mirror of
https://github.com/golang/go
synced 2024-07-21 01:55:06 +00:00
2d41444ad0
When branching at a bounds check for indexing or slicing ops, prove currently only learns from the upper bound. On the positive branch, we currently learn i < len(a) (or i <= len(a)) in both the signed and unsigned domains. This CL makes prove also learn from the lower bound. Specifically, on the positive branch from index or slicing ops, prove will now ALSO learn i >= 0 in the signed domain (this fact is of no value in the unsigned domain). The substantive change itself is only an additional call to addRestrictions, though I've also inverted the nested switch statements around that call for the sake of clarity. This CL removes 92 bounds checks from std and cmd. It passes all tests and shows no deltas on compilecmp. Fixes #28885 Change-Id: I13eccc36e640eb599fa6dc5aa3be3c7d7abd2d9e Reviewed-on: https://go-review.googlesource.com/c/go/+/170121 Run-TryBot: Daniel Martí <mvdan@mvdan.cc> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Giovanni Bajo <rasky@develer.com>
866 lines
16 KiB
Go
866 lines
16 KiB
Go
// +build amd64
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// errorcheck -0 -d=ssa/prove/debug=1
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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 IsInBounds$"
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a[6] = 1
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a[6] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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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 IsInBounds$"
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a[0] = 1 // ERROR "Proved IsInBounds$"
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a[6] = 1
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a[6] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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a[5] = 1 // ERROR "Proved IsInBounds$"
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return 26
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}
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func f1b(a []int, i int, j uint) int {
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if i >= 0 && i < len(a) {
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return a[i] // ERROR "Proved IsInBounds$"
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}
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if i >= 10 && i < len(a) {
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return a[i] // ERROR "Proved IsInBounds$"
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}
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if i >= 10 && i < len(a) {
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return a[i] // ERROR "Proved IsInBounds$"
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}
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if i >= 10 && i < len(a) {
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return a[i-10] // ERROR "Proved IsInBounds$"
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}
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if j < uint(len(a)) {
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return a[j] // ERROR "Proved IsInBounds$"
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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 { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
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a[i+1] = i
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a[i+1] = i // ERROR "Proved IsInBounds$"
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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$"
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return 50
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}
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if a < b { // ERROR "Proved Less64$"
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return 53
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}
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// We can't get to this point and prove knows that, so
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// there's no message for the next (obvious) branch.
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if a != a {
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return 56
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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 Less64$"
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if a < c { // ERROR "Proved Less64$"
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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 Less64$"
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a[b] = 5 // ERROR "Proved IsInBounds$"
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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$"
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return 172
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}
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return 174
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}
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func f9(a, b bool) int {
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if a {
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return 1
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}
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if a || b { // ERROR "Disproved Arg$"
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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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// We optimize comparisons with small constant strings (see cmd/compile/internal/gc/walk.go),
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// so this string literal must be long.
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if a[:n>>1] == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
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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 IsInBounds$"
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}
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func f11b(a []int, i int) {
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useSlice(a[i:])
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useSlice(a[i:]) // ERROR "Proved IsSliceInBounds$"
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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 IsSliceInBounds$"
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}
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func f11d(a []int, i int) {
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useInt(a[2*i+7])
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useInt(a[2*i+7]) // ERROR "Proved IsInBounds$"
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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 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$"
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return 8
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}
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}
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if x {
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if a == -9 { // ERROR "Proved Eq64$"
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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 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$"
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return 1
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}
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}
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return 0
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}
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func f13f(a int64) int64 {
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if a > math.MaxInt64 {
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if a == 0 { // ERROR "Disproved Eq64$"
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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$"
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return 2
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}
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return 3
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}
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func f14(p, q *int, a []int) {
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// This crazy ordering usually gives i1 the lowest value ID,
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// j the middle value ID, and i2 the highest value ID.
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// That used to confuse CSE because it ordered the args
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// of the two + ops below differently.
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// That in turn foiled bounds check elimination.
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i1 := *p
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j := *q
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i2 := *p
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useInt(a[i1+j])
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useInt(a[i2+j]) // ERROR "Proved IsInBounds$"
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}
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func f15(s []int, x int) {
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useSlice(s[x:])
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useSlice(s[:x]) // ERROR "Proved IsSliceInBounds$"
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}
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func f16(s []int) []int {
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if len(s) >= 10 {
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return s[:10] // ERROR "Proved IsSliceInBounds$"
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}
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return nil
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}
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func f17(b []int) {
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for i := 0; i < len(b); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
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// This tests for i <= cap, which we can only prove
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// using the derived relation between len and cap.
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// This depends on finding the contradiction, since we
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// don't query this condition directly.
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useSlice(b[:i]) // ERROR "Proved IsSliceInBounds$"
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}
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}
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func f18(b []int, x int, y uint) {
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_ = b[x]
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_ = b[y]
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if x > len(b) { // ERROR "Disproved Greater64$"
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return
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}
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if y > uint(len(b)) { // ERROR "Disproved Greater64U$"
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return
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}
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if int(y) > len(b) { // ERROR "Disproved Greater64$"
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return
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}
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}
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func f19() (e int64, err error) {
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// Issue 29502: slice[:0] is incorrectly disproved.
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var stack []int64
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stack = append(stack, 123)
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if len(stack) > 1 {
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panic("too many elements")
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}
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last := len(stack) - 1
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e = stack[last]
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// Buggy compiler prints "Disproved Geq64" for the next line.
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stack = stack[:last] // ERROR "Proved IsSliceInBounds"
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return e, nil
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}
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func sm1(b []int, x int) {
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// Test constant argument to slicemask.
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useSlice(b[2:8]) // ERROR "Proved slicemask not needed$"
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// Test non-constant argument with known limits.
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if cap(b) > 10 {
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useSlice(b[2:]) // ERROR "Proved slicemask not needed$"
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}
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}
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func lim1(x, y, z int) {
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// Test relations between signed and unsigned limits.
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if x > 5 {
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if uint(x) > 5 { // ERROR "Proved Greater64U$"
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return
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}
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}
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if y >= 0 && y < 4 {
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if uint(y) > 4 { // ERROR "Disproved Greater64U$"
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return
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}
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if uint(y) < 5 { // ERROR "Proved Less64U$"
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return
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}
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}
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if z < 4 {
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if uint(z) > 4 { // Not provable without disjunctions.
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return
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}
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}
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}
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// fence1–4 correspond to the four fence-post implications.
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func fence1(b []int, x, y int) {
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// Test proofs that rely on fence-post implications.
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if x+1 > y {
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if x < y { // ERROR "Disproved Less64$"
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return
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}
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}
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if len(b) < cap(b) {
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// This eliminates the growslice path.
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b = append(b, 1) // ERROR "Disproved Greater64U$"
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}
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}
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func fence2(x, y int) {
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if x-1 < y {
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if x > y { // ERROR "Disproved Greater64$"
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return
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}
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}
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}
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func fence3(b, c []int, x, y int64) {
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if x-1 >= y {
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if x <= y { // Can't prove because x may have wrapped.
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return
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}
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}
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if x != math.MinInt64 && x-1 >= y {
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if x <= y { // ERROR "Disproved Leq64$"
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return
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}
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}
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c[len(c)-1] = 0 // Can't prove because len(c) might be 0
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if n := len(b); n > 0 {
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b[n-1] = 0 // ERROR "Proved IsInBounds$"
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}
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}
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func fence4(x, y int64) {
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if x >= y+1 {
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if x <= y {
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return
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}
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}
|
||
if y != math.MaxInt64 && x >= y+1 {
|
||
if x <= y { // ERROR "Disproved Leq64$"
|
||
return
|
||
}
|
||
}
|
||
}
|
||
|
||
// Check transitive relations
|
||
func trans1(x, y int64) {
|
||
if x > 5 {
|
||
if y > x {
|
||
if y > 2 { // ERROR "Proved Greater64$"
|
||
return
|
||
}
|
||
} else if y == x {
|
||
if y > 5 { // ERROR "Proved Greater64$"
|
||
return
|
||
}
|
||
}
|
||
}
|
||
if x >= 10 {
|
||
if y > x {
|
||
if y > 10 { // ERROR "Proved Greater64$"
|
||
return
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
func trans2(a, b []int, i int) {
|
||
if len(a) != len(b) {
|
||
return
|
||
}
|
||
|
||
_ = a[i]
|
||
_ = b[i] // ERROR "Proved IsInBounds$"
|
||
}
|
||
|
||
func trans3(a, b []int, i int) {
|
||
if len(a) > len(b) {
|
||
return
|
||
}
|
||
|
||
_ = a[i]
|
||
_ = b[i] // ERROR "Proved IsInBounds$"
|
||
}
|
||
|
||
// Derived from nat.cmp
|
||
func natcmp(x, y []uint) (r int) {
|
||
m := len(x)
|
||
n := len(y)
|
||
if m != n || m == 0 {
|
||
return
|
||
}
|
||
|
||
i := m - 1
|
||
for i > 0 && // ERROR "Induction variable: limits \(0,\?\], increment 1$"
|
||
x[i] == // ERROR "Proved IsInBounds$"
|
||
y[i] { // ERROR "Proved IsInBounds$"
|
||
i--
|
||
}
|
||
|
||
switch {
|
||
case x[i] < // todo, cannot prove this because it's dominated by i<=0 || x[i]==y[i]
|
||
y[i]: // ERROR "Proved IsInBounds$"
|
||
r = -1
|
||
case x[i] > // ERROR "Proved IsInBounds$"
|
||
y[i]: // ERROR "Proved IsInBounds$"
|
||
r = 1
|
||
}
|
||
return
|
||
}
|
||
|
||
func suffix(s, suffix string) bool {
|
||
// todo, we're still not able to drop the bound check here in the general case
|
||
return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
|
||
}
|
||
|
||
func constsuffix(s string) bool {
|
||
return suffix(s, "abc") // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
|
||
// oforuntil tests the pattern created by OFORUNTIL blocks. These are
|
||
// handled by addLocalInductiveFacts rather than findIndVar.
|
||
func oforuntil(b []int) {
|
||
i := 0
|
||
if len(b) > i {
|
||
top:
|
||
println(b[i]) // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Proved IsInBounds$"
|
||
i++
|
||
if i < len(b) {
|
||
goto top
|
||
}
|
||
}
|
||
}
|
||
|
||
// The range tests below test the index variable of range loops.
|
||
|
||
// range1 compiles to the "efficiently indexable" form of a range loop.
|
||
func range1(b []int) {
|
||
for i, v := range b { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
|
||
b[i] = v + 1 // ERROR "Proved IsInBounds$"
|
||
if i < len(b) { // ERROR "Proved Less64$"
|
||
println("x")
|
||
}
|
||
if i >= 0 { // ERROR "Proved Geq64$"
|
||
println("x")
|
||
}
|
||
}
|
||
}
|
||
|
||
// range2 elements are larger, so they use the general form of a range loop.
|
||
func range2(b [][32]int) {
|
||
for i, v := range b {
|
||
b[i][0] = v[0] + 1 // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Proved IsInBounds$"
|
||
if i < len(b) { // ERROR "Proved Less64$"
|
||
println("x")
|
||
}
|
||
if i >= 0 { // ERROR "Proved Geq64$"
|
||
println("x")
|
||
}
|
||
}
|
||
}
|
||
|
||
// signhint1-2 test whether the hint (int >= 0) is propagated into the loop.
|
||
func signHint1(i int, data []byte) {
|
||
if i >= 0 {
|
||
for i < len(data) { // ERROR "Induction variable: limits \[\?,\?\), increment 1$"
|
||
_ = data[i] // ERROR "Proved IsInBounds$"
|
||
i++
|
||
}
|
||
}
|
||
}
|
||
|
||
func signHint2(b []byte, n int) {
|
||
if n < 0 {
|
||
panic("")
|
||
}
|
||
_ = b[25]
|
||
for i := n; i <= 25; i++ { // ERROR "Induction variable: limits \[\?,25\], increment 1$"
|
||
b[i] = 123 // ERROR "Proved IsInBounds$"
|
||
}
|
||
}
|
||
|
||
// indexGT0 tests whether prove learns int index >= 0 from bounds check.
|
||
func indexGT0(b []byte, n int) {
|
||
_ = b[n]
|
||
_ = b[25]
|
||
|
||
for i := n; i <= 25; i++ { // ERROR "Induction variable: limits \[\?,25\], increment 1$"
|
||
b[i] = 123 // ERROR "Proved IsInBounds$"
|
||
}
|
||
}
|
||
|
||
// Induction variable in unrolled loop.
|
||
func unrollUpExcl(a []int) int {
|
||
var i, x int
|
||
for i = 0; i < len(a)-1; i += 2 { // ERROR "Induction variable: limits \[0,\?\), increment 2$"
|
||
x += a[i] // ERROR "Proved IsInBounds$"
|
||
x += a[i+1]
|
||
}
|
||
if i == len(a)-1 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Induction variable in unrolled loop.
|
||
func unrollUpIncl(a []int) int {
|
||
var i, x int
|
||
for i = 0; i <= len(a)-2; i += 2 { // ERROR "Induction variable: limits \[0,\?\], increment 2$"
|
||
x += a[i]
|
||
x += a[i+1]
|
||
}
|
||
if i == len(a)-1 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Induction variable in unrolled loop.
|
||
func unrollDownExcl0(a []int) int {
|
||
var i, x int
|
||
for i = len(a) - 1; i > 0; i -= 2 { // ERROR "Induction variable: limits \(0,\?\], increment 2$"
|
||
x += a[i] // ERROR "Proved IsInBounds$"
|
||
x += a[i-1] // ERROR "Proved IsInBounds$"
|
||
}
|
||
if i == 0 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Induction variable in unrolled loop.
|
||
func unrollDownExcl1(a []int) int {
|
||
var i, x int
|
||
for i = len(a) - 1; i >= 1; i -= 2 { // ERROR "Induction variable: limits \[1,\?\], increment 2$"
|
||
x += a[i] // ERROR "Proved IsInBounds$"
|
||
x += a[i-1] // ERROR "Proved IsInBounds$"
|
||
}
|
||
if i == 0 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Induction variable in unrolled loop.
|
||
func unrollDownInclStep(a []int) int {
|
||
var i, x int
|
||
for i = len(a); i >= 2; i -= 2 { // ERROR "Induction variable: limits \[2,\?\], increment 2$"
|
||
x += a[i-1] // ERROR "Proved IsInBounds$"
|
||
x += a[i-2]
|
||
}
|
||
if i == 1 {
|
||
x += a[i-1]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Not an induction variable (step too large)
|
||
func unrollExclStepTooLarge(a []int) int {
|
||
var i, x int
|
||
for i = 0; i < len(a)-1; i += 3 {
|
||
x += a[i]
|
||
x += a[i+1]
|
||
}
|
||
if i == len(a)-1 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Not an induction variable (step too large)
|
||
func unrollInclStepTooLarge(a []int) int {
|
||
var i, x int
|
||
for i = 0; i <= len(a)-2; i += 3 {
|
||
x += a[i]
|
||
x += a[i+1]
|
||
}
|
||
if i == len(a)-1 {
|
||
x += a[i]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Not an induction variable (min too small, iterating down)
|
||
func unrollDecMin(a []int) int {
|
||
var i, x int
|
||
for i = len(a); i >= math.MinInt64; i -= 2 {
|
||
x += a[i-1]
|
||
x += a[i-2]
|
||
}
|
||
if i == 1 { // ERROR "Disproved Eq64$"
|
||
x += a[i-1]
|
||
}
|
||
return x
|
||
}
|
||
|
||
// Not an induction variable (min too small, iterating up -- perhaps could allow, but why bother?)
|
||
func unrollIncMin(a []int) int {
|
||
var i, x int
|
||
for i = len(a); i >= math.MinInt64; i += 2 {
|
||
x += a[i-1]
|
||
x += a[i-2]
|
||
}
|
||
if i == 1 { // ERROR "Disproved Eq64$"
|
||
x += a[i-1]
|
||
}
|
||
return x
|
||
}
|
||
|
||
//go:noinline
|
||
func useInt(a int) {
|
||
}
|
||
|
||
//go:noinline
|
||
func useSlice(a []int) {
|
||
}
|
||
|
||
func main() {
|
||
}
|