[llvm] [SLP][REVEC] Make ShuffleCostEstimator and ShuffleInstructionBuilder can vectorize vector instructions. (PR #99606)

[Han-Kuan Chen via llvm-commits]

================
@@ -8800,13 +8815,17 @@ class BoUpSLP::ShuffleCostEstimator : public BaseShuffleAnalysis {
       // Shuffle single vector.
       ExtraCost += GetValueMinBWAffectedCost(V1);
       CommonVF = cast<FixedVectorType>(V1->getType())->getNumElements();
+      if (auto *VecTy = dyn_cast<FixedVectorType>(ScalarTy))
+        CommonVF /= VecTy->getNumElements();
----------------
HanKuanChen wrote:

If `CommonVF` is not large enough, the assert should fail.
```
      assert(all_of(Mask,
                    [=](int Idx) {
                      return Idx < 2 * static_cast<int>(CommonVF);
                    }) &&
             "All elements in mask must be less than 2 * CommonVF.");
```

https://github.com/llvm/llvm-project/pull/99606