cmd/compile: use isUnsignedPowerOfTwo rather than isPowerOfTwo for unsigneds

Fixes #76688

Change-Id: Icb8dab54a5ce7d83b656d50d5ea605d2a62b96f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/726680
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/test/prove.go b/test/prove.go
index 1b50317fe3..e04b510e17 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -2718,6 +2718,14 @@ func detectStringLenRelation(s string) bool {
 	return false
 }
 
+func issue76688(x, y uint64) uint64 {
+	if x > 1 || y != 1<<63 {
+		return 42
+	}
+	// We do not want to rewrite the multiply to a condselect here since opt can do a better job with a left shift.
+	return x * y
+}
+
 //go:noinline
 func prove(x int) {
 }