mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-01-17 06:33:21 +00:00
477f28c48d
broken logic for merging shuffle masks in the face of SM_SentinelZero mask operands. While these are '-1' they don't mean 'undef' the way '-1' means in the pre-legalized shuffle masks. Instead, they mean that the shuffle operation is forcibly zeroing that lane. Reflect this and explicitly handle it in a bunch of places. In one place the effect is equivalent but much more clear. In the rest it was really weirdly broken. Also, rewrite the entire merging thing to be a more directy operation with a single loop and just doing math to map the indices through the various masks. Also add a bunch of asserts to try to make in extremely clear what the different masks can possibly look like. Finally, add some comments to clarify that we're merging shuffle masks *up* here rather than *down* as we do everywhere else, and thus the logic is quite confusing. Thanks to several different people for sending test cases, and for Robert Khasanov for an initial attempt at fixing. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215687 91177308-0d34-0410-b5e6-96231b3b80d8