[llvm] [InstCombine] Fix miscompilation for `select` + `FCmp` (PR #177872)

[Tirthankar Mazumder via llvm-commits]

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@@ -4303,16 +4302,29 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
       // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
       if (FCmp->hasOneUse() && FCmpInst::isUnordered(Pred)) {
         FCmpInst::Predicate InvPred = FCmp->getInversePredicate();
-        Value *NewCond = Builder.CreateFCmpFMF(InvPred, Cmp0, Cmp1, FCmp,
+        // Intersect fast-math flags from the original fcmp and select.
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wermos wrote:

I've removed this part.

https://github.com/llvm/llvm-project/pull/177872