[llvm] [VPlan] Change parent of VPReductionRecipe to VPRecipeWithIRFlags. NFC (PR #130881)

[Florian Hahn via llvm-commits]

================
@@ -2224,7 +2224,8 @@ void VPReductionRecipe::execute(VPTransformState &State) {
   RecurKind Kind = RdxDesc.getRecurrenceKind();
   // Propagate the fast-math flags carried by the underlying instruction.
   IRBuilderBase::FastMathFlagGuard FMFGuard(State.Builder);
-  State.Builder.setFastMathFlags(RdxDesc.getFastMathFlags());
+  if (hasFastMathFlags())
+    State.Builder.setFastMathFlags(getFastMathFlags());
----------------
fhahn wrote:

Why only set FMFs? As in `llvm/test/Transforms/LoopVectorize/RISCV/vplan-vp-intrinsics-reduction.ll`, we have a reduction with `nsw`. Should those flags also be set?

https://github.com/llvm/llvm-project/pull/130881