libgomp: Fix up aligned_alloc arguments [PR102838]

C says that aligned_alloc size must be an integral multiple of alignment.
While glibc doesn't care about it, apparently Solaris does.
So, this patch decreases the priority of aligned_alloc among the other
variants because it needs more work and can waste more memory and rounds
up the size to multiple of alignment.

2021-11-18  Jakub Jelinek  <jakub@redhat.com>

	PR libgomp/102838
	* alloc.c (gomp_aligned_alloc): Prefer _aligned_alloc over
	memalign over posix_memalign over aligned_alloc over fallback
	with malloc instead of aligned_alloc over _aligned_alloc over
	posix_memalign over memalign over fallback with malloc.  For
	aligned_alloc, round up size up to multiple of al.

1 files changed, 12 insertions, 6 deletions

diff --git a/libgomp/alloc.c b/libgomp/alloc.c
index 6ff9cb9..3109b86 100644
--- a/libgomp/alloc.c
+++ b/libgomp/alloc.c
@@ -65,18 +65,24 @@ gomp_aligned_alloc (size_t al, size_t size)
   void *ret;
   if (al < sizeof (void *))
     al = sizeof (void *);
-#ifdef HAVE_ALIGNED_ALLOC
-  ret = aligned_alloc (al, size);
-#elif defined(HAVE__ALIGNED_MALLOC)
+#ifdef HAVE__ALIGNED_MALLOC
   ret = _aligned_malloc (size, al);
-#elif defined(HAVE_POSIX_MEMALIGN)
-  if (posix_memalign (&ret, al, size) != 0)
-    ret = NULL;
 #elif defined(HAVE_MEMALIGN)
   {
     extern void *memalign (size_t, size_t);
     ret = memalign (al, size);
   }
+#elif defined(HAVE_POSIX_MEMALIGN)
+  if (posix_memalign (&ret, al, size) != 0)
+    ret = NULL;
+#lif defined(HAVE_ALIGNED_ALLOC)
+  {
+    size_t sz = (size + al - 1) & ~(al - 1);
+    if (__builtin_expect (sz >= size, 1))
+      ret = aligned_alloc (al, sz);
+    else
+      ret = NULL;
+  }
 #else
   ret = NULL;
   if ((al & (al - 1)) == 0 && size)