[llvm] [VPlan] Delay header mask creation until after blend recipes generation (PR #178623)

[Mel Chen via llvm-commits]

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@@ -1293,6 +1293,11 @@ static void simplifyRecipe(VPSingleDefRecipe *Def, VPTypeAnalysis &TypeInfo) {
   if (match(Def, m_LogicalAnd(m_VPValue(X), m_False())))
     return Def->replaceAllUsesWith(Def->getOperand(1));
 
+  // x && true -> x
+  if (match(Def, m_CombineOr(m_LogicalAnd(m_VPValue(X), m_True()),
+                             m_LogicalAnd(m_True(), m_VPValue(X)))))
+    return Def->replaceAllUsesWith(X);
+
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Mel-Chen wrote:

@fhahn Do we have PR for this pattern? I saw some improvement is from this instead of VPPreidicator.

https://github.com/llvm/llvm-project/pull/178623