[llvm] [InstCombine] canonicalize operands of fcmp ord/uno if they are known NaN (PR #97763)

[Yingwei Zheng via llvm-commits]

================
@@ -8103,13 +8103,20 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
   // If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
   // then canonicalize the operand to 0.0.
   if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
-    if (!match(Op0, m_PosZeroFP()) &&
-        isKnownNeverNaN(Op0, 0, getSimplifyQuery().getWithInstruction(&I)))
-      return replaceOperand(I, 0, ConstantFP::getZero(OpType));
-
-    if (!match(Op1, m_PosZeroFP()) &&
-        isKnownNeverNaN(Op1, 0, getSimplifyQuery().getWithInstruction(&I)))
-      return replaceOperand(I, 1, ConstantFP::getZero(OpType));
+    if (!match(Op0, m_PosZeroFP())) {
+      KnownFPClass Known0 = computeKnownFPClass(Op0, fcAllFlags, &I);
+      if (Known0.isKnownNeverNaN())
+        return replaceOperand(I, 0, ConstantFP::getZero(OpType));
+      if (Known0.isKnownAlwaysNaN())
+        return replaceOperand(I, 0, ConstantFP::getNaN(OpType));
----------------
dtcxzyw wrote:

It should be folded into a constant boolean value.
```suggestion
        return replaceInstUsesWith(I, ConstantInt::getBool(Pred == CmpInst::FCMP_UNO));
```


https://github.com/llvm/llvm-project/pull/97763