On 04/26/2011 09:28 AM, Vitor Sessak wrote:
Module: libav
Branch: master
Commit: 13dfce3d44f99a2d7df71aba8ae003d58db726f7
Author: Vitor Sessak<[email protected]>
Committer: Reinhard Tartler<[email protected]>
Date: Sat Apr 23 19:24:31 2011 +0200
Increase alignment of av_malloc() as needed by AVX ASM.
Signed-off-by: Reinhard Tartler<[email protected]>
---
libavutil/mem.c | 16 +++++++---------
1 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/libavutil/mem.c b/libavutil/mem.c
index 2aef9b0..27bb30b 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -69,21 +69,21 @@ void *av_malloc(size_t size)
#endif
/* let's disallow possible ambiguous cases */
- if(size> (INT_MAX-16) )
+ if(size> (INT_MAX-32) )
return NULL;
#if CONFIG_MEMALIGN_HACK
- ptr = malloc(size+16);
+ ptr = malloc(size+32);
if(!ptr)
return ptr;
- diff= ((-(long)ptr - 1)&15) + 1;
+ diff= ((-(long)ptr - 1)&31) + 1;
ptr = (char*)ptr + diff;
((char*)ptr)[-1]= diff;
#elif HAVE_POSIX_MEMALIGN
- if (posix_memalign(&ptr,16,size))
+ if (posix_memalign(&ptr,32,size))
ptr = NULL;
#elif HAVE_MEMALIGN
- ptr = memalign(16,size);
+ ptr = memalign(32,size);
/* Why 64?
Indeed, we should align it:
on 4 for 386
@@ -93,10 +93,8 @@ void *av_malloc(size_t size)
Because L1 and L2 caches are aligned on those values.
But I don't want to code such logic here!
*/
- /* Why 16?
- Because some CPUs need alignment, for example SSE2 on P4,& most RISC
CPUs
- it will just trigger an exception and the unaligned load will be done
in the
- exception handler or it will just segfault (SSE2 on P4).
+ /* Why 32?
+ For AVX ASM. SSE / NEON needs only 16.
Why not larger? Because I did not see a difference in benchmarks ...
*/
/* benchmarks with P3
This commit breaks OSX on SDK 10.6 which has a broken posix_memalign implementation. /Ronald Bultje /has mentioned this
OSX bug in other threads on this list. When alignment >=32 && size == 0, posix_memalign returns an invalid pointer along
with a success code. So subsequent free corrupts the heap. Something like the attached patch fixes the issue.
diff --git a/libavutil/mem.c b/libavutil/mem.c
index 27bb30b..6f29363 100644
--- libavutil/mem.c
+++ libavutil/mem.c
@@ -80,6 +80,11 @@ void *av_malloc(size_t size)
ptr = (char*)ptr + diff;
((char*)ptr)[-1]= diff;
#elif HAVE_POSIX_MEMALIGN
+#if defined(__APPLE__)
+ if (size == 0)
+ ptr = NULL;
+ else
+#endif
if (posix_memalign(&ptr,32,size))
ptr = NULL;
#elif HAVE_MEMALIGN
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