Adding upstream version 1.22.1.upstream/1.22.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1096 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
new file mode 100644
index 0000000..268f793
--- /dev/null
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -0,0 +1,1096 @@
+// 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/abi"
+	"internal/buildcfg"
+	"strings"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/objw"
+	"cmd/compile/internal/reflectdata"
+	"cmd/compile/internal/rttype"
+	"cmd/compile/internal/staticdata"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+	"cmd/internal/objabi"
+)
+
+// 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.OMIN, ir.OMAX:
+		n := n.(*ir.CallExpr)
+		return walkMinMax(n, init)
+
+	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.OMAKEFACE, 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.OUNSAFESTRING:
+		n := n.(*ir.BinaryExpr)
+		return walkUnsafeString(n, init)
+
+	case ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
+		n := n.(*ir.UnaryExpr)
+		return walkUnsafeData(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.OPRINTLN:
+		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.OCONV, ir.OCONVNOP:
+		n := n.(*ir.ConvExpr)
+		return walkConv(n, init)
+
+	case ir.OSLICE2ARR:
+		n := n.(*ir.ConvExpr)
+		return walkSliceToArray(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.OSTRINGHEADER:
+		n := n.(*ir.StringHeaderExpr)
+		return walkStringHeader(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.OCLEAR:
+		n := n.(*ir.UnaryExpr)
+		return walkClear(n)
+
+	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.TempAt(base.Pos, ir.CurFunc, 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, 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
+}
+
+type hookInfo struct {
+	paramType   types.Kind
+	argsNum     int
+	runtimeFunc string
+}
+
+var hooks = map[string]hookInfo{
+	"strings.EqualFold": {paramType: types.TSTRING, argsNum: 2, runtimeFunc: "libfuzzerHookEqualFold"},
+}
+
+// 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.Fun.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.Fun.Op() == ir.OCLOSURE {
+		directClosureCall(n)
+	}
+
+	if ir.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.Fun.(*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 n.Type() != types.Types[types.TUINTPTR] {
+			base.FatalfAt(n.Pos(), "FuncPC intrinsic should return uintptr, got %v", n.Type()) // as expected by typecheck.FuncPC.
+		}
+		n := ir.FuncPC(n.Pos(), arg, wantABI)
+		return walkExpr(n, init)
+	}
+
+	if name, ok := n.Fun.(*ir.Name); ok {
+		sym := name.Sym()
+		if sym.Pkg.Path == "go.runtime" && sym.Name == "deferrangefunc" {
+			// Call to runtime.deferrangefunc is being shared with a range-over-func
+			// body that might add defers to this frame, so we cannot use open-coded defers
+			// and we need to call deferreturn even if we don't see any other explicit defers.
+			ir.CurFunc.SetHasDefer(true)
+			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
+		}
+	}
+
+	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.Fun.Type().Params()
+
+	n.Fun = walkExpr(n.Fun, init)
+	walkExprList(args, init)
+
+	for i, arg := range args {
+		// Validate argument and parameter types match.
+		param := params[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.TempAt(base.Pos, ir.CurFunc, param.Type)
+			init.Append(convas(typecheck.Stmt(ir.NewAssignStmt(base.Pos, tmp, arg)).(*ir.AssignStmt), init))
+			// replace arg with temp
+			args[i] = tmp
+		}
+	}
+
+	funSym := n.Fun.Sym()
+	if base.Debug.Libfuzzer != 0 && funSym != nil {
+		if hook, found := hooks[funSym.Pkg.Path+"."+funSym.Name]; found {
+			if len(args) != hook.argsNum {
+				panic(fmt.Sprintf("%s.%s expects %d arguments, but received %d", funSym.Pkg.Path, funSym.Name, hook.argsNum, len(args)))
+			}
+			var hookArgs []ir.Node
+			for _, arg := range args {
+				hookArgs = append(hookArgs, tracecmpArg(arg, types.Types[hook.paramType], init))
+			}
+			hookArgs = append(hookArgs, fakePC(n))
+			init.Append(mkcall(hook.runtimeFunc, nil, init, hookArgs...))
+		}
+	}
+}
+
+// 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.ITabAddrAt(base.Pos, n.Type(), n.X.Type())
+	}
+	if n.X.Type().IsInterface() && n.Type().IsInterface() && !n.Type().IsEmptyInterface() {
+		// This kind of conversion needs a runtime call. Allocate
+		// a descriptor for that call.
+		n.Descriptor = makeTypeAssertDescriptor(n.Type(), n.Op() == ir.ODOTTYPE2)
+	}
+	return n
+}
+
+func makeTypeAssertDescriptor(target *types.Type, canFail bool) *obj.LSym {
+	// When converting from an interface to a non-empty interface. Needs a runtime call.
+	// Allocate an internal/abi.TypeAssert descriptor for that call.
+	lsym := types.LocalPkg.Lookup(fmt.Sprintf(".typeAssert.%d", typeAssertGen)).LinksymABI(obj.ABI0)
+	typeAssertGen++
+	c := rttype.NewCursor(lsym, 0, rttype.TypeAssert)
+	c.Field("Cache").WritePtr(typecheck.LookupRuntimeVar("emptyTypeAssertCache"))
+	c.Field("Inter").WritePtr(reflectdata.TypeSym(target).Linksym())
+	c.Field("CanFail").WriteBool(canFail)
+	objw.Global(lsym, int32(rttype.TypeAssert.Size()), obj.LOCAL)
+	lsym.Gotype = reflectdata.TypeLinksym(rttype.TypeAssert)
+	return lsym
+}
+
+var typeAssertGen int
+
+// walkDynamicDotType walks an ODYNAMICDOTTYPE or ODYNAMICDOTTYPE2 node.
+func walkDynamicDotType(n *ir.DynamicTypeAssertExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	n.RType = walkExpr(n.RType, init)
+	n.ITab = walkExpr(n.ITab, init)
+	// Convert to non-dynamic if we can.
+	if n.RType != nil && n.RType.Op() == ir.OADDR {
+		addr := n.RType.(*ir.AddrExpr)
+		if addr.X.Op() == ir.OLINKSYMOFFSET {
+			r := ir.NewTypeAssertExpr(n.Pos(), n.X, n.Type())
+			if n.Op() == ir.ODYNAMICDOTTYPE2 {
+				r.SetOp(ir.ODOTTYPE2)
+			}
+			r.SetType(n.Type())
+			r.SetTypecheck(1)
+			return walkExpr(r, 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")
+		}
+	} 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")
+		}
+	}
+	return n
+}
+
+// mapKeyArg returns an expression for key that is suitable to be passed
+// as the key argument for runtime map* functions.
+// n is the map indexing or delete Node (to provide Pos).
+func mapKeyArg(fast int, n, key ir.Node, assigned bool) ir.Node {
+	if fast == mapslow {
+		// standard version takes key by reference.
+		// orderState.expr made sure key is addressable.
+		return typecheck.NodAddr(key)
+	}
+	if assigned {
+		// mapassign does distinguish pointer vs. integer key.
+		return key
+	}
+	// mapaccess and mapdelete don't distinguish pointer vs. integer key.
+	switch fast {
+	case mapfast32ptr:
+		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT32], key)
+	case mapfast64ptr:
+		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.
+// It replaces m[k] with *map{access1,assign}(maptype, m, &k)
+func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
+	n.X = walkExpr(n.X, init)
+	n.Index = walkExpr(n.Index, init)
+	map_ := n.X
+	t := map_.Type()
+	fast := mapfast(t)
+	key := mapKeyArg(fast, n, n.Index, n.Assigned)
+	args := []ir.Node{reflectdata.IndexMapRType(base.Pos, n), map_, key}
+
+	var mapFn ir.Node
+	switch {
+	case n.Assigned:
+		mapFn = mapfn(mapassign[fast], t, false)
+	case t.Elem().Size() > abi.ZeroValSize:
+		args = append(args, reflectdata.ZeroAddr(t.Elem().Size()))
+		mapFn = mapfn("mapaccess1_fat", t, true)
+	default:
+		mapFn = mapfn(mapaccess1[fast], t, false)
+	}
+	call := mkcall1(mapFn, nil, init, args...)
+	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() == 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
+}
+
+// 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
+}
+
+// walkStringHeader walks an OSTRINGHEADER node.
+func walkStringHeader(n *ir.StringHeaderExpr, init *ir.Nodes) ir.Node {
+	n.Ptr = walkExpr(n.Ptr, init)
+	n.Len = walkExpr(n.Len, init)
+	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 Method and MethodByName of reflect.Value,
+// reflect.Type, reflect.(*rtype), and reflect.(*interfaceType).
+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" {
+		// TODO: is there a better way than hardcoding the names?
+		switch fn := ir.CurFunc.Nname.Sym().Name; {
+		case fn == "(*rtype).Method", fn == "(*rtype).MethodByName":
+			return
+		case fn == "(*interfaceType).Method", fn == "(*interfaceType).MethodByName":
+			return
+		case fn == "Value.Method", fn == "Value.MethodByName":
+			return
+		}
+	}
+
+	dot, ok := n.Fun.(*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)
+	//
+	//	reflect.Value.Method       - func(int) reflect.Value
+	//	reflect.Value.MethodByName - func(string) reflect.Value
+	methodName := dot.Sel.Name
+	t := dot.Selection.Type
+
+	// Check the number of arguments and return values.
+	if t.NumParams() != 1 || (t.NumResults() != 1 && t.NumResults() != 2) {
+		return
+	}
+
+	// Check the type of the argument.
+	switch pKind := t.Param(0).Type.Kind(); {
+	case methodName == "Method" && pKind == types.TINT,
+		methodName == "MethodByName" && pKind == types.TSTRING:
+
+	default:
+		// not a call to Method or MethodByName of reflect.{Type,Value}.
+		return
+	}
+
+	// Check that first result type is "reflect.Method" or "reflect.Value".
+	// 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).
+	switch s := t.Result(0).Type.Sym(); {
+	case s != nil && types.ReflectSymName(s) == "Method",
+		s != nil && types.ReflectSymName(s) == "Value":
+
+	default:
+		// not a call to Method or MethodByName of reflect.{Type,Value}.
+		return
+	}
+
+	var targetName ir.Node
+	switch dot.Op() {
+	case ir.ODOTINTER:
+		if methodName == "MethodByName" {
+			targetName = n.Args[0]
+		}
+	case ir.OMETHEXPR:
+		if methodName == "MethodByName" {
+			targetName = n.Args[1]
+		}
+	default:
+		base.FatalfAt(dot.Pos(), "usemethod: unexpected dot.Op() %s", dot.Op())
+	}
+
+	if ir.IsConst(targetName, constant.String) {
+		name := constant.StringVal(targetName.Val())
+
+		r := obj.Addrel(ir.CurFunc.LSym)
+		r.Type = objabi.R_USENAMEDMETHOD
+		r.Sym = staticdata.StringSymNoCommon(name)
+	} else {
+		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")
+	}
+
+	sym := reflectdata.TrackSym(outer, field)
+	if ir.CurFunc.FieldTrack == nil {
+		ir.CurFunc.FieldTrack = make(map[*obj.LSym]struct{})
+	}
+	ir.CurFunc.FieldTrack[sym] = struct{}{}
+}