cmd/compile: add unsigned power-of-two detector

Fixes #74485

Change-Id: Ia22a58ac43bdc36c8414d555672a3a3eafc749ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/689815
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/test/codegen/issue74485.go b/test/codegen/issue74485.go
new file mode 100644
index 0000000000..570707509b
--- /dev/null
+++ b/test/codegen/issue74485.go
@@ -0,0 +1,27 @@
+// 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
+
+func divUint64(b uint64) uint64 {
+	// amd64:"SHRQ	[$]63, AX"
+	return b / 9223372036854775808
+}
+
+func divUint32(b uint32) uint32 {
+	// amd64:"SHRL	[$]31, AX"
+	return b / 2147483648
+}
+
+func divUint16(b uint16) uint16 {
+	// amd64:"SHRW	[$]15, AX"
+	return b / 32768
+}
+
+func divUint8(b uint8) uint8 {
+	// amd64:"SHRB	[$]7, AL"
+	return b / 128
+}