[llvm] [SLPVectorizer] Widen constant strided loads. (PR #162324)

[Alexey Bataev via llvm-commits]

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@@ -6921,36 +6920,105 @@ bool BoUpSLP::isStridedLoad(ArrayRef<Value *> PointerOps, Type *ScalarTy,
 }
 
 bool BoUpSLP::analyzeConstantStrideCandidate(
-    const ArrayRef<Value *> PointerOps, Type *ScalarTy, Align Alignment,
+    ArrayRef<Value *> PointerOps, Type *ElemTy, Align Alignment,
     const SmallVectorImpl<unsigned> &SortedIndices, const int64_t Diff,
     Value *Ptr0, Value *PtrN, StridedPtrInfo &SPtrInfo) const {
-  const size_t Sz = PointerOps.size();
-  if (!isStridedLoad(PointerOps, ScalarTy, Alignment, Diff, Sz))
-    return false;
+  const unsigned Sz = PointerOps.size();
+  SmallVector<int64_t> SortedOffsetsFromBase(Sz);
+  // Go through `PointerOps` in sorted order and record offsets from `Ptr0`.
+  for (unsigned I : seq<unsigned>(Sz)) {
+    Value *Ptr =
+        SortedIndices.empty() ? PointerOps[I] : PointerOps[SortedIndices[I]];
+    SortedOffsetsFromBase[I] =
+        *getPointersDiff(ElemTy, Ptr0, ElemTy, Ptr, *DL, *SE);
+  }
+  assert(SortedOffsetsFromBase.size() > 1 &&
+         "Trying to generate strided load for less than 2 loads");
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alexey-bataev wrote:

Why do you need this assertion? `SortedOffsetsFromBase` is always of size `Sz`

https://github.com/llvm/llvm-project/pull/162324