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Re: PATCH: PR target/39911: The 'z' suffix doesn't work with 16bit integer insn


On Mon, Apr 27, 2009 at 6:58 AM, Paolo Bonzini <bonzini@gnu.org> wrote:
>
>>> Due to this, I don't think that we need to provide backward compatibility
>>> with _undocumented_ %z for x87 insns.
>>
>> The %z on x87 insns is widely used in gcc sources. It is one kind of
>> documentation.
>
> No, it is not. ?Undocumented operand modifiers are, well, undocumented,
> and if we decide to use a letter for something else there's no reason
> not to do so.
>

Are you suggesting we are free to change asm statement behaviors
as long as they aren't mentioned in gcc.info? What is difference
between a feature which we failed to document properly and a
feature purely internal to gcc?

> In fact, operand modifiers are not documented at all except ia64 `%Pn'.

I saw

  `m'
          Memory operand.  Remember that `m' allows postincrement and
          postdecrement which require printing with `%Pn' on IA-64.
          Use `S' to disallow postincrement and postdecrement.

Can you tell how to use it from above? I have to find an example for it.
Guess where I can find such examples?

I don't think you are telling me that it is OK to change those modifiers
used by asm statement, except for ia64 `%Pn'.

-- 
H.J.


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