[llvm] [VPlan] Expand VPBlendRecipes to select instructions. NFC (PR #133993)

[Luke Lau via llvm-commits]

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@@ -7047,6 +7047,13 @@ static bool planContainsAdditionalSimplifications(VPlan &Plan,
       if (isa<VPPartialReductionRecipe>(&R))
         return true;
 
+      // VPBlendRecipes are converted to selects and may have been simplified.
+      using namespace VPlanPatternMatch;
+      if (match(&R, m_VPInstruction<Instruction::Select>(
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lukel97 wrote:

A (very belated) follow up to this, I've posted https://github.com/llvm/llvm-project/pull/171851 which aims to move the expansion earlier

https://github.com/llvm/llvm-project/pull/133993