RE: [AD] malloc() vs align_malloc()

["Robert Ohannessian" <ROhannessian@xxxxxxxxxx>]

Note that for bitmaps, you'll want to align the line member. You
shouldn't care about alignment of the dat member, really.

In fact, aligned_malloc isn't all that useful to Allegro.


> -----Original Message-----
> From: alleg-developers-admin@xxxxxxxxxx [mailto:alleg-
> developers-admin@xxxxxxxxxx] On Behalf Of AJ
> Sent: Saturday, February 19, 2005 11:57 PM
> To: alleg-developers@xxxxxxxxxx
> Subject: Re: [AD] malloc() vs align_malloc()
> 
> further research for this topic:
> 
> these funcs also exist for msvc7
> 
> _aligned_free()
> _aligned_malloc()
> _aligned_realloc()
> 
> so i guess we need to match eahc aligned_malloc() with an
aligned_free()
> 
> 
> my mingw (gcc 3.4.2) has this:
> 
> 
> /* These require msvcr70.dll or higher. */
> #if __MSVCRT_VERSION__ >= 0x0700
> _CRTIMP void * __cdecl _aligned_offset_malloc(size_t, size_t, size_t);
> _CRTIMP void * __cdecl _aligned_offset_realloc(void*, size_t, size_t,
> size_t);
> 
> _CRTIMP void * __cdecl _aligned_malloc (size_t, size_t);
> _CRTIMP void * __cdecl _aligned_realloc (void*, size_t, size_t);
> _CRTIMP void __cdecl _aligned_free (void*);
> #endif /* __MSVCRT_VERSION__ >= 0x0700 */
> 
> 
> which means it can only be defined for systems that are using the
msvc7
> runtime.  not sure if this is a requirement for MSVC6 as the MSDN
> documentaion claims its for systems back to win98.
> 
> this makes if a bit more difficult to implement cleanly, however if it
> potentially can improve things like draw_sprite and masked_blit() by
as
> much as 50% its worth doing.
> 
> 
> 
> 
> 
> AJ wrote:
> > before i go to the trouble of patching allegro i would like to hear
of
> > any arguments against using align_malloc() instead of malloc()
> >
> > SSE/SSE2 instructions require aligned data for performance reasons.
> >
> > i'd like to see at minimum all bitmap->dat*  mallocs be aligned to
16
> > byte boundaries (SSE requirement).
> >
> > on Windows, its called _aligned_malloc
> > details here:
> > http://msdn.microsoft.com/library/default.asp?url=/library/en-
> us/vclib/html/vclrf_aligned_malloc.asp
> >
> >
> > a quick look through allegro, i found many instances were an aligned
> > malloc *may* improve performace, many of these would not have any
side
> > effects as they are internally viewable vars, and would not break
user
> > viewable structs etc.
> >
> > anyone from linux land able to offer the linux view or this
proposal?
> >
> > aj.
> >
> >
> >
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> 
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