From 135ce1c485d0563d285f47a748a6d56594571a91 Mon Sep 17 00:00:00 2001
From: Matthew Dempsky <mdempsky@google.com>
Date: Sat, 26 Dec 2020 18:33:27 -0800
Subject: [PATCH] [dev.regabi] cmd/compile: desugar OMETHEXPR into ONAME during
 walk

A subsequent CL will change FuncName to lazily create the ONAME nodes,
which isn't currently safe to do during SSA construction, because that
phase is concurrent.

Passes toolstash -cmp.

Change-Id: Ic24acc1d1160ad93b70ced3baa468f750e689ea6
Reviewed-on: https://go-review.googlesource.com/c/go/+/280435
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
---
 src/cmd/compile/internal/ssagen/ssa.go |  4 ----
 src/cmd/compile/internal/walk/expr.go  | 26 ++++++++++++++------------
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 9cdf902bcb..082cb7c321 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -2108,10 +2108,6 @@ func (s *state) expr(n ir.Node) *ssa.Value {
 		n := n.(*ir.UnaryExpr)
 		aux := n.X.Sym().Linksym()
 		return s.entryNewValue1A(ssa.OpAddr, n.Type(), aux, s.sb)
-	case ir.OMETHEXPR:
-		n := n.(*ir.MethodExpr)
-		sym := staticdata.FuncSym(n.FuncName().Sym()).Linksym()
-		return s.entryNewValue1A(ssa.OpAddr, types.NewPtr(n.Type()), sym, s.sb)
 	case ir.ONAME:
 		n := n.(*ir.Name)
 		if n.Class_ == ir.PFUNC {
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
index 53bffee181..fd0dd5b062 100644
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -88,7 +88,7 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 		base.Fatalf("walkexpr: switch 1 unknown op %+v", n.Op())
 		panic("unreachable")
 
-	case ir.ONONAME, ir.OGETG, ir.ONEWOBJ, ir.OMETHEXPR:
+	case ir.ONONAME, ir.OGETG, ir.ONEWOBJ:
 		return n
 
 	case ir.OTYPE, ir.ONAME, ir.OLITERAL, ir.ONIL, ir.ONAMEOFFSET:
@@ -98,6 +98,11 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 		// stringsym for constant strings.
 		return n
 
+	case ir.OMETHEXPR:
+		// TODO(mdempsky): Do this right after type checking.
+		n := n.(*ir.MethodExpr)
+		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)
@@ -517,31 +522,28 @@ func walkCall1(n *ir.CallExpr, init *ir.Nodes) {
 		return // already walked
 	}
 
-	args := n.Args
-
-	n.X = walkExpr(n.X, init)
-	walkExprList(args, init)
-
 	// If this is a method call t.M(...),
 	// rewrite into a function call T.M(t, ...).
 	// TODO(mdempsky): Do this right after type checking.
 	if n.Op() == ir.OCALLMETH {
-		withRecv := make([]ir.Node, len(args)+1)
+		withRecv := make([]ir.Node, len(n.Args)+1)
 		dot := n.X.(*ir.SelectorExpr)
 		withRecv[0] = dot.X
-		copy(withRecv[1:], args)
-		args = withRecv
+		copy(withRecv[1:], n.Args)
+		n.Args = withRecv
 
 		dot = ir.NewSelectorExpr(dot.Pos(), ir.OXDOT, ir.TypeNode(dot.X.Type()), dot.Selection.Sym)
-		fn := typecheck.Expr(dot).(*ir.MethodExpr).FuncName()
-		fn.Type().Size()
 
 		n.SetOp(ir.OCALLFUNC)
-		n.X = fn
+		n.X = typecheck.Expr(dot)
 	}
 
+	args := n.Args
 	params := n.X.Type().Params()
 
+	n.X = walkExpr(n.X, init)
+	walkExprList(args, init)
+
 	// 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.