[llvm] [InstCombine] Avoid crash on aggregate types in SimplifyDemandedUseFPClass (PR #111128)

[Benjamin Maxwell via llvm-commits]

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@@ -1919,6 +1919,19 @@ Value *InstCombinerImpl::SimplifyDemandedVectorElts(Value *V,
 /// For floating-point classes that resolve to a single bit pattern, return that
 /// value.
 static Constant *getFPClassConstant(Type *Ty, FPClassTest Mask) {
+  // TODO: Support aggregate types that are allowed by FPMathOperator.
+  switch (Mask) {
+    case fcPosZero:
+    case fcNegZero:
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MacDue wrote:

I've put cases that (I think) _should_ hit these, however, `computeKnownFPClass()` only handles `ConstantAggregateZero` (and that case is now fixed), so I'm not sure it's possible to get fcPosZero, fcNegZero, etc for a constant aggregate.

https://github.com/llvm/llvm-project/pull/111128