[llvm] [InstCombine] Support DemandElts in SimplifyDemandedFPClass (PR #174176)

[Matt Arsenault via llvm-commits]

================
@@ -211,6 +211,15 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
         Depth);
   }
 
+  KnownFPClass computeKnownFPClass(Value *Val, const APInt &DemandedElts,
+                                   FastMathFlags FMF,
+                                   FPClassTest Interested = fcAllFlags,
+                                   const Instruction *CtxI = nullptr,
----------------
arsenm wrote:

As a follow up, this should also probably migrate to using SimplifyQuery as the input instead of a context instruction to match SimplifyDemandedBits 

https://github.com/llvm/llvm-project/pull/174176