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Re: [PATCH][gas][arm] Add -mwarn-restrict-it


Hi Christophe,

>> Exactly, most people just find it annoying.
>
> Sorry, I'd never come across this warning :-)

You will see it a lot if you assemble existing Thumb-2 code for ARMv8-A...

>> I don't believe it's the assembler's job to warn about potentially slow code.
>>
> So... if the code is actually faster, do you mean that the warning is
> in fact wrong? Shouldn't it be removed instead of disabled, then?
> Or does it mean that these instructions with actually be forbidden in
> v9 (my understanding is that things become deprecated in vN before
> being removed/forbidden in vN+1) ?

The warning is useless indeed, and we could remove it in the future (but
that is more work since hundreds of gas tests would fail).

The instructions are not actually deprecated. It just explicitly allows an
implementation to execute them slowly if so desired. No implementation
has done so since it would slow down existing code.

Cheers,
Wilco


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