[PATCH] D36562: [Bitfield] Make the bitfield a separate location if it has width of legal integer type and its bit offset is naturally aligned for the type

Chandler Carruth via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Aug 22 18:37:56 PDT 2017

chandlerc added a comment.

I'm really not a fan of the degree of complexity and subtlety that this introduces into the frontend, all to allow particular backend optimizations.

I feel like this is Clang working around a fundamental deficiency in LLVM and we should instead find a way to fix this in LLVM itself.

As has been pointed out before, user code can synthesize large integers that small bit sequences are extracted from, and Clang and LLVM should handle those just as well as actual bitfields.

Can we see how far we can push the LLVM side before we add complexity to Clang here? I understand that there remain challenges to LLVM's stuff, but I don't think those challenges make *all* of the LLVM improvements off the table, I don't think we've exhausted all ways of improving the LLVM changes being proposed, and I think we should still land all of those and re-evaluate how important these issues are when all of that is in place.



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