scrypt-1.2.1/libcperciva/cpusupport/cpusupport.h

   1 #ifndef _CPUSUPPORT_H_
   2 #define _CPUSUPPORT_H_
   3
   4 /*
   5  * To enable support for non-portable CPU features at compile time, one or
   6  * more CPUSUPPORT_ARCH_FEATURE macros should be defined.  This can be done
   7  * directly on the compiler command line via -D CPUSUPPORT_ARCH_FEATURE or
   8  * -D CPUSUPPORT_ARCH_FEATURE=1; or a file can be created with the
   9  * necessary #define lines and then -D CPUSUPPORT_CONFIG_FILE=cpuconfig.h
  10  * (or similar) can be provided to include that file here.
  11  */
  12 #ifdef CPUSUPPORT_CONFIG_FILE
  13 #include CPUSUPPORT_CONFIG_FILE
  14 #endif
  15
  16 /**
  17  * The CPUSUPPORT_FEATURE macro declares the necessary variables and
  18  * functions for detecting CPU feature support at run time.  The function
  19  * defined in the macro acts to cache the result of the ..._detect function
  20  * using the ..._present and ..._init variables.  The _detect function and the
  21  * _present and _init variables are turn defined by CPUSUPPORT_FEATURE_DECL in
  22  * appropriate cpusupport_foo_bar.c file.
  23  *
  24  * In order to allow CPUSUPPORT_FEATURE to be used for features which do not
  25  * have corresponding CPUSUPPORT_FEATURE_DECL blocks in another source file,
  26  * we abuse the C preprocessor: If CPUSUPPORT_${enabler} is defined to 1, then
  27  * we access _present_1, _init_1, and _detect_1; but if it is not defined, we
  28  * access _present_CPUSUPPORT_${enabler} etc., which we define as static, thus
  29  * preventing the compiler from emitting a reference to an external symbol.
  30  *
  31  * In this way, it becomes possible to issue CPUSUPPORT_FEATURE invocations
  32  * for nonexistent features without running afoul of the requirement that
  33  * "If an identifier declared with external linkage is used... in the entire
  34  * program there shall be exactly one external definition" (C99 standard, 6.9
  35  * paragraph 5).  In practice, this means that users of the cpusupport code
  36  * can omit build and runtime detection files without changing the framework
  37  * code.
  38  */
  39 #define CPUSUPPORT_FEATURE__(arch_feature, enabler, enabled)                                    \
  40         static int cpusupport_ ## arch_feature ## _present ## _CPUSUPPORT_ ## enabler;          \
  41         static int cpusupport_ ## arch_feature ## _init ## _CPUSUPPORT_ ## enabler;             \
  42         static inline int cpusupport_ ## arch_feature ## _detect ## _CPUSUPPORT_ ## enabler(void) { return (0); }       \
  43         extern int cpusupport_ ## arch_feature ## _present_ ## enabled;                         \
  44         extern int cpusupport_ ## arch_feature ## _init_ ## enabled;                            \
  45         int cpusupport_ ## arch_feature ## _detect_ ## enabled(void);                           \
  46                                                                                                 \
  47         static inline int                                                                       \
  48         cpusupport_ ## arch_feature(void)                                                       \
  49         {                                                                                       \
  50                                                                                                 \
  51                 if (cpusupport_ ## arch_feature ## _present_ ## enabled)                        \
  52                         return (1);                                                             \
  53                 else if (cpusupport_ ## arch_feature ## _init_ ## enabled)                      \
  54                         return (0);                                                             \
  55                 cpusupport_ ## arch_feature ## _present_ ## enabled =                           \
  56                     cpusupport_ ## arch_feature ## _detect_ ## enabled();                       \
  57                 cpusupport_ ## arch_feature ## _init_ ## enabled = 1;                           \
  58                 return (cpusupport_ ## arch_feature ## _present_ ## enabled);                   \
  59         }                                                                                       \
  60         static void (* cpusupport_ ## arch_feature ## _dummyptr)(void);                         \
  61         static inline void                                                                      \
  62         cpusupport_ ## arch_feature ## _dummyfunc(void)                                         \
  63         {                                                                                       \
  64                                                                                                 \
  65                 (void)cpusupport_ ## arch_feature ## _present ## _CPUSUPPORT_ ## enabler;       \
  66                 (void)cpusupport_ ## arch_feature ## _init ## _CPUSUPPORT_ ## enabler;          \
  67                 (void)cpusupport_ ## arch_feature ## _detect ## _CPUSUPPORT_ ## enabler;        \
  68                 (void)cpusupport_ ## arch_feature ## _present_ ## enabled;                      \
  69                 (void)cpusupport_ ## arch_feature ## _init_ ## enabled;                         \
  70                 (void)cpusupport_ ## arch_feature ## _detect_ ## enabled;                       \
  71                 (void)cpusupport_ ## arch_feature ## _dummyptr;                                 \
  72         }                                                                                       \
  73         static void (* cpusupport_ ## arch_feature ## _dummyptr)(void) = cpusupport_ ## arch_feature ## _dummyfunc;     \
  74         struct cpusupport_ ## arch_feature ## _dummy
  75 #define CPUSUPPORT_FEATURE_(arch_feature, enabler, enabled)     \
  76         CPUSUPPORT_FEATURE__(arch_feature, enabler, enabled)
  77 #define CPUSUPPORT_FEATURE(arch, feature, enabler)                              \
  78         CPUSUPPORT_FEATURE_(arch ## _ ## feature, enabler, CPUSUPPORT_ ## enabler)
  79
  80 /*
  81  * CPUSUPPORT_FEATURE_DECL(arch, feature):
  82  * Macro which defines variables and provides a function declaration for
  83  * detecting the presence of "feature" on the "arch" architecture.  The
  84  * function body following this macro expansion must return nonzero if the
  85  * feature is present, or zero if the feature is not present or the detection
  86  * fails for any reason.
  87  */
  88 #define CPUSUPPORT_FEATURE_DECL(arch, feature)                          \
  89         int cpusupport_ ## arch ## _ ## feature ## _present_1 = 0;      \
  90         int cpusupport_ ## arch ## _ ## feature ## _init_1 = 0;         \
  91         int cpusupport_ ## arch ## _ ## feature ## _detect_1(void); \
  92         int                                                             \
  93         cpusupport_ ## arch ## _ ## feature ## _detect_1(void)
  94
  95 /*
  96  * List of features.  If a feature here is not enabled by the appropriate
  97  * CPUSUPPORT_ARCH_FEATURE macro being defined, it has no effect; but if the
  98  * relevant macro may be defined (e.g., by Build/cpusupport.sh successfully
  99  * compiling Build/cpusupport-ARCH-FEATURE.c) then the C file containing the
 100  * corresponding run-time detection code (cpusupport_arch_feature.c) must be
 101  * compiled and linked in.
 102  */
 103 CPUSUPPORT_FEATURE(x86, aesni, X86_AESNI);
 104 CPUSUPPORT_FEATURE(x86, sse2, X86_SSE2);
 105
 106 #endif /* !_CPUSUPPORT_H_ */