[llvm] [SLP] Initial vectorization of non-power-of-2 ops. (PR #77790)

[Alexey Bataev via llvm-commits]

================
@@ -14798,14 +14843,23 @@ bool SLPVectorizerPass::vectorizeStores(ArrayRef<StoreInst *> Stores,
         continue;
       }
 
+      std::optional<unsigned> NonPowerOf2VF;
+      if (VectorizeNonPowerOf2) {
+        // First try vectorizing with a non-power-of-2 VF. At the moment, only
+        // consider cases where VF + 1 is a power-of-2, i.e. almost all vector
+        // lanes are used.
+        unsigned CandVF = Operands.size();
+        if (isPowerOf2_32(CandVF + 1) && CandVF <= MaxVF) {
+          NonPowerOf2VF = CandVF;
+        }
----------------
alexey-bataev wrote:

```suggestion
        if (isPowerOf2_32(CandVF + 1) && CandVF <= MaxVF)
          NonPowerOf2VF = CandVF;
```

https://github.com/llvm/llvm-project/pull/77790