[llvm] [SLP]Do not consider non-profitable loads slices (PR #149209)

[Simon Pilgrim via llvm-commits]

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@@ -11772,6 +11776,8 @@ void BoUpSLP::transformNodes() {
           }
           Slices.emplace_back(Cnt, Slice.size());
         }
+        if (VF == 2 && AllStrided && Slices.size() > 2)
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RKSimon wrote:

Add a brief comment explaining the reasoning

https://github.com/llvm/llvm-project/pull/149209