[llvm] [VPlan] Unroll VPReplicateRecipe by VF. (PR #142433)

[Florian Hahn via llvm-commits]

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@@ -1140,6 +1140,22 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
     return;
   }
 
+  // Look through Extract(Last|Penultimate)Element (BuildVector ....).
+  if (match(&R,
+            m_VPInstruction<VPInstruction::ExtractLastElement>(m_VPValue(A))) ||
+      match(&R, m_VPInstruction<VPInstruction::ExtractPenultimateElement>(
+                    m_VPValue(A)))) {
+    unsigned Offset = cast<VPInstruction>(&R)->getOpcode() ==
+                              VPInstruction::ExtractLastElement
+                          ? 1
+                          : 2;
+    auto *BV = dyn_cast<VPInstruction>(A);
+    if (BV && BV->getOpcode() == VPInstruction::BuildVector) {
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fhahn wrote:

I added a m_BuildVector matcher, which for which we don't support matching the operands, which is variable. That seems to work OK with @ayalz's suggestion below.

https://github.com/llvm/llvm-project/pull/142433