrite m[k] op= r into m[k] = m[k] op r so
+			// that we can ensure that if op panics
+			// because r is zero, the panic happens before
+			// the map assignment.
+			// DeepCopy is a big hammer here, but safeExpr
+			// makes sure there is nothing too deep being copied.
+			l1 := o.safeExpr(n.X)
+			l2 := ir.DeepCopy(src.NoXPos, l1)
+			if l2.Op() == ir.OINDEXMAP {
+				l2 := l2.(*ir.IndexExpr)
+				l2.Assigned = false
+			}
+			l2 = o.copyExpr(l2)
+			r := o.expr(typecheck.Expr(ir.NewBinaryExpr(n.Pos(), n.AsOp, l2, n.Y)), nil)
+			as := typecheck.Stmt(ir.NewAssignStmt(n.Pos(), l1, r))
+			o.mapAssign(as)
+			o.cleanTemp(t)
+			return
+		}
+
+		o.mapAssign(n)
+		o.cleanTemp(t)
+
+	case ir.OAS2:
+		n := n.(*ir.AssignListStmt)
+		t := o.markTemp()
+		o.exprList(n.Lhs)
+		o.exprList(n.Rhs)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	// Special: avoid copy of func call n.Right
+	case ir.OAS2FUNC:
+		n := n.(*ir.AssignListStmt)
+		t := o.markTemp()
+		o.exprList(n.Lhs)
+		call := n.Rhs[0]
+		o.init(call)
+		if ic, ok := call.(*ir.InlinedCallExpr); ok {
+			o.stmtList(ic.Body)
+
+			n.SetOp(ir.OAS2)
+			n.Rhs = ic.ReturnVars
+
+			o.exprList(n.Rhs)
+			o.out = append(o.out, n)
+		} else {
+			o.call(call)
+			o.as2func(n)
+		}
+		o.cleanTemp(t)
+
+	// Special: use temporary variables to hold result,
+	// so that runtime can take address of temporary.
+	// No temporary for blank assignment.
+	//
+	// OAS2MAPR: make sure key is addressable if needed,
+	//           and make sure OINDEXMAP is not copied out.
+	case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
+		n := n.(*ir.AssignListStmt)
+		t := o.markTemp()
+		o.exprList(n.Lhs)
+
+		switch r := n.Rhs[0]; r.Op() {
+		case ir.ODOTTYPE2:
+			r := r.(*ir.TypeAssertExpr)
+			r.X = o.expr(r.X, nil)
+		case ir.ODYNAMICDOTTYPE2:
+			r := r.(*ir.DynamicTypeAssertExpr)
+			r.X = o.expr(r.X, nil)
+			r.T = o.expr(r.T, nil)
+		case ir.ORECV:
+			r := r.(*ir.UnaryExpr)
+			r.X = o.expr(r.X, nil)
+		case ir.OINDEXMAP:
+			r := r.(*ir.IndexExpr)
+			r.X = o.expr(r.X, nil)
+			r.Index = o.expr(r.Index, nil)
+			// See similar conversion for OINDEXMAP below.
+			_ = mapKeyReplaceStrConv(r.Index)
+			r.Index = o.mapKeyTemp(r.X.Type(), r.Index)
+		default:
+			base.Fatalf("order.stmt: %v", r.Op())
+		}
+
+		o.as2ok(n)
+		o.cleanTemp(t)
+
+	// Special: does not save n onto out.
+	case ir.OBLOCK:
+		n := n.(*ir.BlockStmt)
+		o.stmtList(n.List)
+
+	// Special: n->left is not an expression; save as is.
+	case ir.OBREAK,
+		ir.OCONTINUE,
+		ir.ODCL,
+		ir.ODCLCONST,
+		ir.ODCLTYPE,
+		ir.OFALL,
+		ir.OGOTO,
+		ir.OLABEL,
+		ir.OTAILCALL:
+		o.out = append(o.out, n)
+
+	// Special: handle call arguments.
+	case ir.OCALLFUNC, ir.OCALLINTER:
+		n := n.(*ir.CallExpr)
+		t := o.markTemp()
+		o.call(n)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	case ir.OINLCALL:
+		n := n.(*ir.InlinedCallExpr)
+		o.stmtList(n.Body)
+
+		// discard results; double-check for no side effects
+		for _, result := range n.ReturnVars {
+			if staticinit.AnySideEffects(result) {
+				base.FatalfAt(result.Pos(), "inlined call result has side effects: %v", result)
+			}
+		}
+
+	case ir.OCHECKNIL, ir.OCLOSE, ir.OPANIC, ir.ORECV:
+		n := n.(*ir.UnaryExpr)
+		t := o.markTemp()
+		n.X = o.expr(n.X, nil)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	case ir.OCOPY:
+		n := n.(*ir.BinaryExpr)
+		t := o.markTemp()
+		n.X = o.expr(n.X, nil)
+		n.Y = o.expr(n.Y, nil)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	case ir.OPRINT, ir.OPRINTN, ir.ORECOVERFP:
+		n := n.(*ir.CallExpr)
+		t := o.markTemp()
+		o.call(n)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	// Special: order arguments to inner call but not call itself.
+	case ir.ODEFER, ir.OGO:
+		n := n.(*ir.GoDeferStmt)
+		t := o.markTemp()
+		o.init(n.Call)
+		o.call(n.Call)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	case ir.ODELETE:
+		n := n.(*ir.CallExpr)
+		t := o.markTemp()
+		n.Args[0] = o.expr(n.Args[0], nil)
+		n.Args[1] = o.expr(n.Args[1], nil)
+		n.Args[1] = o.mapKeyTemp(n.Args[0].Type(), n.Args[1])
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	// Clean temporaries from condition evaluation at
+	// beginning of loop body and after for statement.
+	case ir.OFOR:
+		n := n.(*ir.ForStmt)
+		t := o.markTemp()
+		n.Cond = o.exprInPlace(n.Cond)
+		n.Body.Prepend(o.cleanTempNoPop(t)...)
+		orderBlock(&n.Body, o.free)
+		n.Post = orderStmtInPlace(n.Post, o.free)
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	// Clean temporaries from condition at
+	// beginning of both branches.
+	case ir.OIF:
+		n := n.(*ir.IfStmt)
+		t := o.markTemp()
+		n.Cond = o.exprInPlace(n.Cond)
+		n.Body.Prepend(o.cleanTempNoPop(t)...)
+		n.Else.Prepend(o.cleanTempNoPop(t)...)
+		o.popTemp(t)
+		orderBlock(&n.Body, o.free)
+		orderBlock(&n.Else, o.free)
+		o.out = append(o.out, n)
+
+	case ir.ORANGE:
+		// n.Right is the expression being ranged over.
+		// order it, and then make a copy if we need one.
+		// We almost always do, to ensure that we don't
+		// see any value changes made during the loop.
+		// Usually the copy is cheap (e.g., array pointer,
+		// chan, slice, string are all tiny).
+		// The exception is ranging over an array value
+		// (not a slice, not a pointer to array),
+		// which must make a copy to avoid seeing updates made during
+		// the range body. Ranging over an array value is uncommon though.
+
+		// Mark []byte(str) range expression to reuse string backing storage.
+		// It is safe because the storage cannot be mutated.
+		n := n.(*ir.RangeStmt)
+		if n.X.Op() == ir.OSTR2BYTES {
+			n.X.(*ir.ConvExpr).SetOp(ir.OSTR2BYTESTMP)
+		}
+
+		t := o.markTemp()
+		n.X = o.expr(n.X, nil)
+
+		orderBody := true
+		xt := typecheck.RangeExprType(n.X.Type())
+		switch xt.Kind() {
+		default:
+			base.Fatalf("order.stmt range %v", n.Type())
+
+		case types.TARRAY, types.TSLICE:
+			if n.Value == nil || ir.IsBlank(n.Value) {
+				// for i := range x will only use x once, to compute len(x).
+				// No need to copy it.
+				break
+			}
+			fallthrough
+
+		case types.TCHAN, types.TSTRING:
+			// chan, string, slice, array ranges use value multiple times.
+			// make copy.
+			r := n.X
+
+			if r.Type().IsString() && r.Type() != types.Types[types.TSTRING] {
+				r = ir.NewConvExpr(base.Pos, ir.OCONV, nil, r)
+				r.SetType(types.Types[types.TSTRING])
+				r = typecheck.Expr(r)
+			}
+
+			n.X = o.copyExpr(r)
+
+		case types.TMAP:
+			if isMapClear(n) {
+				// Preserve the body of the map clear pattern so it can
+				// be detected during walk. The loop body will not be used
+				// when optimizing away the range loop to a runtime call.
+				orderBody = false
+				break
+			}
+
+			// copy the map value in case it is a map literal.
+			// TODO(rsc): Make tmp = literal expressions reuse tmp.
+			// For maps tmp is just one word so it hardly matters.
+			r := n.X
+			n.X = o.copyExpr(r)
+
+			// n.Prealloc is the temp for the iterator.
+			// MapIterType contains pointers and needs to be zeroed.
+			n.Prealloc = o.newTemp(reflectdata.MapIterType(xt), true)
+		}
+		n.Key = o.exprInPlace(n.Key)
+		n.Value = o.exprInPlace(n.Value)
+		if orderBody {
+			orderBlock(&n.Body, o.free)
+		}
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	case ir.ORETURN:
+		n := n.(*ir.ReturnStmt)
+		o.exprList(n.Results)
+		o.out = append(o.out, n)
+
+	// Special: clean case temporaries in each block entry.
+	// Select must enter one of its blocks, so there is no
+	// need for a cleaning at the end.
+	// Doubly special: evaluation order for select is stricter
+	// than ordinary expressions. Even something like p.c
+	// has to be hoisted into a temporary, so that it cannot be
+	// reordered after the channel evaluation for a different
+	// case (if p were nil, then the timing of the fault would
+	// give this away).
+	case ir.OSELECT:
+		n := n.(*ir.SelectStmt)
+		t := o.markTemp()
+		for _, ncas := range n.Cases {
+			r := ncas.Comm
+			ir.SetPos(ncas)
+
+			// Append any new body prologue to ninit.
+			// The next loop will insert ninit into nbody.
+			if len(ncas.Init()) != 0 {
+				base.Fatalf("order select ninit")
+			}
+			if r == nil {
+				continue
+			}
+			switch r.Op() {
+			default:
+				ir.Dump("select case", r)
+				base.Fatalf("unknown op in select %v", r.Op())
+
+			case ir.OSELRECV2:
+				// case x, ok = <-c
+				r := r.(*ir.AssignListStmt)
+				recv := r.Rhs[0].(*ir.UnaryExpr)
+				recv.X = o.expr(recv.X, nil)
+				if !ir.IsAutoTmp(recv.X) {
+					recv.X = o.copyExpr(recv.X)
+				}
+				init := ir.TakeInit(r)
+
+				colas := r.Def
+				do := func(i int, t *types.Type) {
+					n := r.Lhs[i]
+					if ir.IsBlank(n) {
+						return
+					}
+					// If this is case x := <-ch or case x, y := <-ch, the case has
+					// the ODCL nodes to declare x and y. We want to delay that
+					// declaration (and possible allocation) until inside the case body.
+					// Delete the ODCL nodes here and recreate them inside the body below.
+					if colas {
+						if len(init) > 0 && init[0].Op() == ir.ODCL && init[0].(*ir.Decl).X == n {
+							init = init[1:]
+
+							// iimport may have added a default initialization assignment,
+							// due to how it handles ODCL statements.
+							if len(init) > 0 && init[0].Op() == ir.OAS && init[0].(*ir.AssignStmt).X == n {
+								init = init[1:]
+							}
+						}
+						dcl := typecheck.Stmt(ir.NewDecl(base.Pos, ir.ODCL, n.(*ir.Name)))
+						ncas.PtrInit().Append(dcl)
+					}
+					tmp := o.newTemp(t, t.HasPointers())
+					as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, n, typecheck.Conv(tmp, n.Type())))
+					ncas.PtrInit().Append(as)
+					r.Lhs[i] = tmp
+				}
+				do(0, recv.X.Type().Elem())
+				do(1, types.Types[types.TBOOL])
+				if len(init) != 0 {
+					ir.DumpList("ninit", r.Init())
+					base.Fatalf("ninit on select recv")
+				}
+				orderBlock(ncas.PtrInit(), o.free)
+
+			case ir.OSEND:
+				r := r.(*ir.SendStmt)
+				if len(r.Init()) != 0 {
+					ir.DumpList("ninit", r.Init())
+					base.Fatalf("ninit on select send")
+				}
+
+				// case c <- x
+				// r->left is c, r->right is x, both are always evaluated.
+				r.Chan = o.expr(r.Chan, nil)
+
+				if !ir.IsAutoTmp(r.Chan) {
+					r.Chan = o.copyExpr(r.Chan)
+				}
+				r.Value = o.expr(r.Value, nil)
+				if !ir.IsAutoTmp(r.Value) {
+					r.Value = o.copyExpr(r.Value)
+				}
+			}
+		}
+		// Now that we have accumulated all the temporaries, clean them.
+		// Also insert any ninit queued during the previous loop.
+		// (The temporary cleaning must follow that ninit work.)
+		for _, cas := range n.Cases {
+			orderBlock(&cas.Body, o.free)
+			cas.Body.Prepend(o.cleanTempNoPop(t)...)
+
+			// TODO(mdempsky): Is this actually necessary?
+			// walkSelect appears to walk Ninit.
+			cas.Body.Prepend(ir.TakeInit(cas)...)
+		}
+
+		o.out = append(o.out, n)
+		o.popTemp(t)
+
+	// Special: value being sent is passed as a pointer; make it addressable.
+	case ir.OSEND:
+		n := n.(*ir.SendStmt)
+		t := o.markTemp()
+		n.Chan = o.expr(n.Chan, nil)
+		n.Value = o.expr(n.Value, nil)
+		if base.Flag.Cfg.Instrumenting {
+			// Force copying to the stack so that (chan T)(nil) <- x
+			// is still instrumented as a read of x.
+			n.Value = o.copyExpr(n.Value)
+		} else {
+			n.Value = o.addrTemp(n.Value)
+		}
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+
+	// TODO(rsc): Clean temporaries more aggressively.
+	// Note that because walkSwitch will rewrite some of the
+	// switch into a binary search, this is not as easy as it looks.
+	// (If we ran that code here we could invoke order.stmt on
+	// the if-else chain instead.)
+	// For now just clean all the temporaries at the end.
+	// In practice that's fine.
+	case ir.OSWITCH:
+		n := n.(*ir.SwitchStmt)
+		if base.Debug.Libfuzzer != 0 && !hasDefaultCase(n) {
+			// Add empty "default:" case for instrumentation.
+			n.Cases = append(n.Cases, ir.NewCaseStmt(base.Pos, nil, nil))
+		}
+
+		t := o.markTemp()
+		n.Tag = o.expr(n.Tag, nil)
+		for _, ncas := range n.Cases {
+			o.exprListInPlace(ncas.List)
+			orderBlock(&ncas.Body, o.free)
+		}
+
+		o.out = append(o.out, n)
+		o.cleanTemp(t)
+	}
+
+	base.Pos = lno
+}
+
+func hasDefaultCase(n *ir.SwitchStmt) bool {
+	for _, ncas := range n.Cases {
+		if len(ncas.List) == 0 {
+			return true
+		}
+	}
+	return false
+}
+
+// exprList orders the expression list l into o.
+func (o *orderState) exprList(l ir.Nodes) {
+	s := l
+	for i := range s {
+		s[i] = o.expr(s[i], nil)
+	}
+}
+
+// exprListInPlace orders the expression list l but saves
+// the side effects on the individual expression ninit lists.
+func (o *orderState) exprListInPlace(l ir.Nodes) {
+	s := l
+	for i := range s {
+		s[i] = o.exprInPlace(s[i])
+	}
+}
+
+func (o *orderState) exprNoLHS(n ir.Node) ir.Node {
+	return o.expr(n, nil)
+}
+
+// expr orders a single expression, appending side
+// effects to o.out as needed.
+// If this is part of an assignment lhs = *np, lhs is given.
+// Otherwise lhs == nil. (When lhs != nil it may be possible
+// to avoid copying the result of the expression to a temporary.)
+// The result of expr MUST be assigned back to n, e.g.
+// 	n.Left = o.expr(n.Left, lhs)
+func (o *orderState) expr(n, lhs ir.Node) ir.Node {
+	if n == nil {
+		return n
+	}
+	lno := ir.SetPos(n)
+	n = o.expr1(n, lhs)
+	base.Pos = lno
+	return n
+}
+
+func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
+	o.init(n)
+
+	switch n.Op() {
+	default:
+		if o.edit == nil {
+			o.edit = o.exprNoLHS // create closure once
+		}
+		ir.EditChildren(n, o.edit)
+		return n
+
+	// Addition of strings turns into a function call.
+	// Allocate a temporary to hold the strings.
+	// Fewer than 5 strings use direct runtime helpers.
+	case ir.OADDSTR:
+		n := n.(*ir.AddStringExpr)
+		o.exprList(n.List)
+
+		if len(n.List) > 5 {
+			t := types.NewArray(types.Types[types.TSTRING], int64(len(n.List)))
+			n.Prealloc = o.newTemp(t, false)
+		}
+
+		// Mark string(byteSlice) arguments to reuse byteSlice backing
+		// buffer during conversion. String concatenation does not
+		// memorize the strings for later use, so it is safe.
+		// However, we can do it only if there is at least one non-empty string literal.
+		// Otherwise if all other arguments are empty strings,
+		// concatstrings will return the reference to the temp string
+		// to the caller.
+		hasbyte := false
+
+		haslit := false
+		for _, n1 := range n.List {
+			hasbyte = hasbyte || n1.Op() == ir.OBYTES2STR
+			haslit = haslit || n1.Op() == ir.OLITERAL && len(ir.StringVal(n1)) != 0
+		}
+
+		if haslit && hasbyte {
+			for _, n2 := range n.List {
+				if n2.Op() == ir.OBYTES2STR {
+					n2 := n2.(*ir.ConvExpr)
+					n2.SetOp(ir.OBYTES2STRTMP)
+				}
+			}
+		}
+		return n
+
+	case ir.OINDEXMAP:
+		n := n.(*ir.IndexExpr)
+		n.X = o.expr(n.X, nil)
+		n.Index = o.expr(n.Index, nil)
+		needCopy := false
+
+		if !n.Assigned {
+			// Enforce that any []byte slices we are not copying
+			// can not be changed before the map index by forcing
+			// the map index to happen immediately following the
+			// conversions. See copyExpr a few lines below.
+			needCopy = mapKeyReplaceStrConv(n.Index)
+
+			if base.Flag.Cfg.Instrumenting {
+				// Race detector needs the copy.
+				needCopy = true
+			}
+		}
+
+		// key must be addressable
+		n.Index = o.mapKeyTemp(n.X.Type(), n.Index)
+		if needCopy {
+			return o.copyExpr(n)
+		}
+		return n
+
+	// concrete type (not interface) argument might need an addressable
+	// temporary to pass to the runtime conversion routine.
+	case ir.OCONVIFACE, ir.OCONVIDATA:
+		n := n.(*ir.ConvExpr)
+		n.X = o.expr(n.X, nil)
+		if n.X.Type().IsInterface() {
+			return n
+		}
+		if _, _, needsaddr := dataWordFuncName(n.X.Type()); needsaddr || isStaticCompositeLiteral(n.X) {
+			// Need a temp if we need to pass the address to the conversion function.
+			// We also process static composite literal node here, making a named static global
+			// whose address we can put directly in an interface (see OCONVIFACE/OCONVIDATA case in walk).
+			n.X = o.addrTemp(n.X)
+		}
+		return n
+
+	case ir.OCONVNOP:
+		n := n.(*ir.ConvExpr)
+		if n.X.Op() == ir.OCALLMETH {
+			base.FatalfAt(n.X.Pos(), "OCALLMETH missed by typecheck")
+		}
+		if n.Type().IsKind(types.TUNSAFEPTR) && n.X.Type().IsKind(types.TUINTPTR) && (n.X.Op() == ir.OCALLFUNC || n.X.Op() == ir.OCALLINTER) {
+			call := n.X.(*ir.CallExpr)
+			// When reordering unsafe.Pointer(f()) into a separate
+			// statement, the conversion and function call must stay
+			// together. See golang.org/issue/15329.
+			o.init(call)
+			o.call(call)
+			if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
+				return o.copyExpr(n)
+			}
+		} else {
+			n.X = o.expr(n.X, nil)
+		}
+		return n
+
+	case ir.OANDAND, ir.OOROR:
+		// ... = LHS && RHS
+		//
+		// var r bool
+		// r = LHS
+		// if r {       // or !r, for OROR
+		//     r = RHS
+		// }
+		// ... = r
+
+		n := n.(*ir.LogicalExpr)
+		r := o.newTemp(n.Type(), false)
+
+		// Evaluate left-hand side.
+		lhs := o.expr(n.X, nil)
+		o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, lhs)))
+
+		// Evaluate right-hand side, save generated code.
+		saveout := o.out
+		o.out = nil
+		t := o.markTemp()
+		o.edge()
+		rhs := o.expr(n.Y, nil)
+		o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, rhs)))
+		o.cleanTemp(t)
+		gen := o.out
+		o.out = saveout
+
+		// If left-hand side doesn't cause a short-circuit, issue right-hand side.
+		nif := ir.NewIfStmt(base.Pos, r, nil, nil)
+		if n.Op() == ir.OANDAND {
+			nif.Body = gen
+		} else {
+			nif.Else = gen
+		}
+		o.out = append(o.out, nif)
+		return r
+
+	case ir.OCALLMETH:
+		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
+		panic("unreachable")
+
+	case ir.OCALLFUNC,
+		ir.OCALLINTER,
+		ir.OCAP,
+		ir.OCOMPLEX,
+		ir.OCOPY,
+		ir.OIMAG,
+		ir.OLEN,
+		ir.OMAKECHAN,
+		ir.OMAKEMAP,
+		ir.OMAKESLICE,
+		ir.OMAKESLICECOPY,
+		ir.ONEW,
+		ir.OREAL,
+		ir.ORECOVERFP,
+		ir.OSTR2BYTES,
+		ir.OSTR2BYTESTMP,
+		ir.OSTR2RUNES:
+
+		if isRuneCount(n) {
+			// len([]rune(s)) is rewritten to runtime.countrunes(s) later.
+			conv := n.(*ir.UnaryExpr).X.(*ir.ConvExpr)
+			conv.X = o.expr(conv.X, nil)
+		} else {
+			o.call(n)
+		}
+
+		if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
+			return o.copyExpr(n)
+		}
+		return n
+
+	case ir.OINLCALL:
+		n := n.(*ir.InlinedCallExpr)
+		o.stmtList(n.Body)
+		return n.SingleResult()
+
+	case ir.OAPPEND:
+		// Check for append(x, make([]T, y)...) .
+		n := n.(*ir.CallExpr)
+		if isAppendOfMake(n) {
+			n.Args[0] = o.expr(n.Args[0], nil) // order x
+			mk := n.Args[1].(*ir.MakeExpr)
+			mk.Len = o.expr(mk.Len, nil) // order y
+		} else {
+			o.exprList(n.Args)
+		}
+
+		if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.Args[0]) {
+			return o.copyExpr(n)
+		}
+		return n
+
+	case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
+		n := n.(*ir.SliceExpr)
+		n.X = o.expr(n.X, nil)
+		n.Low = o.cheapExpr(o.expr(n.Low, nil))
+		n.High = o.cheapExpr(o.expr(n.High, nil))
+		n.Max = o.cheapExpr(o.expr(n.Max, nil))
+		if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.X) {
+			return o.copyExpr(n)
+		}
+		return n
+
+	case ir.OCLOSURE:
+		n := n.(*ir.ClosureExpr)
+		if n.Transient() && len(n.Func.ClosureVars) > 0 {
+			n.Prealloc = o.newTemp(typecheck.ClosureType(n), false)
+		}
+		return n
+
+	case ir.OMETHVALUE:
+		n := n.(*ir.SelectorExpr)
+		n.X = o.expr(n.X, nil)
+		if n.Transient() {
+			t := typecheck.MethodValueType(n)
+			n.Prealloc = o.newTemp(t, false)
+		}
+		return n
+
+	case ir.OSLICELIT:
+		n := n.(*ir.CompLitExpr)
+		o.exprList(n.List)
+		if n.Transient() {
+			t := types.NewArray(n.Type().Elem(), n.Len)
+			n.Prealloc = o.newTemp(t, false)
+		}
+		return n
+
+	case ir.ODOTTYPE, ir.ODOTTYPE2:
+		n := n.(*ir.TypeAssertExpr)
+		n.X = o.expr(n.X, nil)
+		if !types.IsDirectIface(n.Type()) || base.Flag.Cfg.Instrumenting {
+			return o.copyExprClear(n)
+		}
+		return n
+
+	case ir.ORECV:
+		n := n.(*ir.UnaryExpr)
+		n.X = o.expr(n.X, nil)
+		return o.copyExprClear(n)
+
+	case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
+		n := n.(*ir.BinaryExpr)
+		n.X = o.expr(n.X, nil)
+		n.Y = o.expr(n.Y, nil)
+
+		t := n.X.Type()
+		switch {
+		case t.IsString():
+			// Mark string(byteSlice) arguments to reuse byteSlice backing
+			// buffer during conversion. String comparison does not
+			// memorize the strings for later use, so it is safe.
+			if n.X.Op() == ir.OBYTES2STR {
+				n.X.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
+			}
+			if n.Y.Op() == ir.OBYTES2STR {
+				n.Y.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
+			}
+
+		case t.IsStruct() || t.IsArray():
+			// for complex comparisons, we need both args to be
+			// addressable so we can pass them to the runtime.
+			n.X = o.addrTemp(n.X)
+			n.Y = o.addrTemp(n.Y)
+		}
+		return n
+
+	case ir.OMAPLIT:
+		// Order map by converting:
+		//   map[int]int{
+		//     a(): b(),
+		//     c(): d(),
+		//     e(): f(),
+		//   }
+		// to
+		//   m := map[int]int{}
+		//   m[a()] = b()
+		//   m[c()] = d()
+		//   m[e()] = f()
+		// Then order the result.
+		// Without this special case, order would otherwise compute all
+		// the keys and values before storing any of them to the map.
+		// See issue 26552.
+		n := n.(*ir.CompLitExpr)
+		entries := n.List
+		statics := entries[:0]
+		var dynamics []*ir.KeyExpr
+		for _, r := range entries {
+			r := r.(*ir.KeyExpr)
+
+			if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
+				dynamics = append(dynamics, r)
+				continue
+			}
+
+			// Recursively ordering some static entries can change them to dynamic;
+			// e.g., OCONVIFACE nodes. See #31777.
+			r = o.expr(r, nil).(*ir.KeyExpr)
+			if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
+				dynamics = append(dynamics, r)
+				continue
+			}
+
+			statics = append(statics, r)
+		}
+		n.List = statics
+
+		if len(dynamics) == 0 {
+			return n
+		}
+
+		// Emit the creation of the map (with all its static entries).
+		m := o.newTemp(n.Type(), false)
+		as := ir.NewAssignStmt(base.Pos, m, n)
+		typecheck.Stmt(as)
+		o.stmt(as)
+
+		// Emit eval+insert of dynamic entries, one at a time.
+		for _, r := range dynamics {
+			as := ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, r.Key), r.Value)
+			typecheck.Stmt(as) // Note: this converts the OINDEX to an OINDEXMAP
+			o.stmt(as)
+		}
+		return m
+	}
+
+	// No return - type-assertions above. Each case must return for itself.
+}
+
+// as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
+// The caller should order the right-hand side of the assignment before calling order.as2func.
+// It rewrites,
+//	a, b, a = ...
+// as
+//	tmp1, tmp2, tmp3 = ...
+//	a, b, a = tmp1, tmp2, tmp3
+// This is necessary to ensure left to right assignment order.
+func (o *orderState) as2func(n *ir.AssignListStmt) {
+	results := n.Rhs[0].Type()
+	as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
+	for i, nl := range n.Lhs {
+		if !ir.IsBlank(nl) {
+			typ := results.Field(i).Type
+			tmp := o.newTemp(typ, typ.HasPointers())
+			n.Lhs[i] = tmp
+			as.Lhs = append(as.Lhs, nl)
+			as.Rhs = append(as.Rhs, tmp)
+		}
+	}
+
+	o.out = append(o.out, n)
+	o.stmt(typecheck.Stmt(as))
+}
+
+// as2ok orders OAS2XXX with ok.
+// Just like as2func, this also adds temporaries to ensure left-to-right assignment.
+func (o *orderState) as2ok(n *ir.AssignListStmt) {
+	as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
+
+	do := func(i int, typ *types.Type) {
+		if nl := n.Lhs[i]; !ir.IsBlank(nl) {
+			var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
+			n.Lhs[i] = tmp
+			as.Lhs = append(as.Lhs, nl)
+			if i == 1 {
+				// The "ok" result is an untyped boolean according to the Go
+				// spec. We need to explicitly convert it to the LHS type in
+				// case the latter is a defined boolean type (#8475).
+				tmp = typecheck.Conv(tmp, nl.Type())
+			}
+			as.Rhs = append(as.Rhs, tmp)
+		}
+	}
+
+	do(0, n.Rhs[0].Type())
+	do(1, types.Types[types.TBOOL])
+
+	o.out = append(o.out, n)
+	o.stmt(typecheck.Stmt(as))
+}
+
+// isFuncPCIntrinsic returns whether n is a direct call of internal/abi.FuncPCABIxxx functions.
+func isFuncPCIntrinsic(n *ir.CallExpr) bool {
+	if n.Op() != ir.OCALLFUNC || n.X.Op() != ir.ONAME {
+		return false
+	}
+	fn := n.X.(*ir.Name).Sym()
+	return (fn.Name == "FuncPCABI0" || fn.Name == "FuncPCABIInternal") &&
+		(fn.Pkg.Path == "internal/abi" || fn.Pkg == types.LocalPkg && base.Ctxt.Pkgpath == "internal/abi")
+}
+
+// isIfaceOfFunc returns whether n is an interface conversion from a direct reference of a func.
+func isIfaceOfFunc(n ir.Node) bool {
+	return n.Op() == ir.OCONVIFACE && n.(*ir.ConvExpr).X.Op() == ir.ONAME && n.(*ir.ConvExpr).X.(*ir.Name).Class == ir.PFUNC
+}
diff --git a/src/cmd/compile/internal/walk/race.go b/src/cmd/compile/internal/walk/race.go
new file mode 100644
index 0000000..859e5c5
--- /dev/null
+++ b/src/cmd/compile/internal/walk/race.go
@@ -0,0 +1,34 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+func instrument(fn *ir.Func) {
+	if fn.Pragma&ir.Norace != 0 || (fn.Linksym() != nil && fn.Linksym().ABIWrapper()) {
+		return
+	}
+
+	if !base.Flag.Race || !base.Compiling(base.NoRacePkgs) {
+		fn.SetInstrumentBody(true)
+	}
+
+	if base.Flag.Race {
+		lno := base.Pos
+		base.Pos = src.NoXPos
+		var init ir.Nodes
+		fn.Enter.Prepend(mkcallstmt("racefuncenter", mkcall("getcallerpc", types.Types[types.TUINTPTR], &init)))
+		if len(init) != 0 {
+			base.Fatalf("race walk: unexpected init for getcallerpc")
+		}
+		fn.Exit.Append(mkcallstmt("racefuncexit"))
+		base.Pos = lno
+	}
+}
diff --git a/src/cmd/compile/internal/walk/range.go b/src/cmd/compile/internal/walk/range.go
new file mode 100644
index 0000000..aa8c548
--- /dev/null
+++ b/src/cmd/compile/internal/walk/range.go
@@ -0,0 +1,475 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"unicode/utf8"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/ssagen"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/sys"
+)
+
+func cheapComputableIndex(width int64) bool {
+	switch ssagen.Arch.LinkArch.Family {
+	// MIPS does not have R+R addressing
+	// Arm64 may lack ability to generate this code in our assembler,
+	// but the architecture supports it.
+	case sys.PPC64, sys.S390X:
+		return width == 1
+	case sys.AMD64, sys.I386, sys.ARM64, sys.ARM:
+		switch width {
+		case 1, 2, 4, 8:
+			return true
+		}
+	}
+	return false
+}
+
+// walkRange transforms various forms of ORANGE into
+// simpler forms.  The result must be assigned back to n.
+// Node n may also be modified in place, and may also be
+// the returned node.
+func walkRange(nrange *ir.RangeStmt) ir.Node {
+	if isMapClear(nrange) {
+		m := nrange.X
+		lno := ir.SetPos(m)
+		n := mapClear(m)
+		base.Pos = lno
+		return n
+	}
+
+	nfor := ir.NewForStmt(nrange.Pos(), nil, nil, nil, nil)
+	nfor.SetInit(nrange.Init())
+	nfor.Label = nrange.Label
+
+	// variable name conventions:
+	//	ohv1, hv1, hv2: hidden (old) val 1, 2
+	//	ha, hit: hidden aggregate, iterator
+	//	hn, hp: hidden len, pointer
+	//	hb: hidden bool
+	//	a, v1, v2: not hidden aggregate, val 1, 2
+
+	a := nrange.X
+	t := typecheck.RangeExprType(a.Type())
+	lno := ir.SetPos(a)
+
+	v1, v2 := nrange.Key, nrange.Value
+
+	if ir.IsBlank(v2) {
+		v2 = nil
+	}
+
+	if ir.IsBlank(v1) && v2 == nil {
+		v1 = nil
+	}
+
+	if v1 == nil && v2 != nil {
+		base.Fatalf("walkRange: v2 != nil while v1 == nil")
+	}
+
+	var ifGuard *ir.IfStmt
+
+	var body []ir.Node
+	var init []ir.Node
+	switch t.Kind() {
+	default:
+		base.Fatalf("walkRange")
+
+	case types.TARRAY, types.TSLICE:
+		if nn := arrayClear(nrange, v1, v2, a); nn != nil {
+			base.Pos = lno
+			return nn
+		}
+
+		// order.stmt arranged for a copy of the array/slice variable if needed.
+		ha := a
+
+		hv1 := typecheck.Temp(types.Types[types.TINT])
+		hn := typecheck.Temp(types.Types[types.TINT])
+
+		init = append(init, ir.NewAssignStmt(base.Pos, hv1, nil))
+		init = append(init, ir.NewAssignStmt(base.Pos, hn, ir.NewUnaryExpr(base.Pos, ir.OLEN, ha)))
+
+		nfor.Cond = ir.NewBinaryExpr(base.Pos, ir.OLT, hv1, hn)
+		nfor.Post = ir.NewAssignStmt(base.Pos, hv1, ir.NewBinaryExpr(base.Pos, ir.OADD, hv1, ir.NewInt(1)))
+
+		// for range ha { body }
+		if v1 == nil {
+			break
+		}
+
+		// for v1 := range ha { body }
+		if v2 == nil {
+			body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, hv1)}
+			break
+		}
+
+		// for v1, v2 := range ha { body }
+		if cheapComputableIndex(t.Elem().Size()) {
+			// v1, v2 = hv1, ha[hv1]
+			tmp := ir.NewIndexExpr(base.Pos, ha, hv1)
+			tmp.SetBounded(true)
+			// Use OAS2 to correctly handle assignments
+			// of the form "v1, a[v1] := range".
+			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, tmp})
+			body = []ir.Node{a}
+			break
+		}
+
+		// TODO(austin): OFORUNTIL is a strange beast, but is
+		// necessary for expressing the control flow we need
+		// while also making "break" and "continue" work. It
+		// would be nice to just lower ORANGE during SSA, but
+		// racewalk needs to see many of the operations
+		// involved in ORANGE's implementation. If racewalk
+		// moves into SSA, consider moving ORANGE into SSA and
+		// eliminating OFORUNTIL.
+
+		// TODO(austin): OFORUNTIL inhibits bounds-check
+		// elimination on the index variable (see #20711).
+		// Enhance the prove pass to understand this.
+		ifGuard = ir.NewIfStmt(base.Pos, nil, nil, nil)
+		ifGuard.Cond = ir.NewBinaryExpr(base.Pos, ir.OLT, hv1, hn)
+		nfor.SetOp(ir.OFORUNTIL)
+
+		hp := typecheck.Temp(types.NewPtr(t.Elem()))
+		tmp := ir.NewIndexExpr(base.Pos, ha, ir.NewInt(0))
+		tmp.SetBounded(true)
+		init = append(init, ir.NewAssignStmt(base.Pos, hp, typecheck.NodAddr(tmp)))
+
+		// Use OAS2 to correctly handle assignments
+		// of the form "v1, a[v1] := range".
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, ir.NewStarExpr(base.Pos, hp)})
+		body = append(body, a)
+
+		// Advance pointer as part of the late increment.
+		//
+		// This runs *after* the condition check, so we know
+		// advancing the pointer is safe and won't go past the
+		// end of the allocation.
+		as := ir.NewAssignStmt(base.Pos, hp, addptr(hp, t.Elem().Size()))
+		nfor.Late = []ir.Node{typecheck.Stmt(as)}
+
+	case types.TMAP:
+		// order.stmt allocated the iterator for us.
+		// we only use a once, so no copy needed.
+		ha := a
+
+		hit := nrange.Prealloc
+		th := hit.Type()
+		// depends on layout of iterator struct.
+		// See cmd/compile/internal/reflectdata/reflect.go:MapIterType
+		keysym := th.Field(0).Sym
+		elemsym := th.Field(1).Sym // ditto
+
+		fn := typecheck.LookupRuntime("mapiterinit")
+
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem(), th)
+		init = append(init, mkcallstmt1(fn, reflectdata.TypePtr(t), ha, typecheck.NodAddr(hit)))
+		nfor.Cond = ir.NewBinaryExpr(base.Pos, ir.ONE, ir.NewSelectorExpr(base.Pos, ir.ODOT, hit, keysym), typecheck.NodNil())
+
+		fn = typecheck.LookupRuntime("mapiternext")
+		fn = typecheck.SubstArgTypes(fn, th)
+		nfor.Post = mkcallstmt1(fn, typecheck.NodAddr(hit))
+
+		key := ir.NewStarExpr(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, hit, keysym))
+		if v1 == nil {
+			body = nil
+		} else if v2 == nil {
+			body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, key)}
+		} else {
+			elem := ir.NewStarExpr(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, hit, elemsym))
+			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{key, elem})
+			body = []ir.Node{a}
+		}
+
+	case types.TCHAN:
+		// order.stmt arranged for a copy of the channel variable.
+		ha := a
+
+		hv1 := typecheck.Temp(t.Elem())
+		hv1.SetTypecheck(1)
+		if t.Elem().HasPointers() {
+			init = append(init, ir.NewAssignStmt(base.Pos, hv1, nil))
+		}
+		hb := typecheck.Temp(types.Types[types.TBOOL])
+
+		nfor.Cond = ir.NewBinaryExpr(base.Pos, ir.ONE, hb, ir.NewBool(false))
+		lhs := []ir.Node{hv1, hb}
+		rhs := []ir.Node{ir.NewUnaryExpr(base.Pos, ir.ORECV, ha)}
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2RECV, lhs, rhs)
+		a.SetTypecheck(1)
+		nfor.Cond = ir.InitExpr([]ir.Node{a}, nfor.Cond)
+		if v1 == nil {
+			body = nil
+		} else {
+			body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, hv1)}
+		}
+		// Zero hv1. This prevents hv1 from being the sole, inaccessible
+		// reference to an otherwise GC-able value during the next channel receive.
+		// See issue 15281.
+		body = append(body, ir.NewAssignStmt(base.Pos, hv1, nil))
+
+	case types.TSTRING:
+		// Transform string range statements like "for v1, v2 = range a" into
+		//
+		// ha := a
+		// for hv1 := 0; hv1 < len(ha); {
+		//   hv1t := hv1
+		//   hv2 := rune(ha[hv1])
+		//   if hv2 < utf8.RuneSelf {
+		//      hv1++
+		//   } else {
+		//      hv2, hv1 = decoderune(ha, hv1)
+		//   }
+		//   v1, v2 = hv1t, hv2
+		//   // original body
+		// }
+
+		// order.stmt arranged for a copy of the string variable.
+		ha := a
+
+		hv1 := typecheck.Temp(types.Types[types.TINT])
+		hv1t := typecheck.Temp(types.Types[types.TINT])
+		hv2 := typecheck.Temp(types.RuneType)
+
+		// hv1 := 0
+		init = append(init, ir.NewAssignStmt(base.Pos, hv1, nil))
+
+		// hv1 < len(ha)
+		nfor.Cond = ir.NewBinaryExpr(base.Pos, ir.OLT, hv1, ir.NewUnaryExpr(base.Pos, ir.OLEN, ha))
+
+		if v1 != nil {
+			// hv1t = hv1
+			body = append(body, ir.NewAssignStmt(base.Pos, hv1t, hv1))
+		}
+
+		// hv2 := rune(ha[hv1])
+		nind := ir.NewIndexExpr(base.Pos, ha, hv1)
+		nind.SetBounded(true)
+		body = append(body, ir.NewAssignStmt(base.Pos, hv2, typecheck.Conv(nind, types.RuneType)))
+
+		// if hv2 < utf8.RuneSelf
+		nif := ir.NewIfStmt(base.Pos, nil, nil, nil)
+		nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OLT, hv2, ir.NewInt(utf8.RuneSelf))
+
+		// hv1++
+		nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, hv1, ir.NewBinaryExpr(base.Pos, ir.OADD, hv1, ir.NewInt(1)))}
+
+		// } else {
+		// hv2, hv1 = decoderune(ha, hv1)
+		fn := typecheck.LookupRuntime("decoderune")
+		call := mkcall1(fn, fn.Type().Results(), &nif.Else, ha, hv1)
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{hv2, hv1}, []ir.Node{call})
+		nif.Else.Append(a)
+
+		body = append(body, nif)
+
+		if v1 != nil {
+			if v2 != nil {
+				// v1, v2 = hv1t, hv2
+				a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1t, hv2})
+				body = append(body, a)
+			} else {
+				// v1 = hv1t
+				body = append(body, ir.NewAssignStmt(base.Pos, v1, hv1t))
+			}
+		}
+	}
+
+	typecheck.Stmts(init)
+
+	if ifGuard != nil {
+		ifGuard.PtrInit().Append(init...)
+		ifGuard = typecheck.Stmt(ifGuard).(*ir.IfStmt)
+	} else {
+		nfor.PtrInit().Append(init...)
+	}
+
+	typecheck.Stmts(nfor.Cond.Init())
+
+	nfor.Cond = typecheck.Expr(nfor.Cond)
+	nfor.Cond = typecheck.DefaultLit(nfor.Cond, nil)
+	nfor.Post = typecheck.Stmt(nfor.Post)
+	typecheck.Stmts(body)
+	nfor.Body.Append(body...)
+	nfor.Body.Append(nrange.Body...)
+
+	var n ir.Node = nfor
+	if ifGuard != nil {
+		ifGuard.Body = []ir.Node{n}
+		n = ifGuard
+	}
+
+	n = walkStmt(n)
+
+	base.Pos = lno
+	return n
+}
+
+// isMapClear checks if n is of the form:
+//
+// for k := range m {
+//   delete(m, k)
+// }
+//
+// where == for keys of map m is reflexive.
+func isMapClear(n *ir.RangeStmt) bool {
+	if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
+		return false
+	}
+
+	t := n.X.Type()
+	if n.Op() != ir.ORANGE || t.Kind() != types.TMAP || n.Key == nil || n.Value != nil {
+		return false
+	}
+
+	k := n.Key
+	// Require k to be a new variable name.
+	if !ir.DeclaredBy(k, n) {
+		return false
+	}
+
+	if len(n.Body) != 1 {
+		return false
+	}
+
+	stmt := n.Body[0] // only stmt in body
+	if stmt == nil || stmt.Op() != ir.ODELETE {
+		return false
+	}
+
+	m := n.X
+	if delete := stmt.(*ir.CallExpr); !ir.SameSafeExpr(delete.Args[0], m) || !ir.SameSafeExpr(delete.Args[1], k) {
+		return false
+	}
+
+	// Keys where equality is not reflexive can not be deleted from maps.
+	if !types.IsReflexive(t.Key()) {
+		return false
+	}
+
+	return true
+}
+
+// mapClear constructs a call to runtime.mapclear for the map m.
+func mapClear(m ir.Node) ir.Node {
+	t := m.Type()
+
+	// instantiate mapclear(typ *type, hmap map[any]any)
+	fn := typecheck.LookupRuntime("mapclear")
+	fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem())
+	n := mkcallstmt1(fn, reflectdata.TypePtr(t), m)
+	return walkStmt(typecheck.Stmt(n))
+}
+
+// Lower n into runtime·memclr if possible, for
+// fast zeroing of slices and arrays (issue 5373).
+// Look for instances of
+//
+// for i := range a {
+// 	a[i] = zero
+// }
+//
+// in which the evaluation of a is side-effect-free.
+//
+// Parameters are as in walkRange: "for v1, v2 = range a".
+func arrayClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {
+	if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
+		return nil
+	}
+
+	if v1 == nil || v2 != nil {
+		return nil
+	}
+
+	if len(loop.Body) != 1 || loop.Body[0] == nil {
+		return nil
+	}
+
+	stmt1 := loop.Body[0] // only stmt in body
+	if stmt1.Op() != ir.OAS {
+		return nil
+	}
+	stmt := stmt1.(*ir.AssignStmt)
+	if stmt.X.Op() != ir.OINDEX {
+		return nil
+	}
+	lhs := stmt.X.(*ir.IndexExpr)
+
+	if !ir.SameSafeExpr(lhs.X, a) || !ir.SameSafeExpr(lhs.Index, v1) {
+		return nil
+	}
+
+	elemsize := typecheck.RangeExprType(loop.X.Type()).Elem().Size()
+	if elemsize <= 0 || !ir.IsZero(stmt.Y) {
+		return nil
+	}
+
+	// Convert to
+	// if len(a) != 0 {
+	// 	hp = &a[0]
+	// 	hn = len(a)*sizeof(elem(a))
+	// 	memclr{NoHeap,Has}Pointers(hp, hn)
+	// 	i = len(a) - 1
+	// }
+	n := ir.NewIfStmt(base.Pos, nil, nil, nil)
+	n.Cond = ir.NewBinaryExpr(base.Pos, ir.ONE, ir.NewUnaryExpr(base.Pos, ir.OLEN, a), ir.NewInt(0))
+
+	// hp = &a[0]
+	hp := typecheck.Temp(types.Types[types.TUNSAFEPTR])
+
+	ix := ir.NewIndexExpr(base.Pos, a, ir.NewInt(0))
+	ix.SetBounded(true)
+	addr := typecheck.ConvNop(typecheck.NodAddr(ix), types.Types[types.TUNSAFEPTR])
+	n.Body.Append(ir.NewAssignStmt(base.Pos, hp, addr))
+
+	// hn = len(a) * sizeof(elem(a))
+	hn := typecheck.Temp(types.Types[types.TUINTPTR])
+	mul := typecheck.Conv(ir.NewBinaryExpr(base.Pos, ir.OMUL, ir.NewUnaryExpr(base.Pos, ir.OLEN, a), ir.NewInt(elemsize)), types.Types[types.TUINTPTR])
+	n.Body.Append(ir.NewAssignStmt(base.Pos, hn, mul))
+
+	var fn ir.Node
+	if a.Type().Elem().HasPointers() {
+		// memclrHasPointers(hp, hn)
+		ir.CurFunc.SetWBPos(stmt.Pos())
+		fn = mkcallstmt("memclrHasPointers", hp, hn)
+	} else {
+		// memclrNoHeapPointers(hp, hn)
+		fn = mkcallstmt("memclrNoHeapPointers", hp, hn)
+	}
+
+	n.Body.Append(fn)
+
+	// i = len(a) - 1
+	v1 = ir.NewAssignStmt(base.Pos, v1, ir.NewBinaryExpr(base.Pos, ir.OSUB, ir.NewUnaryExpr(base.Pos, ir.OLEN, a), ir.NewInt(1)))
+
+	n.Body.Append(v1)
+
+	n.Cond = typecheck.Expr(n.Cond)
+	n.Cond = typecheck.DefaultLit(n.Cond, nil)
+	typecheck.Stmts(n.Body)
+	return walkStmt(n)
+}
+
+// addptr returns (*T)(uintptr(p) + n).
+func addptr(p ir.Node, n int64) ir.Node {
+	t := p.Type()
+
+	p = ir.NewConvExpr(base.Pos, ir.OCONVNOP, nil, p)
+	p.SetType(types.Types[types.TUINTPTR])
+
+	p = ir.NewBinaryExpr(base.Pos, ir.OADD, p, ir.NewInt(n))
+
+	p = ir.NewConvExpr(base.Pos, ir.OCONVNOP, nil, p)
+	p.SetType(t)
+
+	return p
+}
diff --git a/src/cmd/compile/internal/walk/select.go b/src/cmd/compile/internal/walk/select.go
new file mode 100644
index 0000000..fde8f50
--- /dev/null
+++ b/src/cmd/compile/internal/walk/select.go
@@ -0,0 +1,291 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+)
+
+func walkSelect(sel *ir.SelectStmt) {
+	lno := ir.SetPos(sel)
+	if sel.Walked() {
+		base.Fatalf("double walkSelect")
+	}
+	sel.SetWalked(true)
+
+	init := ir.TakeInit(sel)
+
+	init = append(init, walkSelectCases(sel.Cases)...)
+	sel.Cases = nil
+
+	sel.Compiled = init
+	walkStmtList(sel.Compiled)
+
+	base.Pos = lno
+}
+
+func walkSelectCases(cases []*ir.CommClause) []ir.Node {
+	ncas := len(cases)
+	sellineno := base.Pos
+
+	// optimization: zero-case select
+	if ncas == 0 {
+		return []ir.Node{mkcallstmt("block")}
+	}
+
+	// optimization: one-case select: single op.
+	if ncas == 1 {
+		cas := cases[0]
+		ir.SetPos(cas)
+		l := cas.Init()
+		if cas.Comm != nil { // not default:
+			n := cas.Comm
+			l = append(l, ir.TakeInit(n)...)
+			switch n.Op() {
+			default:
+				base.Fatalf("select %v", n.Op())
+
+			case ir.OSEND:
+				// already ok
+
+			case ir.OSELRECV2:
+				r := n.(*ir.AssignListStmt)
+				if ir.IsBlank(r.Lhs[0]) && ir.IsBlank(r.Lhs[1]) {
+					n = r.Rhs[0]
+					break
+				}
+				r.SetOp(ir.OAS2RECV)
+			}
+
+			l = append(l, n)
+		}
+
+		l = append(l, cas.Body...)
+		l = append(l, ir.NewBranchStmt(base.Pos, ir.OBREAK, nil))
+		return l
+	}
+
+	// convert case value arguments to addresses.
+	// this rewrite is used by both the general code and the next optimization.
+	var dflt *ir.CommClause
+	for _, cas := range cases {
+		ir.SetPos(cas)
+		n := cas.Comm
+		if n == nil {
+			dflt = cas
+			continue
+		}
+		switch n.Op() {
+		case ir.OSEND:
+			n := n.(*ir.SendStmt)
+			n.Value = typecheck.NodAddr(n.Value)
+			n.Value = typecheck.Expr(n.Value)
+
+		case ir.OSELRECV2:
+			n := n.(*ir.AssignListStmt)
+			if !ir.IsBlank(n.Lhs[0]) {
+				n.Lhs[0] = typecheck.NodAddr(n.Lhs[0])
+				n.Lhs[0] = typecheck.Expr(n.Lhs[0])
+			}
+		}
+	}
+
+	// optimization: two-case select but one is default: single non-blocking op.
+	if ncas == 2 && dflt != nil {
+		cas := cases[0]
+		if cas == dflt {
+			cas = cases[1]
+		}
+
+		n := cas.Comm
+		ir.SetPos(n)
+		r := ir.NewIfStmt(base.Pos, nil, nil, nil)
+		r.SetInit(cas.Init())
+		var cond ir.Node
+		switch n.Op() {
+		default:
+			base.Fatalf("select %v", n.Op())
+
+		case ir.OSEND:
+			// if selectnbsend(c, v) { body } else { default body }
+			n := n.(*ir.SendStmt)
+			ch := n.Chan
+			cond = mkcall1(chanfn("selectnbsend", 2, ch.Type()), types.Types[types.TBOOL], r.PtrInit(), ch, n.Value)
+
+		case ir.OSELRECV2:
+			n := n.(*ir.AssignListStmt)
+			recv := n.Rhs[0].(*ir.UnaryExpr)
+			ch := recv.X
+			elem := n.Lhs[0]
+			if ir.IsBlank(elem) {
+				elem = typecheck.NodNil()
+			}
+			cond = typecheck.Temp(types.Types[types.TBOOL])
+			fn := chanfn("selectnbrecv", 2, ch.Type())
+			call := mkcall1(fn, fn.Type().Results(), r.PtrInit(), elem, ch)
+			as := ir.NewAssignListStmt(r.Pos(), ir.OAS2, []ir.Node{cond, n.Lhs[1]}, []ir.Node{call})
+			r.PtrInit().Append(typecheck.Stmt(as))
+		}
+
+		r.Cond = typecheck.Expr(cond)
+		r.Body = cas.Body
+		r.Else = append(dflt.Init(), dflt.Body...)
+		return []ir.Node{r, ir.NewBranchStmt(base.Pos, ir.OBREAK, nil)}
+	}
+
+	if dflt != nil {
+		ncas--
+	}
+	casorder := make([]*ir.CommClause, ncas)
+	nsends, nrecvs := 0, 0
+
+	var init []ir.Node
+
+	// generate sel-struct
+	base.Pos = sellineno
+	selv := typecheck.Temp(types.NewArray(scasetype(), int64(ncas)))
+	init = append(init, typecheck.Stmt(ir.NewAssignStmt(base.Pos, selv, nil)))
+
+	// No initialization for order; runtime.selectgo is responsible for that.
+	order := typecheck.Temp(types.NewArray(types.Types[types.TUINT16], 2*int64(ncas)))
+
+	var pc0, pcs ir.Node
+	if base.Flag.Race {
+		pcs = typecheck.Temp(types.NewArray(types.Types[types.TUINTPTR], int64(ncas)))
+		pc0 = typecheck.Expr(typecheck.NodAddr(ir.NewIndexExpr(base.Pos, pcs, ir.NewInt(0))))
+	} else {
+		pc0 = typecheck.NodNil()
+	}
+
+	// register cases
+	for _, cas := range cases {
+		ir.SetPos(cas)
+
+		init = append(init, ir.TakeInit(cas)...)
+
+		n := cas.Comm
+		if n == nil { // default:
+			continue
+		}
+
+		var i int
+		var c, elem ir.Node
+		switch n.Op() {
+		default:
+			base.Fatalf("select %v", n.Op())
+		case ir.OSEND:
+			n := n.(*ir.SendStmt)
+			i = nsends
+			nsends++
+			c = n.Chan
+			elem = n.Value
+		case ir.OSELRECV2:
+			n := n.(*ir.AssignListStmt)
+			nrecvs++
+			i = ncas - nrecvs
+			recv := n.Rhs[0].(*ir.UnaryExpr)
+			c = recv.X
+			elem = n.Lhs[0]
+		}
+
+		casorder[i] = cas
+
+		setField := func(f string, val ir.Node) {
+			r := ir.NewAssignStmt(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, ir.NewIndexExpr(base.Pos, selv, ir.NewInt(int64(i))), typecheck.Lookup(f)), val)
+			init = append(init, typecheck.Stmt(r))
+		}
+
+		c = typecheck.ConvNop(c, types.Types[types.TUNSAFEPTR])
+		setField("c", c)
+		if !ir.IsBlank(elem) {
+			elem = typecheck.ConvNop(elem, types.Types[types.TUNSAFEPTR])
+			setField("elem", elem)
+		}
+
+		// TODO(mdempsky): There should be a cleaner way to
+		// handle this.
+		if base.Flag.Race {
+			r := mkcallstmt("selectsetpc", typecheck.NodAddr(ir.NewIndexExpr(base.Pos, pcs, ir.NewInt(int64(i)))))
+			init = append(init, r)
+		}
+	}
+	if nsends+nrecvs != ncas {
+		base.Fatalf("walkSelectCases: miscount: %v + %v != %v", nsends, nrecvs, ncas)
+	}
+
+	// run the select
+	base.Pos = sellineno
+	chosen := typecheck.Temp(types.Types[types.TINT])
+	recvOK := typecheck.Temp(types.Types[types.TBOOL])
+	r := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+	r.Lhs = []ir.Node{chosen, recvOK}
+	fn := typecheck.LookupRuntime("selectgo")
+	var fnInit ir.Nodes
+	r.Rhs = []ir.Node{mkcall1(fn, fn.Type().Results(), &fnInit, bytePtrToIndex(selv, 0), bytePtrToIndex(order, 0), pc0, ir.NewInt(int64(nsends)), ir.NewInt(int64(nrecvs)), ir.NewBool(dflt == nil))}
+	init = append(init, fnInit...)
+	init = append(init, typecheck.Stmt(r))
+
+	// selv and order are no longer alive after selectgo.
+	init = append(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, selv))
+	init = append(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, order))
+	if base.Flag.Race {
+		init = append(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, pcs))
+	}
+
+	// dispatch cases
+	dispatch := func(cond ir.Node, cas *ir.CommClause) {
+		cond = typecheck.Expr(cond)
+		cond = typecheck.DefaultLit(cond, nil)
+
+		r := ir.NewIfStmt(base.Pos, cond, nil, nil)
+
+		if n := cas.Comm; n != nil && n.Op() == ir.OSELRECV2 {
+			n := n.(*ir.AssignListStmt)
+			if !ir.IsBlank(n.Lhs[1]) {
+				x := ir.NewAssignStmt(base.Pos, n.Lhs[1], recvOK)
+				r.Body.Append(typecheck.Stmt(x))
+			}
+		}
+
+		r.Body.Append(cas.Body.Take()...)
+		r.Body.Append(ir.NewBranchStmt(base.Pos, ir.OBREAK, nil))
+		init = append(init, r)
+	}
+
+	if dflt != nil {
+		ir.SetPos(dflt)
+		dispatch(ir.NewBinaryExpr(base.Pos, ir.OLT, chosen, ir.NewInt(0)), dflt)
+	}
+	for i, cas := range casorder {
+		ir.SetPos(cas)
+		dispatch(ir.NewBinaryExpr(base.Pos, ir.OEQ, chosen, ir.NewInt(int64(i))), cas)
+	}
+
+	return init
+}
+
+// bytePtrToIndex returns a Node representing "(*byte)(&n[i])".
+func bytePtrToIndex(n ir.Node, i int64) ir.Node {
+	s := typecheck.NodAddr(ir.NewIndexExpr(base.Pos, n, ir.NewInt(i)))
+	t := types.NewPtr(types.Types[types.TUINT8])
+	return typecheck.ConvNop(s, t)
+}
+
+var scase *types.Type
+
+// Keep in sync with src/runtime/select.go.
+func scasetype() *types.Type {
+	if scase == nil {
+		scase = types.NewStruct(types.NoPkg, []*types.Field{
+			types.NewField(base.Pos, typecheck.Lookup("c"), types.Types[types.TUNSAFEPTR]),
+			types.NewField(base.Pos, typecheck.Lookup("elem"), types.Types[types.TUNSAFEPTR]),
+		})
+		scase.SetNoalg(true)
+	}
+	return scase
+}
diff --git a/src/cmd/compile/internal/walk/stmt.go b/src/cmd/compile/internal/walk/stmt.go
new file mode 100644
index 0000000..f09e916
--- /dev/null
+++ b/src/cmd/compile/internal/walk/stmt.go
@@ -0,0 +1,231 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+)
+
+// The result of walkStmt MUST be assigned back to n, e.g.
+// 	n.Left = walkStmt(n.Left)
+func walkStmt(n ir.Node) ir.Node {
+	if n == nil {
+		return n
+	}
+
+	ir.SetPos(n)
+
+	walkStmtList(n.Init())
+
+	switch n.Op() {
+	default:
+		if n.Op() == ir.ONAME {
+			n := n.(*ir.Name)
+			base.Errorf("%v is not a top level statement", n.Sym())
+		} else {
+			base.Errorf("%v is not a top level statement", n.Op())
+		}
+		ir.Dump("nottop", n)
+		return n
+
+	case ir.OAS,
+		ir.OASOP,
+		ir.OAS2,
+		ir.OAS2DOTTYPE,
+		ir.OAS2RECV,
+		ir.OAS2FUNC,
+		ir.OAS2MAPR,
+		ir.OCLOSE,
+		ir.OCOPY,
+		ir.OCALLINTER,
+		ir.OCALL,
+		ir.OCALLFUNC,
+		ir.ODELETE,
+		ir.OSEND,
+		ir.OPRINT,
+		ir.OPRINTN,
+		ir.OPANIC,
+		ir.ORECOVERFP,
+		ir.OGETG:
+		if n.Typecheck() == 0 {
+			base.Fatalf("missing typecheck: %+v", n)
+		}
+		init := ir.TakeInit(n)
+		n = walkExpr(n, &init)
+		if n.Op() == ir.ONAME {
+			// copy rewrote to a statement list and a temp for the length.
+			// Throw away the temp to avoid plain values as statements.
+			n = ir.NewBlockStmt(n.Pos(), init)
+			init = nil
+		}
+		if len(init) > 0 {
+			switch n.Op() {
+			case ir.OAS, ir.OAS2, ir.OBLOCK:
+				n.(ir.InitNode).PtrInit().Prepend(init...)
+
+			default:
+				init.Append(n)
+				n = ir.NewBlockStmt(n.Pos(), init)
+			}
+		}
+		return n
+
+	// special case for a receive where we throw away
+	// the value received.
+	case ir.ORECV:
+		n := n.(*ir.UnaryExpr)
+		return walkRecv(n)
+
+	case ir.OBREAK,
+		ir.OCONTINUE,
+		ir.OFALL,
+		ir.OGOTO,
+		ir.OLABEL,
+		ir.ODCL,
+		ir.ODCLCONST,
+		ir.ODCLTYPE,
+		ir.OCHECKNIL,
+		ir.OVARDEF,
+		ir.OVARKILL,
+		ir.OVARLIVE:
+		return n
+
+	case ir.OBLOCK:
+		n := n.(*ir.BlockStmt)
+		walkStmtList(n.List)
+		return n
+
+	case ir.OCASE:
+		base.Errorf("case statement out of place")
+		panic("unreachable")
+
+	case ir.ODEFER:
+		n := n.(*ir.GoDeferStmt)
+		ir.CurFunc.SetHasDefer(true)
+		ir.CurFunc.NumDefers++
+		if ir.CurFunc.NumDefers > maxOpenDefers {
+			// Don't allow open-coded defers if there are more than
+			// 8 defers in the function, since we use a single
+			// byte to record active defers.
+			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
+		}
+		if n.Esc() != ir.EscNever {
+			// If n.Esc is not EscNever, then this defer occurs in a loop,
+			// so open-coded defers cannot be used in this function.
+			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
+		}
+		fallthrough
+	case ir.OGO:
+		n := n.(*ir.GoDeferStmt)
+		return walkGoDefer(n)
+
+	case ir.OFOR, ir.OFORUNTIL:
+		n := n.(*ir.ForStmt)
+		return walkFor(n)
+
+	case ir.OIF:
+		n := n.(*ir.IfStmt)
+		return walkIf(n)
+
+	case ir.ORETURN:
+		n := n.(*ir.ReturnStmt)
+		return walkReturn(n)
+
+	case ir.OTAILCALL:
+		n := n.(*ir.TailCallStmt)
+
+		var init ir.Nodes
+		n.Call.X = walkExpr(n.Call.X, &init)
+
+		if len(init) > 0 {
+			init.Append(n)
+			return ir.NewBlockStmt(n.Pos(), init)
+		}
+		return n
+
+	case ir.OINLMARK:
+		n := n.(*ir.InlineMarkStmt)
+		return n
+
+	case ir.OSELECT:
+		n := n.(*ir.SelectStmt)
+		walkSelect(n)
+		return n
+
+	case ir.OSWITCH:
+		n := n.(*ir.SwitchStmt)
+		walkSwitch(n)
+		return n
+
+	case ir.ORANGE:
+		n := n.(*ir.RangeStmt)
+		return walkRange(n)
+	}
+
+	// No return! Each case must return (or panic),
+	// to avoid confusion about what gets returned
+	// in the presence of type assertions.
+}
+
+func walkStmtList(s []ir.Node) {
+	for i := range s {
+		s[i] = walkStmt(s[i])
+	}
+}
+
+// walkFor walks an OFOR or OFORUNTIL node.
+func walkFor(n *ir.ForStmt) ir.Node {
+	if n.Cond != nil {
+		init := ir.TakeInit(n.Cond)
+		walkStmtList(init)
+		n.Cond = walkExpr(n.Cond, &init)
+		n.Cond = ir.InitExpr(init, n.Cond)
+	}
+
+	n.Post = walkStmt(n.Post)
+	if n.Op() == ir.OFORUNTIL {
+		walkStmtList(n.Late)
+	}
+	walkStmtList(n.Body)
+	return n
+}
+
+// validGoDeferCall reports whether call is a valid call to appear in
+// a go or defer statement; that is, whether it's a regular function
+// call without arguments or results.
+func validGoDeferCall(call ir.Node) bool {
+	if call, ok := call.(*ir.CallExpr); ok && call.Op() == ir.OCALLFUNC && len(call.KeepAlive) == 0 {
+		sig := call.X.Type()
+		return sig.NumParams()+sig.NumResults() == 0
+	}
+	return false
+}
+
+// walkGoDefer walks an OGO or ODEFER node.
+func walkGoDefer(n *ir.GoDeferStmt) ir.Node {
+	if !validGoDeferCall(n.Call) {
+		base.FatalfAt(n.Pos(), "invalid %v call: %v", n.Op(), n.Call)
+	}
+
+	var init ir.Nodes
+
+	call := n.Call.(*ir.CallExpr)
+	call.X = walkExpr(call.X, &init)
+
+	if len(init) > 0 {
+		init.Append(n)
+		return ir.NewBlockStmt(n.Pos(), init)
+	}
+	return n
+}
+
+// walkIf walks an OIF node.
+func walkIf(n *ir.IfStmt) ir.Node {
+	n.Cond = walkExpr(n.Cond, n.PtrInit())
+	walkStmtList(n.Body)
+	walkStmtList(n.Else)
+	return n
+}
diff --git a/src/cmd/compile/internal/walk/switch.go b/src/cmd/compile/internal/walk/switch.go
new file mode 100644
index 0000000..3705c5b
--- /dev/null
+++ b/src/cmd/compile/internal/walk/switch.go
@@ -0,0 +1,597 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"go/constant"
+	"go/token"
+	"sort"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// walkSwitch walks a switch statement.
+func walkSwitch(sw *ir.SwitchStmt) {
+	// Guard against double walk, see #25776.
+	if sw.Walked() {
+		return // Was fatal, but eliminating every possible source of double-walking is hard
+	}
+	sw.SetWalked(true)
+
+	if sw.Tag != nil && sw.Tag.Op() == ir.OTYPESW {
+		walkSwitchType(sw)
+	} else {
+		walkSwitchExpr(sw)
+	}
+}
+
+// walkSwitchExpr generates an AST implementing sw.  sw is an
+// expression switch.
+func walkSwitchExpr(sw *ir.SwitchStmt) {
+	lno := ir.SetPos(sw)
+
+	cond := sw.Tag
+	sw.Tag = nil
+
+	// convert switch {...} to switch true {...}
+	if cond == nil {
+		cond = ir.NewBool(true)
+		cond = typecheck.Expr(cond)
+		cond = typecheck.DefaultLit(cond, nil)
+	}
+
+	// Given "switch string(byteslice)",
+	// with all cases being side-effect free,
+	// use a zero-cost alias of the byte slice.
+	// Do this before calling walkExpr on cond,
+	// because walkExpr will lower the string
+	// conversion into a runtime call.
+	// See issue 24937 for more discussion.
+	if cond.Op() == ir.OBYTES2STR && allCaseExprsAreSideEffectFree(sw) {
+		cond := cond.(*ir.ConvExpr)
+		cond.SetOp(ir.OBYTES2STRTMP)
+	}
+
+	cond = walkExpr(cond, sw.PtrInit())
+	if cond.Op() != ir.OLITERAL && cond.Op() != ir.ONIL {
+		cond = copyExpr(cond, cond.Type(), &sw.Compiled)
+	}
+
+	base.Pos = lno
+
+	s := exprSwitch{
+		exprname: cond,
+	}
+
+	var defaultGoto ir.Node
+	var body ir.Nodes
+	for _, ncase := range sw.Cases {
+		label := typecheck.AutoLabel(".s")
+		jmp := ir.NewBranchStmt(ncase.Pos(), ir.OGOTO, label)
+
+		// Process case dispatch.
+		if len(ncase.List) == 0 {
+			if defaultGoto != nil {
+				base.Fatalf("duplicate default case not detected during typechecking")
+			}
+			defaultGoto = jmp
+		}
+
+		for _, n1 := range ncase.List {
+			s.Add(ncase.Pos(), n1, jmp)
+		}
+
+		// Process body.
+		body.Append(ir.NewLabelStmt(ncase.Pos(), label))
+		body.Append(ncase.Body...)
+		if fall, pos := endsInFallthrough(ncase.Body); !fall {
+			br := ir.NewBranchStmt(base.Pos, ir.OBREAK, nil)
+			br.SetPos(pos)
+			body.Append(br)
+		}
+	}
+	sw.Cases = nil
+
+	if defaultGoto == nil {
+		br := ir.NewBranchStmt(base.Pos, ir.OBREAK, nil)
+		br.SetPos(br.Pos().WithNotStmt())
+		defaultGoto = br
+	}
+
+	s.Emit(&sw.Compiled)
+	sw.Compiled.Append(defaultGoto)
+	sw.Compiled.Append(body.Take()...)
+	walkStmtList(sw.Compiled)
+}
+
+// An exprSwitch walks an expression switch.
+type exprSwitch struct {
+	exprname ir.Node // value being switched on
+
+	done    ir.Nodes
+	clauses []exprClause
+}
+
+type exprClause struct {
+	pos    src.XPos
+	lo, hi ir.Node
+	jmp    ir.Node
+}
+
+func (s *exprSwitch) Add(pos src.XPos, expr, jmp ir.Node) {
+	c := exprClause{pos: pos, lo: expr, hi: expr, jmp: jmp}
+	if types.IsOrdered[s.exprname.Type().Kind()] && expr.Op() == ir.OLITERAL {
+		s.clauses = append(s.clauses, c)
+		return
+	}
+
+	s.flush()
+	s.clauses = append(s.clauses, c)
+	s.flush()
+}
+
+func (s *exprSwitch) Emit(out *ir.Nodes) {
+	s.flush()
+	out.Append(s.done.Take()...)
+}
+
+func (s *exprSwitch) flush() {
+	cc := s.clauses
+	s.clauses = nil
+	if len(cc) == 0 {
+		return
+	}
+
+	// Caution: If len(cc) == 1, then cc[0] might not an OLITERAL.
+	// The code below is structured to implicitly handle this case
+	// (e.g., sort.Slice doesn't need to invoke the less function
+	// when there's only a single slice element).
+
+	if s.exprname.Type().IsString() && len(cc) >= 2 {
+		// Sort strings by length and then by value. It is
+		// much cheaper to compare lengths than values, and
+		// all we need here is consistency. We respect this
+		// sorting below.
+		sort.Slice(cc, func(i, j int) bool {
+			si := ir.StringVal(cc[i].lo)
+			sj := ir.StringVal(cc[j].lo)
+			if len(si) != len(sj) {
+				return len(si) < len(sj)
+			}
+			return si < sj
+		})
+
+		// runLen returns the string length associated with a
+		// particular run of exprClauses.
+		runLen := func(run []exprClause) int64 { return int64(len(ir.StringVal(run[0].lo))) }
+
+		// Collapse runs of consecutive strings with the same length.
+		var runs [][]exprClause
+		start := 0
+		for i := 1; i < len(cc); i++ {
+			if runLen(cc[start:]) != runLen(cc[i:]) {
+				runs = append(runs, cc[start:i])
+				start = i
+			}
+		}
+		runs = append(runs, cc[start:])
+
+		// Perform two-level binary search.
+		binarySearch(len(runs), &s.done,
+			func(i int) ir.Node {
+				return ir.NewBinaryExpr(base.Pos, ir.OLE, ir.NewUnaryExpr(base.Pos, ir.OLEN, s.exprname), ir.NewInt(runLen(runs[i-1])))
+			},
+			func(i int, nif *ir.IfStmt) {
+				run := runs[i]
+				nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OEQ, ir.NewUnaryExpr(base.Pos, ir.OLEN, s.exprname), ir.NewInt(runLen(run)))
+				s.search(run, &nif.Body)
+			},
+		)
+		return
+	}
+
+	sort.Slice(cc, func(i, j int) bool {
+		return constant.Compare(cc[i].lo.Val(), token.LSS, cc[j].lo.Val())
+	})
+
+	// Merge consecutive integer cases.
+	if s.exprname.Type().IsInteger() {
+		consecutive := func(last, next constant.Value) bool {
+			delta := constant.BinaryOp(next, token.SUB, last)
+			return constant.Compare(delta, token.EQL, constant.MakeInt64(1))
+		}
+
+		merged := cc[:1]
+		for _, c := range cc[1:] {
+			last := &merged[len(merged)-1]
+			if last.jmp == c.jmp && consecutive(last.hi.Val(), c.lo.Val()) {
+				last.hi = c.lo
+			} else {
+				merged = append(merged, c)
+			}
+		}
+		cc = merged
+	}
+
+	s.search(cc, &s.done)
+}
+
+func (s *exprSwitch) search(cc []exprClause, out *ir.Nodes) {
+	binarySearch(len(cc), out,
+		func(i int) ir.Node {
+			return ir.NewBinaryExpr(base.Pos, ir.OLE, s.exprname, cc[i-1].hi)
+		},
+		func(i int, nif *ir.IfStmt) {
+			c := &cc[i]
+			nif.Cond = c.test(s.exprname)
+			nif.Body = []ir.Node{c.jmp}
+		},
+	)
+}
+
+func (c *exprClause) test(exprname ir.Node) ir.Node {
+	// Integer range.
+	if c.hi != c.lo {
+		low := ir.NewBinaryExpr(c.pos, ir.OGE, exprname, c.lo)
+		high := ir.NewBinaryExpr(c.pos, ir.OLE, exprname, c.hi)
+		return ir.NewLogicalExpr(c.pos, ir.OANDAND, low, high)
+	}
+
+	// Optimize "switch true { ...}" and "switch false { ... }".
+	if ir.IsConst(exprname, constant.Bool) && !c.lo.Type().IsInterface() {
+		if ir.BoolVal(exprname) {
+			return c.lo
+		} else {
+			return ir.NewUnaryExpr(c.pos, ir.ONOT, c.lo)
+		}
+	}
+
+	return ir.NewBinaryExpr(c.pos, ir.OEQ, exprname, c.lo)
+}
+
+func allCaseExprsAreSideEffectFree(sw *ir.SwitchStmt) bool {
+	// In theory, we could be more aggressive, allowing any
+	// side-effect-free expressions in cases, but it's a bit
+	// tricky because some of that information is unavailable due
+	// to the introduction of temporaries during order.
+	// Restricting to constants is simple and probably powerful
+	// enough.
+
+	for _, ncase := range sw.Cases {
+		for _, v := range ncase.List {
+			if v.Op() != ir.OLITERAL {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// endsInFallthrough reports whether stmts ends with a "fallthrough" statement.
+func endsInFallthrough(stmts []ir.Node) (bool, src.XPos) {
+	// Search backwards for the index of the fallthrough
+	// statement. Do not assume it'll be in the last
+	// position, since in some cases (e.g. when the statement
+	// list contains autotmp_ variables), one or more OVARKILL
+	// nodes will be at the end of the list.
+
+	i := len(stmts) - 1
+	for i >= 0 && stmts[i].Op() == ir.OVARKILL {
+		i--
+	}
+	if i < 0 {
+		return false, src.NoXPos
+	}
+	return stmts[i].Op() == ir.OFALL, stmts[i].Pos()
+}
+
+// walkSwitchType generates an AST that implements sw, where sw is a
+// type switch.
+func walkSwitchType(sw *ir.SwitchStmt) {
+	var s typeSwitch
+	s.facename = sw.Tag.(*ir.TypeSwitchGuard).X
+	sw.Tag = nil
+
+	s.facename = walkExpr(s.facename, sw.PtrInit())
+	s.facename = copyExpr(s.facename, s.facename.Type(), &sw.Compiled)
+	s.okname = typecheck.Temp(types.Types[types.TBOOL])
+
+	// Get interface descriptor word.
+	// For empty interfaces this will be the type.
+	// For non-empty interfaces this will be the itab.
+	itab := ir.NewUnaryExpr(base.Pos, ir.OITAB, s.facename)
+
+	// For empty interfaces, do:
+	//     if e._type == nil {
+	//         do nil case if it exists, otherwise default
+	//     }
+	//     h := e._type.hash
+	// Use a similar strategy for non-empty interfaces.
+	ifNil := ir.NewIfStmt(base.Pos, nil, nil, nil)
+	ifNil.Cond = ir.NewBinaryExpr(base.Pos, ir.OEQ, itab, typecheck.NodNil())
+	base.Pos = base.Pos.WithNotStmt() // disable statement marks after the first check.
+	ifNil.Cond = typecheck.Expr(ifNil.Cond)
+	ifNil.Cond = typecheck.DefaultLit(ifNil.Cond, nil)
+	// ifNil.Nbody assigned at end.
+	sw.Compiled.Append(ifNil)
+
+	// Load hash from type or itab.
+	dotHash := typeHashFieldOf(base.Pos, itab)
+	s.hashname = copyExpr(dotHash, dotHash.Type(), &sw.Compiled)
+
+	br := ir.NewBranchStmt(base.Pos, ir.OBREAK, nil)
+	var defaultGoto, nilGoto ir.Node
+	var body ir.Nodes
+	for _, ncase := range sw.Cases {
+		caseVar := ncase.Var
+
+		// For single-type cases with an interface type,
+		// we initialize the case variable as part of the type assertion.
+		// In other cases, we initialize it in the body.
+		var singleType *types.Type
+		if len(ncase.List) == 1 && ncase.List[0].Op() == ir.OTYPE {
+			singleType = ncase.List[0].Type()
+		}
+		caseVarInitialized := false
+
+		label := typecheck.AutoLabel(".s")
+		jmp := ir.NewBranchStmt(ncase.Pos(), ir.OGOTO, label)
+
+		if len(ncase.List) == 0 { // default:
+			if defaultGoto != nil {
+				base.Fatalf("duplicate default case not detected during typechecking")
+			}
+			defaultGoto = jmp
+		}
+
+		for _, n1 := range ncase.List {
+			if ir.IsNil(n1) { // case nil:
+				if nilGoto != nil {
+					base.Fatalf("duplicate nil case not detected during typechecking")
+				}
+				nilGoto = jmp
+				continue
+			}
+
+			if singleType != nil && singleType.IsInterface() {
+				s.Add(ncase.Pos(), n1, caseVar, jmp)
+				caseVarInitialized = true
+			} else {
+				s.Add(ncase.Pos(), n1, nil, jmp)
+			}
+		}
+
+		body.Append(ir.NewLabelStmt(ncase.Pos(), label))
+		if caseVar != nil && !caseVarInitialized {
+			val := s.facename
+			if singleType != nil {
+				// We have a single concrete type. Extract the data.
+				if singleType.IsInterface() {
+					base.Fatalf("singleType interface should have been handled in Add")
+				}
+				val = ifaceData(ncase.Pos(), s.facename, singleType)
+			}
+			if len(ncase.List) == 1 && ncase.List[0].Op() == ir.ODYNAMICTYPE {
+				dt := ncase.List[0].(*ir.DynamicType)
+				x := ir.NewDynamicTypeAssertExpr(ncase.Pos(), ir.ODYNAMICDOTTYPE, val, dt.X)
+				if dt.ITab != nil {
+					// TODO: make ITab a separate field in DynamicTypeAssertExpr?
+					x.T = dt.ITab
+				}
+				x.SetType(caseVar.Type())
+				x.SetTypecheck(1)
+				val = x
+			}
+			l := []ir.Node{
+				ir.NewDecl(ncase.Pos(), ir.ODCL, caseVar),
+				ir.NewAssignStmt(ncase.Pos(), caseVar, val),
+			}
+			typecheck.Stmts(l)
+			body.Append(l...)
+		}
+		body.Append(ncase.Body...)
+		body.Append(br)
+	}
+	sw.Cases = nil
+
+	if defaultGoto == nil {
+		defaultGoto = br
+	}
+	if nilGoto == nil {
+		nilGoto = defaultGoto
+	}
+	ifNil.Body = []ir.Node{nilGoto}
+
+	s.Emit(&sw.Compiled)
+	sw.Compiled.Append(defaultGoto)
+	sw.Compiled.Append(body.Take()...)
+
+	walkStmtList(sw.Compiled)
+}
+
+// typeHashFieldOf returns an expression to select the type hash field
+// from an interface's descriptor word (whether a *runtime._type or
+// *runtime.itab pointer).
+func typeHashFieldOf(pos src.XPos, itab *ir.UnaryExpr) *ir.SelectorExpr {
+	if itab.Op() != ir.OITAB {
+		base.Fatalf("expected OITAB, got %v", itab.Op())
+	}
+	var hashField *types.Field
+	if itab.X.Type().IsEmptyInterface() {
+		// runtime._type's hash field
+		if rtypeHashField == nil {
+			rtypeHashField = runtimeField("hash", int64(2*types.PtrSize), types.Types[types.TUINT32])
+		}
+		hashField = rtypeHashField
+	} else {
+		// runtime.itab's hash field
+		if itabHashField == nil {
+			itabHashField = runtimeField("hash", int64(2*types.PtrSize), types.Types[types.TUINT32])
+		}
+		hashField = itabHashField
+	}
+	return boundedDotPtr(pos, itab, hashField)
+}
+
+var rtypeHashField, itabHashField *types.Field
+
+// A typeSwitch walks a type switch.
+type typeSwitch struct {
+	// Temporary variables (i.e., ONAMEs) used by type switch dispatch logic:
+	facename ir.Node // value being type-switched on
+	hashname ir.Node // type hash of the value being type-switched on
+	okname   ir.Node // boolean used for comma-ok type assertions
+
+	done    ir.Nodes
+	clauses []typeClause
+}
+
+type typeClause struct {
+	hash uint32
+	body ir.Nodes
+}
+
+func (s *typeSwitch) Add(pos src.XPos, n1 ir.Node, caseVar *ir.Name, jmp ir.Node) {
+	typ := n1.Type()
+	var body ir.Nodes
+	if caseVar != nil {
+		l := []ir.Node{
+			ir.NewDecl(pos, ir.ODCL, caseVar),
+			ir.NewAssignStmt(pos, caseVar, nil),
+		}
+		typecheck.Stmts(l)
+		body.Append(l...)
+	} else {
+		caseVar = ir.BlankNode.(*ir.Name)
+	}
+
+	// cv, ok = iface.(type)
+	as := ir.NewAssignListStmt(pos, ir.OAS2, nil, nil)
+	as.Lhs = []ir.Node{caseVar, s.okname} // cv, ok =
+	switch n1.Op() {
+	case ir.OTYPE:
+		// Static type assertion (non-generic)
+		dot := ir.NewTypeAssertExpr(pos, s.facename, nil)
+		dot.SetType(typ) // iface.(type)
+		as.Rhs = []ir.Node{dot}
+	case ir.ODYNAMICTYPE:
+		// Dynamic type assertion (generic)
+		dt := n1.(*ir.DynamicType)
+		dot := ir.NewDynamicTypeAssertExpr(pos, ir.ODYNAMICDOTTYPE, s.facename, dt.X)
+		if dt.ITab != nil {
+			dot.T = dt.ITab
+		}
+		dot.SetType(typ)
+		dot.SetTypecheck(1)
+		as.Rhs = []ir.Node{dot}
+	default:
+		base.Fatalf("unhandled type case %s", n1.Op())
+	}
+	appendWalkStmt(&body, as)
+
+	// if ok { goto label }
+	nif := ir.NewIfStmt(pos, nil, nil, nil)
+	nif.Cond = s.okname
+	nif.Body = []ir.Node{jmp}
+	body.Append(nif)
+
+	if n1.Op() == ir.OTYPE && !typ.IsInterface() {
+		// Defer static, noninterface cases so they can be binary searched by hash.
+		s.clauses = append(s.clauses, typeClause{
+			hash: types.TypeHash(n1.Type()),
+			body: body,
+		})
+		return
+	}
+
+	s.flush()
+	s.done.Append(body.Take()...)
+}
+
+func (s *typeSwitch) Emit(out *ir.Nodes) {
+	s.flush()
+	out.Append(s.done.Take()...)
+}
+
+func (s *typeSwitch) flush() {
+	cc := s.clauses
+	s.clauses = nil
+	if len(cc) == 0 {
+		return
+	}
+
+	sort.Slice(cc, func(i, j int) bool { return cc[i].hash < cc[j].hash })
+
+	// Combine adjacent cases with the same hash.
+	merged := cc[:1]
+	for _, c := range cc[1:] {
+		last := &merged[len(merged)-1]
+		if last.hash == c.hash {
+			last.body.Append(c.body.Take()...)
+		} else {
+			merged = append(merged, c)
+		}
+	}
+	cc = merged
+
+	binarySearch(len(cc), &s.done,
+		func(i int) ir.Node {
+			return ir.NewBinaryExpr(base.Pos, ir.OLE, s.hashname, ir.NewInt(int64(cc[i-1].hash)))
+		},
+		func(i int, nif *ir.IfStmt) {
+			// TODO(mdempsky): Omit hash equality check if
+			// there's only one type.
+			c := cc[i]
+			nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OEQ, s.hashname, ir.NewInt(int64(c.hash)))
+			nif.Body.Append(c.body.Take()...)
+		},
+	)
+}
+
+// binarySearch constructs a binary search tree for handling n cases,
+// and appends it to out. It's used for efficiently implementing
+// switch statements.
+//
+// less(i) should return a boolean expression. If it evaluates true,
+// then cases before i will be tested; otherwise, cases i and later.
+//
+// leaf(i, nif) should setup nif (an OIF node) to test case i. In
+// particular, it should set nif.Left and nif.Nbody.
+func binarySearch(n int, out *ir.Nodes, less func(i int) ir.Node, leaf func(i int, nif *ir.IfStmt)) {
+	const binarySearchMin = 4 // minimum number of cases for binary search
+
+	var do func(lo, hi int, out *ir.Nodes)
+	do = func(lo, hi int, out *ir.Nodes) {
+		n := hi - lo
+		if n < binarySearchMin {
+			for i := lo; i < hi; i++ {
+				nif := ir.NewIfStmt(base.Pos, nil, nil, nil)
+				leaf(i, nif)
+				base.Pos = base.Pos.WithNotStmt()
+				nif.Cond = typecheck.Expr(nif.Cond)
+				nif.Cond = typecheck.DefaultLit(nif.Cond, nil)
+				out.Append(nif)
+				out = &nif.Else
+			}
+			return
+		}
+
+		half := lo + n/2
+		nif := ir.NewIfStmt(base.Pos, nil, nil, nil)
+		nif.Cond = less(half)
+		base.Pos = base.Pos.WithNotStmt()
+		nif.Cond = typecheck.Expr(nif.Cond)
+		nif.Cond = typecheck.DefaultLit(nif.Cond, nil)
+		do(lo, half, &nif.Body)
+		do(half, hi, &nif.Else)
+		out.Append(nif)
+	}
+
+	do(0, n, out)
+}
diff --git a/src/cmd/compile/internal/walk/temp.go b/src/cmd/compile/internal/walk/temp.go
new file mode 100644
index 0000000..9879a6c
--- /dev/null
+++ b/src/cmd/compile/internal/walk/temp.go
@@ -0,0 +1,40 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+)
+
+// initStackTemp appends statements to init to initialize the given
+// temporary variable to val, and then returns the expression &tmp.
+func initStackTemp(init *ir.Nodes, tmp *ir.Name, val ir.Node) *ir.AddrExpr {
+	if val != nil && !types.Identical(tmp.Type(), val.Type()) {
+		base.Fatalf("bad initial value for %L: %L", tmp, val)
+	}
+	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmp, val))
+	return typecheck.Expr(typecheck.NodAddr(tmp)).(*ir.AddrExpr)
+}
+
+// stackTempAddr returns the expression &tmp, where tmp is a newly
+// allocated temporary variable of the given type. Statements to
+// zero-initialize tmp are appended to init.
+func stackTempAddr(init *ir.Nodes, typ *types.Type) *ir.AddrExpr {
+	return initStackTemp(init, typecheck.Temp(typ), nil)
+}
+
+// stackBufAddr returns thte expression &tmp, where tmp is a newly
+// allocated temporary variable of type [len]elem. This variable is
+// initialized, and elem must not contain pointers.
+func stackBufAddr(len int64, elem *types.Type) *ir.AddrExpr {
+	if elem.HasPointers() {
+		base.FatalfAt(base.Pos, "%v has pointers", elem)
+	}
+	tmp := typecheck.Temp(types.NewArray(elem, len))
+	return typecheck.Expr(typecheck.NodAddr(tmp)).(*ir.AddrExpr)
+}
diff --git a/src/cmd/compile/internal/walk/walk.go b/src/cmd/compile/internal/walk/walk.go
new file mode 100644
index 0000000..78cc2e6
--- /dev/null
+++ b/src/cmd/compile/internal/walk/walk.go
@@ -0,0 +1,402 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package walk
+
+import (
+	"errors"
+	"fmt"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/ssagen"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// The constant is known to runtime.
+const tmpstringbufsize = 32
+const zeroValSize = 1024 // must match value of runtime/map.go:maxZero
+
+func Walk(fn *ir.Func) {
+	ir.CurFunc = fn
+	errorsBefore := base.Errors()
+	order(fn)
+	if base.Errors() > errorsBefore {
+		return
+	}
+
+	if base.Flag.W != 0 {
+		s := fmt.Sprintf("\nbefore walk %v", ir.CurFunc.Sym())
+		ir.DumpList(s, ir.CurFunc.Body)
+	}
+
+	lno := base.Pos
+
+	base.Pos = lno
+	if base.Errors() > errorsBefore {
+		return
+	}
+	walkStmtList(ir.CurFunc.Body)
+	if base.Flag.W != 0 {
+		s := fmt.Sprintf("after walk %v", ir.CurFunc.Sym())
+		ir.DumpList(s, ir.CurFunc.Body)
+	}
+
+	if base.Flag.Cfg.Instrumenting {
+		instrument(fn)
+	}
+
+	// Eagerly compute sizes of all variables for SSA.
+	for _, n := range fn.Dcl {
+		types.CalcSize(n.Type())
+	}
+}
+
+// walkRecv walks an ORECV node.
+func walkRecv(n *ir.UnaryExpr) ir.Node {
+	if n.Typecheck() == 0 {
+		base.Fatalf("missing typecheck: %+v", n)
+	}
+	init := ir.TakeInit(n)
+
+	n.X = walkExpr(n.X, &init)
+	call := walkExpr(mkcall1(chanfn("chanrecv1", 2, n.X.Type()), nil, &init, n.X, typecheck.NodNil()), &init)
+	return ir.InitExpr(init, call)
+}
+
+func convas(n *ir.AssignStmt, init *ir.Nodes) *ir.AssignStmt {
+	if n.Op() != ir.OAS {
+		base.Fatalf("convas: not OAS %v", n.Op())
+	}
+	n.SetTypecheck(1)
+
+	if n.X == nil || n.Y == nil {
+		return n
+	}
+
+	lt := n.X.Type()
+	rt := n.Y.Type()
+	if lt == nil || rt == nil {
+		return n
+	}
+
+	if ir.IsBlank(n.X) {
+		n.Y = typecheck.DefaultLit(n.Y, nil)
+		return n
+	}
+
+	if !types.Identical(lt, rt) {
+		n.Y = typecheck.AssignConv(n.Y, lt, "assignment")
+		n.Y = walkExpr(n.Y, init)
+	}
+	types.CalcSize(n.Y.Type())
+
+	return n
+}
+
+var stop = errors.New("stop")
+
+func vmkcall(fn ir.Node, t *types.Type, init *ir.Nodes, va []ir.Node) *ir.CallExpr {
+	if init == nil {
+		base.Fatalf("mkcall with nil init: %v", fn)
+	}
+	if fn.Type() == nil || fn.Type().Kind() != types.TFUNC {
+		base.Fatalf("mkcall %v %v", fn, fn.Type())
+	}
+
+	n := fn.Type().NumParams()
+	if n != len(va) {
+		base.Fatalf("vmkcall %v needs %v args got %v", fn, n, len(va))
+	}
+
+	call := typecheck.Call(base.Pos, fn, va, false).(*ir.CallExpr)
+	call.SetType(t)
+	return walkExpr(call, init).(*ir.CallExpr)
+}
+
+func mkcall(name string, t *types.Type, init *ir.Nodes, args ...ir.Node) *ir.CallExpr {
+	return vmkcall(typecheck.LookupRuntime(name), t, init, args)
+}
+
+func mkcallstmt(name string, args ...ir.Node) ir.Node {
+	return mkcallstmt1(typecheck.LookupRuntime(name), args...)
+}
+
+func mkcall1(fn ir.Node, t *types.Type, init *ir.Nodes, args ...ir.Node) *ir.CallExpr {
+	return vmkcall(fn, t, init, args)
+}
+
+func mkcallstmt1(fn ir.Node, args ...ir.Node) ir.Node {
+	var init ir.Nodes
+	n := vmkcall(fn, nil, &init, args)
+	if len(init) == 0 {
+		return n
+	}
+	init.Append(n)
+	return ir.NewBlockStmt(n.Pos(), init)
+}
+
+func chanfn(name string, n int, t *types.Type) ir.Node {
+	if !t.IsChan() {
+		base.Fatalf("chanfn %v", t)
+	}
+	fn := typecheck.LookupRuntime(name)
+	switch n {
+	default:
+		base.Fatalf("chanfn %d", n)
+	case 1:
+		fn = typecheck.SubstArgTypes(fn, t.Elem())
+	case 2:
+		fn = typecheck.SubstArgTypes(fn, t.Elem(), t.Elem())
+	}
+	return fn
+}
+
+func mapfn(name string, t *types.Type, isfat bool) ir.Node {
+	if !t.IsMap() {
+		base.Fatalf("mapfn %v", t)
+	}
+	fn := typecheck.LookupRuntime(name)
+	if mapfast(t) == mapslow || isfat {
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem(), t.Key(), t.Elem())
+	} else {
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem(), t.Elem())
+	}
+	return fn
+}
+
+func mapfndel(name string, t *types.Type) ir.Node {
+	if !t.IsMap() {
+		base.Fatalf("mapfn %v", t)
+	}
+	fn := typecheck.LookupRuntime(name)
+	if mapfast(t) == mapslow {
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem(), t.Key())
+	} else {
+		fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem())
+	}
+	return fn
+}
+
+const (
+	mapslow = iota
+	mapfast32
+	mapfast32ptr
+	mapfast64
+	mapfast64ptr
+	mapfaststr
+	nmapfast
+)
+
+type mapnames [nmapfast]string
+
+func mkmapnames(base string, ptr string) mapnames {
+	return mapnames{base, base + "_fast32", base + "_fast32" + ptr, base + "_fast64", base + "_fast64" + ptr, base + "_faststr"}
+}
+
+var mapaccess1 = mkmapnames("mapaccess1", "")
+var mapaccess2 = mkmapnames("mapaccess2", "")
+var mapassign = mkmapnames("mapassign", "ptr")
+var mapdelete = mkmapnames("mapdelete", "")
+
+func mapfast(t *types.Type) int {
+	// Check runtime/map.go:maxElemSize before changing.
+	if t.Elem().Size() > 128 {
+		return mapslow
+	}
+	switch reflectdata.AlgType(t.Key()) {
+	case types.AMEM32:
+		if !t.Key().HasPointers() {
+			return mapfast32
+		}
+		if types.PtrSize == 4 {
+			return mapfast32ptr
+		}
+		base.Fatalf("small pointer %v", t.Key())
+	case types.AMEM64:
+		if !t.Key().HasPointers() {
+			return mapfast64
+		}
+		if types.PtrSize == 8 {
+			return mapfast64ptr
+		}
+		// Two-word object, at least one of which is a pointer.
+		// Use the slow path.
+	case types.ASTRING:
+		return mapfaststr
+	}
+	return mapslow
+}
+
+func walkAppendArgs(n *ir.CallExpr, init *ir.Nodes) {
+	walkExprListSafe(n.Args, init)
+
+	// walkExprListSafe will leave OINDEX (s[n]) alone if both s
+	// and n are name or literal, but those may index the slice we're
+	// modifying here. Fix explicitly.
+	ls := n.Args
+	for i1, n1 := range ls {
+		ls[i1] = cheapExpr(n1, init)
+	}
+}
+
+// appendWalkStmt typechecks and walks stmt and then appends it to init.
+func appendWalkStmt(init *ir.Nodes, stmt ir.Node) {
+	op := stmt.Op()
+	n := typecheck.Stmt(stmt)
+	if op == ir.OAS || op == ir.OAS2 {
+		// If the assignment has side effects, walkExpr will append them
+		// directly to init for us, while walkStmt will wrap it in an OBLOCK.
+		// We need to append them directly.
+		// TODO(rsc): Clean this up.
+		n = walkExpr(n, init)
+	} else {
+		n = walkStmt(n)
+	}
+	init.Append(n)
+}
+
+// The max number of defers in a function using open-coded defers. We enforce this
+// limit because the deferBits bitmask is currently a single byte (to minimize code size)
+const maxOpenDefers = 8
+
+// backingArrayPtrLen extracts the pointer and length from a slice or string.
+// This constructs two nodes referring to n, so n must be a cheapExpr.
+func backingArrayPtrLen(n ir.Node) (ptr, length ir.Node) {
+	var init ir.Nodes
+	c := cheapExpr(n, &init)
+	if c != n || len(init) != 0 {
+		base.Fatalf("backingArrayPtrLen not cheap: %v", n)
+	}
+	ptr = ir.NewUnaryExpr(base.Pos, ir.OSPTR, n)
+	if n.Type().IsString() {
+		ptr.SetType(types.Types[types.TUINT8].PtrTo())
+	} else {
+		ptr.SetType(n.Type().Elem().PtrTo())
+	}
+	length = ir.NewUnaryExpr(base.Pos, ir.OLEN, n)
+	length.SetType(types.Types[types.TINT])
+	return ptr, length
+}
+
+// mayCall reports whether evaluating expression n may require
+// function calls, which could clobber function call arguments/results
+// currently on the stack.
+func mayCall(n ir.Node) bool {
+	// When instrumenting, any expression might require function calls.
+	if base.Flag.Cfg.Instrumenting {
+		return true
+	}
+
+	isSoftFloat := func(typ *types.Type) bool {
+		return types.IsFloat[typ.Kind()] || types.IsComplex[typ.Kind()]
+	}
+
+	return ir.Any(n, func(n ir.Node) bool {
+		// walk should have already moved any Init blocks off of
+		// expressions.
+		if len(n.Init()) != 0 {
+			base.FatalfAt(n.Pos(), "mayCall %+v", n)
+		}
+
+		switch n.Op() {
+		default:
+			base.FatalfAt(n.Pos(), "mayCall %+v", n)
+
+		case ir.OCALLFUNC, ir.OCALLINTER,
+			ir.OUNSAFEADD, ir.OUNSAFESLICE:
+			return true
+
+		case ir.OINDEX, ir.OSLICE, ir.OSLICEARR, ir.OSLICE3, ir.OSLICE3ARR, ir.OSLICESTR,
+			ir.ODEREF, ir.ODOTPTR, ir.ODOTTYPE, ir.ODYNAMICDOTTYPE, ir.ODIV, ir.OMOD, ir.OSLICE2ARRPTR:
+			// These ops might panic, make sure they are done
+			// before we start marshaling args for a call. See issue 16760.
+			return true
+
+		case ir.OANDAND, ir.OOROR:
+			n := n.(*ir.LogicalExpr)
+			// The RHS expression may have init statements that
+			// should only execute conditionally, and so cannot be
+			// pulled out to the top-level init list. We could try
+			// to be more precise here.
+			return len(n.Y.Init()) != 0
+
+		// When using soft-float, these ops might be rewritten to function calls
+		// so we ensure they are evaluated first.
+		case ir.OADD, ir.OSUB, ir.OMUL, ir.ONEG:
+			return ssagen.Arch.SoftFloat && isSoftFloat(n.Type())
+		case ir.OLT, ir.OEQ, ir.ONE, ir.OLE, ir.OGE, ir.OGT:
+			n := n.(*ir.BinaryExpr)
+			return ssagen.Arch.SoftFloat && isSoftFloat(n.X.Type())
+		case ir.OCONV:
+			n := n.(*ir.ConvExpr)
+			return ssagen.Arch.SoftFloat && (isSoftFloat(n.Type()) || isSoftFloat(n.X.Type()))
+
+		case ir.OLITERAL, ir.ONIL, ir.ONAME, ir.OLINKSYMOFFSET, ir.OMETHEXPR,
+			ir.OAND, ir.OANDNOT, ir.OLSH, ir.OOR, ir.ORSH, ir.OXOR, ir.OCOMPLEX, ir.OEFACE,
+			ir.OADDR, ir.OBITNOT, ir.ONOT, ir.OPLUS,
+			ir.OCAP, ir.OIMAG, ir.OLEN, ir.OREAL,
+			ir.OCONVNOP, ir.ODOT,
+			ir.OCFUNC, ir.OIDATA, ir.OITAB, ir.OSPTR,
+			ir.OBYTES2STRTMP, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OSLICEHEADER:
+			// ok: operations that don't require function calls.
+			// Expand as needed.
+		}
+
+		return false
+	})
+}
+
+// itabType loads the _type field from a runtime.itab struct.
+func itabType(itab ir.Node) ir.Node {
+	if itabTypeField == nil {
+		// runtime.itab's _type field
+		itabTypeField = runtimeField("_type", int64(types.PtrSize), types.NewPtr(types.Types[types.TUINT8]))
+	}
+	return boundedDotPtr(base.Pos, itab, itabTypeField)
+}
+
+var itabTypeField *types.Field
+
+// boundedDotPtr returns a selector expression representing ptr.field
+// and omits nil-pointer checks for ptr.
+func boundedDotPtr(pos src.XPos, ptr ir.Node, field *types.Field) *ir.SelectorExpr {
+	sel := ir.NewSelectorExpr(pos, ir.ODOTPTR, ptr, field.Sym)
+	sel.Selection = field
+	sel.SetType(field.Type)
+	sel.SetTypecheck(1)
+	sel.SetBounded(true) // guaranteed not to fault
+	return sel
+}
+
+func runtimeField(name string, offset int64, typ *types.Type) *types.Field {
+	f := types.NewField(src.NoXPos, ir.Pkgs.Runtime.Lookup(name), typ)
+	f.Offset = offset
+	return f
+}
+
+// ifaceData loads the data field from an interface.
+// The concrete type must be known to have type t.
+// It follows the pointer if !IsDirectIface(t).
+func ifaceData(pos src.XPos, n ir.Node, t *types.Type) ir.Node {
+	if t.IsInterface() {
+		base.Fatalf("ifaceData interface: %v", t)
+	}
+	ptr := ir.NewUnaryExpr(pos, ir.OIDATA, n)
+	if types.IsDirectIface(t) {
+		ptr.SetType(t)
+		ptr.SetTypecheck(1)
+		return ptr
+	}
+	ptr.SetType(types.NewPtr(t))
+	ptr.SetTypecheck(1)
+	ind := ir.NewStarExpr(pos, ptr)
+	ind.SetType(t)
+	ind.SetTypecheck(1)
+	ind.SetBounded(true)
+	return ind
+}