[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Sam Tebbs via llvm-commits]

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@@ -4527,6 +4507,11 @@ static bool willGenerateVectors(VPlan &Plan, ElementCount VF,
 }
 
 #ifndef NDEBUG
+static SmallVector<LoopVectorizationCostModel::RegisterUsage, 8>
+calculateRegisterUsage(VPlan &Plan, ArrayRef<ElementCount> VFs,
+                       const TargetTransformInfo &TTI,
+                       const SmallPtrSetImpl<const Value *> &ValuesToIgnore);
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SamTebbs33 wrote:

It's used in and defined above `selectInterleaveCount` . I originally moved the function from there to above `selectVectorizationFactor` but that produced a big diff that was harder to review.

https://github.com/llvm/llvm-project/pull/132190