Currently SLP vectorizer tries to keep only GEPs as scalar, if they are
vectorized but used externally. Same approach can be used for all scalar
values. This patch tries to keep original scalars if all its operands
remain scalar or externally used, the cost of the original scalar is
lower than the cost of the extractelement instruction, or if the number
of externally used scalars in the same entry is power of 2. Last
criterion allows better revectorization for multiply used scalars.
Reviewers: RKSimon
Reviewed By: RKSimon
Pull Request: https://github.com/llvm/llvm-project/pull/100904
b10ecfa914