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| -rw-r--r-- | src/include/c.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/src/include/c.h b/src/include/c.h index 4ab3f8027a5..672e21e03ea 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -939,6 +939,22 @@ typedef NameData *Name; #endif +/* + * Hints to the compiler about the likelihood of a branch. Both likely() and + * unlikely() return the boolean value of the contained expression. + * + * These should only be used sparingly, in very hot code paths. It's very easy + * to mis-estimate likelihoods. + */ +#if __GNUC__ >= 3 +#define likely(x) __builtin_expect((x) != 0, 1) +#define unlikely(x) __builtin_expect((x) != 0, 0) +#else +#define likely(x) ((x) != 0) +#define unlikely(x) ((x) != 0) +#endif + + /* ---------------------------------------------------------------- * Section 8: random stuff * ---------------------------------------------------------------- |