[llvm] [VPlan] Simplify VPBlendRecipes to select instructions (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>(
+                        m_VPValue(), m_VPValue(), m_VPValue())) &&
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lukel97 wrote:

Good catch, I didn't notice this at the time. But I tried it out and it turns out m_Select also matches VPWidenSelectRecipes and VPReplicateRecipes too which we don't want to skip

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