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Remove __builtin_expect prediction assistance

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In microbenchmarks I tried, using `__builtin_expect` to indicate which branch was likely/unlikely was never faster, and often slower, than just omitting. In GSL, this is used only for `Expects` and `Ensures` which are nearly always true, and all processors have long been great at predicting such branches well.
This commit is contained in:
Herb Sutter 2020-11-27 11:07:55 -08:00
parent 0140ab1d73
commit c20a54c8e7
1 changed files with 1 additions and 11 deletions
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12
include/gsl/assert
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@ -57,16 +57,6 @@
#define GSL_STRINGIFY_DETAIL(x) #x #define GSL_STRINGIFY_DETAIL(x) #x
#define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x) #define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x)
#if defined(__clang__) || defined(__GNUC__)
#define GSL_LIKELY(x) __builtin_expect(!!(x), 1)
#define GSL_UNLIKELY(x) __builtin_expect(!!(x), 0)
#else
#define GSL_LIKELY(x) (!!(x))
#define GSL_UNLIKELY(x) (!!(x))
#endif // defined(__clang__) || defined(__GNUC__)
// //
// GSL_ASSUME(cond) // GSL_ASSUME(cond)
// //
@ -123,7 +113,7 @@ namespace details
} // namespace gsl } // namespace gsl
#define GSL_CONTRACT_CHECK(type, cond) \ #define GSL_CONTRACT_CHECK(type, cond) \
(GSL_LIKELY(cond) ? static_cast<void>(0) : gsl::details::terminate()) ((cond) ? static_cast<void>(0) : gsl::details::terminate())
#define Expects(cond) GSL_CONTRACT_CHECK("Precondition", cond) #define Expects(cond) GSL_CONTRACT_CHECK("Precondition", cond)
#define Ensures(cond) GSL_CONTRACT_CHECK("Postcondition", cond) #define Ensures(cond) GSL_CONTRACT_CHECK("Postcondition", cond)