Statistics
| Branch: | Tag: | Revision:

root / LUFA / Common / CompilerSpecific.h @ 978b99e5

History | View | Annotate | Download (4.28 KB)

1
/*
2
             LUFA Library
3
     Copyright (C) Dean Camera, 2011.
4

5
  dean [at] fourwalledcubicle [dot] com
6
           www.lufa-lib.org
7
*/
8

    
9
/*
10
  Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)
11

12
  Permission to use, copy, modify, distribute, and sell this
13
  software and its documentation for any purpose is hereby granted
14
  without fee, provided that the above copyright notice appear in
15
  all copies and that both that the copyright notice and this
16
  permission notice and warranty disclaimer appear in supporting
17
  documentation, and that the name of the author not be used in
18
  advertising or publicity pertaining to distribution of the
19
  software without specific, written prior permission.
20

21
  The author disclaim all warranties with regard to this
22
  software, including all implied warranties of merchantability
23
  and fitness.  In no event shall the author be liable for any
24
  special, indirect or consequential damages or any damages
25
  whatsoever resulting from loss of use, data or profits, whether
26
  in an action of contract, negligence or other tortious action,
27
  arising out of or in connection with the use or performance of
28
  this software.
29
*/
30

    
31
/** \file
32
 *  \brief Compiler specific definitions for code optimization and correctness.
33
 *
34
 *  \copydetails Group_CompilerSpecific
35
 *
36
 *  \note Do not include this file directly, rather include the Common.h header file instead to gain this file's
37
 *        functionality.
38
 */
39

    
40
/** \ingroup Group_Common
41
 *  \defgroup Group_CompilerSpecific Compiler Specific Definitions
42
 *  \brief Compiler specific definitions for code optimization and correctness.
43
 *
44
 *  Compiler specific definitions to expose certain compiler features which may increase the level of code optimization
45
 *  for a specific compiler, or correct certain issues that may be present such as memory barriers for use in conjunction
46
 *  with atomic variable access. 
47
 *
48
 *  Where possible, on alternative compilers, these macros will either have no effect, or default to returning a sane value
49
 *  so that they can be used in existing code without the need for extra compiler checks in the user application code.
50
 *
51
 *  @{
52
 */
53

    
54
#ifndef __LUFA_COMPILERSPEC_H__
55
#define __LUFA_COMPILERSPEC_H__
56

    
57
        /* Preprocessor Checks: */
58
                #if !defined(__INCLUDE_FROM_COMMON_H)
59
                        #error Do not include this file directly. Include LUFA/Common/Common.h instead to gain this functionality.
60
                #endif
61

    
62
        /* Public Interface - May be used in end-application: */
63
                /* Macros: */
64
                        #if defined(__GNUC__) || defined(__DOXYGEN__)
65
                                /** Forces GCC to use pointer indirection (via the device's pointer register pairs) when accessing the given
66
                                 *  struct pointer. In some cases GCC will emit non-optimal assembly code when accessing a structure through
67
                                 *  a pointer, resulting in a larger binary. When this macro is used on a (non \c const) structure pointer before
68
                                 *  use, it will force GCC to use pointer indirection on the elements rather than direct store and load
69
                                 *  instructions.
70
                                 *
71
                                 *  \param[in, out] StructPtr  Pointer to a structure which is to be forced into indirect access mode.
72
                                 */
73
                                #define GCC_FORCE_POINTER_ACCESS(StructPtr)   __asm__ __volatile__("" : "=b" (StructPtr) : "0" (StructPtr))
74

    
75
                                /** Forces GCC to create a memory barrier, ensuring that memory accesses are not reordered past the barrier point.
76
                                 *  This can be used before ordering-critical operations, to ensure that the compiler does not re-order the resulting
77
                                 *  assembly output in an unexpected manner on sections of code that are ordering-specific.
78
                                 */
79
                                #define GCC_MEMORY_BARRIER()                  __asm__ __volatile__("" ::: "memory");
80
                                
81
                                /** Evaluates to boolean true if the specified value can be determined at compile time to be a constant value
82
                                 *  when compiling under GCC.
83
                                 *
84
                                 *  \param[in] x  Value to check compile time constantness of.
85
                                 *
86
                                 *  \return Boolean true if the given value is known to be a compile time constant, false otherwise.
87
                                 */
88
                                #define GCC_IS_COMPILE_CONST(x)               __builtin_constant_p(x)
89
                        #else
90
                                #define GCC_FORCE_POINTER_ACCESS(StructPtr)
91
                                #define GCC_MEMORY_BARRIER()
92
                                #define GCC_IS_COMPILE_CONST(x)               0
93
                        #endif
94

    
95
#endif
96

    
97
/** @} */
98