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

[Sam Tebbs via llvm-commits]

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@@ -4526,6 +4506,253 @@ static bool willGenerateVectors(VPlan &Plan, ElementCount VF,
   return false;
 }
 
+/// Get the VF scaling factor applied to the recipe's output, if the recipe has
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SamTebbs33 wrote:

Great idea, done.

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