std::kill_dependency
STD：杀死[医]依赖性
| Defined in header | | |
|---|---|---|
| template< class T > T kill_dependency( T y | | (since C++11) |
通知编译器，依赖树由std::memory_order_consume原子加载操作不会扩展到std::kill_dependency也就是说，该参数不将依赖项携带到返回值中。
这可能是用来避免不必要的。std::memory_order_acquire当依赖链离开函数作用域%28且函数没有[[载运[医][受抚养人]]属性%29。
参数
| y | - | the expression whose return value is to be removed from a dependency tree |
|---|
返回值
回报y不再是依赖树的一部分。
例外
noexcept规格：
noexcept
实例
二次
//file1.cpp
struct foo { int* a; int* b; };
std::atomic<struct foo*> foo_head[10];
int foo_array[10][10];
// consume operation starts a dependency chain, which escapes this function
[[carries_dependency]] struct foo* f(int i) {
return foo_head[i].load(memory_order_consume
}
// the dependency chain enters this function through the right parameter
// and is killed before the function ends (so no extra acquire operation takes place)
int g(int* x, int* y [[carries_dependency]]) {
return std::kill_dependency(foo_array[*x][*y]
}
二次
二次
//file2.cpp
[[carries_dependency]] struct foo* f(int i
int g(int* x, int* y [[carries_dependency]]
int c = 3;
void h(int i) {
struct foo* p;
p = f(i // dependency chain started inside f continues into p without undue acquire
do_something_with(g(&c, p->a) // p->b is not brought in from the cache
do_something_with(g(p->a, &c) // left argument does not have the carries_dependency
// attribute: memory acquire fence may be issued
// p->b becomes visible before g() is entered
}
二次
另见
| memory_order (C++11) | defines memory ordering constraints for the given atomic operation (typedef) |
|---|
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