[llvm] [VPlan] Add new VPInstruction ocpode for header mask. (PR #89603)

[via llvm-commits]

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@@ -552,6 +515,16 @@ createScalarIVSteps(VPlan &Plan, InductionDescriptor::InductionKind Kind,
   return Steps;
 }
 
+/// Return the header mask recipe of the VPlan, if there is one.
+static VPInstruction *getHeaderMask(VPlan &Plan) {
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ayalz wrote:

Having loop region provide getHeaderMask() should save this search for a singleton VPValue.

https://github.com/llvm/llvm-project/pull/89603