cmd/compile: add generic rules to remove bool → int → bool roundtrips

Change-Id: I8b0a3b64c89fe167d304f901a5d38470f35400ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/715200
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/test/codegen/condmove.go b/test/codegen/condmove.go
index 97be0ced75..6d3a46b03c 100644
--- a/test/codegen/condmove.go
+++ b/test/codegen/condmove.go
@@ -507,3 +507,23 @@ func cmovmathhalveu(a uint, b bool) uint {
 	// wasm:"I64ShrU", -"Select"
 	return a
 }
+
+func branchlessBoolToUint8(b bool) (r uint8) {
+	if b {
+		r = 1
+	}
+	return
+}
+
+func cmovFromMulFromFlags64(x uint64, b bool) uint64 {
+	// amd64:-"MOVB.ZX"
+	r := uint64(branchlessBoolToUint8(b))
+	// amd64:"CMOV",-"MOVB.ZX",-"MUL"
+	return x * r
+}
+func cmovFromMulFromFlags64sext(x int64, b bool) int64 {
+	// amd64:-"MOVB.ZX"
+	r := int64(int8(branchlessBoolToUint8(b)))
+	// amd64:"CMOV",-"MOVB.ZX",-"MUL"
+	return x * r
+}