[llvm] [SLPVectorizer] Widen strided loads. (PR #153074)

[Alexey Bataev via llvm-commits]

================
@@ -6324,18 +6367,12 @@ static bool isReverseOrder(ArrayRef<unsigned> Order) {
   });
 }
 
-/// Checks if the provided list of pointers \p Pointers represents the strided
-/// pointers for type ElemTy. If they are not, std::nullopt is returned.
-/// Otherwise, if \p Inst is not specified, just initialized optional value is
-/// returned to show that the pointers represent strided pointers. If \p Inst
-/// specified, the runtime stride is materialized before the given \p Inst.
-/// \returns std::nullopt if the pointers are not pointers with the runtime
-/// stride, nullptr or actual stride value, otherwise.
-static std::optional<Value *>
-calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
-                  const DataLayout &DL, ScalarEvolution &SE,
-                  SmallVectorImpl<unsigned> &SortedIndices,
-                  Instruction *Inst = nullptr) {
+/// Returns a SCEV expression for the stride if PointerOps is a set of strided
+/// pointers, or nullptr otherwise.
+static const SCEV *calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
+                                     const DataLayout &DL, ScalarEvolution &SE,
+                                     SmallVectorImpl<unsigned> &SortedIndices,
+                                     SmallVectorImpl<int64_t> &Coeffs) {
----------------
alexey-bataev wrote:

I mean, make it return `SCEV *` instead of optional and move SCEV expansion to a callee function 

https://github.com/llvm/llvm-project/pull/153074