-This is more of a synopsis than a true description. The compiler supplies all -of the intrinsics as described below. This list of intrinsics roughly parallels -the requirements of the C and C++ atomics proposals. The C and C++ library -imlpementations simply drop through to these intrinsics. Anything the platform -does not support in hardware, the compiler arranges for a (compiler-rt) library -call to be made which will do the job with a mutex, and in this case ignoring -the memory ordering parameter. +The compiler supplies all of the intrinsics as described below. This list of +intrinsics roughly parallels the requirements of the C and C++ atomics +proposals. The C and C++ library imlpementations simply drop through to these +intrinsics. Anything the platform does not support in hardware, the compiler +arranges for a (compiler-rt) library call to be made which will do the job with +a mutex, and in this case ignoring the memory ordering parameter (effectively +implementing memory_order_seq_cst). +
+ ++Ultimate efficiency is preferred over run time error checking. Undefined +behavior is acceptable when the inputs do not conform as defined below.
// In every intrinsic signature below, type* atomic_obj may be a pointer to a
// volatile-qualifed type.
+// Memory ordering values map to the following meanings:
+// memory_order_relaxed == 0
+// memory_order_consume == 1
+// memory_order_acquire == 2
+// memory_order_release == 3
+// memory_order_acq_rel == 4
+// memory_order_seq_cst == 5
// type must be trivially copyable
-bool __atomic_is_lock_free(const type* atomic_obj);
+// type represents a "type argument"
+bool __atomic_is_lock_free(type);
// type must be trivially copyable
// Behavior is defined for mem_ord = 0, 1, 2, 5
@@ -67,6 +80,8 @@ type __atomic_exchange(type* atomic_obj, type desired, int mem_ord);
// type must be trivially copyable
// Behavior is defined for mem_success = [0 ... 5],
// mem_falure <= mem_success
+// mem_falure != 3
+// mem_falure != 4
bool __atomic_compare_exchange_strong(type* atomic_obj,
type* expected, type desired,
int mem_success, int mem_failure);
@@ -74,6 +89,8 @@ bool __atomic_compare_exchange_strong(type* atomic_obj,
// type must be trivially copyable
// Behavior is defined for mem_success = [0 ... 5],
// mem_falure <= mem_success
+// mem_falure != 3
+// mem_falure != 4
bool __atomic_compare_exchange_weak(type* atomic_obj,
type* expected, type desired,
int mem_success, int mem_failure);
@@ -124,9 +141,25 @@ this argument to 5.
If desired the intrinsics taking two ordering parameters can default
-mem_success to 5, and mem_failure to mem_success.
+mem_success to 5, and mem_failure to
+translate_memory_order(mem_success) where
+translate_memory_order(mem_success) is defined as:
+
+int
+translate_memory_order(int o)
+{
+ switch (o)
+ {
+ case 4:
+ return 2;
+ case 3:
+ return 0;
+ }
+ return o;
+}
+