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

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Replace %x in my testcase with 3, and you get the same result. Granted, there are better ways to generate code than what the x86 backend currently does, but the end result would still be worse than the version with pinsrw.

I'd be more comfortable special-casing insertelement into a undef vector (so there's an obvious efficient lowering on any architecture).


https://reviews.llvm.org/D30137