alignment issues for sse

[corey taylor]

I see the definition, but I've never seen any documentation on them.
Can you point to some useful documentation?

Currently, we develop for many platforms, so portability is better in
most instances although we do use MMX and some SSE for speed where
available.

corey


On Thu, 17 Feb 2005 01:51:44 +0200 (EET), Kimmo Fredriksson
<kfredrik@cs.joensuu.fi> wrote:
> Hi,
> 
> [Disclaimer: I haven't really been following this discussion...]
> 
> On Wed, 16 Feb 2005, corey taylor wrote:
> 
> >  However, after looking into the current public project I'm on, I
> > realize that it doesn't use SSE for the allocation.  It simply
> > advances to an aligned location and manually forces the alignment,
> > hides the actual allocation pointer, and returns the aligned pointer.
> 
> Why not use:
> 
> void * _mm_malloc (size_t size, size_t alignment)
> void _mm_free (void * ptr)
> 
> ?
> 
> Defined in xmmintrin.h (I think).
> 
> > On Wed, 16 Feb 2005 17:58:15 +0100, Brian Budge <brian.budge@gmail.com> wrote:
> 
> >> On Wed, 16 Feb 2005 10:46:54 -0600, corey taylor <corey.taylor@gmail.com> wrote:
> >>> Implementation's I've used and worked on always do aligned allocations
> >>> manually.  Typically the hidden and real sizes of the allocation are
> >>> put into the memory allocation itself and the returned pointer is
> >>> incremented a few bytes.  The downside to this is that you must be
> >>> strict in using the aligned free routine also.
> 
> See above.
> 
> >>> On Wed, 16 Feb 2005 10:09:27 -0600, Eljay Love-Jensen <eljay@adobe.com> wrote:
> 
> >>>> >But surely thousands of people are writing sse code... how do they make
> >>>> it work?
> >>>>
> >>>> I presume by taking measures to assure the SSE structs are properly
> >>>> aligned.
> >>>>
> >>>> >Do I need to switch to the intel compiler/linker?
> >>>>
> >>>> I do not know.
> 
> I do not know either, but that was my solution...
> 
> But: my sse code used to work just fine with gcc. Then something happened,
> and I just get seg faults. Don't remember exactly anymore, but I think at
> the time it actually worked with gcc, I was using some early gcc 3.4
> snapshot, since it was the only one that worked. No version before, no
> version after (that I have tried, excluding e.g. 4.0)... And of course
> there is also the possibility that something else changed, I do/did
> something wrong, etc. Anyways, currently I use icc for sse code, and use
> _mm_malloc/_mm_free for dynamic allocation, statics are automagically 16
> byte aligned.
> 
> For other things, I still use mostly gcc.
> 
> K
> 
>