[PATCH] D158648: InstCombine: Introduce SimplifyDemandedUseFPClass

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp:1825
+    Known = computeKnownFPClass(V, DL, fcAllFlags, Depth, &TLI, &AC, CxtI, &DT);
+    if ((DemandedMask & Known.KnownFPClasses) == fcNone)
+      return PoisonValue::get(VTy);
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nikic wrote:
> Should this be using getFPClassConstant() instead, just like the main code path?
No, otherwise it will infinite loop since constants will always yield the same result after simplification. The isa<UndefValue> check above is the special case that works for poison


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  https://reviews.llvm.org/D158648/new/

https://reviews.llvm.org/D158648