diff options
| author | hboehm <hboehm> | 2008-01-04 00:45:32 +0000 |
|---|---|---|
| committer | Ivan Maidanski <ivmai@mail.ru> | 2011-07-25 16:03:24 +0400 |
| commit | 8bb45851c47e376b6c2ef29cadd56f6ba49f959e (patch) | |
| tree | c7550e0e41064ace46c2d75568a081fdb1fdad5b | |
| parent | aad33e603caa9a88559c5f384103bb93051068d5 (diff) | |
| download | libatomic_ops-8bb45851c47e376b6c2ef29cadd56f6ba49f959e.tar.gz | |
2008-01-03 Hans Boehm <Hans.Boehm@hp.com>
(Merge from separate atomic_ops tree)
* src/atomic_ops/sysdeps/gcc/x86.h: Define correct macro for
double-width cas, and fix its implementation.
* doc/README.txt: Clarify use of _full. Add more warnings about
data dependencies.
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | doc/README.txt | 8 | ||||
| -rw-r--r-- | src/atomic_ops/sysdeps/gcc/x86.h | 10 |
3 files changed, 21 insertions, 4 deletions
@@ -1,3 +1,10 @@ +2008-01-03 Hans Boehm <Hans.Boehm@hp.com> + (Merge from separate atomic_ops tree) + * src/atomic_ops/sysdeps/gcc/x86.h: Define correct macro for + double-width cas, and fix its implementation. + * doc/README.txt: Clarify use of _full. Add more warnings about + data dependencies. + 2008-01-02 Hans Boehm <Hans.Boehm@hp.com> * src/atomic_ops/sysdeps/gcc/powerpc.h (AO_load_acquire): Add %X1 modifier to support indexed addressing. diff --git a/doc/README.txt b/doc/README.txt index fa8f07e..e7c2f0d 100644 --- a/doc/README.txt +++ b/doc/README.txt @@ -154,6 +154,8 @@ _read: Subsequent reads must become visible after reads included in _write: Earlier writes become visible before writes during or after the atomic operation. Rarely useful for clients? _full: Ordered with respect to both earlier and later memops. + AO_store_full or AO_nop_full are the normal ways to force a store + to be ordered with respect to a later load. _release_write: Ordered with respect to earlier writes. This is normally implemented as either a _write or _release barrier. @@ -163,7 +165,11 @@ _dd_acquire_read: Ordered with respect to later reads that are data second value, with the expectation that the second read is ordered after the first one. On most architectures, this is equivalent to no barrier. (This is very - hard to define precisely. It should probably be avoided.) + hard to define precisely. It should probably be avoided. + A major problem is that optimizers tend to try to + eliminate dependencies from the generated code, since + dependencies force the hardware to execute the code + serially.) _release_read: Ordered with respect to earlier reads. Useful for implementing read locks. Can be implemented as _release, but not as _read, since _read groups the current operation diff --git a/src/atomic_ops/sysdeps/gcc/x86.h b/src/atomic_ops/sysdeps/gcc/x86.h index 27e047e..0b344a7 100644 --- a/src/atomic_ops/sysdeps/gcc/x86.h +++ b/src/atomic_ops/sysdeps/gcc/x86.h @@ -141,13 +141,17 @@ AO_compare_double_and_swap_double_full(volatile AO_double_t *addr, AO_t new_val1, AO_t new_val2) { char result; + register AO_t nv1 asm("%ebx") = new_val1; + /* The above hack seems to avoid a gcc error complaining */ + /* that ebx is unavailable. */ + __asm__ __volatile__("lock; cmpxchg8b %0; setz %1" : "=m"(*addr), "=q"(result) - : "m"(*addr), "d" (old_val1), "a" (old_val2), - "c" (new_val1), "b" (new_val2) : "memory"); + : "m"(*addr), "a" (old_val1), "d" (old_val2), + "b" (nv1), "c" (new_val2) : "memory"); return (int) result; } -#define AO_HAVE_double_compare_and_swap_full +#define AO_HAVE_compare_double_and_swap_double_full #include "../ao_t_is_int.h" |