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cmd/compile: use isUnsignedPowerOfTwo rather than isPowerOfTwo for unsigneds

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Fixes #76688

Change-Id: Icb8dab54a5ce7d83b656d50d5ea605d2a62b96f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/726680
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
This commit is contained in:
Jorropo 2025-12-04 04:17:58 +01:00 • committed by Gopher Robot
parent 2b62144069
commit 7b67b68a0d
2 changed files with 10 additions and 2 deletions
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4
src/cmd/compile/internal/ssa/prove.go
View file

@ -2885,9 +2885,9 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) {
xl := ft.limits[x.ID] xl := ft.limits[x.ID]
y := v.Args[1] y := v.Args[1]
yl := ft.limits[y.ID] yl := ft.limits[y.ID]
if xl.umin == xl.umax && isPowerOfTwo(int64(xl.umin)) || if xl.umin == xl.umax && isUnsignedPowerOfTwo(xl.umin) ||
xl.min == xl.max && isPowerOfTwo(xl.min) || xl.min == xl.max && isPowerOfTwo(xl.min) ||
yl.umin == yl.umax && isPowerOfTwo(int64(yl.umin)) || yl.umin == yl.umax && isUnsignedPowerOfTwo(yl.umin) ||
yl.min == yl.max && isPowerOfTwo(yl.min) { yl.min == yl.max && isPowerOfTwo(yl.min) {
// 0,1 * a power of two is better done as a shift // 0,1 * a power of two is better done as a shift
break break

8
test/prove.go
View file

@ -2718,6 +2718,14 @@ func detectStringLenRelation(s string) bool {
return false return false
} }
func issue76688(x, y uint64) uint64 {
if x > 1 || y != 1<<63 {
return 42
}
// We do not want to rewrite the multiply to a condselect here since opt can do a better job with a left shift.
return x * y
}
//go:noinline //go:noinline
func prove(x int) { func prove(x int) {
} }