cmd/compile: fix missing init nodes for len(string([]byte)) optimization

CL 497276 added optimization for len(string([]byte)) by avoiding call to slicebytetostring. However, the bytes to string expression may contain init nodes, which need to be preserved. Otherwise, it would make the liveness analysis confusing about the lifetime of temporary variables created by init nodes. Fixes golang#61778 Change-Id: I6d1280a7d61bcc75f11132af41bda086f084ab54 Reviewed-on: https://go-review.googlesource.com/c/go/+/516375 Run-TryBot: Cuong Manh Le <[email protected]> Reviewed-by: Keith Randall <[email protected]> Reviewed-by: Keith Randall <[email protected]> Auto-Submit: Cuong Manh Le <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Matthew Dempsky <[email protected]>
cellularmitosis · Aug 7, 2023 · ea565f1 · ea565f1
1 parent 4198193
commit ea565f1
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diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
@@ -255,7 +255,10 @@ func walkLenCap(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
 		return mkcall("countrunes", n.Type(), init, typecheck.Conv(n.X.(*ir.ConvExpr).X, types.Types[types.TSTRING]))
 	}
 	if isByteCount(n) {
-		_, len := backingArrayPtrLen(cheapExpr(n.X.(*ir.ConvExpr).X, init))
+		conv := n.X.(*ir.ConvExpr)
+		walkStmtList(conv.Init())
+		init.Append(ir.TakeInit(conv)...)
+		_, len := backingArrayPtrLen(cheapExpr(conv.X, init))
 		return len
 	}
 

diff --git a/test/fixedbugs/issue61778.go b/test/fixedbugs/issue61778.go
@@ -0,0 +1,13 @@
+// compile
+
+// Copyright 2023 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 p
+
+func f(s []byte) {
+	switch "" {
+	case string(append(s, 'a')):
+	}
+}