mirror of
https://github.com/golang/go
synced 2024-11-17 11:44:51 -07:00
6436270dad
This adds four new deductions to the prove pass, all related to adding
or subtracting one from a value. This is the first hint of actual
arithmetic relations in the prove pass.
The most effective of these is
x-1 >= w && x > min ⇒ x > w
This helps eliminate bounds checks in code like
if x > 0 {
// do something with s[x-1]
}
Altogether, these deductions prove an additional 260 branches in std
and cmd. Furthermore, they will let us eliminate some tricky
compiler-inserted panics in the runtime that are interfering with
static analysis.
Fixes #23354.
Change-Id: I7088223e0e0cd6ff062a75c127eb4bb60e6dce02
Reviewed-on: https://go-review.googlesource.com/87480
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
573 lines
9.3 KiB
Go
573 lines
9.3 KiB
Go
// +build amd64
|
||
// errorcheck -0 -d=ssa/prove/debug=1
|
||
|
||
// Copyright 2016 The Go Authors. All rights reserved.
|
||
// Use of this source code is governed by a BSD-style
|
||
// license that can be found in the LICENSE file.
|
||
|
||
package main
|
||
|
||
import "math"
|
||
|
||
func f0(a []int) int {
|
||
a[0] = 1
|
||
a[0] = 1 // ERROR "Proved IsInBounds$"
|
||
a[6] = 1
|
||
a[6] = 1 // ERROR "Proved IsInBounds$"
|
||
a[5] = 1 // ERROR "Proved IsInBounds$"
|
||
a[5] = 1 // ERROR "Proved IsInBounds$"
|
||
return 13
|
||
}
|
||
|
||
func f1(a []int) int {
|
||
if len(a) <= 5 {
|
||
return 18
|
||
}
|
||
a[0] = 1 // ERROR "Proved IsInBounds$"
|
||
a[0] = 1 // ERROR "Proved IsInBounds$"
|
||
a[6] = 1
|
||
a[6] = 1 // ERROR "Proved IsInBounds$"
|
||
a[5] = 1 // ERROR "Proved IsInBounds$"
|
||
a[5] = 1 // ERROR "Proved IsInBounds$"
|
||
return 26
|
||
}
|
||
|
||
func f1b(a []int, i int, j uint) int {
|
||
if i >= 0 && i < len(a) {
|
||
return a[i] // ERROR "Proved IsInBounds$"
|
||
}
|
||
if i >= 10 && i < len(a) {
|
||
return a[i] // ERROR "Proved IsInBounds$"
|
||
}
|
||
if i >= 10 && i < len(a) {
|
||
return a[i] // ERROR "Proved IsInBounds$"
|
||
}
|
||
if i >= 10 && i < len(a) { // todo: handle this case
|
||
return a[i-10]
|
||
}
|
||
if j < uint(len(a)) {
|
||
return a[j] // ERROR "Proved IsInBounds$"
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f1c(a []int, i int64) int {
|
||
c := uint64(math.MaxInt64 + 10) // overflows int
|
||
d := int64(c)
|
||
if i >= d && i < int64(len(a)) {
|
||
// d overflows, should not be handled.
|
||
return a[i]
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f2(a []int) int {
|
||
for i := range a {
|
||
a[i+1] = i
|
||
a[i+1] = i // ERROR "Proved IsInBounds$"
|
||
}
|
||
return 34
|
||
}
|
||
|
||
func f3(a []uint) int {
|
||
for i := uint(0); i < uint(len(a)); i++ {
|
||
a[i] = i // ERROR "Proved IsInBounds$"
|
||
}
|
||
return 41
|
||
}
|
||
|
||
func f4a(a, b, c int) int {
|
||
if a < b {
|
||
if a == b { // ERROR "Disproved Eq64$"
|
||
return 47
|
||
}
|
||
if a > b { // ERROR "Disproved Greater64$"
|
||
return 50
|
||
}
|
||
if a < b { // ERROR "Proved Less64$"
|
||
return 53
|
||
}
|
||
// We can't get to this point and prove knows that, so
|
||
// there's no message for the next (obvious) branch.
|
||
if a != a {
|
||
return 56
|
||
}
|
||
return 61
|
||
}
|
||
return 63
|
||
}
|
||
|
||
func f4b(a, b, c int) int {
|
||
if a <= b {
|
||
if a >= b {
|
||
if a == b { // ERROR "Proved Eq64$"
|
||
return 70
|
||
}
|
||
return 75
|
||
}
|
||
return 77
|
||
}
|
||
return 79
|
||
}
|
||
|
||
func f4c(a, b, c int) int {
|
||
if a <= b {
|
||
if a >= b {
|
||
if a != b { // ERROR "Disproved Neq64$"
|
||
return 73
|
||
}
|
||
return 75
|
||
}
|
||
return 77
|
||
}
|
||
return 79
|
||
}
|
||
|
||
func f4d(a, b, c int) int {
|
||
if a < b {
|
||
if a < c {
|
||
if a < b { // ERROR "Proved Less64$"
|
||
if a < c { // ERROR "Proved Less64$"
|
||
return 87
|
||
}
|
||
return 89
|
||
}
|
||
return 91
|
||
}
|
||
return 93
|
||
}
|
||
return 95
|
||
}
|
||
|
||
func f4e(a, b, c int) int {
|
||
if a < b {
|
||
if b > a { // ERROR "Proved Greater64$"
|
||
return 101
|
||
}
|
||
return 103
|
||
}
|
||
return 105
|
||
}
|
||
|
||
func f4f(a, b, c int) int {
|
||
if a <= b {
|
||
if b > a {
|
||
if b == a { // ERROR "Disproved Eq64$"
|
||
return 112
|
||
}
|
||
return 114
|
||
}
|
||
if b >= a { // ERROR "Proved Geq64$"
|
||
if b == a { // ERROR "Proved Eq64$"
|
||
return 118
|
||
}
|
||
return 120
|
||
}
|
||
return 122
|
||
}
|
||
return 124
|
||
}
|
||
|
||
func f5(a, b uint) int {
|
||
if a == b {
|
||
if a <= b { // ERROR "Proved Leq64U$"
|
||
return 130
|
||
}
|
||
return 132
|
||
}
|
||
return 134
|
||
}
|
||
|
||
// These comparisons are compile time constants.
|
||
func f6a(a uint8) int {
|
||
if a < a { // ERROR "Disproved Less8U$"
|
||
return 140
|
||
}
|
||
return 151
|
||
}
|
||
|
||
func f6b(a uint8) int {
|
||
if a < a { // ERROR "Disproved Less8U$"
|
||
return 140
|
||
}
|
||
return 151
|
||
}
|
||
|
||
func f6x(a uint8) int {
|
||
if a > a { // ERROR "Disproved Greater8U$"
|
||
return 143
|
||
}
|
||
return 151
|
||
}
|
||
|
||
func f6d(a uint8) int {
|
||
if a <= a { // ERROR "Proved Leq8U$"
|
||
return 146
|
||
}
|
||
return 151
|
||
}
|
||
|
||
func f6e(a uint8) int {
|
||
if a >= a { // ERROR "Proved Geq8U$"
|
||
return 149
|
||
}
|
||
return 151
|
||
}
|
||
|
||
func f7(a []int, b int) int {
|
||
if b < len(a) {
|
||
a[b] = 3
|
||
if b < len(a) { // ERROR "Proved Less64$"
|
||
a[b] = 5 // ERROR "Proved IsInBounds$"
|
||
}
|
||
}
|
||
return 161
|
||
}
|
||
|
||
func f8(a, b uint) int {
|
||
if a == b {
|
||
return 166
|
||
}
|
||
if a > b {
|
||
return 169
|
||
}
|
||
if a < b { // ERROR "Proved Less64U$"
|
||
return 172
|
||
}
|
||
return 174
|
||
}
|
||
|
||
func f9(a, b bool) int {
|
||
if a {
|
||
return 1
|
||
}
|
||
if a || b { // ERROR "Disproved Arg$"
|
||
return 2
|
||
}
|
||
return 3
|
||
}
|
||
|
||
func f10(a string) int {
|
||
n := len(a)
|
||
// We optimize comparisons with small constant strings (see cmd/compile/internal/gc/walk.go),
|
||
// so this string literal must be long.
|
||
if a[:n>>1] == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
|
||
return 0
|
||
}
|
||
return 1
|
||
}
|
||
|
||
func f11a(a []int, i int) {
|
||
useInt(a[i])
|
||
useInt(a[i]) // ERROR "Proved IsInBounds$"
|
||
}
|
||
|
||
func f11b(a []int, i int) {
|
||
useSlice(a[i:])
|
||
useSlice(a[i:]) // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
|
||
func f11c(a []int, i int) {
|
||
useSlice(a[:i])
|
||
useSlice(a[:i]) // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
|
||
func f11d(a []int, i int) {
|
||
useInt(a[2*i+7])
|
||
useInt(a[2*i+7]) // ERROR "Proved IsInBounds$"
|
||
}
|
||
|
||
func f12(a []int, b int) {
|
||
useSlice(a[:b])
|
||
}
|
||
|
||
func f13a(a, b, c int, x bool) int {
|
||
if a > 12 {
|
||
if x {
|
||
if a < 12 { // ERROR "Disproved Less64$"
|
||
return 1
|
||
}
|
||
}
|
||
if x {
|
||
if a <= 12 { // ERROR "Disproved Leq64$"
|
||
return 2
|
||
}
|
||
}
|
||
if x {
|
||
if a == 12 { // ERROR "Disproved Eq64$"
|
||
return 3
|
||
}
|
||
}
|
||
if x {
|
||
if a >= 12 { // ERROR "Proved Geq64$"
|
||
return 4
|
||
}
|
||
}
|
||
if x {
|
||
if a > 12 { // ERROR "Proved Greater64$"
|
||
return 5
|
||
}
|
||
}
|
||
return 6
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13b(a int, x bool) int {
|
||
if a == -9 {
|
||
if x {
|
||
if a < -9 { // ERROR "Disproved Less64$"
|
||
return 7
|
||
}
|
||
}
|
||
if x {
|
||
if a <= -9 { // ERROR "Proved Leq64$"
|
||
return 8
|
||
}
|
||
}
|
||
if x {
|
||
if a == -9 { // ERROR "Proved Eq64$"
|
||
return 9
|
||
}
|
||
}
|
||
if x {
|
||
if a >= -9 { // ERROR "Proved Geq64$"
|
||
return 10
|
||
}
|
||
}
|
||
if x {
|
||
if a > -9 { // ERROR "Disproved Greater64$"
|
||
return 11
|
||
}
|
||
}
|
||
return 12
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13c(a int, x bool) int {
|
||
if a < 90 {
|
||
if x {
|
||
if a < 90 { // ERROR "Proved Less64$"
|
||
return 13
|
||
}
|
||
}
|
||
if x {
|
||
if a <= 90 { // ERROR "Proved Leq64$"
|
||
return 14
|
||
}
|
||
}
|
||
if x {
|
||
if a == 90 { // ERROR "Disproved Eq64$"
|
||
return 15
|
||
}
|
||
}
|
||
if x {
|
||
if a >= 90 { // ERROR "Disproved Geq64$"
|
||
return 16
|
||
}
|
||
}
|
||
if x {
|
||
if a > 90 { // ERROR "Disproved Greater64$"
|
||
return 17
|
||
}
|
||
}
|
||
return 18
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13d(a int) int {
|
||
if a < 5 {
|
||
if a < 9 { // ERROR "Proved Less64$"
|
||
return 1
|
||
}
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13e(a int) int {
|
||
if a > 9 {
|
||
if a > 5 { // ERROR "Proved Greater64$"
|
||
return 1
|
||
}
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13f(a int64) int64 {
|
||
if a > math.MaxInt64 {
|
||
// Unreachable, but prove doesn't know that.
|
||
if a == 0 {
|
||
return 1
|
||
}
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13g(a int) int {
|
||
if a < 3 {
|
||
return 5
|
||
}
|
||
if a > 3 {
|
||
return 6
|
||
}
|
||
if a == 3 { // ERROR "Proved Eq64$"
|
||
return 7
|
||
}
|
||
return 8
|
||
}
|
||
|
||
func f13h(a int) int {
|
||
if a < 3 {
|
||
if a > 1 {
|
||
if a == 2 { // ERROR "Proved Eq64$"
|
||
return 5
|
||
}
|
||
}
|
||
}
|
||
return 0
|
||
}
|
||
|
||
func f13i(a uint) int {
|
||
if a == 0 {
|
||
return 1
|
||
}
|
||
if a > 0 { // ERROR "Proved Greater64U$"
|
||
return 2
|
||
}
|
||
return 3
|
||
}
|
||
|
||
func f14(p, q *int, a []int) {
|
||
// This crazy ordering usually gives i1 the lowest value ID,
|
||
// j the middle value ID, and i2 the highest value ID.
|
||
// That used to confuse CSE because it ordered the args
|
||
// of the two + ops below differently.
|
||
// That in turn foiled bounds check elimination.
|
||
i1 := *p
|
||
j := *q
|
||
i2 := *p
|
||
useInt(a[i1+j])
|
||
useInt(a[i2+j]) // ERROR "Proved IsInBounds$"
|
||
}
|
||
|
||
func f15(s []int, x int) {
|
||
useSlice(s[x:])
|
||
useSlice(s[:x]) // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
|
||
func f16(s []int) []int {
|
||
if len(s) >= 10 {
|
||
return s[:10] // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
return nil
|
||
}
|
||
|
||
func f17(b []int) {
|
||
for i := 0; i < len(b); i++ {
|
||
useSlice(b[i:]) // Learns i <= len
|
||
// This tests for i <= cap, which we can only prove
|
||
// using the derived relation between len and cap.
|
||
// This depends on finding the contradiction, since we
|
||
// don't query this condition directly.
|
||
useSlice(b[:i]) // ERROR "Proved IsSliceInBounds$"
|
||
}
|
||
}
|
||
|
||
func sm1(b []int, x int) {
|
||
// Test constant argument to slicemask.
|
||
useSlice(b[2:8]) // ERROR "Proved slicemask not needed$"
|
||
// Test non-constant argument with known limits.
|
||
if cap(b) > 10 {
|
||
useSlice(b[2:]) // ERROR "Proved slicemask not needed$"
|
||
}
|
||
}
|
||
|
||
func lim1(x, y, z int) {
|
||
// Test relations between signed and unsigned limits.
|
||
if x > 5 {
|
||
if uint(x) > 5 { // ERROR "Proved Greater64U$"
|
||
return
|
||
}
|
||
}
|
||
if y >= 0 && y < 4 {
|
||
if uint(y) > 4 { // ERROR "Disproved Greater64U$"
|
||
return
|
||
}
|
||
if uint(y) < 5 { // ERROR "Proved Less64U$"
|
||
return
|
||
}
|
||
}
|
||
if z < 4 {
|
||
if uint(z) > 4 { // Not provable without disjunctions.
|
||
return
|
||
}
|
||
}
|
||
}
|
||
|
||
// fence1–4 correspond to the four fence-post implications.
|
||
|
||
func fence1(b []int, x, y int) {
|
||
// Test proofs that rely on fence-post implications.
|
||
if x+1 > y {
|
||
if x < y { // ERROR "Disproved Less64$"
|
||
return
|
||
}
|
||
}
|
||
if len(b) < cap(b) {
|
||
// This eliminates the growslice path.
|
||
b = append(b, 1) // ERROR "Disproved Greater64$"
|
||
}
|
||
}
|
||
|
||
func fence2(x, y int) {
|
||
if x-1 < y {
|
||
if x > y { // ERROR "Disproved Greater64$"
|
||
return
|
||
}
|
||
}
|
||
}
|
||
|
||
func fence3(b []int, x, y int64) {
|
||
if x-1 >= y {
|
||
if x <= y { // Can't prove because x may have wrapped.
|
||
return
|
||
}
|
||
}
|
||
|
||
if x != math.MinInt64 && x-1 >= y {
|
||
if x <= y { // ERROR "Disproved Leq64$"
|
||
return
|
||
}
|
||
}
|
||
|
||
if n := len(b); n > 0 {
|
||
b[n-1] = 0 // ERROR "Proved IsInBounds$"
|
||
}
|
||
}
|
||
|
||
func fence4(x, y int64) {
|
||
if x >= y+1 {
|
||
if x <= y {
|
||
return
|
||
}
|
||
}
|
||
if y != math.MaxInt64 && x >= y+1 {
|
||
if x <= y { // ERROR "Disproved Leq64$"
|
||
return
|
||
}
|
||
}
|
||
}
|
||
|
||
//go:noinline
|
||
func useInt(a int) {
|
||
}
|
||
|
||
//go:noinline
|
||
func useSlice(a []int) {
|
||
}
|
||
|
||
func main() {
|
||
}
|