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34 <!--*********************************************************************-->
35 <h1>&lt;atomic&gt; design</h1>
36 <!--*********************************************************************-->
37
38<p>
39This is more of a synopsis than a true description. The compiler supplies all
40of the intrinsics as described below. This list of intrinsics roughly parallels
41the requirements of the C and C++ atomics proposals. The C and C++ library
42imlpementations simply drop through to these intrinsics. Anything the platform
43does not support in hardware, the compiler arranges for a (compiler-rt) library
44call to be made which will do the job with a mutex, and in this case ignoring
45the memory ordering parameter.
46</p>
47
48<blockquote><pre>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]49<font color="#C80000">// In every intrinsic signature below, type* atomic_obj may be a pointer to a</font>
50<font color="#C80000">// volatile-qualifed type.</font>
51
52<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant08f29692010-10-08 17:36:50 +0000[diff] [blame]53bool __atomic_is_lock_free(const type* atomic_obj);
54
55<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]56<font color="#C80000">// Behavior is defined for mem_ord = 0, 1, 2, 5</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]57type __atomic_load(const type* atomic_obj, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]58
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]59<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]60<font color="#C80000">// Behavior is defined for mem_ord = 0, 3, 5</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]61type __atomic_store(type* atomic_obj, type desired, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]62
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]63<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]64<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]65type __atomic_exchange(type* atomic_obj, type desired, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]66
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]67<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]68<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]69<font color="#C80000">// mem_falure &lt;= mem_success</font>
70bool __atomic_compare_exchange_strong(type* atomic_obj,
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]71 type* expected, type desired,
72 int mem_success, int mem_failure);
73
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]74<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]75<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]76<font color="#C80000">// mem_falure &lt;= mem_success</font>
77bool __atomic_compare_exchange_weak(type* atomic_obj,
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]78 type* expected, type desired,
79 int mem_success, int mem_failure);
80
81<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
82<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
83<font color="#C80000">// char16_t, char32_t, wchar_t</font>
84<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]85type __atomic_fetch_add(type* atomic_obj, type operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]86
87<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
88<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
89<font color="#C80000">// char16_t, char32_t, wchar_t</font>
90<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]91type __atomic_fetch_sub(type* atomic_obj, type operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]92
93<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
94<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
95<font color="#C80000">// char16_t, char32_t, wchar_t</font>
96<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]97type __atomic_fetch_and(type* atomic_obj, type operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]98
99<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
100<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
101<font color="#C80000">// char16_t, char32_t, wchar_t</font>
102<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]103type __atomic_fetch_or(type* atomic_obj, type operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]104
105<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
106<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
107<font color="#C80000">// char16_t, char32_t, wchar_t</font>
108<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]109type __atomic_fetch_xor(type* atomic_obj, type operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]110
111<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnant77868b92010-10-07 14:18:37 +0000[diff] [blame]112void* __atomic_fetch_add(void** atomic_obj, ptrdiff_t operand, int mem_ord);
113void* __atomic_fetch_sub(void** atomic_obj, ptrdiff_t operand, int mem_ord);
Howard Hinnant086b7182010-10-06 16:15:10 +0000[diff] [blame]114
115<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
116void __atomic_thread_fence(int mem_ord);
117void __atomic_signal_fence(int mem_ord);
118</pre></blockquote>
119
120<p>
121If desired the intrinsics taking a single <tt>mem_ord</tt> parameter can default
122this argument to 5.
123</p>
124
125<p>
126If desired the intrinsics taking two ordering parameters can default
127<tt>mem_success</tt> to 5, and <tt>mem_failure</tt> to <tt>mem_success</tt>.
128</p>
129
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