/vendor/gc/libatomic_ops-1.2/src/atomic_ops/sysdeps/gcc/s390.h

 1/* 
 2 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
 3 * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
 4 * Copyright (c) 1999-2003 by Hewlett-Packard Company. All rights reserved.
 5 *
 6 *
 7 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 8 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 9 *
10 * Permission is hereby granted to use or copy this program
11 * for any purpose,  provided the above notices are retained on all copies.
12 * Permission to modify the code and to distribute modified code is granted,
13 * provided the above notices are retained, and a notice that the code was
14 * modified is included with the above copyright notice.
15 *
16 */
17
18/* FIXME: untested.						*/
19/* The relevant documentation appears to be at			*/
20/* http://publibz.boulder.ibm.com/epubs/pdf/dz9zr003.pdf	*/
21/* around page 5-96.  Apparently:				*/
22/* - Memory references in general are atomic only for a single 	*/
23/*   byte.  But it appears that the most common load/store	*/
24/*   instructions also guarantee atomicity for aligned 		*/
25/*   operands of standard types.  WE FOOLISHLY ASSUME that	*/
26/*   compilers only generate those.  If that turns out to be	*/
27/*   wrong, we need inline assembly code for AO_load and	*/
28/*   AO_store.							*/
29/* - A store followed by a load is unordered since the store	*/
30/*   may be delayed.  Otherwise everything is ordered.		*/
31/* - There is a hardware compare-and-swap (CS) instruction.	*/
32
33#include "ordered_except_wr.h"
34#include "all_aligned_atomic_load_store.h"
35
36#include "../test_and_set_t_is_ao_t.h"
37/* FIXME: Is there a way to do byte-sized test-and-set?	*/
38
39/* FIXME: AO_nop_full should probably be implemented directly.	*/
40/* It appears that certain BCR instructions have that effect.	*/
41/* Presumably they're cheaper than CS?				*/
42
43AO_INLINE AO_t AO_compare_and_swap_full(volatile AO_t *addr,
44                                               AO_t old, AO_t new_val)
45{
46  int retval;
47  __asm__ __volatile__ (
48# ifndef __s390x__
49    "     cs  %1,%2,0(%3)\n"
50# else
51    "     csg %1,%2,0(%3)\n"
52# endif
53  "     ipm %0\n"
54  "     srl %0,28\n"
55  : "=&d" (retval), "+d" (old)
56  : "d" (new_val), "a" (addr)
57  : "cc", "memory");
58  return retval == 0;
59}
60
61#define AO_HAVE_compare_and_swap_full
62
63/* FIXME: Add double-wide compare-and-swap for 32-bit executables.	*/