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cmd/compile: compute min's & max's limits from argument's limits inside flowLimit

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Updates #68857

Change-Id: Ied07e656bba42f3b1b5f9b9f5442806aa2e7959b
Reviewed-on: https://go-review.googlesource.com/c/go/+/656157
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
This commit is contained in:
Jorropo 2025-03-09 14:37:30 +01:00
parent bcd0ebbd2a
commit d2842229fc
2 changed files with 394 additions and 0 deletions
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83
src/cmd/compile/internal/ssa/prove.go
View File

@ -1882,6 +1882,89 @@ func (ft *factsTable) flowLimit(v *Value) bool {
return ft.newLimit(v, lim) return ft.newLimit(v, lim)
case OpPhi: case OpPhi:
{
// Work around for go.dev/issue/68857, look for min(x, y) and max(x, y).
b := v.Block
if len(b.Preds) != 2 {
goto notMinNorMax
}
// FIXME: this code searches for the following losange pattern
// because that what ssagen produce for min and max builtins:
// conditionBlock → (firstBlock, secondBlock) → v.Block
// there are three non losange equivalent constructions
// we could match for, but I didn't bother:
// conditionBlock → (v.Block, secondBlock → v.Block)
// conditionBlock → (firstBlock → v.Block, v.Block)
// conditionBlock → (v.Block, v.Block)
firstBlock, secondBlock := b.Preds[0].b, b.Preds[1].b
if firstBlock.Kind != BlockPlain || secondBlock.Kind != BlockPlain {
goto notMinNorMax
}
if len(firstBlock.Preds) != 1 || len(secondBlock.Preds) != 1 {
goto notMinNorMax
}
conditionBlock := firstBlock.Preds[0].b
if conditionBlock != secondBlock.Preds[0].b {
goto notMinNorMax
}
if conditionBlock.Kind != BlockIf {
goto notMinNorMax
}
less := conditionBlock.Controls[0]
var unsigned bool
switch less.Op {
case OpLess64U, OpLess32U, OpLess16U, OpLess8U,
OpLeq64U, OpLeq32U, OpLeq16U, OpLeq8U:
unsigned = true
case OpLess64, OpLess32, OpLess16, OpLess8,
OpLeq64, OpLeq32, OpLeq16, OpLeq8:
default:
goto notMinNorMax
}
small, big := less.Args[0], less.Args[1]
truev, falsev := v.Args[0], v.Args[1]
if conditionBlock.Succs[0].b == secondBlock {
truev, falsev = falsev, truev
}
bigl, smalll := ft.limits[big.ID], ft.limits[small.ID]
if truev == big {
if falsev == small {
// v := big if small <¿=? big else small
if unsigned {
maximum := max(bigl.umax, smalll.umax)
minimum := max(bigl.umin, smalll.umin)
return ft.unsignedMinMax(v, minimum, maximum)
} else {
maximum := max(bigl.max, smalll.max)
minimum := max(bigl.min, smalll.min)
return ft.signedMinMax(v, minimum, maximum)
}
} else {
goto notMinNorMax
}
} else if truev == small {
if falsev == big {
// v := small if small <¿=? big else big
if unsigned {
maximum := min(bigl.umax, smalll.umax)
minimum := min(bigl.umin, smalll.umin)
return ft.unsignedMinMax(v, minimum, maximum)
} else {
maximum := min(bigl.max, smalll.max)
minimum := min(bigl.min, smalll.min)
return ft.signedMinMax(v, minimum, maximum)
}
} else {
goto notMinNorMax
}
} else {
goto notMinNorMax
}
}
notMinNorMax:
// Compute the union of all the input phis. // Compute the union of all the input phis.
// Often this will convey no information, because the block // Often this will convey no information, because the block
// is not dominated by its predecessors and hence the // is not dominated by its predecessors and hence the

311
test/prove.go
View File

@ -1691,6 +1691,317 @@ func phiMin(a, b []byte) {
_ = b[:y] // ERROR "Proved IsSliceInBounds" _ = b[:y] // ERROR "Proved IsSliceInBounds"
} }
func minPhiLeq[T uint | int](x, y T) (z T) {
if x <= y {
z = x
} else {
z = y
}
return z
}
func maxPhiLeq[T uint | int](x, y T) (z T) {
if y <= x {
z = x
} else {
z = y
}
return z
}
func mathBasedOnPhiLosangeMinUFirstLeq(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = minPhiLeq(x, maxc)
x = maxPhiLeq(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinUSecondLeq(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = maxPhiLeq(x, minc)
x = minPhiLeq(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinFirstLeq(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = minPhiLeq(x, maxc)
x = maxPhiLeq(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinSecondLeq(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = maxPhiLeq(x, minc)
x = minPhiLeq(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func minPhiLess[T uint | int](x, y T) (z T) {
if x < y {
z = x
} else {
z = y
}
return z
}
func maxPhiLess[T uint | int](x, y T) (z T) {
if y < x {
z = x
} else {
z = y
}
return z
}
func mathBasedOnPhiLosangeMinUFirstLess(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = minPhiLess(x, maxc)
x = maxPhiLess(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinUSecondLess(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = maxPhiLess(x, minc)
x = minPhiLess(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinFirstLess(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = minPhiLess(x, maxc)
x = maxPhiLess(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func mathBasedOnPhiLosangeMinSecondLess(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = maxPhiLess(x, minc)
x = minPhiLess(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func mathBasedOnPhiBuiltinMinUFirst(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = min(x, maxc)
x = max(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiBuiltinMinUSecond(x uint, ensureAllBranchesCouldHappen func() bool) uint {
const maxc = 0xf2a
const minc = 0xf0a
x = max(x, minc)
x = min(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64U$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64U$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64U$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64U$"
return 42424242
}
return x
}
func mathBasedOnPhiBuiltinMinFirst(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = min(x, maxc)
x = max(x, minc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func mathBasedOnPhiBuiltinMinSecond(x int, ensureAllBranchesCouldHappen func() bool) int {
const maxc = 0xf2a
const minc = 0xf0a
x = max(x, minc)
x = min(x, maxc)
const k = 1
x += k
if ensureAllBranchesCouldHappen() && x > maxc+k { // ERROR "Disproved Less64$"
return 42
}
if ensureAllBranchesCouldHappen() && x <= maxc+k { // ERROR "Proved Leq64$"
return 4242
}
if ensureAllBranchesCouldHappen() && x < minc+k { // ERROR "Disproved Less64$"
return 424242
}
if ensureAllBranchesCouldHappen() && x >= minc+k { // ERROR "Proved Leq64$"
return 42424242
}
return x
}
func issue16833(a, b []byte) { func issue16833(a, b []byte) {
n := copy(a, b) n := copy(a, b)
_ = a[n:] // ERROR "Proved IsSliceInBounds" _ = a[n:] // ERROR "Proved IsSliceInBounds"