[llvm] [VPlan] Plumb recurrence FMFs through VPReductionPHIRecipe via VPIRFlags. NFC (PR #181694)

[Luke Lau via llvm-commits]

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@@ -5742,7 +5734,8 @@ void VPlanTransforms::optimizeFindIVReductions(VPlan &Plan,
 
     auto *NewPhiR = new VPReductionPHIRecipe(
         cast<PHINode>(PhiR->getUnderlyingInstr()), RecurKind::FindIV, *Sentinel,
-        *BackedgeVal, RdxUnordered{1}, PhiR->hasUsesOutsideReductionChain());
+        *BackedgeVal, RdxUnordered{1}, {},
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lukel97 wrote:

Phis already use OperationType::FPMathOp, which is why it already asserts when passing in something else other than fastmathflags. 

https://github.com/llvm/llvm-project/pull/181694