[VPlan] Use alloc-type to compute interleave group offset.

Use getAllocTypeSize to get compute the offset to the start of
interleave groups instead getScalarSizeInBits, which may return 0 for
pointers. This is in line with the analysis building the interleave
groups and fixes a mis-compile reported for
#106431.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1646,8 +1646,9 @@ void VPlanTransforms::createInterleaveGroups(
       // zero.
       assert(IG->getIndex(IRInsertPos) != 0 &&
              "index of insert position shouldn't be zero");
+      auto &DL = IRInsertPos->getDataLayout();
       APInt Offset(32,
-                   getLoadStoreType(IRInsertPos)->getScalarSizeInBits() / 8 *
+                   DL.getTypeAllocSize(getLoadStoreType(IRInsertPos)) *
                        IG->getIndex(IRInsertPos),
                    /*IsSigned=*/true);
       VPValue *OffsetVPV = Plan.getOrAddLiveIn(

llvm/test/Transforms/LoopVectorize/interleaved-accesses-different-insert-position.ll

@@ -183,7 +183,7 @@ define i64 @interleave_group_load_pointer_type(ptr %start, ptr %end) {
 ; CHECK-NEXT:    [[TMP6:%.*]] = add i64 [[OFFSET_IDX]], 0
 ; CHECK-NEXT:    [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[START]], i64 [[TMP6]]
 ; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr i8, ptr [[NEXT_GEP]], i64 16
-; CHECK-NEXT:    [[TMP8:%.*]] = getelementptr i8, ptr [[TMP7]], i32 0
+; CHECK-NEXT:    [[TMP8:%.*]] = getelementptr i8, ptr [[TMP7]], i32 -8
 ; CHECK-NEXT:    [[WIDE_VEC:%.*]] = load <12 x ptr>, ptr [[TMP8]], align 8
 ; CHECK-NEXT:    [[STRIDED_VEC:%.*]] = shufflevector <12 x ptr> [[WIDE_VEC]], <12 x ptr> poison, <4 x i32> <i32 0, i32 3, i32 6, i32 9>
 ; CHECK-NEXT:    [[STRIDED_VEC3:%.*]] = shufflevector <12 x ptr> [[WIDE_VEC]], <12 x ptr> poison, <4 x i32> <i32 1, i32 4, i32 7, i32 10>