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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 Hinnantdc2394f2010-10-07 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 Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]53<font color="#C80000">// Behavior is defined for mem_ord = 0, 1, 2, 5</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]54type __atomic_load(const type* atomic_obj, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]55
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]56<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]57<font color="#C80000">// Behavior is defined for mem_ord = 0, 3, 5</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]58type __atomic_store(type* atomic_obj, type desired, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]59
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]60<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]61<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]62type __atomic_exchange(type* atomic_obj, type desired, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]63
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]64<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]65<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]66<font color="#C80000">// mem_falure &lt;= mem_success</font>
67bool __atomic_compare_exchange_strong(type* atomic_obj,
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]68 type* expected, type desired,
69 int mem_success, int mem_failure);
70
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]71<font color="#C80000">// type must be trivially copyable</font>
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]72<font color="#C80000">// Behavior is defined for mem_success = [0 ... 5],</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]73<font color="#C80000">// mem_falure &lt;= mem_success</font>
74bool __atomic_compare_exchange_weak(type* atomic_obj,
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]75 type* expected, type desired,
76 int mem_success, int mem_failure);
77
78<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
79<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
80<font color="#C80000">// char16_t, char32_t, wchar_t</font>
81<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]82type __atomic_fetch_add(type* atomic_obj, type operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]83
84<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
85<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
86<font color="#C80000">// char16_t, char32_t, wchar_t</font>
87<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]88type __atomic_fetch_sub(type* atomic_obj, type operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]89
90<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
91<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
92<font color="#C80000">// char16_t, char32_t, wchar_t</font>
93<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]94type __atomic_fetch_and(type* atomic_obj, type operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]95
96<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
97<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
98<font color="#C80000">// char16_t, char32_t, wchar_t</font>
99<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]100type __atomic_fetch_or(type* atomic_obj, type operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]101
102<font color="#C80000">// type is one of: char, signed char, unsigned char, short, unsigned short, int,</font>
103<font color="#C80000">// unsigned int, long, unsigned long, long long, unsigned long long,</font>
104<font color="#C80000">// char16_t, char32_t, wchar_t</font>
105<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]106type __atomic_fetch_xor(type* atomic_obj, type operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]107
108<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
Howard Hinnantdc2394f2010-10-07 14:18:37 +0000[diff] [blame]109void* __atomic_fetch_add(void** atomic_obj, ptrdiff_t operand, int mem_ord);
110void* __atomic_fetch_sub(void** atomic_obj, ptrdiff_t operand, int mem_ord);
Howard Hinnanta35a35f2010-10-06 16:15:10 +0000[diff] [blame]111
112<font color="#C80000">// Behavior is defined for mem_ord = [0 ... 5]</font>
113void __atomic_thread_fence(int mem_ord);
114void __atomic_signal_fence(int mem_ord);
115</pre></blockquote>
116
117<p>
118If desired the intrinsics taking a single <tt>mem_ord</tt> parameter can default
119this argument to 5.
120</p>
121
122<p>
123If desired the intrinsics taking two ordering parameters can default
124<tt>mem_success</tt> to 5, and <tt>mem_failure</tt> to <tt>mem_success</tt>.
125</p>
126
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