[llvm] [LoopVectorize] Generate wide active lane masks (PR #147535)

[Kerry McLaughlin via llvm-commits]

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@@ -846,6 +849,14 @@ Value *VPInstruction::generate(VPTransformState &State) {
       Res->setName(Name);
     return Res;
   }
+  case VPInstruction::ExtractSubvector: {
+    Value *Vec = State.get(getOperand(0));
+    assert(State.VF.isVector());
+    auto Idx = cast<ConstantInt>(getOperand(1)->getLiveInIRValue());
+    auto ResTy = VectorType::get(
+        State.TypeAnalysis.inferScalarType(getOperand(0)), State.VF);
+    return Builder.CreateExtractVector(ResTy, Vec, Idx);
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kmclaughlin-arm wrote:

I did initially use VPWidenIntrinsic when I started working on this, but I wasn't sure if that should only be used when the intrinsic exists in the original IR. I've changed this back to use VPWidenIntrinsic to create a `vector_extract` now.

https://github.com/llvm/llvm-project/pull/147535