================
@@ -5553,6 +5553,37 @@ void computeKnownFPClass(const Value *V, const APInt
&DemandedElts,
// TODO: Copy inf handling from instructions
break;
+ case Intrinsic::amdgcn_rsq: {
+ KnownFPClass KnownSrc;
+ // The only negative value that can be returned is -0 for -0 inputs.
+ Known.knownNot(fcNegInf | fcNegSubnormal | fcNegNormal);
+
+ computeKnownFPClass(II->getArgOperand(0), DemandedElts,
InterestedClasses,
+ KnownSrc, Q, Depth + 1);
+
+ if (KnownSrc.isKnownNever(fcSNan))
+ Known.knownNot(fcSNan);
+
+ // Negative -> nan
+ if (KnownSrc.isKnownNeverNaN() && KnownSrc.cannotBeOrderedLessThanZero())
+ Known.knownNot(fcNan);
+
+ Type *EltTy = II->getType()->getScalarType();
+
+ // f32 denormal always flushed.
+ if (EltTy->isFloatTy())
+ Known.knownNot(fcPosSubnormal);
----------------
arsenm wrote:
There was just no documentation before, the instruction never changed
https://github.com/llvm/llvm-project/pull/171837
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