[llvm] [SLP] Compute a shuffle mask for SK_InsertSubvector (PR #85408)

[Alexey Bataev via llvm-commits]

================
@@ -4328,9 +4328,12 @@ BoUpSLP::LoadsState BoUpSLP::canVectorizeLoads(
               llvm_unreachable(
                   "Expected only consecutive, strided or masked gather loads.");
             }
+            SmallVector<int> ShuffleMask(VL.size());
+            for (int i = 0; i < VL.size(); i++)
----------------
alexey-bataev wrote:

```suggestion
            for (int Idx : seq<int>(0, VL.size()))
```


https://github.com/llvm/llvm-project/pull/85408