[PATCH] D30137: [InstCombine] shrink truncated insertelement with constant operand

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

On the integer side, I'm sort of worried this could make code generation worse on targets which don't have insert instructions for all relevant widths (for example, SSE2 has i16 insertelement, but not i8 insertelement).

For fptrunc, you could in theory hurt performance if the insert is overwriting a denormal float, but I guess that's unlikely to happen in practice.


https://reviews.llvm.org/D30137