cmd/compile: memcombine different size stores

This CL implements the TODO in combineStores to allow combining
stores of different sizes, as long as the total size aligns to
2, 4, 8.

Fixes #72832.

Change-Id: I6d1d471335da90d851ad8f3b5a0cf10bdcfa17c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/661855
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/test/codegen/issue72832.go b/test/codegen/issue72832.go
new file mode 100644
index 0000000000..a7f6ca8c5c
--- /dev/null
+++ b/test/codegen/issue72832.go
@@ -0,0 +1,41 @@
+// asmcheck
+
+// Copyright 2025 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
+
+type tile1 struct {
+	a uint16
+	b uint16
+	c uint32
+}
+
+func store_tile1(t *tile1) {
+	// amd64:`MOVQ`
+	t.a, t.b, t.c = 1, 1, 1
+}
+
+type tile2 struct {
+	a, b, c, d, e int8
+}
+
+func store_tile2(t *tile2) {
+	// amd64:`MOVW`
+	t.a, t.b = 1, 1
+	// amd64:`MOVW`
+	t.d, t.e = 1, 1
+}
+
+type tile3 struct {
+	a, b uint8
+	c    uint16
+}
+
+func store_shifted(t *tile3, x uint32) {
+	// amd64:`MOVL`
+	t.a = uint8(x)
+	t.b = uint8(x >> 8)
+	t.c = uint16(x >> 16)
+}