[llvm] [LV][EVL] Generate negative strided load/store for reversed load/store (PR #123608)

[Luke Lau via llvm-commits]

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@@ -2765,11 +2760,26 @@ void VPWidenStoreEVLRecipe::execute(VPTransformState &State) {
                                     Intrinsic::vp_scatter,
                                     {StoredVal, Addr, Mask, EVL});
   } else {
-    VectorBuilder VBuilder(Builder);
-    VBuilder.setEVL(EVL).setMask(Mask);
-    NewSI = cast<CallInst>(VBuilder.createVectorInstruction(
-        Instruction::Store, Type::getVoidTy(EVL->getContext()),
-        {StoredVal, Addr}));
+    if (isReverse()) {
+      Type *StoredValTy = StoredVal->getType();
+      auto *EltTy = cast<VectorType>(StoredValTy)->getElementType();
+      auto *PtrTy = Addr->getType();
+      Value *Operands[] = {
+          StoredVal, Addr,
+          ConstantInt::getSigned(
+              Builder.getInt32Ty(),
+              -static_cast<int64_t>(EltTy->getScalarSizeInBits()) / 8),
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lukel97 wrote:

Probably should use `DL.getTypeAllocSize(EltTy);`?

https://github.com/llvm/llvm-project/pull/123608