215e12b884
This attribute is gcc specific (also implemented by clang for compatibility), and so should be behind a level of abstraction to make using different compilers easier. Change-Id: I7495f011f617268dd7a589dc0bcf1b3b7f515046 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35976 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Gabe Black <gabeblack@google.com> Tested-by: kokoro <noreply+kokoro@google.com>
130 lines
5.1 KiB
C++
130 lines
5.1 KiB
C++
/*
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* Copyright (c) 2012,2017-2018 ARM Limited
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* All rights reserved
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Copyright (c) 2006 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __BASE_COMPILER_HH__
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#define __BASE_COMPILER_HH__
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#include <memory>
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// http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
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/*
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* Attributes that become standard in later versions of c++.
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*/
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// Use M5_FALLTHROUGH to mark when you're intentionally falling through from
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// one case to another in a switch statement.
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#if __has_cpp_attribute(fallthrough) // Standard in c++17.
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# define M5_FALLTHROUGH [[fallthrough]]
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#else
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// Not supported, so it's not necessary to avoid warnings.
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# define M5_FALLTHROUGH
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#endif
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// When the return value of a function should not be discarded, mark it with
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// M5_NODISCARD.
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#if __has_cpp_attribute(nodiscard) // Standard in c++17, with message in c++20.
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# define M5_NODISCARD [[nodiscard]]
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#else
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// Not supported, but it's optional so we can just omit it.
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# define M5_NODISCARD
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#endif
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// When a variable may purposefully not be used, for instance if it's only used
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// in debug statements which might be disabled, mark it with M5_VAR_USED.
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#if __has_cpp_attribute(maybe_unused) // Standard in c++17.
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# define M5_VAR_USED [[maybe_unused]]
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#elif defined(__GNUC__)
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// gcc and clang support a custom attribute which is essentially the same
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// thing.
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# define M5_VAR_USED [[gnu::unused]]
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#else
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# error "Don't know what to do for your compiler."
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#endif
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/*
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* Compiler specific features.
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*/
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#if defined(__GNUC__) // clang or gcc.
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// Mark a structure as packed, so that no padding is added to its layout. This
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// padding might be added to, for instance, ensure certain fields have certain
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// alignment.
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# define M5_ATTR_PACKED [[gnu::packed]]
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// Prevent a function from being inlined.
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# define M5_NO_INLINE [[gnu::noinline]]
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// Set the visibility of a symbol.
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# define M5_PUBLIC [[gnu:visibility("default")]]
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# define M5_LOCAL [[gnu::visibility("hidden")]]
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# define M5_WEAK [[gnu::weak]]
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// Force an alignment for a variable.
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# define M5_ALIGNED(alignment) [[gnu::aligned(alignment)]]
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// Marker for what should be an unreachable point in the code.
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# define M5_UNREACHABLE __builtin_unreachable()
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// To mark a branch condition as likely taken, wrap it's condition with
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// M5_LIKELY. To mark it as likely not taken, wrap it's condition with
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// M5_UNLIKELY. These can be replaced with the standard attributes [[likely]]
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// and [[unlikely]] in c++20, although the syntax is different enough that
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// we can't do that with direct substitution.
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# define M5_LIKELY(cond) __builtin_expect(!!(cond), 1)
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# define M5_UNLIKELY(cond) __builtin_expect(!!(cond), 0)
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#else
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# error "Don't know what to do for your compiler."
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#endif
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// When a member variable may be unused, mark it with M5_CLASS_VAR_USED. This
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// needs to be limitted to clang only since clang warns on these unused
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// variables, and g++ will actually warn if you use this attribute since it
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// won't do anything there.
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#if defined(__clang__) // clang only.
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# define M5_CLASS_VAR_USED M5_VAR_USED
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#else
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# define M5_CLASS_VAR_USED
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#endif
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#endif // __BASE_COMPILER_HH__
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