================
@@ -5587,11 +5587,20 @@ Instruction
*InstCombinerImpl::foldICmpWithZextOrSext(ICmpInst &ICmp) {
return new ICmpInst(ICmp.getPredicate(), Builder.CreateOr(X, Y),
Constant::getNullValue(X->getType()));
+ // Treat "zext nneg" as "sext"
+ auto *NonNegInst0 = dyn_cast<PossiblyNonNegInst>(ICmp.getOperand(0));
+ auto *NonNegInst1 = dyn_cast<PossiblyNonNegInst>(ICmp.getOperand(1));
+
+ bool IsNonNeg0 = NonNegInst0 && NonNegInst0->hasNonNeg();
+ bool IsNonNeg1 = NonNegInst1 && NonNegInst1->hasNonNeg();
+
// If we have mismatched casts, treat the zext of a non-negative source
as
// a sext to simulate matching casts. Otherwise, we are done.
// TODO: Can we handle some predicates (equality) without non-negative?
- if ((IsZext0 && isKnownNonNegative(X, DL, 0, &AC, &ICmp, &DT)) ||
- (IsZext1 && isKnownNonNegative(Y, DL, 0, &AC, &ICmp, &DT)))
+ if ((IsZext0 &&
+ (IsNonNeg0 || isKnownNonNegative(X, DL, 0, &AC, &ICmp, &DT))) ||
----------------
nikic wrote:
After rebasing over
https://github.com/llvm/llvm-project/commit/5918f62301788b53e7d3a23f3203c483e9d4d791
it's possible to drop the isKnownNonNegative() call here entirely. We should
only check for zext nneg.
https://github.com/llvm/llvm-project/pull/70845
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