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assume.h
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#ifndef RBIMPL_ASSUME_H /*-*-C++-*-vi:se ft=cpp:*/ #define RBIMPL_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 #RBIMPL_ASSUME / #RBIMPL_UNREACHABLE. * * These macros must be defined at once because: * * - #RBIMPL_ASSUME could fallback to #RBIMPL_UNREACHABLE. * - #RBIMPL_UNREACHABLE could fallback to #RBIMPL_ASSUME. */ #include "ruby/internal/config.h" #include "ruby/internal/cast.h" #include "ruby/internal/compiler_since.h" #include "ruby/internal/has/builtin.h" #include "ruby/internal/warning_push.h" /** @cond INTERNAL_MACRO */ #if defined(HAVE___ASSUME) # define RBIMPL_HAVE___ASSUME #endif /** @endcond */ /** Wraps (or simulates) `__builtin_unreachable`. */ #if RBIMPL_HAS_BUILTIN(__builtin_unreachable) # define RBIMPL_UNREACHABLE_RETURN(_) __builtin_unreachable() #elif defined(RBIMPL_HAVE___ASSUME) # define RBIMPL_UNREACHABLE_RETURN(_) return (__assume(0), (_)) #else # define RBIMPL_UNREACHABLE_RETURN(_) return (_) #endif /** Wraps (or simulates) `__builtin_unreachable`. */ #if RBIMPL_HAS_BUILTIN(__builtin_unreachable) # define RBIMPL_UNREACHABLE __builtin_unreachable #elif defined(RBIMPL_HAVE___ASSUME) # define RBIMPL_UNREACHABLE() __assume(0) #endif /** Wraps (or simulates) `__assume`. */ #if RBIMPL_COMPILER_SINCE(Intel, 13, 0, 0) # /* icc warnings are false positives. Ignore them. */ # /* "warning #2261: __assume expression with side effects discarded" */ # define RBIMPL_ASSUME(expr) \ RBIMPL_WARNING_PUSH() \ RBIMPL_WARNING_IGNORED(2261) \ __assume(expr) \ RBIMPL_WARNING_POP() #elif defined(RBIMPL_HAVE___ASSUME) # define RBIMPL_ASSUME __assume #elif RBIMPL_HAS_BUILTIN(__builtin_assume) # define RBIMPL_ASSUME __builtin_assume #elif ! defined(RBIMPL_UNREACHABLE) # define RBIMPL_ASSUME(_) RBIMPL_CAST((void)(_)) #else # define RBIMPL_ASSUME(_) \ (RB_LIKELY(!!(_)) ? RBIMPL_CAST((void)0) : RBIMPL_UNREACHABLE()) #endif #if ! defined(RBIMPL_UNREACHABLE) # define RBIMPL_UNREACHABLE() RBIMPL_ASSUME(0) #endif #endif /* RBIMPL_ASSUME_H */