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From: Avi Kivity on 2 Dec 2009 09:20
On 12/02/2009 04:06 PM, Jan Beulich wrote:
>>>> Ingo Molnar<mingo(a)elte.hu> 02.12.09 14:29>>>
>>>>
>> at first quick sight, this bit looks odd:
>>
>> + union { int i; bool b; } new;
>>
>> + return new.b;
>>
>> shouldnt that be short based, to work correctly in the 0-255 CPUs case?
>>
> No, I can't see why. In both instances, we're using (and had been
> using previously, just with the added movzbl) the outcome of a
> setCC instruction, which produces valid bool (single byte) values.
> It is precisely that reason why I needed to introduce these unions,
> since the upper bytes of the register aren't valid (and shouldn't be
> looked at by the caller).
>
>

Wouldn't 'u8 ret', as an additional argument be sufficient? gcc still
ought to be able to use the same register for new and ret if we remove
the early clobber.

--
error compiling committee.c: too many arguments to function

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From: Avi Kivity on 2 Dec 2009 09:40
On 12/02/2009 04:25 PM, Jan Beulich wrote:
>>>> Avi Kivity<avi(a)redhat.com> 02.12.09 15:12>>>
>>>>
>> Wouldn't 'u8 ret', as an additional argument be sufficient? gcc still
>> ought to be able to use the same register for new and ret if we remove
>> the early clobber.
>>
> We can't (validly) remove the early-clobber, otherwise the compiler
> would be permitted to use a register also used for addressing the lock
> structure for "new".
>

I meant for 'ret'.

--
error compiling committee.c: too many arguments to function

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