[llvm] [LV] Support strided load with a stride of -1 (PR #128718)

[Mel Chen via llvm-commits]

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@@ -2126,8 +2126,13 @@ void VPVectorPointerRecipe::execute(VPTransformState &State) {
   Value *Ptr = State.get(getOperand(0), VPLane(0));
 
   Value *Increment = createStepForVF(Builder, IndexTy, State.VF, CurrentPart);
+  // TODO: Support non-unit-reverse strided accesses.
+  Value *Index =
+      Strided
+          ? Builder.CreateMul(Increment, ConstantInt::getSigned(IndexTy, -1))
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Mel-Chen wrote:

@fhahn Do you think we should introduce a new pointer recipe, or is it better to just extend the existing vector-pointer recipe? I prefer the later one.

https://github.com/llvm/llvm-project/pull/128718