[dev.simd] cmd/compile: handle rematerialized op for incompatible reg constraint

This CL fixes an issue raised by contributor dominikh@.

Change-Id: I941b330a6ba6f6c120c69951ddd24933f2f0b3ec
Reviewed-on: https://go-review.googlesource.com/c/go/+/704056
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/test/simd/bug2.go b/test/simd/bug2.go
new file mode 100644
index 0000000000..2d2094b5a4
--- /dev/null
+++ b/test/simd/bug2.go
@@ -0,0 +1,26 @@
+// compile
+
+//go:build amd64 && goexperiment.simd
+
+// 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.
+
+// Test case for rematerialization ignoring the register constraint
+// during regalloc's shuffle phase.
+
+package p
+
+import (
+	"simd"
+)
+
+func PackComplex(b bool) {
+	for {
+		if b {
+			var indices [4]uint32
+			simd.Uint32x4{}.ShiftAllRight(20).Store(&indices)
+			_ = indices[indices[0]]
+		}
+	}
+}