cmd/compile: mark unused values as invalid to prevent problems in expandCalls

Leftover values that have been replaced can cause problems in later
passes (within expandCalls).  For example, a struct select that
itself yields a struct will have a problematic rewrite, if the chance
is presented.

Updates #40724.

Change-Id: I1b445c47c301c3705f7fc0a9d39f1f5c84f4e190
Reviewed-on: https://go-review.googlesource.com/c/go/+/306869
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/test/abi/zombie_struct_select.go b/test/abi/zombie_struct_select.go
new file mode 100644
index 0000000000..d0cab98182
--- /dev/null
+++ b/test/abi/zombie_struct_select.go
@@ -0,0 +1,36 @@
+// run
+
+// Copyright 2021 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 main
+
+type patchlist struct {
+	head, tail uint32
+}
+
+type frag struct {
+	i   uint32
+	out patchlist
+}
+
+//go:noinline
+//go:registerparams
+func patch(l patchlist, i uint32) {
+}
+
+//go:noinline
+//go:registerparams
+func badbad(f1, f2 frag) frag {
+	// concat of failure is failure
+	if f1.i == 0 || f2.i == 0 { // internal compiler error: 'badbad': incompatible OpArgIntReg [4]: v42 and v26
+		return frag{}
+	}
+	patch(f1.out, f2.i)
+	return frag{f1.i, f2.out}
+}
+
+func main() {
+	badbad(frag{i: 2}, frag{i: 3})
+}