[llvm] [VPlan] Only store RecurKind + FastMathFlags in VPReductionRecipe. NFCI (PR #131300)

[Luke Lau via llvm-commits]

================
@@ -2301,9 +2300,11 @@ class VPReductionRecipe : public VPRecipeWithIRFlags {
              VPSlotTracker &SlotTracker) const override;
 #endif
 
-  /// Return the recurrence decriptor for the in-loop reduction.
-  const RecurrenceDescriptor &getRecurrenceDescriptor() const {
-    return RdxDesc;
+  /// Return the recurrence kind for the in-loop reduction.
+  RecurKind getRecurrenceKind() const { return RdxKind; }
+  /// Return the opcode for the recurrence for the in-loop reduction.
+  unsigned getOpcode() const {
+    return RecurrenceDescriptor::getOpcode(RdxKind);
----------------
lukel97 wrote:

This was just a helper method to save having to call `RecurrenceDescriptor::getOpcode` at the use sites, we could also just call it directly there if that's simpler?

https://github.com/llvm/llvm-project/pull/131300