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

[AJ <aj@xxxxxxxxxx>]

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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