1/* Copyright (C) 2012-2015 Free Software Foundation, Inc.
2   Contributed by Richard Henderson <rth@redhat.com>.
3
4   This file is part of the GNU Atomic Library (libatomic).
5
6   Libatomic is free software; you can redistribute it and/or modify it
7   under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 3 of the License, or
9   (at your option) any later version.
10
11   Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
12   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
13   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
14   more details.
15
16   Under Section 7 of GPL version 3, you are granted additional
17   permissions described in the GCC Runtime Library Exception, version
18   3.1, as published by the Free Software Foundation.
19
20   You should have received a copy of the GNU General Public License and
21   a copy of the GCC Runtime Library Exception along with this program;
22   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23   <http://www.gnu.org/licenses/>.  */
24
25#include "libatomic_i.h"
26
27
28/* If we natively support the exchange, and if we're unconcerned with extra
29   barriers (e.g. fully in-order cpu for which barriers are a nop), then
30   go ahead and expand the operation inline.  */
31#if !defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
32# define EXACT_INLINE(N)					\
33  if (C2(HAVE_ATOMIC_EXCHANGE_,N))				\
34    {								\
35      *PTR(N,rptr) = __atomic_exchange_n			\
36	(PTR(N,mptr), *PTR(N,vptr), __ATOMIC_SEQ_CST);		\
37      return;							\
38    }
39#else
40# define EXACT_INLINE(N)
41#endif
42
43
44#define EXACT(N)						\
45  do {								\
46    if (!C2(HAVE_INT,N)) break;					\
47    if ((uintptr_t)mptr & (N - 1)) break;			\
48    EXACT_INLINE (N);						\
49    *PTR(N,rptr) = C3(local_,exchange_,N)			\
50      (PTR(N,mptr), *PTR(N,vptr), smodel);			\
51    return;							\
52  } while (0)
53
54
55#define LARGER(N)						\
56  do {								\
57    if (!C2(HAVE_INT,N)) break;					\
58    if (!C2(MAYBE_HAVE_ATOMIC_CAS_,N)) break;			\
59    r = (uintptr_t)mptr & (N - 1);				\
60    a = (uintptr_t)mptr & -N;					\
61    if (r + n <= N)						\
62      {								\
63	pre_barrier (smodel);					\
64	u.C2(i,N) = *PTR(N,a);					\
65	do {							\
66	  v = u;						\
67	  memcpy (v.b + r, vptr, n);				\
68	} while (!(C2(HAVE_ATOMIC_CAS_,N)			\
69		   ? __atomic_compare_exchange_n (PTR(N,a),	\
70			&u.C2(i,N), v.C2(i,N), true,		\
71			__ATOMIC_RELAXED, __ATOMIC_RELAXED)	\
72		   : C3(local_,compare_exchange_,N) (PTR(N,a),	\
73			&u.C2(i,N), v.C2(i,N),			\
74			__ATOMIC_RELAXED, __ATOMIC_RELAXED)));	\
75	goto Lfinish;						\
76      }								\
77  } while (0)
78
79
80static void __attribute__((noinline))
81libat_exchange_large_inplace (size_t n, void *mptr, void *vptr)
82{
83#define BUF	1024
84
85  char temp[BUF];
86  size_t i = 0;
87
88  for (i = 0; n >= BUF; i += BUF, n -= BUF)
89    {
90      memcpy (temp, mptr + i, BUF);
91      memcpy (mptr + i, vptr + i, BUF);
92      memcpy (vptr + i, temp, BUF);
93    }
94  if (n > 0)
95    {
96      memcpy (temp, mptr + i, n);
97      memcpy (mptr + i, vptr + i, n);
98      memcpy (vptr + i, temp, n);
99    }
100
101#undef BUF
102}
103
104void
105libat_exchange (size_t n, void *mptr, void *vptr, void *rptr, int smodel)
106{
107  union max_size_u u, v;
108  uintptr_t r, a;
109
110  switch (n)
111    {
112    case 0:				return;
113    case 1:		EXACT(1);	goto L4;
114    case 2:		EXACT(2);	goto L4;
115    case 4:		EXACT(4);	goto L8;
116    case 8:		EXACT(8);	goto L16;
117    case 16:		EXACT(16);	break;
118
119    case 3: L4:		LARGER(4);	/* FALLTHRU */
120    case 5 ... 7: L8:	LARGER(8);	/* FALLTHRU */
121    case 9 ... 15: L16:	LARGER(16);	break;
122
123    Lfinish:
124      post_barrier (smodel);
125      memcpy (rptr, u.b + r, n);
126      return;
127    }
128
129  pre_seq_barrier (smodel);
130  libat_lock_n (mptr, n);
131
132  if (vptr != rptr)
133    {
134      memcpy (rptr, mptr, n);
135      memcpy (mptr, vptr, n);
136    }
137  else
138    libat_exchange_large_inplace (n, mptr, vptr);
139
140  libat_unlock_n (mptr, n);
141  post_seq_barrier (smodel);
142}
143
144EXPORT_ALIAS (exchange);
145