[dev.unified] cmd/compile: plumb rtype through for OMAPLIT

OMAPLIT gets lowered into a bunch of OINDEXMAP operations, which in
general may require a *runtime._type argument. This CL adds
CompLitExpr.RType, updates the GOEXPERIMENT=unified frontend to start
setting it, and updates walk to propagate it through to any generated
OINDEXMAP operations.

Change-Id: I278e7e8e615ea6d01f65a5eba6d6fc8e00045735
Reviewed-on: https://go-review.googlesource.com/c/go/+/413360
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/ir/expr.go

@@ -194,6 +194,7 @@ type CompLitExpr struct {
 	miniExpr
 	origNode
 	List     Nodes // initialized values
+	RType    Node  `mknode:"-"` // *runtime._type for OMAPLIT map types
 	Prealloc *Name
 	// For OSLICELIT, Len is the backing array length.
 	// For OMAPLIT, Len is the number of entries that we've removed from List and

src/cmd/compile/internal/noder/reader.go

@@ -1812,6 +1812,11 @@ func (r *reader) compLit() ir.Node {
 	}
 
 	lit := typecheck.Expr(ir.NewCompLitExpr(pos, ir.OCOMPLIT, typ, elems))
+	switch lit.Op() {
+	case ir.OMAPLIT:
+		lit := lit.(*ir.CompLitExpr)
+		lit.RType = reflectdata.TypePtrAt(pos, typ)
+	}
 	if typ0.IsPtr() {
 		lit = typecheck.Expr(typecheck.NodAddrAt(pos, lit))
 		lit.SetType(typ0)

src/cmd/compile/internal/reflectdata/helpers.go

@@ -160,9 +160,7 @@ func DeleteMapRType(pos src.XPos, n *ir.CallExpr) ir.Node {
 // map type.
 func IndexMapRType(pos src.XPos, n *ir.IndexExpr) ir.Node {
 	assertOp(n, ir.OINDEXMAP)
-	// TODO(mdempsky): Need to propagate RType from OMAPLIT nodes to
-	// emitted OINDEXMAP nodes.
-	if haveRType(n, n.RType, "RType", false) {
+	if haveRType(n, n.RType, "RType", true) {
 		return n.RType
 	}
 	return mapRType(pos, n.X.Type())
@@ -184,9 +182,7 @@ func MakeChanRType(pos src.XPos, n *ir.MakeExpr) ir.Node {
 // representing that map type.
 func MakeMapRType(pos src.XPos, n *ir.MakeExpr) ir.Node {
 	assertOp(n, ir.OMAKEMAP)
-	// TODO(mdempsky): Need to propagate RType from OMAPLIT nodes to
-	// emitted OMAKEMAP nodes.
-	if haveRType(n, n.RType, "RType", false) {
+	if haveRType(n, n.RType, "RType", true) {
 		return n.RType
 	}
 	return mapRType(pos, n.Type())

src/cmd/compile/internal/walk/complit.go

@@ -416,6 +416,7 @@ func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
 	// make the map var
 	args := []ir.Node{ir.TypeNode(n.Type()), ir.NewInt(n.Len + int64(len(n.List)))}
 	a := typecheck.Expr(ir.NewCallExpr(base.Pos, ir.OMAKE, nil, args)).(*ir.MakeExpr)
+	a.RType = n.RType
 	a.SetEsc(n.Esc())
 	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, m, a))
 
@@ -471,6 +472,7 @@ func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
 		// typechecker rewrites OINDEX to OINDEXMAP
 		lhs := typecheck.AssignExpr(ir.NewIndexExpr(base.Pos, m, kidx)).(*ir.IndexExpr)
 		base.AssertfAt(lhs.Op() == ir.OINDEXMAP, lhs.Pos(), "want OINDEXMAP, have %+v", lhs)
+		lhs.RType = n.RType
 
 		zero := ir.NewAssignStmt(base.Pos, i, ir.NewInt(0))
 		cond := ir.NewBinaryExpr(base.Pos, ir.OLT, i, ir.NewInt(tk.NumElem()))
@@ -510,6 +512,7 @@ func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
 		// typechecker rewrites OINDEX to OINDEXMAP
 		lhs := typecheck.AssignExpr(ir.NewIndexExpr(base.Pos, m, tmpkey)).(*ir.IndexExpr)
 		base.AssertfAt(lhs.Op() == ir.OINDEXMAP, lhs.Pos(), "want OINDEXMAP, have %+v", lhs)
+		lhs.RType = n.RType
 
 		var a ir.Node = ir.NewAssignStmt(base.Pos, lhs, tmpelem)
 		a = typecheck.Stmt(a)

src/cmd/compile/internal/walk/order.go

@@ -1452,6 +1452,7 @@ func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
 		for _, r := range dynamics {
 			lhs := typecheck.AssignExpr(ir.NewIndexExpr(base.Pos, m, r.Key)).(*ir.IndexExpr)
 			base.AssertfAt(lhs.Op() == ir.OINDEXMAP, lhs.Pos(), "want OINDEXMAP, have %+v", lhs)
+			lhs.RType = n.RType
 
 			as := ir.NewAssignStmt(base.Pos, lhs, r.Value)
 			typecheck.Stmt(as)