================
@@ -2280,6 +2290,127 @@ Value
*InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
Known = KnownLHS | KnownRHS;
break;
}
+ case Instruction::FMul: {
+ KnownFPClass KnownLHS, KnownRHS;
+
+ Value *X = I->getOperand(0);
+ Value *Y = I->getOperand(1);
+
+ FPClassTest SrcDemandedMask =
+ DemandedMask & (fcNan | fcZero | fcSubnormal | fcNormal);
+
+ if (DemandedMask & fcInf) {
+ // mul x, inf = inf
+ // mul large_x, large_y = inf
+ SrcDemandedMask |= fcSubnormal | fcNormal | fcInf;
+ }
+
+ if (DemandedMask & fcNan) {
+ // mul +/-inf, 0 => nan
+ SrcDemandedMask |= fcZero | fcInf;
+
+ // TODO: Mode check
+ // mul +/-inf, sub => nan if daz
+ SrcDemandedMask |= fcSubnormal;
+ }
+
+ if (X == Y) {
+ if (SimplifyDemandedFPClass(I, 0, SrcDemandedMask, KnownLHS, Depth + 1))
+ return I;
+ Type *EltTy = VTy->getScalarType();
+
+ DenormalMode Mode = F.getDenormalMode(EltTy->getFltSemantics());
+ Known = KnownFPClass::square(KnownLHS, Mode);
+
+ // Propagate known result to simplify edge case checks.
+ if ((DemandedMask & fcNan) == fcNone)
+ Known.knownNot(fcNan);
+ if ((DemandedMask & fcPosInf) == fcNone)
+ Known.knownNot(fcInf);
+
+ FPClassTest ValidResults = DemandedMask & Known.KnownFPClasses;
+ if (Constant *Folded =
+ getFPClassConstant(VTy, ValidResults, /*IsCanonicalizing=*/true))
+ return Folded;
+
+ if (Known.isKnownAlways(fcPosZero | fcPosInf | fcNan)) {
----------------
dtcxzyw wrote:
The square of a large normal value can produce +inf. But it doesn't happen in
the KnownFPClass propagation.
https://github.com/llvm/llvm-project/pull/173872
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