[PATCH] Introduce abi_word_mode

[Mark Mitchell]

Ian Lance Taylor wrote:

>> So, are we converging towards telling Andreas that there is no way to
>> do what he wishes?  In other words, are going to declare that
>> attribute ((mode (word))) is not something that back ends can
>> configure independently of BITS_PER_WORD, and that, therefore, if you
>> have 32-bit code involving that type, that this binary code cannot be
>> recompiled without change to use 64-bit registers?
>
> I would be OK with that, in which case we should change
> unwind-generic.h and libgcc2.h.

I like this option.  Concretely, I would propose:

(a) deprecating attribute ((mode ((word)))
(b) adjusting the current documentation to reflect that, and to indicate 
the ABI issue,
(c) changing the bits of GCC's libraries that use this construct.

I'd also be OK with adding:

(d) allow back-ends to override the mode used

I don't really like (d), but I wouldn't fight against it in conjuction 
with (a), (b), (c); if we're making this go away anyhow, and its more 
expedient for the S/390 users to have (d), then that seems OK.

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713