[PATCH] D35569: [ARM] Remove FeatureNoARM implies ModeThumb.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

I've created https://reviews.llvm.org/D35569, in case we want to go with an error message, which I think makes sense, as we emit a similar error for hand-written assembler.

Either way I think we have to remove the implication, as for functions with "-thumb-mode" in target-features, we also set "-no-arm", as target-features are added after the CPU/architecture features haven been added. For such functions, we would then generate ARM code even though the target does not support ARM execution mode, which is a violation of the ACLE I think, which states

> The implementation must generate code in the required state unless it is impossible to do so (section 7.3 Target selection).

The alternative to generating an error would be to switch -thumb-mode to +thumb-mode in that case. I think recent versions of GCC report an error in that case though, which seems sensible to me.


https://reviews.llvm.org/D35569