cmd/compile/internal/walk: copy SSA-able variables

order.go ensures expressions that are passed to the runtime by address
are in fact addressable. However, in the case of local variables, if the
variable hasn't already been marked as addrtaken, then taking its
address here will effectively prevent the variable from being converted
to SSA form.

Instead, it's better to just copy the variable into a new temporary,
which we can pass by address instead. This ensures the original variable
can still be converted to SSA form.

Fixes #63332.

Change-Id: I182376d98d419df8bf07c400d84c344c9b82c0fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/541715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/test/codegen/issue63332.go b/test/codegen/issue63332.go
new file mode 100644
index 0000000000..dbe671d247
--- /dev/null
+++ b/test/codegen/issue63332.go
@@ -0,0 +1,14 @@
+// asmcheck
+
+// 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 codegen
+
+func issue63332(c chan int) {
+	x := 0
+	// amd64:-`MOVQ`
+	x += 2
+	c <- x
+}