[llvm] InstCombine: Clean up SimplifyDemandedFPClass use context application (PR #176886)

[Yingwei Zheng via llvm-commits]

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@@ -2375,12 +2358,6 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Instruction *I,
         SimplifyDemandedFPClass(I, 0, SrcDemandedMask, KnownLHS, Depth + 1))
       return I;
 
-    // Propagate nnan-ness to sources to simplify source checks.
-    if ((DemandedMask & fcNan) == fcNone) {
-      KnownLHS.knownNot(fcNan);
-      KnownRHS.knownNot(fcNan);
-    }
-
     if (FMF.noInfs()) {
       // Flag implies inputs cannot be infinity.
       KnownLHS.knownNot(fcInf);
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dtcxzyw wrote:

Do we still need this propagation? FMF -> DemandedMask -> SrcDemandedMask -> nested call to SimplifyDemandedFPClass(DemandedMask  -> Known) -> KnownLHS/RHS

https://github.com/llvm/llvm-project/pull/176886