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Re: [PATCH] Introduce abi_word_mode

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
(650) 331-3385 x713

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