mirror of
https://gcc.gnu.org/git/gcc.git
synced 2024-11-23 19:03:59 +08:00
121 lines
3.7 KiB
C
121 lines
3.7 KiB
C
/* Copyright (C) 2012-2024 Free Software Foundation, Inc.
|
|
Contributed by Richard Henderson <rth@redhat.com>.
|
|
|
|
This file is part of the GNU Atomic Library (libatomic).
|
|
|
|
Libatomic is free software; you can redistribute it and/or modify it
|
|
under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
|
|
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
|
|
FOR A PARTICULAR PURPOSE. See the GNU General Public License for
|
|
more details.
|
|
|
|
Under Section 7 of GPL version 3, you are granted additional
|
|
permissions described in the GCC Runtime Library Exception, version
|
|
3.1, as published by the Free Software Foundation.
|
|
|
|
You should have received a copy of the GNU General Public License and
|
|
a copy of the GCC Runtime Library Exception along with this program;
|
|
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include "libatomic_i.h"
|
|
|
|
|
|
/* If we natively support the cas, and if we're unconcerned with extra
|
|
barriers (e.g. fully in-order cpu for which barriers are a nop), then
|
|
go ahead and expand the operation inline. */
|
|
#if !defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
|
|
# define EXACT_INLINE(N) \
|
|
if (C2(HAVE_ATOMIC_CAS_,N)) \
|
|
return __atomic_compare_exchange_n \
|
|
(PTR(N,mptr), PTR(N,eptr), *PTR(N,dptr), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
|
|
#else
|
|
# define EXACT_INLINE(N)
|
|
#endif
|
|
|
|
/* ... and if all that fails, invoke the function we generated elsewhere.
|
|
Worst case, this will *also* use locks. */
|
|
#define EXACT(N) \
|
|
do { \
|
|
if (!C2(HAVE_INT,N)) break; \
|
|
if ((uintptr_t)mptr & (N - 1)) break; \
|
|
EXACT_INLINE (N); \
|
|
return C3(local_,compare_exchange_,N) \
|
|
(PTR(N,mptr), PTR(N,eptr), *PTR(N,dptr), smodel, fmodel); \
|
|
} while (0)
|
|
|
|
#define LARGER(N) \
|
|
do { \
|
|
if (!C2(HAVE_INT,N)) break; \
|
|
if (!C2(HAVE_ATOMIC_LDST_,N)) break; \
|
|
if (!C2(MAYBE_HAVE_ATOMIC_CAS_,N)) break; \
|
|
r = (uintptr_t)mptr & (N - 1); \
|
|
a = (uintptr_t)mptr & -N; \
|
|
if (r + n <= N) \
|
|
{ \
|
|
pre_barrier (smodel); \
|
|
u.C2(i,N) = __atomic_load_n (PTR(N,a), __ATOMIC_RELAXED); \
|
|
do { \
|
|
if (memcmp (u.b + r, eptr, n) != 0) goto Lfail; \
|
|
v = u; memcpy (v.b + r, dptr, n); \
|
|
} while (!(C2(HAVE_ATOMIC_CAS_,N) \
|
|
? __atomic_compare_exchange_n (PTR(N,a), \
|
|
&u.C2(i,N), v.C2(i,N), true, \
|
|
__ATOMIC_RELAXED, __ATOMIC_RELAXED) \
|
|
: C3(local_,compare_exchange_,N) (PTR(N,a), \
|
|
&u.C2(i,N), v.C2(i,N), \
|
|
__ATOMIC_RELAXED, __ATOMIC_RELAXED))); \
|
|
goto Lsucc; \
|
|
} \
|
|
} while (0)
|
|
|
|
|
|
|
|
bool
|
|
libat_compare_exchange (size_t n, void *mptr, void *eptr, void *dptr,
|
|
int smodel, int fmodel)
|
|
{
|
|
union max_size_u u, v;
|
|
uintptr_t r, a;
|
|
bool ret;
|
|
|
|
switch (n)
|
|
{
|
|
case 0: return true;
|
|
case 1: EXACT(1); goto L4;
|
|
case 2: EXACT(2); goto L4;
|
|
case 4: EXACT(4); goto L8;
|
|
case 8: EXACT(8); goto L16;
|
|
case 16: EXACT(16); break;
|
|
|
|
case 3: L4: LARGER(4); /* FALLTHRU */
|
|
case 5 ... 7: L8: LARGER(8); /* FALLTHRU */
|
|
case 9 ... 15: L16: LARGER(16); break;
|
|
|
|
Lsucc:
|
|
post_barrier (smodel);
|
|
return true;
|
|
Lfail:
|
|
post_barrier (fmodel);
|
|
memcpy (eptr, u.b + r, n);
|
|
return false;
|
|
}
|
|
|
|
pre_seq_barrier (smodel);
|
|
libat_lock_n (mptr, n);
|
|
|
|
ret = memcmp (mptr, eptr, n) == 0;
|
|
memcpy ((ret ? mptr : eptr), (ret ? dptr : mptr), n);
|
|
|
|
libat_unlock_n (mptr, n);
|
|
post_seq_barrier (ret ? smodel : fmodel);
|
|
|
|
return ret;
|
|
}
|
|
|
|
EXPORT_ALIAS (compare_exchange);
|