[llvm] [SLP][REVEC] Fix CommonMask is transformed into vector form but used outside finalize. (PR #120952)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> What do you mean "actual-sized"? Determined by `unsigned VecVF = cast<FixedVectorType>(Vec->getType())->getNumElements();` If that is true, it will modify a lot of code. Especially we don't have test to make sure it is true.
> 

It is not a problem. The main problem - to make the code completely correct

> A code like `unsigned VecVF = cast<FixedVectorType>(Vec->getType())->getNumElements();` should be divided by the number of elements of ScalarTy. Just like `getVF`. e.g.,
> 
> ```
>     unsigned ScalarTyNumElements = getNumElements(ScalarTy);
>     unsigned VNumElements =
>         cast<FixedVectorType>(V->getType())->getNumElements();
>     assert(VNumElements > ScalarTyNumElements &&
>            "the number of elements of V is not large enough");
>     assert(VNumElements % ScalarTyNumElements == 0 &&
>            "the number of elements of V is not a vectorized value");
>     return VNumElements / ScalarTyNumElements;
> ```

No, it should not be. You should operate with the full masks from the very beginning

https://github.com/llvm/llvm-project/pull/120952