explow.c (allocate_dynamic_stack_space): Check MALLOC_ABI_ALIGNMENT.

	* explow.c (allocate_dynamic_stack_space): Check
	MALLOC_ABI_ALIGNMENT.

From-SVN: r166393

gcc/ChangeLog

+2010-11-05  Ian Lance Taylor  <iant@google.com>
+
+	* explow.c (allocate_dynamic_stack_space): Check
+	MALLOC_ABI_ALIGNMENT.
+
 2010-11-05  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/44772

gcc/explow.c

@@ -1356,13 +1356,18 @@ allocate_dynamic_stack_space (rtx size, unsigned size_align,
 #endif
 
       /* The __morestack_allocate_stack_space function will allocate
-	 memory using malloc.  We don't know that the alignment of the
-	 memory returned by malloc will meet REQUIRED_ALIGN.  Increase
-	 SIZE to make sure we allocate enough space.  */
-      ask = expand_binop (Pmode, add_optab, size,
-			  GEN_INT (required_align / BITS_PER_UNIT - 1),
-			  NULL_RTX, 1, OPTAB_LIB_WIDEN);
-      must_align = true;
+	 memory using malloc.  If the alignment of the memory returned
+	 by malloc does not meet REQUIRED_ALIGN, we increase SIZE to
+	 make sure we allocate enough space.  */
+      if (MALLOC_ABI_ALIGNMENT >= required_align)
+	ask = size;
+      else
+	{
+	  ask = expand_binop (Pmode, add_optab, size,
+			      GEN_INT (required_align / BITS_PER_UNIT - 1),
+			      NULL_RTX, 1, OPTAB_LIB_WIDEN);
+	  must_align = true;
+	}
 
       func = init_one_libfunc ("__morestack_allocate_stack_space");