[PATCH] [RFC] Deprecated feature in TableGen

[Hal Finkel]

----- Original Message -----
> 
>   Hi Joey,
> 
>   I'm not convinced the three instructions ARM is deprecating really
>   warrant a change like this. TableGen is hairy enough as it is,
>   without adding barely used features. Of course, there could be
>   hundreds of uses in other architectures, just waiting for
>   something like this; that would obviously change things.

FWIW, PowerPC also has some deprecated instructions, and we could also add some warning if they're used. Maybe, however, this could be generalized to some kind of 'warning' attribute of which a deprecation warning is a special case?

 -Hal

> 
> 
> ================
> Comment at: tools/llvm-mc/Disassembler.cpp:90
> @@ -88,1 +89,3 @@
>      case MCDisassembler::Success:
> +      if (MII.get(Inst.getOpcode()).isDeprecated(Inst, STI))
> +        Streamer.AddComment(Twine("DEPRECATED"));
> ----------------
> I think this is the line I'm most worried about. It seems rather
> ad-hoc. I wonder if a more general "CustomComment" method (plumbed
> in somewhere else, obviously) might solve this and the potential
> limited applicability of deprecation as a concept.
> 
> 
> http://llvm-reviews.chandlerc.com/D1399
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory