[PATCH] D34028: [Bitcode] Add thumb-mode to target-features in metadata loader.

[Florian Hahn via llvm-commits]

On 09/06/2017 18:18, David Blaikie wrote:
> I'd wonder if the code in ARMSubtarget could be refactored into 
> something generically reusable (for splitting and examining the 
> attributes) that could be used here and there, perhaps.
> 

I'll take a look and try to find similar uses.

> 
>     Re your second comment: yes the idea is that code generated by clang
>     now sets +/-thumb-mode for all functions. For functions without a
>     thumb-mode target feature and  a thumb triple, Thumb code should be
>     generated, thus +thumb-mode is added.
> 
> 
> Should this be a verifier check/invariant that modern bitcode (I guess 
> there's no version number, so no way to identify the old versus the new) 
> & textual IR have +/-thumb on all functions?

I think it would make sense to add a check to the verifier. Should I do 
that as part of this patch?

> 
> I'm not sure how situations like this are usually handled in the 
> verifier/upgrade where the semantics haven't changed, but it won't 
> roundtrip through bitcode as such - it'll get sort of upgraded to a 
> newer representation of the same semantics.
> 
> Maybe that's fine... I dunno.
> 

Do you know anyone who could know?
> 
> 
>     ================
>     Comment at: test/Bitcode/thumb-mode-upgrade-arm.ll:1
>     +; RUN: llvm-dis -o - %s.bc | FileCheck %s
>     +
>     ----------------
>     javed.absar wrote:
>      > Could the same check be achieved  using something like 'llvm-as <
>     %s | llvm-dis ..."?
>     I think the reason to include a bitcode file is to make sure older
>     versions of the bitcode format are handled correctly going forward
> 
> 
>     https://reviews.llvm.org/D34028
> 
> 
>