[llvm] [SLP]Enable interleaved stores support (PR #115354)

[Simon Pilgrim via llvm-commits]

================
@@ -9759,6 +9759,29 @@ void BoUpSLP::transformNodes() {
           // Strided store is more profitable than reverse + consecutive store -
           // transform the node to strided store.
           E.State = TreeEntry::StridedVectorize;
+      } else if (!E.ReorderIndices.empty()) {
+        // Check for interleaved stores.
+        auto IsInterleaveMask = [&, &TTI = *TTI](ArrayRef<int> Mask) {
+          assert(Mask.size() > 1 && "Expected mask greater than 1 element.");
+          if (Mask.size() < 4)
+            return 0u;
+          for (unsigned Factor : seq<unsigned>(2, Mask.size() / 2 + 1)) {
+            if (ShuffleVectorInst::isInterleaveMask(
----------------
RKSimon wrote:

Pull out repeated cast:
`auto *SclStore = cast<StoreInst>(E.Scalars.front());`

https://github.com/llvm/llvm-project/pull/115354