[SLP]Use last pointer instead of first for reversed strided stores.

Need to use the last address of the vectorized stores for the strided
stores, not the first one, to correctly store the data.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -13169,6 +13169,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E, bool PostponedPHIs) {
       } else {
         assert(E->State == TreeEntry::StridedVectorize &&
                "Expected either strided or conseutive stores.");
+        if (!E->ReorderIndices.empty()) {
+          SI = cast<StoreInst>(E->Scalars[E->ReorderIndices.front()]);
+          Ptr = SI->getPointerOperand();
+        }
         Align CommonAlignment = computeCommonAlignment<StoreInst>(E->Scalars);
         Type *StrideTy = DL->getIndexType(SI->getPointerOperandType());
         auto *Inst = Builder.CreateIntrinsic(

llvm/test/Transforms/SLPVectorizer/RISCV/strided-stores-vectorized.ll

@@ -5,11 +5,11 @@ define void @store_reverse(ptr %p3) {
 ; CHECK-LABEL: @store_reverse(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ARRAYIDX1:%.*]] = getelementptr inbounds i64, ptr [[P3:%.*]], i64 8
-; CHECK-NEXT:    [[ARRAYIDX14:%.*]] = getelementptr inbounds i64, ptr [[P3]], i64 4
+; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds i64, ptr [[P3]], i64 7
 ; CHECK-NEXT:    [[TMP0:%.*]] = load <4 x i64>, ptr [[P3]], align 8
 ; CHECK-NEXT:    [[TMP1:%.*]] = load <4 x i64>, ptr [[ARRAYIDX1]], align 8
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <4 x i64> [[TMP0]], [[TMP1]]
-; CHECK-NEXT:    call void @llvm.experimental.vp.strided.store.v4i64.p0.i64(<4 x i64> [[TMP2]], ptr align 8 [[ARRAYIDX14]], i64 -8, <4 x i1> <i1 true, i1 true, i1 true, i1 true>, i32 4)
+; CHECK-NEXT:    call void @llvm.experimental.vp.strided.store.v4i64.p0.i64(<4 x i64> [[TMP2]], ptr align 8 [[ARRAYIDX2]], i64 -8, <4 x i1> <i1 true, i1 true, i1 true, i1 true>, i32 4)
 ; CHECK-NEXT:    ret void
 ;
 entry: