Re: [Qemu-devel] Re: Performances on Mac OS X

[Fabrice Bellard <fabrice@bellard.org>]

Don't spend your time in using another compiler than gcc : most of the 
time is spent in the generated code, and the quality of this code relies 
on very small functions which are too simple for being optimized better.

Fabrice.

Roine Gustafsson wrote:
> Joshua Root [z3022016@student.unsw.edu.au] wrote:
> 
>>Laurent Amon <amon@stanfordalumni.org> wrote:
>>
>>
>>>I was wondering whether the implementation of qemu is tied to gcc or
>>>if it might
>>>be interesting to try to compile using IBM's compiler, which is able 
>>>to generate
>>>Altivec code...
>>
>>I have tried compiling qemu with xlc and it chokes on the asm. I 
>>believe that it uses a different syntax than gcc for this. I don't 
>>know what its syntax is, but if anybody does it shouldn't be too hard 
>>to make a patch which lets it compile.
>>
>>Using xlc does seem to give substantially better performance than 
>>gcc, and not just on floating point code.
>>
> 
> 
> xlc is picky with the source and takes FOREVER to compile with -O6. However,
> xlc is object compatible with gcc, so usually you just use xlc on core stuff
> that needs the speed, and gcc for everything else.
> Compile everything with gcc, rm the object files you want to remake with xlc
> (based on profiling), edit the makefiles to use xlc and make again. 
> 
>   /Roine
> 
> 
> 
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