cmd/compile: do not treat OpLocalAddr as load in DSE

Fixes #70409
Fixes #47107

Change-Id: I82a66c46f6b76c68e156b5d937273b0316975d44
Reviewed-on: https://go-review.googlesource.com/c/go/+/629016
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

diff --git a/src/cmd/compile/internal/ssa/deadstore.go b/src/cmd/compile/internal/ssa/deadstore.go
index 9f61ef29b9d527aef1200bd20908c81dbdf4227a..29cf1e91e0f1a6526735090c7ef899ed98683b65 100644 (file)
--- a/src/cmd/compile/internal/ssa/deadstore.go
+++ b/src/cmd/compile/internal/ssa/deadstore.go
@@ -52,9 +52,8 @@ func dse(f *Func) {
                                if v.Op == OpLocalAddr {
                                        if _, ok := localAddrs[v.Aux]; !ok {
                                                localAddrs[v.Aux] = v
-                                       } else {
-                                               continue
                                        }
+                                       continue
                                }
                                if v.Op == OpInlMark {
                                        // Not really a use of the memory. See #67957.

diff --git a/test/codegen/issue70409.go b/test/codegen/issue70409.go
new file mode 100644 (file)
index 0000000..bfb4560
--- /dev/null
+++ b/test/codegen/issue70409.go
@@ -0,0 +1,20 @@
+// asmcheck -gcflags=-d=ssa/check/on
+
+// Copyright 2024 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
+
+// amd64:-"MOVQ"
+func foo(v uint64) (b [8]byte) {
+       b[0] = byte(v)
+       b[1] = byte(v >> 8)
+       b[2] = byte(v >> 16)
+       b[3] = byte(v >> 24)
+       b[4] = byte(v >> 32)
+       b[5] = byte(v >> 40)
+       b[6] = byte(v >> 48)
+       b[7] = byte(v >> 56)
+       return b
+}