| compiler.h | compiler.h | |||
|---|---|---|---|---|
| skipping to change at line 26 | skipping to change at line 26 | |||
| * Permission to modify the code and to distribute modified code is granted , | * Permission to modify the code and to distribute modified code is granted , | |||
| * provided the above notices are retained, and a notice that the code was | * provided the above notices are retained, and a notice that the code was | |||
| * modified is included with the above copyright notice. | * modified is included with the above copyright notice. | |||
| */ | */ | |||
| #include <stddef.h> /* for offsetof */ | #include <stddef.h> /* for offsetof */ | |||
| #define likely(x) __builtin_expect(!!(x), 1) | #define likely(x) __builtin_expect(!!(x), 1) | |||
| #define unlikely(x) __builtin_expect(!!(x), 0) | #define unlikely(x) __builtin_expect(!!(x), 0) | |||
| #define barrier() asm volatile("" : : : "memory"); | #define barrier() asm volatile("" : : : "memory") | |||
| /* | /* | |||
| * Instruct the compiler to perform only a single access to a variable | * Instruct the compiler to perform only a single access to a variable | |||
| * (prohibits merging and refetching). The compiler is also forbidden to re order | * (prohibits merging and refetching). The compiler is also forbidden to re order | |||
| * successive instances of ACCESS_ONCE(), but only when the compiler is awa re of | * successive instances of ACCESS_ONCE(), but only when the compiler is awa re of | |||
| * particular ordering. Compiler ordering can be ensured, for example, by | * particular ordering. Compiler ordering can be ensured, for example, by | |||
| * putting two ACCESS_ONCE() in separate C statements. | * putting two ACCESS_ONCE() in separate C statements. | |||
| * | * | |||
| * This macro does absolutely -nothing- to prevent the CPU from reordering, | * This macro does absolutely -nothing- to prevent the CPU from reordering, | |||
| * merging, or refetching absolutely anything at any time. Its main intend ed | * merging, or refetching absolutely anything at any time. Its main intend ed | |||
| End of changes. 1 change blocks. | ||||
| 1 lines changed or deleted | 1 lines changed or added | |||