[llvm] [LV][EVL] Attach a new metadata on EVL vectorized loops (PR #131000)

[Pengcheng Wang via llvm-commits]

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@@ -1013,6 +1013,32 @@ void VPlan::execute(VPTransformState *State) {
     Value *Val = State->get(PhiR->getBackedgeValue(), NeedsScalar);
     cast<PHINode>(Phi)->addIncoming(Val, VectorLatchBB);
   }
+
+  // Check if it's EVL-vectorized and mark the corresponding metadata.
+  // Note that we could have done this during the codegen of
+  // ExplictVectorLength, but the enclosing vector loop was not in a good shape
+  // for us to attach the metadata.
+  bool IsEVLVectorized = llvm::any_of(*Header, [](const VPRecipeBase &Recipe) {
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wangpc-pp wrote:

I think we can add a field `IsWithEVL` to `VPlan` and set it to true when converting to EVL recipes: https://github.com/llvm/llvm-project/blob/62e37a8a0ae882c3ae1c994aa22953d6279458d4/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp#L8987-L8992

https://github.com/llvm/llvm-project/pull/131000