[llvm] [SelectionDAG] Remove `NoNaNsFPMath` in `visitFCmp` (PR #163519)

[Matt Arsenault via llvm-commits]

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@@ -5869,6 +5869,12 @@ bool SelectionDAG::isKnownNeverNaN(SDValue Op, bool SNaN,
                            ? APInt::getAllOnes(VT.getVectorNumElements())
                            : APInt(1, 1);
 
+  // If all users of this operand is annotated with nnan, we can assume
+  // this operand is not NaN, since nnan also affects inputs.
+  if (llvm::all_of(Op->users(),
+                   [](const SDNode *N) { return N->getFlags().hasNoNaNs(); }))
+    return true;
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arsenm wrote:

I'm not sure it's a good idea to let isKnownNeverNaN inspect the users. Can you drop this from this patch? If we're going to do this, it should be done separately.

https://github.com/llvm/llvm-project/pull/163519