[FFmpeg-devel] [PATCH] avutil/mem: use C11 aligned_malloc()

[James Almer]

Save for the Microsoft C Runtime library, where free() can't handle aligned
buffers, aligned_malloc() should be available and working on all supported
targets.
Also, malloc() alone may be sufficient if alignment requirement is low, so add
a check for it.

Signed-off-by: James Almer <jamrial at gmail.com>
---
 configure       |  2 --
 libavutil/mem.c | 42 ++++++------------------------------------
 2 files changed, 6 insertions(+), 38 deletions(-)

diff --git a/configure b/configure
index 7c45ac25c8..8fd2895ac2 100755
--- a/configure
+++ b/configure
@@ -6450,8 +6450,6 @@ if test -n "$custom_allocator"; then
 fi
 
 check_func_headers malloc.h _aligned_malloc     && enable aligned_malloc
-check_func  ${malloc_prefix}memalign            && enable memalign
-check_func  ${malloc_prefix}posix_memalign      && enable posix_memalign
 
 check_func  access
 check_func_headers stdlib.h arc4random_buf
diff --git a/libavutil/mem.c b/libavutil/mem.c
index 36b8940a0c..a72981d1ab 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -100,44 +100,14 @@ void *av_malloc(size_t size)
     if (size > atomic_load_explicit(&max_alloc_size, memory_order_relaxed))
         return NULL;
 
-#if HAVE_POSIX_MEMALIGN
-    if (size) //OS X on SDK 10.6 has a broken posix_memalign implementation
-    if (posix_memalign(&ptr, ALIGN, size))
-        ptr = NULL;
-#elif HAVE_ALIGNED_MALLOC
+#if HAVE_ALIGNED_MALLOC
     ptr = _aligned_malloc(size, ALIGN);
-#elif HAVE_MEMALIGN
-#ifndef __DJGPP__
-    ptr = memalign(ALIGN, size);
-#else
-    ptr = memalign(size, ALIGN);
-#endif
-    /* Why 64?
-     * Indeed, we should align it:
-     *   on  4 for 386
-     *   on 16 for 486
-     *   on 32 for 586, PPro - K6-III
-     *   on 64 for K7 (maybe for P3 too).
-     * Because L1 and L2 caches are aligned on those values.
-     * But I don't want to code such logic here!
-     */
-    /* 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
-     * memalign(64) + 1          3071, 3051, 3032
-     * memalign(64) + 2          3051, 3032, 3041
-     * memalign(64) + 4          2911, 2896, 2915
-     * memalign(64) + 8          2545, 2554, 2550
-     * memalign(64) + 16         2543, 2572, 2563
-     * memalign(64) + 32         2546, 2545, 2571
-     * memalign(64) + 64         2570, 2533, 2558
-     *
-     * BTW, malloc seems to do 8-byte alignment by default here.
-     */
 #else
-    ptr = malloc(size);
+    // malloc may already allocate sufficiently aligned buffers
+    if (ALIGN > _Alignof(max_align_t))
+        ptr = aligned_malloc(size, ALIGN);
+    else
+        ptr = malloc(size);
 #endif
     if(!ptr && !size) {
         size = 1;
-- 
2.43.1