/vendor/gc/libatomic_ops-1.2/src/atomic_ops.h
http://github.com/feyeleanor/RubyGoLightly · C++ Header · 300 lines · 128 code · 21 blank · 151 comment · 39 complexity · 1974cb5b0bbc57256091ae4d8f87042c MD5 · raw file
- /*
- * Copyright (c) 2003 Hewlett-Packard Development Company, L.P.
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
- #ifndef ATOMIC_OPS_H
- #define ATOMIC_OPS_H
- #include <assert.h>
- #include <stddef.h>
- /* We define various atomic operations on memory in a */
- /* machine-specific way. Unfortunately, this is complicated */
- /* by the fact that these may or may not be combined with */
- /* various memory barriers. Thus the actual operations we */
- /* define have the form AO_<atomic-op>_<barrier>, for all */
- /* plausible combinations of <atomic-op> and <barrier>. */
- /* This of course results in a mild combinatorial explosion. */
- /* To deal with it, we try to generate derived */
- /* definitions for as many of the combinations as we can, as */
- /* automatically as possible. */
- /* */
- /* Our assumption throughout is that the programmer will */
- /* specify the least demanding operation and memory barrier */
- /* that will guarantee correctness for the implementation. */
- /* Our job is to find the least expensive way to implement it */
- /* on the applicable hardware. In many cases that will */
- /* involve, for example, a stronger memory barrier, or a */
- /* combination of hardware primitives. */
- /* */
- /* Conventions: */
- /* "plain" atomic operations are not guaranteed to include */
- /* a barrier. The suffix in the name specifies the barrier */
- /* type. Suffixes are: */
- /* _release: Earlier operations may not be delayed past it. */
- /* _acquire: Later operations may not move ahead of it. */
- /* _read: Subsequent reads must follow this operation and */
- /* preceding reads. */
- /* _write: Earlier writes precede both this operation and */
- /* later writes. */
- /* _full: Ordered with respect to both earlier and later memops.*/
- /* _release_write: Ordered with respect to earlier writes. */
- /* _acquire_read: Ordered with repsect to later reads. */
- /* */
- /* Currently we try to define the following atomic memory */
- /* operations, in combination with the above barriers: */
- /* AO_nop */
- /* AO_load */
- /* AO_store */
- /* AO_test_and_set (binary) */
- /* AO_fetch_and_add */
- /* AO_fetch_and_add1 */
- /* AO_fetch_and_sub1 */
- /* AO_or */
- /* AO_compare_and_swap */
- /* */
- /* Note that atomicity guarantees are valid only if both */
- /* readers and writers use AO_ operations to access the */
- /* shared value, while ordering constraints are intended to */
- /* apply all memory operations. If a location can potentially */
- /* be accessed simultaneously from multiple threads, and one of */
- /* those accesses may be a write access, then all such */
- /* accesses to that location should be through AO_ primitives. */
- /* However if AO_ operations enforce sufficient ordering to */
- /* ensure that a location x cannot be accessed concurrently, */
- /* or can only be read concurrently, then x can be accessed */
- /* via ordinary references and assignments. */
- /* */
- /* Compare_and_exchange takes an address and an expected old */
- /* value and a new value, and returns an int. Nonzero */
- /* indicates that it succeeded. */
- /* Test_and_set takes an address, atomically replaces it by */
- /* AO_TS_SET, and returns the prior value. */
- /* An AO_TS_t location can be reset with the */
- /* AO_CLEAR macro, which normally uses AO_store_release. */
- /* AO_fetch_and_add takes an address and an AO_t increment */
- /* value. The AO_fetch_and_add1 and AO_fetch_and_sub1 variants */
- /* are provided, since they allow faster implementations on */
- /* some hardware. AO_or atomically ors an AO_t value into a */
- /* memory location, but does not provide access to the original.*/
- /* */
- /* We expect this list to grow slowly over time. */
- /* */
- /* Note that AO_nop_full is a full memory barrier. */
- /* */
- /* Note that if some data is initialized with */
- /* data.x = ...; data.y = ...; ... */
- /* AO_store_release_write(&data_is_initialized, 1) */
- /* then data is guaranteed to be initialized after the test */
- /* if (AO_load_release_read(&data_is_initialized)) ... */
- /* succeeds. Furthermore, this should generate near-optimal */
- /* code on all common platforms. */
- /* */
- /* All operations operate on unsigned AO_t, which */
- /* is the natural word size, and usually unsigned long. */
- /* It is possible to check whether a particular operation op */
- /* is available on a particular platform by checking whether */
- /* AO_HAVE_op is defined. We make heavy use of these macros */
- /* internally. */
- /* The rest of this file basically has three sections: */
- /* */
- /* Some utility and default definitions. */
- /* */
- /* The architecture dependent section: */
- /* This defines atomic operations that have direct hardware */
- /* support on a particular platform, mostly by uncluding the */
- /* appropriate compiler- and hardware-dependent file. */
- /* */
- /* The synthesis section: */
- /* This tries to define other atomic operations in terms of */
- /* those that are explicitly available on the platform. */
- /* This section is hardware independent. */
- /* We make no attempt to synthesize operations in ways that */
- /* effectively introduce locks, except for the debugging/demo */
- /* pthread-based implementation at the beginning. A more */
- /* relistic implementation that falls back to locks could be */
- /* added as a higher layer. But that would sacrifice */
- /* usability from signal handlers. */
- /* The synthesis section is implemented almost entirely in */
- /* atomic_ops_generalize.h. */
- /* Some common defaults. Overridden for some architectures. */
- #define AO_t size_t
- /* The test_and_set primitive returns an AO_TS_VAL_t value. */
- /* AO_TS_t is the type of an in-memory test-and-set location. */
- #define AO_TS_INITIALIZER (AO_t)AO_TS_CLEAR
- /* Platform-dependent stuff: */
- #if defined(__GNUC__) || defined(_MSC_VER) || defined(__INTEL_COMPILER)
- # define AO_INLINE static __inline
- #else
- # define AO_INLINE static
- #endif
- #if defined(__GNUC__) && !defined(__INTEL_COMPILER)
- # define AO_compiler_barrier() __asm__ __volatile__("" : : : "memory")
- #elif defined(_MSC_VER)
- # if defined(_AMD64_)
- # pragma intrinsic(_ReadWriteBarrier)
- # define AO_compiler_barrier() _ReadWriteBarrier()
- /* We assume this does not generate a fence instruction. */
- /* The documentation is a bit unclear. */
- # else
- # define AO_compiler_barrier() __asm { }
- /* The preceding implementation may be preferable here too. */
- /* But the documentation warns about VC++ 2003 and earlier. */
- # endif
- #elif defined(__INTEL_COMPILER)
- # define AO_compiler_barrier() __memory_barrier() /* Too strong? IA64-only? */
- #elif defined(_HPUX_SOURCE)
- # if defined(__ia64)
- # include <machine/sys/inline.h>
- # define AO_compiler_barrier() _Asm_sched_fence()
- # else
- /* FIXME - We dont know how to do this. This is a guess. */
- /* And probably a bad one. */
- static volatile int AO_barrier_dummy;
- # define AO_compiler_barrier() AO_barrier_dummy = AO_barrier_dummy
- # endif
- #else
- /* We conjecture that the following usually gives us the right */
- /* semantics or an error. */
- # define AO_compiler_barrier() asm("")
- #endif
- #if defined(AO_USE_PTHREAD_DEFS)
- # include "atomic_ops/sysdeps/generic_pthread.h"
- #endif /* AO_USE_PTHREAD_DEFS */
- #if defined(__GNUC__) && !defined(AO_USE_PTHREAD_DEFS) \
- && !defined(__INTEL_COMPILER)
- # if defined(__i386__)
- # include "atomic_ops/sysdeps/gcc/x86.h"
- # endif /* __i386__ */
- # if defined(__x86_64__)
- # include "atomic_ops/sysdeps/gcc/x86_64.h"
- # endif /* __i386__ */
- # if defined(__ia64__)
- # include "atomic_ops/sysdeps/gcc/ia64.h"
- # define AO_GENERALIZE_TWICE
- # endif /* __ia64__ */
- # if defined(__hppa__)
- # include "atomic_ops/sysdeps/gcc/hppa.h"
- # define AO_CAN_EMUL_CAS
- # endif /* __hppa__ */
- # if defined(__alpha__)
- # include "atomic_ops/sysdeps/gcc/alpha.h"
- # define AO_GENERALIZE_TWICE
- # endif /* __alpha__ */
- # if defined(__s390__)
- # include "atomic_ops/sysdeps/gcc/s390.h"
- # endif /* __s390__ */
- # if defined(__sparc__)
- # include "atomic_ops/sysdeps/gcc/sparc.h"
- # define AO_CAN_EMUL_CAS
- # endif /* __sparc__ */
- # if defined(__m68k__)
- # include "atomic_ops/sysdeps/gcc/m68k.h"
- # endif /* __m68k__ */
- # if defined(__powerpc__) || defined(__ppc__) || defined(__PPC__) \
- || defined(__powerpc64__) || defined(__ppc64__)
- # include "atomic_ops/sysdeps/gcc/powerpc.h"
- # endif /* __powerpc__ */
- # if defined(__arm__) && !defined(AO_USE_PTHREAD_DEFS)
- # include "atomic_ops/sysdeps/gcc/arm.h"
- # define AO_CAN_EMUL_CAS
- # endif /* __arm__ */
- # if defined(__cris__) || defined(CRIS)
- # include "atomic_ops/sysdeps/gcc/cris.h"
- # endif
- #endif /* __GNUC__ && !AO_USE_PTHREAD_DEFS */
- #if defined(__INTEL_COMPILER) && !defined(AO_USE_PTHREAD_DEFS)
- # if defined(__ia64__)
- # include "atomic_ops/sysdeps/icc/ia64.h"
- # define AO_GENERALIZE_TWICE
- # endif
- #endif
- #if defined(_HPUX_SOURCE) && !defined(__GNUC__) && !defined(AO_USE_PTHREAD_DEFS)
- # if defined(__ia64)
- # include "atomic_ops/sysdeps/hpc/ia64.h"
- # define AO_GENERALIZE_TWICE
- # else
- # include "atomic_ops/sysdeps/hpc/hppa.h"
- # define AO_CAN_EMUL_CAS
- # endif
- #endif
- #if !defined(__GNUC__) && (defined(sparc) || defined(__sparc)) \
- && !defined(AO_USE_PTHREAD_DEFS)
- # include "atomic_ops/sysdeps/sunc/sparc.h"
- # define AO_CAN_EMUL_CAS
- #endif
- #if defined(_MSC_VER)
- # if defined(_AMD64_)
- # include "atomic_ops/sysdeps/msftc/x86_64.h"
- # elif _M_IX86 >= 400
- # include "atomic_ops/sysdeps/msftc/x86.h"
- # endif
- #endif
- #if defined(AO_REQUIRE_CAS) && !defined(AO_HAVE_compare_and_swap) \
- && !defined(AO_HAVE_compare_and_swap_full) \
- && !defined(AO_HAVE_compare_and_swap_acquire)
- # if defined(AO_CAN_EMUL_CAS)
- # include "atomic_ops/sysdeps/emul_cas.h"
- # else
- # error Cannot implement AO_compare_and_swap_full on this architecture.
- # endif
- #endif /* AO_REQUIRE_CAS && !AO_HAVE_compare_and_swap ... */
- /* The most common way to clear a test-and-set location */
- /* at the end of a critical section. */
- #if AO_AO_TS_T && !defined(AO_CLEAR)
- # define AO_CLEAR(addr) AO_store_release((AO_TS_t *)addr, AO_TS_CLEAR)
- #endif
- #if AO_CHAR_TS_T && !defined(AO_CLEAR)
- # define AO_CLEAR(addr) AO_char_store_release((AO_TS_t *)addr, AO_TS_CLEAR)
- #endif
- /*
- * The generalization section.
- * Theoretically this should repeatedly include atomic_ops_generalize.h.
- * In fact, we observe that this converges after a small fixed number
- * of iterations, usually one.
- */
- #include "atomic_ops/generalize.h"
- #ifdef AO_GENERALIZE_TWICE
- # include "atomic_ops/generalize.h"
- #endif
- /* For compatibility with version 0.4 and earlier */
- #define AO_TS_T AO_TS_t
- #define AO_T AO_t
- #define AO_TS_VAL AO_TS_VAL_t
- #endif /* ATOMIC_OPS_H */