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Re: [PATCH] Introduce abi_word_mode


Ulrich Weigand wrote:
(I apologize for duplicate messages, I used a broken mailer ...)
Mark Mitchell <mark@codesourcery.com> wrote on 10/09/2006 11:15:44 PM:

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?

That would be quite unfortunate. I do hope we can get to a common understanding of what attribute ((mode (word))) means that does not preclude this type of optimization, that is not only important for s390, but also for rs6000 and possibly even for x86_64 ...

I think the optimization is just fine -- but I think that it might be that some code (namely, code that uses attribute ((mode (word)))) would need to change to take advantage of the optimization. (For example, it could use SImode instead, or just "int".) In other words, I think it's too strong a statement to say that not allowing the change to mode(word) prevents the optimization. You could even add a warning for uses of mode(word) to help catch problems when recompiling programs; it would be a mechanical change.


What do you think of my current proposal as outlined in my replies to
Richard and Ian?

Frankly, I think it adds more complexity where we should have less. I'd rather we move away from this feature entirely than that we introduce abi_word.


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


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