cmd/compile: use stricter rule for possible partial overlap

Partial overlaps can only happen for strict sub-pieces of larger arrays.
That's a much stronger condition than the current optimization rules.

Update #54467

Change-Id: I11e539b71099e50175f37ee78fddf69283f83ee5
Reviewed-on: https://go-review.googlesource.com/c/go/+/433056
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/test/codegen/issue54467.go b/test/codegen/issue54467.go
new file mode 100644
index 0000000000..d34b3278f0
--- /dev/null
+++ b/test/codegen/issue54467.go
@@ -0,0 +1,59 @@
+// asmcheck
+
+// Copyright 2022 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 f1(x *[4]int, y *[4]int) {
+	// amd64:".*memmove"
+	*x = *y
+}
+func f2(x *[4]int, y [4]int) {
+	// amd64:-".*memmove"
+	*x = y
+}
+func f3(x *[4]int, y *[4]int) {
+	// amd64:-".*memmove"
+	t := *y
+	// amd64:-".*memmove"
+	*x = t
+}
+func f4(x *[4]int, y [4]int) {
+	// amd64:-".*memmove"
+	t := y
+	// amd64:-".*memmove"
+	*x = t
+}
+
+type T struct {
+	a [4]int
+}
+
+func f5(x, y *T) {
+	// amd64:-".*memmove"
+	x.a = y.a
+}
+func f6(x *T, y T) {
+	// amd64:-".*memmove"
+	x.a = y.a
+}
+func f7(x *T, y *[4]int) {
+	// amd64:-".*memmove"
+	x.a = *y
+}
+func f8(x *[4]int, y *T) {
+	// amd64:-".*memmove"
+	*x = y.a
+}
+
+func f9(x [][4]int, y [][4]int, i, j int) {
+	// amd64:-".*memmove"
+	x[i] = y[j]
+}
+
+func f10() []byte {
+	// amd64:-".*memmove"
+	return []byte("aReasonablyBigTestString")
+}