mirror of
https://github.com/golang/go
synced 2024-11-20 07:54:39 -07:00
f03c9202c4
Recognize loops of the form
for i := range a {
a[i] = zero
}
in which the evaluation of a is free from side effects.
Replace these loops with calls to memclr.
This occurs in the stdlib in 18 places.
The motivating example is clearing a byte slice:
benchmark old ns/op new ns/op delta
BenchmarkGoMemclr5 3.31 3.26 -1.51%
BenchmarkGoMemclr16 13.7 3.28 -76.06%
BenchmarkGoMemclr64 50.8 4.14 -91.85%
BenchmarkGoMemclr256 157 6.02 -96.17%
Update #5373.
Change-Id: I99d3e6f5f268e8c6499b7e661df46403e5eb83e4
Reviewed-on: https://go-review.googlesource.com/2520
Reviewed-by: Keith Randall <khr@golang.org>
310 lines
7.1 KiB
Go
310 lines
7.1 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime_test
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import (
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. "runtime"
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"testing"
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)
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func TestMemmove(t *testing.T) {
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size := 256
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if testing.Short() {
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size = 128 + 16
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}
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src := make([]byte, size)
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dst := make([]byte, size)
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for i := 0; i < size; i++ {
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src[i] = byte(128 + (i & 127))
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}
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for i := 0; i < size; i++ {
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dst[i] = byte(i & 127)
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}
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for n := 0; n <= size; n++ {
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for x := 0; x <= size-n; x++ { // offset in src
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for y := 0; y <= size-n; y++ { // offset in dst
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copy(dst[y:y+n], src[x:x+n])
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for i := 0; i < y; i++ {
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if dst[i] != byte(i&127) {
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t.Fatalf("prefix dst[%d] = %d", i, dst[i])
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}
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}
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for i := y; i < y+n; i++ {
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if dst[i] != byte(128+((i-y+x)&127)) {
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t.Fatalf("copied dst[%d] = %d", i, dst[i])
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}
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dst[i] = byte(i & 127) // reset dst
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}
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for i := y + n; i < size; i++ {
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if dst[i] != byte(i&127) {
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t.Fatalf("suffix dst[%d] = %d", i, dst[i])
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}
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}
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}
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}
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}
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}
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func TestMemmoveAlias(t *testing.T) {
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size := 256
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if testing.Short() {
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size = 128 + 16
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}
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buf := make([]byte, size)
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for i := 0; i < size; i++ {
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buf[i] = byte(i)
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}
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for n := 0; n <= size; n++ {
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for x := 0; x <= size-n; x++ { // src offset
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for y := 0; y <= size-n; y++ { // dst offset
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copy(buf[y:y+n], buf[x:x+n])
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for i := 0; i < y; i++ {
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if buf[i] != byte(i) {
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t.Fatalf("prefix buf[%d] = %d", i, buf[i])
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}
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}
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for i := y; i < y+n; i++ {
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if buf[i] != byte(i-y+x) {
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t.Fatalf("copied buf[%d] = %d", i, buf[i])
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}
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buf[i] = byte(i) // reset buf
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}
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for i := y + n; i < size; i++ {
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if buf[i] != byte(i) {
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t.Fatalf("suffix buf[%d] = %d", i, buf[i])
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}
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}
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}
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}
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}
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}
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func bmMemmove(b *testing.B, n int) {
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x := make([]byte, n)
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y := make([]byte, n)
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b.SetBytes(int64(n))
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for i := 0; i < b.N; i++ {
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copy(x, y)
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}
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}
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func BenchmarkMemmove0(b *testing.B) { bmMemmove(b, 0) }
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func BenchmarkMemmove1(b *testing.B) { bmMemmove(b, 1) }
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func BenchmarkMemmove2(b *testing.B) { bmMemmove(b, 2) }
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func BenchmarkMemmove3(b *testing.B) { bmMemmove(b, 3) }
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func BenchmarkMemmove4(b *testing.B) { bmMemmove(b, 4) }
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func BenchmarkMemmove5(b *testing.B) { bmMemmove(b, 5) }
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func BenchmarkMemmove6(b *testing.B) { bmMemmove(b, 6) }
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func BenchmarkMemmove7(b *testing.B) { bmMemmove(b, 7) }
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func BenchmarkMemmove8(b *testing.B) { bmMemmove(b, 8) }
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func BenchmarkMemmove9(b *testing.B) { bmMemmove(b, 9) }
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func BenchmarkMemmove10(b *testing.B) { bmMemmove(b, 10) }
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func BenchmarkMemmove11(b *testing.B) { bmMemmove(b, 11) }
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func BenchmarkMemmove12(b *testing.B) { bmMemmove(b, 12) }
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func BenchmarkMemmove13(b *testing.B) { bmMemmove(b, 13) }
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func BenchmarkMemmove14(b *testing.B) { bmMemmove(b, 14) }
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func BenchmarkMemmove15(b *testing.B) { bmMemmove(b, 15) }
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func BenchmarkMemmove16(b *testing.B) { bmMemmove(b, 16) }
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func BenchmarkMemmove32(b *testing.B) { bmMemmove(b, 32) }
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func BenchmarkMemmove64(b *testing.B) { bmMemmove(b, 64) }
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func BenchmarkMemmove128(b *testing.B) { bmMemmove(b, 128) }
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func BenchmarkMemmove256(b *testing.B) { bmMemmove(b, 256) }
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func BenchmarkMemmove512(b *testing.B) { bmMemmove(b, 512) }
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func BenchmarkMemmove1024(b *testing.B) { bmMemmove(b, 1024) }
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func BenchmarkMemmove2048(b *testing.B) { bmMemmove(b, 2048) }
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func BenchmarkMemmove4096(b *testing.B) { bmMemmove(b, 4096) }
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func TestMemclr(t *testing.T) {
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size := 512
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if testing.Short() {
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size = 128 + 16
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}
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mem := make([]byte, size)
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for i := 0; i < size; i++ {
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mem[i] = 0xee
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}
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for n := 0; n < size; n++ {
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for x := 0; x <= size-n; x++ { // offset in mem
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MemclrBytes(mem[x : x+n])
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for i := 0; i < x; i++ {
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if mem[i] != 0xee {
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t.Fatalf("overwrite prefix mem[%d] = %d", i, mem[i])
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}
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}
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for i := x; i < x+n; i++ {
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if mem[i] != 0 {
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t.Fatalf("failed clear mem[%d] = %d", i, mem[i])
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}
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mem[i] = 0xee
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}
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for i := x + n; i < size; i++ {
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if mem[i] != 0xee {
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t.Fatalf("overwrite suffix mem[%d] = %d", i, mem[i])
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}
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}
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}
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}
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}
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func bmMemclr(b *testing.B, n int) {
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x := make([]byte, n)
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b.SetBytes(int64(n))
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for i := 0; i < b.N; i++ {
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MemclrBytes(x)
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}
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}
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func BenchmarkMemclr5(b *testing.B) { bmMemclr(b, 5) }
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func BenchmarkMemclr16(b *testing.B) { bmMemclr(b, 16) }
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func BenchmarkMemclr64(b *testing.B) { bmMemclr(b, 64) }
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func BenchmarkMemclr256(b *testing.B) { bmMemclr(b, 256) }
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func BenchmarkMemclr4096(b *testing.B) { bmMemclr(b, 4096) }
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func BenchmarkMemclr65536(b *testing.B) { bmMemclr(b, 65536) }
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func bmGoMemclr(b *testing.B, n int) {
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x := make([]byte, n)
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b.SetBytes(int64(n))
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for i := 0; i < b.N; i++ {
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for j := range x {
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x[j] = 0
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}
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}
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}
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func BenchmarkGoMemclr5(b *testing.B) { bmGoMemclr(b, 5) }
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func BenchmarkGoMemclr16(b *testing.B) { bmGoMemclr(b, 16) }
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func BenchmarkGoMemclr64(b *testing.B) { bmGoMemclr(b, 64) }
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func BenchmarkGoMemclr256(b *testing.B) { bmGoMemclr(b, 256) }
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func BenchmarkClearFat8(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [8 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat12(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [12 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat16(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [16 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat24(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [24 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat32(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [32 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat64(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [64 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat128(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [128 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat256(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [256 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat512(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [512 / 4]uint32
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_ = x
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}
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}
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func BenchmarkClearFat1024(b *testing.B) {
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for i := 0; i < b.N; i++ {
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var x [1024 / 4]uint32
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_ = x
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}
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}
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func BenchmarkCopyFat8(b *testing.B) {
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var x [8 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat12(b *testing.B) {
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var x [12 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat16(b *testing.B) {
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var x [16 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat24(b *testing.B) {
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var x [24 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat32(b *testing.B) {
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var x [32 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat64(b *testing.B) {
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var x [64 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat128(b *testing.B) {
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var x [128 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat256(b *testing.B) {
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var x [256 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat512(b *testing.B) {
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var x [512 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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func BenchmarkCopyFat1024(b *testing.B) {
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var x [1024 / 4]uint32
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for i := 0; i < b.N; i++ {
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y := x
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_ = y
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}
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}
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