Re: gcc and SIMD

[Maurizio Vitale <maurizio_vitale at verizon dot net>]

you can answer your questions yourself with a few Unix commands.
If you want to know where __builtin_X is defined, start with all  
files in which it is used:

	find . -type f | xargs egrep -l __builtin_X                 [run  
from the top gcc directory]

if you suspect that something is architecture specific you can limit  
the search to your architecture of interest by replacing '.' with the  
correct directory.

But for the __builtin_* functions, you may end up with nothing:  
defined by the compiler means that GCC knows how to replace those  
calls with RTL (or maybe these days w/ higher level representations).  
So there's no function called __builtin_X.
It is still likely that the __builtin_X names are mentioned somewhere  
in the code or comments around where the replacement happens.


On Mar 5, 2007, at 5:31 AM, ranjith kumar wrote:

> --- Ian Lance Taylor <iant@google.com> wrote:
>
> > ranjith kumar <ranjit_kumar_b4u@yahoo.co.uk> writes:
> >
> > >  1) Seems that all defintions for MMX, SSE and
> > SSE2
> > > are deinred in mmtrin.h,xmmintrin.h and
> > emmintrin.h
> > > header files respectively. Am I right?
> >
> > Yes.
> >
> > > 2) In those header files all functions call
> > > _builtin_ia32_*. Where those functions(body) are
> > > defined?
> >
> > They are intrinsic functions automatically defined
> > by the compiler.
> Please tell me in what file they are defined.
>
> > > 3) I thought that associated with each SIMD
> > > instruction defined in Intel-ia-32-architectures
> > > manual(Basic architecture) there is one function
> > > defined in those header files.
> > > But for some instructions no functions were
> > defined in
> > > those header files.(For example MOVDQA
> > instruction)
> > > Also those header files contain some more
> > functions
> > > for which no SIMD assembly instruction
> > exist.Example
> > > in emmintrin.h
> > > static __inline __m128i
> > > _mm_load_si128 (__m128i const *__P)
> > > {
> > >   return (__m128i) __builtin_ia32_loaddqa  ((char
> > > const *)__P);
> > > }
> > > What could be the reason?
> >
> > Those header files follow the implementation
> > described by Intel.
> In which file they are described?
> The thing is that I want to go into internals of it.
> Thanks in advance.
> > Ian
>
>
>
> 		
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