go switch_test 源码
golang switch_test 代码
文件路径：/src/cmd/compile/internal/test/switch_test.go
// Copyright 2021 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 test
import (
"math/bits"
"testing"
)
func BenchmarkSwitch8Predictable(b *testing.B) {
benchmarkSwitch8(b, true)
}
func BenchmarkSwitch8Unpredictable(b *testing.B) {
benchmarkSwitch8(b, false)
}
func benchmarkSwitch8(b *testing.B, predictable bool) {
n := 0
rng := newRNG()
for i := 0; i < b.N; i++ {
rng = rng.next(predictable)
switch rng.value() & 7 {
case 0:
n += 1
case 1:
n += 2
case 2:
n += 3
case 3:
n += 4
case 4:
n += 5
case 5:
n += 6
case 6:
n += 7
case 7:
n += 8
}
}
sink = n
}
func BenchmarkSwitch32Predictable(b *testing.B) {
benchmarkSwitch32(b, true)
}
func BenchmarkSwitch32Unpredictable(b *testing.B) {
benchmarkSwitch32(b, false)
}
func benchmarkSwitch32(b *testing.B, predictable bool) {
n := 0
rng := newRNG()
for i := 0; i < b.N; i++ {
rng = rng.next(predictable)
switch rng.value() & 31 {
case 0, 1, 2:
n += 1
case 4, 5, 6:
n += 2
case 8, 9, 10:
n += 3
case 12, 13, 14:
n += 4
case 16, 17, 18:
n += 5
case 20, 21, 22:
n += 6
case 24, 25, 26:
n += 7
case 28, 29, 30:
n += 8
default:
n += 9
}
}
sink = n
}
func BenchmarkSwitchStringPredictable(b *testing.B) {
benchmarkSwitchString(b, true)
}
func BenchmarkSwitchStringUnpredictable(b *testing.B) {
benchmarkSwitchString(b, false)
}
func benchmarkSwitchString(b *testing.B, predictable bool) {
a := []string{
"foo",
"foo1",
"foo22",
"foo333",
"foo4444",
"foo55555",
"foo666666",
"foo7777777",
}
n := 0
rng := newRNG()
for i := 0; i < b.N; i++ {
rng = rng.next(predictable)
switch a[rng.value()&7] {
case "foo":
n += 1
case "foo1":
n += 2
case "foo22":
n += 3
case "foo333":
n += 4
case "foo4444":
n += 5
case "foo55555":
n += 6
case "foo666666":
n += 7
case "foo7777777":
n += 8
}
}
sink = n
}
// A simple random number generator used to make switches conditionally predictable.
type rng uint64
func newRNG() rng {
return 1
}
func (r rng) next(predictable bool) rng {
if predictable {
return r + 1
}
return rng(bits.RotateLeft64(uint64(r), 13) * 0x3c374d)
}
func (r rng) value() uint64 {
return uint64(r)
}
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