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Update atomic Design A spec

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@116707 91177308-0d34-0410-b5e6-96231b3b80d8
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Howard Hinnant 2010-10-18 16:02:24 +00:00
parent 0d5dff1897
commit f6fe084fd4
1 changed files with 42 additions and 9 deletions
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@ -36,21 +36,34 @@
<!--*********************************************************************--> <!--*********************************************************************-->
<p> <p>
This is more of a synopsis than a true description. The compiler supplies all The compiler supplies all of the intrinsics as described below. This list of
of the intrinsics as described below. This list of intrinsics roughly parallels intrinsics roughly parallels the requirements of the C and C++ atomics
the requirements of the C and C++ atomics proposals. The C and C++ library proposals. The C and C++ library imlpementations simply drop through to these
imlpementations simply drop through to these intrinsics. Anything the platform intrinsics. Anything the platform does not support in hardware, the compiler
does not support in hardware, the compiler arranges for a (compiler-rt) library arranges for a (compiler-rt) library call to be made which will do the job with
call to be made which will do the job with a mutex, and in this case ignoring a mutex, and in this case ignoring the memory ordering parameter (effectively
the memory ordering parameter. implementing <tt>memory_order_seq_cst</tt>).
</p>
<p>
Ultimate efficiency is preferred over run time error checking. Undefined
behavior is acceptable when the inputs do not conform as defined below.
</p> </p>
<blockquote><pre> <blockquote><pre>
<font color="#C80000">// In every intrinsic signature below, type* atomic_obj may be a pointer to a</font> <font color="#C80000">// In every intrinsic signature below, type* atomic_obj may be a pointer to a</font>
<font color="#C80000">// volatile-qualifed type.</font> <font color="#C80000">// volatile-qualifed type.</font>
<font color="#C80000">// Memory ordering values map to the following meanings:</font>
<font color="#C80000">// memory_order_relaxed == 0</font>
<font color="#C80000">// memory_order_consume == 1</font>
<font color="#C80000">// memory_order_acquire == 2</font>
<font color="#C80000">// memory_order_release == 3</font>
<font color="#C80000">// memory_order_acq_rel == 4</font>
<font color="#C80000">// memory_order_seq_cst == 5</font>
<font color="#C80000">// type must be trivially copyable</font> <font color="#C80000">// type must be trivially copyable</font>
bool __atomic_is_lock_free(const type* atomic_obj); <font color="#C80000">// type represents a "type argument"</font>
bool __atomic_is_lock_free(type);
<font color="#C80000">// type must be trivially copyable</font> <font color="#C80000">// type must be trivially copyable</font>
<font color="#C80000">// Behavior is defined for mem_ord = 0, 1, 2, 5</font> <font color="#C80000">// Behavior is defined for mem_ord = 0, 1, 2, 5</font>
@ -67,6 +80,8 @@ type __atomic_exchange(type* atomic_obj, type desired, int mem_ord);
<font color="#C80000">// type must be trivially copyable</font> <font color="#C80000">// type must be trivially copyable</font>
<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font> <font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
<font color="#C80000">// mem_falure &lt;= mem_success</font> <font color="#C80000">// mem_falure &lt;= mem_success</font>
<font color="#C80000">// mem_falure != 3</font>
<font color="#C80000">// mem_falure != 4</font>
bool __atomic_compare_exchange_strong(type* atomic_obj, bool __atomic_compare_exchange_strong(type* atomic_obj,
type* expected, type desired, type* expected, type desired,
int mem_success, int mem_failure); int mem_success, int mem_failure);
@ -74,6 +89,8 @@ bool __atomic_compare_exchange_strong(type* atomic_obj,
<font color="#C80000">// type must be trivially copyable</font> <font color="#C80000">// type must be trivially copyable</font>
<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font> <font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
<font color="#C80000">// mem_falure &lt;= mem_success</font> <font color="#C80000">// mem_falure &lt;= mem_success</font>
<font color="#C80000">// mem_falure != 3</font>
<font color="#C80000">// mem_falure != 4</font>
bool __atomic_compare_exchange_weak(type* atomic_obj, bool __atomic_compare_exchange_weak(type* atomic_obj,
type* expected, type desired, type* expected, type desired,
int mem_success, int mem_failure); int mem_success, int mem_failure);
@ -124,9 +141,25 @@ this argument to 5.
<p> <p>
If desired the intrinsics taking two ordering parameters can default If desired the intrinsics taking two ordering parameters can default
<tt>mem_success</tt> to 5, and <tt>mem_failure</tt> to <tt>mem_success</tt>. <tt>mem_success</tt> to 5, and <tt>mem_failure</tt> to
<tt>translate_memory_order(mem_success)</tt> where
<tt>translate_memory_order(mem_success)</tt> is defined as:
</p> </p>
<blockquote><pre>
int
translate_memory_order(int o)
{
switch (o)
{
case 4:
return 2;
case 3:
return 0;
}
return o;
}
</pre></blockquote>
</div> </div>
</body> </body>
</html> </html>