blob: d148710127d2fcf6df8ce40ea13ec31e1b259b85 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
#ifndef RUBY_BACKWARD2_ASSUME_H /*-*-C++-*-vi:se ft=cpp:*/
#define RUBY_BACKWARD2_ASSUME_H
/**
* @file
* @author Ruby developers <ruby-core@ruby-lang.org>
* @copyright This file is a part of the programming language Ruby.
* Permission is hereby granted, to either redistribute and/or
* modify this file, provided that the conditions mentioned in the
* file COPYING are met. Consult the file for details.
* @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are
* implementation details. Don't take them as canon. They could
* rapidly appear then vanish. The name (path) of this header file
* is also an implementation detail. Do not expect it to persist
* at the place it is now. Developers are free to move it anywhere
* anytime at will.
* @note To ruby-core: remember that this header can be possibly
* recursively included from extension libraries written in C++.
* Do not expect for instance `__VA_ARGS__` is always available.
* We assume C99 for ruby itself but we don't assume languages of
* extension libraries. They could be written in C++98.
* @brief Defines #ASSUME / #RB_LIKELY / #UNREACHABLE
*/
#include "ruby/internal/config.h"
#include "ruby/internal/assume.h"
#include "ruby/internal/has/builtin.h"
#define ASSUME RBIMPL_ASSUME /**< @old{RBIMPL_ASSUME} */
#define UNREACHABLE RBIMPL_UNREACHABLE() /**< @old{RBIMPL_UNREACHABLE} */
#define UNREACHABLE_RETURN RBIMPL_UNREACHABLE_RETURN /**< @old{RBIMPL_UNREACHABLE_RETURN} */
/* likely */
#if RBIMPL_HAS_BUILTIN(__builtin_expect)
/**
* Asserts that the given Boolean expression likely holds.
*
* @param x An expression that likely holds.
*
* @note Consider this macro carefully. It has been here since when CPUs were
* like babies, but contemporary processors are beasts. They are
* smarter than mare mortals like us today. Their branch predictions
* highly expectedly outperform your use of this macro.
*/
# define RB_LIKELY(x) (__builtin_expect(!!(x), 1))
/**
* Asserts that the given Boolean expression likely doesn't hold.
*
* @param x An expression that likely doesn't hold.
*/
# define RB_UNLIKELY(x) (__builtin_expect(!!(x), 0))
#else
# define RB_LIKELY(x) (x)
# define RB_UNLIKELY(x) (x)
#endif
#endif /* RUBY_BACKWARD2_ASSUME_H */
|
