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87 lines
3.2 KiB
C++
87 lines
3.2 KiB
C++
#ifndef RBIMPL_ASSUME_H /*-*-C++-*-vi:se ft=cpp:*/
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#define RBIMPL_ASSUME_H
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/**
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* @file
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* @author Ruby developers <ruby-core@ruby-lang.org>
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* @copyright This file is a part of the programming language Ruby.
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* Permission is hereby granted, to either redistribute and/or
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* modify this file, provided that the conditions mentioned in the
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* file COPYING are met. Consult the file for details.
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* @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are
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* implementation details. Don't take them as canon. They could
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* rapidly appear then vanish. The name (path) of this header file
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* is also an implementation detail. Do not expect it to persist
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* at the place it is now. Developers are free to move it anywhere
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* anytime at will.
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* @note To ruby-core: remember that this header can be possibly
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* recursively included from extension libraries written in C++.
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* Do not expect for instance `__VA_ARGS__` is always available.
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* We assume C99 for ruby itself but we don't assume languages of
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* extension libraries. They could be written in C++98.
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* @brief Defines #RBIMPL_ASSUME / #RBIMPL_UNREACHABLE.
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*
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* These macros must be defined at once because:
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*
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* - #RBIMPL_ASSUME could fallback to #RBIMPL_UNREACHABLE.
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* - #RBIMPL_UNREACHABLE could fallback to #RBIMPL_ASSUME.
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*/
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#include "ruby/internal/config.h"
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#include "ruby/internal/cast.h"
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#include "ruby/internal/compiler_since.h"
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#include "ruby/internal/has/builtin.h"
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#include "ruby/internal/warning_push.h"
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/** @cond INTERNAL_MACRO */
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#if defined(HAVE___ASSUME)
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# define RBIMPL_HAVE___ASSUME
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#endif
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/** @endcond */
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/** Wraps (or simulates) `__builtin_unreachable`. */
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#if RBIMPL_HAS_BUILTIN(__builtin_unreachable)
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# define RBIMPL_UNREACHABLE_RETURN(_) __builtin_unreachable()
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#elif defined(RBIMPL_HAVE___ASSUME)
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# define RBIMPL_UNREACHABLE_RETURN(_) return (__assume(0), (_))
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#else
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# define RBIMPL_UNREACHABLE_RETURN(_) return (_)
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#endif
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/** Wraps (or simulates) `__builtin_unreachable`. */
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#if RBIMPL_HAS_BUILTIN(__builtin_unreachable)
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# define RBIMPL_UNREACHABLE __builtin_unreachable
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#elif defined(RBIMPL_HAVE___ASSUME)
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# define RBIMPL_UNREACHABLE() __assume(0)
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#endif
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/** Wraps (or simulates) `__assume`. */
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#if RBIMPL_COMPILER_SINCE(Intel, 13, 0, 0)
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# /* icc warnings are false positives. Ignore them. */
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# /* "warning #2261: __assume expression with side effects discarded" */
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# define RBIMPL_ASSUME(expr) \
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RBIMPL_WARNING_PUSH() \
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RBIMPL_WARNING_IGNORED(2261) \
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__assume(expr) \
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RBIMPL_WARNING_POP()
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#elif defined(RBIMPL_HAVE___ASSUME)
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# define RBIMPL_ASSUME __assume
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#elif RBIMPL_HAS_BUILTIN(__builtin_assume)
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# define RBIMPL_ASSUME __builtin_assume
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#elif ! defined(RBIMPL_UNREACHABLE)
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# define RBIMPL_ASSUME(_) RBIMPL_CAST((void)(_))
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#else
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# define RBIMPL_ASSUME(_) \
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(RB_LIKELY(!!(_)) ? RBIMPL_CAST((void)0) : RBIMPL_UNREACHABLE())
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#endif
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#if ! defined(RBIMPL_UNREACHABLE)
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# define RBIMPL_UNREACHABLE() RBIMPL_ASSUME(0)
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#endif
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#endif /* RBIMPL_ASSUME_H */
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