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cmd/compile: propagate unsigned relations for Rsh if arguments are positive

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Updates #76332

Change-Id: Ifaa4d12897138d88d56b9d4e530c53dcee70bd58
Reviewed-on: https://go-review.googlesource.com/c/go/+/721205
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: Keith Randall <khr@google.com>
This commit is contained in:
Jorropo 2025-11-18 01:33:40 +01:00 • committed by Gopher Robot
parent d474f1fd21
commit 3820f94c1d
2 changed files with 27 additions and 5 deletions
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22
src/cmd/compile/internal/ssa/prove.go
View file

@ -2474,9 +2474,18 @@ func addLocalFacts(ft *factsTable, b *Block) {
//ft.update(b, v, v.Args[0], unsigned, gt|eq)
//ft.update(b, v, v.Args[1], unsigned, gt|eq)
case OpDiv64, OpDiv32, OpDiv16, OpDiv8:
if ft.isNonNegative(v.Args[0]) && ft.isNonNegative(v.Args[1]) {
ft.update(b, v, v.Args[0], unsigned, lt|eq)
if !ft.isNonNegative(v.Args[1]) {
break
}
fallthrough
case OpRsh8x64, OpRsh8x32, OpRsh8x16, OpRsh8x8,
OpRsh16x64, OpRsh16x32, OpRsh16x16, OpRsh16x8,
OpRsh32x64, OpRsh32x32, OpRsh32x16, OpRsh32x8,
OpRsh64x64, OpRsh64x32, OpRsh64x16, OpRsh64x8:
if !ft.isNonNegative(v.Args[0]) {
break
}
fallthrough
case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u,
OpRsh8Ux64, OpRsh8Ux32, OpRsh8Ux16, OpRsh8Ux8,
OpRsh16Ux64, OpRsh16Ux32, OpRsh16Ux16, OpRsh16Ux8,
@ -2491,12 +2500,17 @@ func addLocalFacts(ft *factsTable, b *Block) {
zl := ft.limits[z.ID]
var uminDivisor uint64
switch v.Op {
case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u:
case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u,
OpDiv64, OpDiv32, OpDiv16, OpDiv8:
uminDivisor = zl.umin
case OpRsh8Ux64, OpRsh8Ux32, OpRsh8Ux16, OpRsh8Ux8,
OpRsh16Ux64, OpRsh16Ux32, OpRsh16Ux16, OpRsh16Ux8,
OpRsh32Ux64, OpRsh32Ux32, OpRsh32Ux16, OpRsh32Ux8,
OpRsh64Ux64, OpRsh64Ux32, OpRsh64Ux16, OpRsh64Ux8:
OpRsh64Ux64, OpRsh64Ux32, OpRsh64Ux16, OpRsh64Ux8,
OpRsh8x64, OpRsh8x32, OpRsh8x16, OpRsh8x8,
OpRsh16x64, OpRsh16x32, OpRsh16x16, OpRsh16x8,
OpRsh32x64, OpRsh32x32, OpRsh32x16, OpRsh32x8,
OpRsh64x64, OpRsh64x32, OpRsh64x16, OpRsh64x8:
uminDivisor = 1 << zl.umin
default:
panic("unreachable")

10
test/prove.go
View file

@ -253,9 +253,10 @@ func f9(a, b bool) int {
func f10(a string) int {
n := len(a)
b := a[:n>>1] // ERROR "Proved IsSliceInBounds$"
// We optimize comparisons with small constant strings (see cmd/compile/internal/gc/walk.go),
// so this string literal must be long.
if a[:n>>1] == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
if b == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
return 0
}
return 1
@ -1084,6 +1085,13 @@ func issue57077(s []int) (left, right []int) {
return
}
func issue76332(s []int) (left, right []int) {
middle := len(s) >> 1
left = s[:middle] // ERROR "Proved IsSliceInBounds$"
right = s[middle:] // ERROR "Proved IsSliceInBounds$"
return
}
func issue51622(b []byte) int {
if len(b) >= 3 && b[len(b)-3] == '#' { // ERROR "Proved IsInBounds$"
return len(b)