cmd/compile: optimize unsigned comparisons to 0/1 on arm64

For an unsigned integer, it's useful to convert its order test with 0/1
to its equality test with 0. We can save a comparison instruction that
followed by a conditional branch on arm64 since it supports
compare-with-zero-and-branch instructions. For example,

  if x > 0 { ... } else { ... }

the original version:
  CMP $0, R0
  BLS 9

the optimized version:
  CBZ R0, 8

Updates #21439

Change-Id: Id1de6f865f6aa72c5d45b29f7894818857288425
Reviewed-on: https://go-review.googlesource.com/c/go/+/246857
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/test/codegen/comparisons.go b/test/codegen/comparisons.go
index f3c15538a8..3c2dcb7eba 100644
--- a/test/codegen/comparisons.go
+++ b/test/codegen/comparisons.go
@@ -424,3 +424,35 @@ func UintGeqZero(a uint8, b uint16, c uint32, d uint64) int {
 	}
 	return 0
 }
+
+func UintGtZero(a uint8, b uint16, c uint32, d uint64) int {
+	// arm64: `CBZW`, `CBNZW`, `CBNZ`, -`(CMPW|CMP|BLS|BHI)`
+	if a > 0 || b > 0 || c > 0 || d > 0 {
+		return 1
+	}
+	return 0
+}
+
+func UintLeqZero(a uint8, b uint16, c uint32, d uint64) int {
+	// arm64: `CBNZW`, `CBZW`, `CBZ`, -`(CMPW|CMP|BHI|BLS)`
+	if a <= 0 || b <= 0 || c <= 0 || d <= 0 {
+		return 1
+	}
+	return 0
+}
+
+func UintLtOne(a uint8, b uint16, c uint32, d uint64) int {
+	// arm64: `CBNZW`, `CBZW`, `CBZW`, `CBZ`, -`(CMPW|CMP|BHS|BLO)`
+	if a < 1 || b < 1 || c < 1 || d < 1 {
+		return 1
+	}
+	return 0
+}
+
+func UintGeqOne(a uint8, b uint16, c uint32, d uint64) int {
+	// arm64: `CBZW`, `CBNZW`, `CBNZ`, -`(CMPW|CMP|BLO|BHS)`
+	if a >= 1 || b >= 1 || c >= 1 || d >= 1 {
+		return 1
+	}
+	return 0
+}