Split out compiler specific helper macros into a new CompilerSpecific.h header file inside the library, for future expansion.
Dean Camera
14 years ago
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/*
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LUFA Library
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Copyright (C) Dean Camera, 2011.
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dean [at] fourwalledcubicle [dot] com
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www.lufa-lib.org
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*/
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/*
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Copyright 2011 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, distribute, and sell this
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software and its documentation for any purpose is hereby granted
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without fee, provided that the above copyright notice appear in
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all copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
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The author disclaim all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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/** \file
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* \brief Compiler specific macros for code optimization and correctness.
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*
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* \copydetails Group_CompilerSpecific
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*
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* \note Do not include this file directly, rather include the Common.h header file instead to gain this file's
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* functionality.
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*/
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/** \ingroup Group_Common
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* \defgroup Group_CompilerSpecific Compiler Specific Macros
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* \brief Compiler specific macros for code optimization and correctness.
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*
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* Compiler specific macros to expose certain compiler features which may increase the level of code optimization
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* for a specific compiler, or correct certain issues that may be present such as memory barriers for use in conjunction
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* with atomic variable access.
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*
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* Where possible, on alternative compilers, these macros will either have no effect, or default to returning a sane value
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* so that they can be used in existing code without the need for extra compiler checks in the user application code.
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*
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* @{
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*/
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#ifndef __LUFA_COMPILERSPEC_H__
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#define __LUFA_COMPILERSPEC_H__
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/* Preprocessor Checks: */
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#if !defined(__INCLUDE_FROM_COMMON_H)
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#error Do not include this file directly. Include LUFA/Common/Common.h instead to gain this functionality.
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#endif
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/* Public Interface - May be used in end-application: */
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/* Macros: */
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#if defined(__GNUC__) || defined(__DOXYGEN__)
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/** Forces GCC to use pointer indirection (via the device's pointer register pairs) when accessing the given
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* struct pointer. In some cases GCC will emit non-optimal assembly code when accessing a structure through
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* a pointer, resulting in a larger binary. When this macro is used on a (non \c const) structure pointer before
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* use, it will force GCC to use pointer indirection on the elements rather than direct store and load
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* instructions.
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*
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* \param[in, out] StructPtr Pointer to a structure which is to be forced into indirect access mode.
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*/
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#define GCC_FORCE_POINTER_ACCESS(StructPtr) __asm__ __volatile__("" : "=b" (StructPtr) : "0" (StructPtr))
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/** Forces GCC to create a memory barrier, ensuring that memory accesses are not reordered past the barrier point.
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* This can be used before ordering-critical operations, to ensure that the compiler does not re-order the resulting
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* assembly output in an unexpected manner on sections of code that are ordering-specific.
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*/
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#define GCC_MEMORY_BARRIER() __asm__ __volatile__("" ::: "memory");
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/** Evaluates to boolean true if the specified value can be determined at compile time to be a constant value
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* when compiling under GCC.
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*
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* \param[in] x Value to check compile time constantness of.
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*
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* \return Boolean true if the given value is known to be a compile time constant.
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*/
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#define GCC_IS_COMPILE_CONST(x) __builtin_constant_p(x)
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#else
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#define GCC_FORCE_POINTER_ACCESS(StructPtr)
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#define GCC_MEMORY_BARRIER()
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#define GCC_IS_COMPILE_CONST(x) 0
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#endif
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#endif
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