mirror of
https://github.com/golang/go
synced 2024-11-18 13:54:59 -07:00
c9fd997524
Unroll s == "ab" to len(s) == 2 && s[0] == 'a' && s[1] == 'b' This generates faster and shorter code by avoiding a runtime call. Do something similar for !=. The cutoff length is 6. This was chosen empirically by examining binary sizes on arm, arm64, 386, and amd64 using the SSA backend. For all architectures examined, 4, 5, and 6 were the ideal cutoff, with identical binary sizes. The distribution of constant string equality sizes during 'go build -a std' is: 40.81% 622 len 0 14.11% 215 len 4 9.45% 144 len 1 7.81% 119 len 3 7.48% 114 len 5 5.12% 78 len 7 4.13% 63 len 2 3.54% 54 len 8 2.69% 41 len 6 1.18% 18 len 10 0.85% 13 len 9 0.66% 10 len 14 0.59% 9 len 17 0.46% 7 len 11 0.26% 4 len 12 0.20% 3 len 19 0.13% 2 len 13 0.13% 2 len 15 0.13% 2 len 16 0.07% 1 len 20 0.07% 1 len 23 0.07% 1 len 33 0.07% 1 len 36 A cutoff of length 6 covers most of the cases. Benchmarks on amd64 comparing a string to a constant of length 3: Cmp/1same-8 4.78ns ± 6% 0.94ns ± 9% -80.26% (p=0.000 n=20+20) Cmp/1diffbytes-8 6.43ns ± 6% 0.96ns ±11% -85.13% (p=0.000 n=20+20) Cmp/3same-8 4.71ns ± 5% 1.28ns ± 5% -72.90% (p=0.000 n=20+20) Cmp/3difffirstbyte-8 6.33ns ± 7% 1.27ns ± 7% -79.90% (p=0.000 n=20+20) Cmp/3difflastbyte-8 6.34ns ± 8% 1.26ns ± 9% -80.13% (p=0.000 n=20+20) The change to the prove test preserves the existing intent of the test. When the string was short, there was a new "proved in bounds" report that referred to individual byte comparisons. Change-Id: I593ac303b0d11f275672090c5c786ea0c6b8da13 Reviewed-on: https://go-review.googlesource.com/26758 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
451 lines
6.8 KiB
Go
451 lines
6.8 KiB
Go
// +build amd64
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// errorcheck -0 -d=ssa/prove/debug=3
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// Copyright 2016 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 main
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import "math"
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func f0(a []int) int {
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a[0] = 1
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a[0] = 1 // ERROR "Proved boolean IsInBounds$"
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a[6] = 1
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a[6] = 1 // ERROR "Proved boolean IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved boolean IsInBounds$"
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return 13
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}
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func f1(a []int) int {
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if len(a) <= 5 {
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return 18
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}
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a[0] = 1 // ERROR "Proved non-negative bounds IsInBounds$"
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a[0] = 1 // ERROR "Proved boolean IsInBounds$"
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a[6] = 1
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a[6] = 1 // ERROR "Proved boolean IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved boolean IsInBounds$"
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return 26
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}
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func f1b(a []int, i int, j uint) int {
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if i >= 0 && i < len(a) {
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return a[i] // ERROR "Proved non-negative bounds IsInBounds$"
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}
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if i >= 10 && i < len(a) {
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return a[i] // ERROR "Proved non-negative bounds IsInBounds$"
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}
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if i >= 10 && i < len(a) {
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return a[i] // ERROR "Proved non-negative bounds IsInBounds$"
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}
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if i >= 10 && i < len(a) { // todo: handle this case
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return a[i-10]
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}
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if j < uint(len(a)) {
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return a[j] // ERROR "Proved IsInBounds$"
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}
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return 0
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}
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func f1c(a []int, i int64) int {
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c := uint64(math.MaxInt64 + 10) // overflows int
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d := int64(c)
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if i >= d && i < int64(len(a)) {
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// d overflows, should not be handled.
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return a[i]
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}
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return 0
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}
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func f2(a []int) int {
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for i := range a {
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a[i+1] = i
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a[i+1] = i // ERROR "Proved boolean IsInBounds$"
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}
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return 34
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}
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func f3(a []uint) int {
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for i := uint(0); i < uint(len(a)); i++ {
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a[i] = i // ERROR "Proved IsInBounds$"
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}
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return 41
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}
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func f4a(a, b, c int) int {
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if a < b {
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if a == b { // ERROR "Disproved Eq64$"
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return 47
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}
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if a > b { // ERROR "Disproved Greater64$"
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return 50
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}
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if a < b { // ERROR "Proved boolean Less64$"
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return 53
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}
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if a == b { // ERROR "Disproved boolean Eq64$"
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return 56
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}
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if a > b { // ERROR "Disproved boolean Greater64$"
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return 59
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}
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return 61
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}
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return 63
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}
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func f4b(a, b, c int) int {
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if a <= b {
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if a >= b {
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if a == b { // ERROR "Proved Eq64$"
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return 70
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}
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return 75
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}
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return 77
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}
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return 79
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}
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func f4c(a, b, c int) int {
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if a <= b {
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if a >= b {
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if a != b { // ERROR "Disproved Neq64$"
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return 73
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}
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return 75
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}
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return 77
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}
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return 79
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}
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func f4d(a, b, c int) int {
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if a < b {
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if a < c {
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if a < b { // ERROR "Proved boolean Less64$"
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if a < c { // ERROR "Proved boolean Less64$"
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return 87
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}
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return 89
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}
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return 91
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}
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return 93
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}
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return 95
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}
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func f4e(a, b, c int) int {
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if a < b {
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if b > a { // ERROR "Proved Greater64$"
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return 101
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}
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return 103
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}
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return 105
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}
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func f4f(a, b, c int) int {
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if a <= b {
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if b > a {
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if b == a { // ERROR "Disproved Eq64$"
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return 112
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}
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return 114
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}
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if b >= a { // ERROR "Proved Geq64$"
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if b == a { // ERROR "Proved Eq64$"
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return 118
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}
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return 120
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}
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return 122
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}
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return 124
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}
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func f5(a, b uint) int {
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if a == b {
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if a <= b { // ERROR "Proved Leq64U$"
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return 130
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}
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return 132
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}
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return 134
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}
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// These comparisons are compile time constants.
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func f6a(a uint8) int {
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if a < a { // ERROR "Disproved Less8U$"
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return 140
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}
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return 151
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}
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func f6b(a uint8) int {
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if a < a { // ERROR "Disproved Less8U$"
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return 140
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}
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return 151
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}
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func f6x(a uint8) int {
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if a > a { // ERROR "Disproved Greater8U$"
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return 143
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}
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return 151
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}
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func f6d(a uint8) int {
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if a <= a { // ERROR "Proved Leq8U$"
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return 146
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}
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return 151
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}
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func f6e(a uint8) int {
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if a >= a { // ERROR "Proved Geq8U$"
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return 149
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}
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return 151
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}
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func f7(a []int, b int) int {
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if b < len(a) {
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a[b] = 3
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if b < len(a) { // ERROR "Proved boolean Less64$"
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a[b] = 5 // ERROR "Proved boolean IsInBounds$"
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}
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}
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return 161
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}
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func f8(a, b uint) int {
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if a == b {
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return 166
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}
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if a > b {
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return 169
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}
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if a < b { // ERROR "Proved Less64U$"
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return 172
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}
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return 174
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}
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func f9(a, b bool) int {
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if a {
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return 1
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}
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if a || b { // ERROR "Disproved boolean Arg$"
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return 2
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}
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return 3
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}
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func f10(a string) int {
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n := len(a)
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if a[:n>>1] == "aaaaaaaaaaaaaa" {
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return 0
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}
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return 1
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}
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func f11a(a []int, i int) {
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useInt(a[i])
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useInt(a[i]) // ERROR "Proved boolean IsInBounds$"
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}
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func f11b(a []int, i int) {
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useSlice(a[i:])
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useSlice(a[i:]) // ERROR "Proved boolean IsSliceInBounds$"
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}
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func f11c(a []int, i int) {
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useSlice(a[:i])
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useSlice(a[:i]) // ERROR "Proved boolean IsSliceInBounds$"
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}
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func f11d(a []int, i int) {
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useInt(a[2*i+7])
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useInt(a[2*i+7])
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}
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func f12(a []int, b int) {
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useSlice(a[:b])
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}
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func f13a(a, b, c int, x bool) int {
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if a > 12 {
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if x {
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if a < 12 { // ERROR "Disproved Less64$"
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return 1
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}
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}
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if x {
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if a <= 12 { // ERROR "Disproved Leq64$"
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return 2
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}
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}
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if x {
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if a == 12 { // ERROR "Disproved Eq64$"
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return 3
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}
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}
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if x {
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if a >= 12 { // ERROR "Proved Geq64$"
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return 4
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}
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}
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if x {
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if a > 12 { // ERROR "Proved boolean Greater64$"
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return 5
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}
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}
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return 6
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}
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return 0
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}
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func f13b(a int, x bool) int {
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if a == -9 {
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if x {
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if a < -9 { // ERROR "Disproved Less64$"
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return 7
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}
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}
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if x {
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if a <= -9 { // ERROR "Proved Leq64$"
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return 8
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}
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}
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if x {
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if a == -9 { // ERROR "Proved boolean Eq64$"
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return 9
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}
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}
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if x {
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if a >= -9 { // ERROR "Proved Geq64$"
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return 10
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}
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}
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if x {
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if a > -9 { // ERROR "Disproved Greater64$"
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return 11
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}
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}
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return 12
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}
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return 0
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}
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func f13c(a int, x bool) int {
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if a < 90 {
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if x {
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if a < 90 { // ERROR "Proved boolean Less64$"
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return 13
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}
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}
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if x {
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if a <= 90 { // ERROR "Proved Leq64$"
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return 14
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}
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}
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if x {
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if a == 90 { // ERROR "Disproved Eq64$"
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return 15
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}
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}
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if x {
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if a >= 90 { // ERROR "Disproved Geq64$"
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return 16
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}
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}
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if x {
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if a > 90 { // ERROR "Disproved Greater64$"
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return 17
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}
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}
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return 18
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}
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return 0
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}
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func f13d(a int) int {
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if a < 5 {
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if a < 9 { // ERROR "Proved Less64$"
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return 1
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}
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}
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return 0
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}
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func f13e(a int) int {
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if a > 9 {
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if a > 5 { // ERROR "Proved Greater64$"
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return 1
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}
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}
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return 0
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}
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func f13f(a int64) int64 {
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if a > math.MaxInt64 {
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// Unreachable, but prove doesn't know that.
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if a == 0 {
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return 1
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}
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}
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return 0
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}
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func f13g(a int) int {
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if a < 3 {
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return 5
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}
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if a > 3 {
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return 6
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}
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if a == 3 { // ERROR "Proved Eq64$"
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return 7
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}
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return 8
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}
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func f13h(a int) int {
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if a < 3 {
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if a > 1 {
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if a == 2 { // ERROR "Proved Eq64$"
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return 5
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}
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}
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}
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return 0
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}
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func f13i(a uint) int {
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if a == 0 {
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return 1
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}
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if a > 0 { // ERROR "Proved Greater64U$"
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return 2
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}
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return 3
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}
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//go:noinline
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func useInt(a int) {
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}
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//go:noinline
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func useSlice(a []int) {
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}
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func main() {
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}
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