[PATCH] D128501: [CodeGen] Make uninitialized Lvalue bit-field stores poison compatible

[Nuno Lopes via Phabricator via cfe-commits]

nlopes added a comment.

In D128501#3608846 <https://reviews.llvm.org/D128501#3608846>, @efriedma wrote:

> Under this scheme, is it illegal to link together object files built with -ffine-grained-bitfield-accesses and object files built with -fno-fine-grained-bitfield-accesses?

No, you can still link those. There's no ABI change nor any interference at IR level.
Thanks for the pointer, I wasn't aware of that option. What we can do is to optimize away the freezes with -ffine-grained-bitfield-accesses. The freeze is only needed when a struct field is shared between more than one bitfield.

Regarding perf, it's looking good, but @jmciver will post here a summary later.


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