cmd/compile: enable const division for arm64

performance:
benchmark                   old ns/op     new ns/op     delta
BenchmarkDivconstI64-8      8.28          2.70          -67.39%
BenchmarkDivconstU64-8      8.28          4.69          -43.36%
BenchmarkDivconstI32-8      8.28          6.39          -22.83%
BenchmarkDivconstU32-8      8.28          4.43          -46.50%
BenchmarkDivconstI16-8      5.17          5.17          +0.00%
BenchmarkDivconstU16-8      5.33          5.34          +0.19%
BenchmarkDivconstI8-8       3.50          3.50          +0.00%
BenchmarkDivconstU8-8       3.51          3.50          -0.28%

Fixes #15382

Change-Id: Ibce7b28f0586d593b33c4d4ecc5d5e7e7c905d13
Reviewed-on: https://go-review.googlesource.com/22292
Reviewed-by: Michael Munday <munday@ca.ibm.com>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/test/bench/go1/divconst_test.go b/test/bench/go1/divconst_test.go
new file mode 100644
index 0000000000..3cf6c26094
--- /dev/null
+++ b/test/bench/go1/divconst_test.go
@@ -0,0 +1,73 @@
+// Copyright 2016 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 go1
+
+import (
+	"testing"
+)
+
+var i64res int64
+
+func BenchmarkDivconstI64(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		i64res = int64(i) / 7
+	}
+}
+
+var u64res uint64
+
+func BenchmarkDivconstU64(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		u64res = uint64(i) / 7
+	}
+}
+
+var i32res int32
+
+func BenchmarkDivconstI32(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		i32res = int32(i) / 7
+	}
+}
+
+var u32res uint32
+
+func BenchmarkDivconstU32(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		u32res = uint32(i) / 7
+	}
+}
+
+var i16res int16
+
+func BenchmarkDivconstI16(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		i16res = int16(i) / 7
+	}
+}
+
+var u16res uint16
+
+func BenchmarkDivconstU16(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		u16res = uint16(i) / 7
+	}
+}
+
+var i8res int8
+
+func BenchmarkDivconstI8(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		i8res = int8(i) / 7
+	}
+}
+
+var u8res uint8
+
+func BenchmarkDivconstU8(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		u8res = uint8(i) / 7
+	}
+}