Re: [PATCH 4/6] Add macros for increasing data alignment

[Eric Wong <normalperson@yhbt.net>]

Måns Rullgård <mans@mansr.com> wrote:
> That CPU doesn't have AVX so 16-byte alignment is enough, and plain
> malloc usually provides that.  It obviously doesn't hurt to add support
> for memalign as well even though it is considered obsolete.  If you do
> that, you should also take care of #including malloc.h.

Yes, added memalign(3) and posix_memalign(3) fallbacks.
I also went ahead and stole a bit from Ruby to provide a
fallback when none of the 3 functions exist.

Will still need to deal with systems without LSX_ALIGN...

Anyways, pushed the following to git://bogomips.org/sox ew/align

-----------------8<------------------
Subject: [PATCH] always support aligned heap allocation

The new sdm effect will not work correctly on AVX systems without
32-byte alignment; so we need to support older systems without
C11 aligned_alloc.

The fallback emulation is based on code found in gc.c in Ruby 2.0+
(BSD-licensed)
---
 configure.ac | 11 ++++++++++-
 src/util.h   | 31 +++++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 8570638..017a9dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -207,7 +207,16 @@ AC_HEADER_STDC
 AC_CHECK_HEADERS(fcntl.h unistd.h byteswap.h sys/stat.h sys/time.h sys/timeb.h sys/types.h sys/utsname.h termios.h glob.h fenv.h)
 
 dnl Checks for library functions.
-AC_CHECK_FUNCS(strcasecmp strdup popen vsnprintf gettimeofday mkstemp fmemopen aligned_alloc)
+AC_CHECK_FUNCS(strcasecmp strdup popen vsnprintf gettimeofday mkstemp fmemopen)
+
+dnl aligned alloc required for sdm using AVX (32-byte) or SSE2 (16-byte)
+AC_CHECK_FUNCS(aligned_alloc)
+AS_IF([test "x$ac_cv_func_aligned_alloc" != xyes], [
+	AC_CHECK_FUNCS([memalign])
+	AS_IF([test "x$ac_cv_func_memalign" != xyes], [
+		AC_CHECK_FUNCS([posix_memalign])
+	])
+])
 
 dnl Check if math library is needed.
 AC_SEARCH_LIBS([pow], [m])
diff --git a/src/util.h b/src/util.h
index b5cc9b8..3a9686d 100644
--- a/src/util.h
+++ b/src/util.h
@@ -196,12 +196,39 @@
 
 #ifdef HAVE_ALIGNED_ALLOC
   #define aligned_free(p) free(p)
+#elif defined(HAVE_MEMALIGN)
+  #include <malloc.h>
+  #define aligned_alloc(a, s) memalign(a, s)
+  #define aligned_free(p) free(p)
+#elif defined(HAVE_POSIX_MEMALIGN)
+  #include <errno.h>
+static inline void *sox_aligned_alloc_pm(size_t align, size_t size)
+{
+  void *ptr;
+  int err = posix_memalign(&ptr, align, size);
+
+  if (!err) return ptr;
+  errno = err;
+  return 0;
+}
+  #define aligned_alloc(a, s) sox_aligned_alloc_pm(a, s)
+  #define aligned_free(p) free(p)
 #elif defined _MSC_VER
   #define aligned_alloc(a, s) _aligned_malloc(s, a)
   #define aligned_free(p) _aligned_free(p)
 #else
-  #define aligned_alloc(a, s) malloc(s)
-  #define aligned_free(p) free(p)
+static inline void *sox_aligned_alloc_m(size_t align, size_t size)
+{
+  void *res = malloc(align + size + sizeof(void *));
+  char *aligned = (char *)res + align + sizeof(void *);
+
+  aligned -= ((size_t)aligned & (align - 1));
+  ((void **)aligned)[-1] = res;
+  return (void *)aligned;
+}
+
+  #define aligned_alloc(a, s) sox_aligned_alloc_m(a, s)
+  #define aligned_free(p) free(((void**)p)[-1]);
 #endif
 
 /*------------------------------- Maths stuff --------------------------------*/
-- 
EW

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