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cmd/compile: remove 68857 ModU flowLimit workaround in prove

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We can know this is correct because all the testcases added by CL 605156 are still passing.
Partial revert of CL 605156 (everything but the testcases).

Change-Id: I5d8daadb4cb35a9de29daaabc22baee642511fe0
Reviewed-on: https://go-review.googlesource.com/c/go/+/714941
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Jorropo 2025-10-25 18:38:23 +02:00 • committed by Gopher Robot
parent a50de4bda7
commit 2ce5aab79e
1 changed files with 8 additions and 13 deletions
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21
src/cmd/compile/internal/ssa/prove.go
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@ -1962,19 +1962,6 @@ func (ft *factsTable) flowLimit(v *Value) bool {
b := ft.limits[v.Args[1].ID]
bitsize := uint(v.Type.Size()) * 8
return ft.newLimit(v, a.mul(b.exp2(bitsize), bitsize))
case OpMod64, OpMod32, OpMod16, OpMod8:
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
if !(a.nonnegative() && b.nonnegative()) {
// TODO: we could handle signed limits but I didn't bother.
break
}
fallthrough
case OpMod64u, OpMod32u, OpMod16u, OpMod8u:
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
// Underflow in the arithmetic below is ok, it gives to MaxUint64 which does nothing to the limit.
return ft.unsignedMax(v, min(a.umax, b.umax-1))
case OpDiv64, OpDiv32, OpDiv16, OpDiv8:
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
@ -2484,6 +2471,14 @@ func addLocalFacts(ft *factsTable, b *Block) {
OpRsh32Ux64, OpRsh32Ux32, OpRsh32Ux16, OpRsh32Ux8,
OpRsh64Ux64, OpRsh64Ux32, OpRsh64Ux16, OpRsh64Ux8:
ft.update(b, v, v.Args[0], unsigned, lt|eq)
case OpMod64, OpMod32, OpMod16, OpMod8:
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
if !(a.nonnegative() && b.nonnegative()) {
// TODO: we could handle signed limits but I didn't bother.
break
}
fallthrough
case OpMod64u, OpMod32u, OpMod16u, OpMod8u:
ft.update(b, v, v.Args[0], unsigned, lt|eq)
// Note: we have to be careful that this doesn't imply