[llvm] [SLP][modularisation][NFC] Move clusterSortPtrAccesses to SLPMemoryUtils (PR #222235)

[Alexey Bataev via llvm-commits]

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@@ -90,6 +91,14 @@ bool isMaskedStoreCompress(ArrayRef<Value *> VL, ArrayRef<Value *> PointerOps,
                            SmallVectorImpl<int> &ReuseShuffleIndices,
                            FixedVectorType *&StoreVecTy);
 
+/// Clusters \p VL pointers by underlying object and sorts each cluster by
+/// offset, producing \p SortedIndices when the accesses are consecutive.
+/// \p MaxDepth is the recursion limit for getUnderlyingObject.
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alexey-bataev wrote:

```suggestion
/// Clusters \p VL pointers by (basic block, underlying object) pair and sorts
/// each cluster by offset. Returns false and leaves \p SortedIndices empty if
/// the accesses are not worth reordering.
```

https://github.com/llvm/llvm-project/pull/222235