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cmd/compile: rewrite the constant parts of the prove pass

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Handles a lot more cases where constant ranges can eliminate
various (mostly bounds failure) paths.

Fixes #66826
Fixes #66692
Fixes #48213
Update #57959

TODO: remove constant logic from poset code, no longer needed.

Change-Id: Id196436fcd8a0c84c7d59c04f93bd92e26a0fd7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/599096
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
khr@golang.org 2024-06-14 22:29:09 -07:00 committed by Keith Randall
parent 553443d41f
commit 3b96eebcbd
8 changed files with 815 additions and 439 deletions
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2
src/cmd/compile/internal/ssa/func.go
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@ -796,7 +796,7 @@ func (f *Func) invalidateCFG() {
// base.DebugHashMatch(this function's package.name)
//
// for use in bug isolation. The return value is true unless
// environment variable GOSSAHASH is set, in which case "it depends".
// environment variable GOCOMPILEDEBUG=gossahash=X is set, in which case "it depends on X".
// See [base.DebugHashMatch] for more information.
func (f *Func) DebugHashMatch() bool {
if !base.HasDebugHash() {

1135
src/cmd/compile/internal/ssa/prove.go
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File diff suppressed because it is too large Load Diff

14
src/cmd/compile/internal/ssa/rewrite.go
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@ -1188,6 +1188,8 @@ func logRule(s string) {
var ruleFile io.Writer
// TODO: replace these with the built-in min/max once they are available
// during bootstrap (when bootstrapping with 1.21 or later).
func min(x, y int64) int64 {
if x < y {
return x
@ -1200,6 +1202,18 @@ func max(x, y int64) int64 {
}
return y
}
func minU(x, y uint64) uint64 {
if x < y {
return x
}
return y
}
func maxU(x, y uint64) uint64 {
if x > y {
return x
}
return y
}
func isConstZero(v *Value) bool {
switch v.Op {

8
test/checkbce.go
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@ -159,16 +159,14 @@ func decode1(data []byte) (x uint64) {
}
func decode2(data []byte) (x uint64) {
// TODO(rasky): this should behave like decode1 and compile to no
// boundchecks. We're currently not able to remove all of them.
for len(data) >= 32 {
x += binary.BigEndian.Uint64(data)
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
x += binary.BigEndian.Uint64(data)
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
x += binary.BigEndian.Uint64(data)
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
x += binary.BigEndian.Uint64(data)
data = data[8:]
}
return x

4
test/codegen/comparisons.go
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@ -268,7 +268,7 @@ func CmpToZero(a, b, d int32, e, f int64, deOptC0, deOptC1 bool) int32 {
}
}
func CmpLogicalToZero(a, b, c uint32, d, e uint64) uint64 {
func CmpLogicalToZero(a, b, c uint32, d, e, f, g uint64) uint64 {
// ppc64x:"ANDCC",-"CMPW"
// wasm:"I64Eqz",-"I32Eqz",-"I64ExtendI32U",-"I32WrapI64"
@ -289,7 +289,7 @@ func CmpLogicalToZero(a, b, c uint32, d, e uint64) uint64 {
}
// ppc64x:"ORCC",-"CMP"
// wasm:"I64Eqz",-"I32Eqz",-"I64ExtendI32U",-"I32WrapI64"
if d|e == 0 {
if f|g == 0 {
return 1
}

22
test/loopbce.go
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@ -27,7 +27,7 @@ func f0c(a []int) int {
x := 0
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
b := a[:i+1] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
x += b[0]
x += b[0] // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
}
return x
}
@ -168,7 +168,7 @@ func g2() int {
func g3a() {
a := "this string has length 25"
for i := 0; i < len(a); i += 5 { // ERROR "Induction variable: limits \[0,20\], increment 5$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+3]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+5]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+6])
@ -294,8 +294,10 @@ func k3neg2(a [100]int) [100]int {
}
func k4(a [100]int) [100]int {
min := (-1) << 63
for i := min; i < min+50; i++ { // ERROR "Induction variable: limits \[-9223372036854775808,-9223372036854775758\), increment 1$"
// Note: can't use (-1)<<63 here, because i-min doesn't get rewritten to i+(-min),
// and it isn't worth adding that special case to prove.
min := (-1)<<63 + 1
for i := min; i < min+50; i++ { // ERROR "Induction variable: limits \[-9223372036854775807,-9223372036854775757\), increment 1$"
a[i-min] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
}
return a
@ -314,7 +316,7 @@ func d1(a [100]int) [100]int {
for i := 0; i < 100; i++ { // ERROR "Induction variable: limits \[0,100\), increment 1$"
for j := 0; j < i; j++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
a[j] = 0 // ERROR "Proved IsInBounds$"
a[j+1] = 0 // FIXME: this boundcheck should be eliminated
a[j+1] = 0 // ERROR "Proved IsInBounds$"
a[j+2] = 0
}
}
@ -325,7 +327,7 @@ func d2(a [100]int) [100]int {
for i := 0; i < 100; i++ { // ERROR "Induction variable: limits \[0,100\), increment 1$"
for j := 0; i > j; j++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
a[j] = 0 // ERROR "Proved IsInBounds$"
a[j+1] = 0 // FIXME: this boundcheck should be eliminated
a[j+1] = 0 // ERROR "Proved IsInBounds$"
a[j+2] = 0
}
}
@ -419,12 +421,12 @@ func nobce2(a string) {
for i := int64(0); i < int64(len(a))-31337; i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
}
for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Disproved Less64"
useString(a[i:])
}
j := int64(len(a)) - 123
for i := int64(0); i < j+123+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
for i := int64(0); i < j+123+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Disproved Less64"
useString(a[i:])
}
for i := int64(0); i < j+122+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
// len(a)-123+122+MinInt overflows when len(a) == 0, so a bound check is needed here

65
test/prove.go
View File

@ -400,8 +400,8 @@ func f13f(a, b int64) int64 {
if b != math.MaxInt64 {
return 42
}
if a > b {
if a == 0 { // ERROR "Disproved Eq64$"
if a > b { // ERROR "Disproved Less64$"
if a == 0 {
return 1
}
}
@ -684,20 +684,6 @@ 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
}
}
}
func atexit(foobar []func()) {
for i := len(foobar) - 1; i >= 0; i-- { // ERROR "Induction variable: limits \[0,\?\], increment 1"
f := foobar[i]
@ -877,11 +863,11 @@ func unrollDecMin(a []int, b int) int {
return 42
}
var i, x int
for i = len(a); i >= b; i -= 2 {
for i = len(a); i >= b; i -= 2 { // ERROR "Proved Leq64"
x += a[i-1]
x += a[i-2]
}
if i == 1 { // ERROR "Disproved Eq64$"
if i == 1 {
x += a[i-1]
}
return x
@ -893,11 +879,11 @@ func unrollIncMin(a []int, b int) int {
return 42
}
var i, x int
for i = len(a); i >= b; i += 2 {
for i = len(a); i >= b; i += 2 { // ERROR "Proved Leq64"
x += a[i-1]
x += a[i-2]
}
if i == 1 { // ERROR "Disproved Eq64$"
if i == 1 {
x += a[i-1]
}
return x
@ -1107,7 +1093,7 @@ func modu2(x, y uint) int {
func issue57077(s []int) (left, right []int) {
middle := len(s) / 2
left = s[:middle] // ERROR "Proved IsSliceInBounds$"
left = s[:middle] // ERROR "Proved IsSliceInBounds$"
right = s[middle:] // ERROR "Proved IsSliceInBounds$"
return
}
@ -1124,6 +1110,43 @@ func issue45928(x int) {
useInt(combinedFrac)
}
func constantBounds1(i, j uint) int {
var a [10]int
if j < 11 && i < j {
return a[i] // ERROR "Proved IsInBounds$"
}
return 0
}
func constantBounds2(i, j uint) int {
var a [10]int
if i < j && j < 11 {
return a[i] // ERROR "Proved IsInBounds"
}
return 0
}
func constantBounds3(i, j, k, l uint) int {
var a [8]int
if i < j && j < k && k < l && l < 11 {
return a[i] // ERROR "Proved IsInBounds"
}
return 0
}
func equalityPropagation(a [1]int, i, j uint) int {
if i == j && i == 5 {
return a[j-5] // ERROR "Proved IsInBounds"
}
return 0
}
func inequalityPropagation(a [1]int, i, j uint) int {
if i != j && j >= 5 && j <= 6 && i == 5 {
return a[j-6] // ERROR "Proved IsInBounds"
}
return 0
}
//go:noinline
func useInt(a int) {
}

4
test/prove_constant_folding.go
View File

@ -14,7 +14,7 @@ func f0i(x int) int {
}
if (x + 20) == 20 {
return x + 5 // ERROR "Proved.+is constant 0$"
return x + 5 // ERROR "Proved.+is constant 0$" "Proved.+is constant 5$"
}
return x / 2
@ -26,7 +26,7 @@ func f0u(x uint) uint {
}
if (x + 20) == 20 {
return x + 5 // ERROR "Proved.+is constant 0$"
return x + 5 // ERROR "Proved.+is constant 0$" "Proved.+is constant 5$"
}
return x / 2