1 files changed, 231 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/walk/closure.go b/src/cmd/compile/internal/walk/closure.go
new file mode 100644
index 0000000..1fa3ac0
--- /dev/null
+++ b/src/cmd/compile/internal/walk/closure.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"
+	"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(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, 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, 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())
+	}
+
+	meth := dot.Sel
+	rcvrtype := dot.X.Type()
+	sym := ir.MethodSymSuffix(rcvrtype, meth, "-fm")
+
+	if sym.Uniq() {
+		return sym.Def.(*ir.Name)
+	}
+	sym.SetUniq(true)
+
+	base.FatalfAt(dot.Pos(), "missing wrapper for %v", meth)
+	panic("unreachable")
+}