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

[via llvm-commits]

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@@ -493,6 +493,9 @@ Value *VPInstruction::generate(VPTransformState &State) {
   }
   case Instruction::ExtractElement: {
     assert(State.VF.isVector() && "Only extract elements from vectors");
+    return State.get(getOperand(0),
+                     VPLane(cast<ConstantInt>(getOperand(1)->getLiveInIRValue())
+                                ->getZExtValue()));
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ayalz wrote:

Agreed theoretically, but this deals with explicit unrolling by VF, which may be worth bounding to prevent code bloat, which may also impact performance. I.e., VF's larger than 255 could still be supported if only vectors are produced. (OTOH, legalization could also take place later...).

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