uclibc-ng/libm/math_private.h

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifndef _MATH_PRIVATE_H_
#define _MATH_PRIVATE_H_

#include <endian.h>
#include <sys/types.h>

/* The original fdlibm code used statements like:
	n0 = ((*(int*)&one)>>29)^1;		* index of high word *
	ix0 = *(n0+(int*)&x);			* high word of x *
	ix1 = *((1-n0)+(int*)&x);		* low word of x *
   to dig two 32 bit words out of the 64 bit IEEE floating point
   value.  That is non-ANSI, and, moreover, the gcc instruction
   scheduler gets it wrong.  We instead use the following macros.
   Unlike the original code, we determine the endianness at compile
   time, not at run time; I don't see much benefit to selecting
   endianness at run time.  */

/* A union which permits us to convert between a double and two 32 bit
   ints.  */

/*
 * Math on arm is special (read: stupid):
 * For FPA, float words are always big-endian.
 * For VFP, float words follow the memory system mode.
 * For Maverick, float words are always little-endian.
 */

#if !defined(__MAVERICK__) && ((__BYTE_ORDER == __BIG_ENDIAN) || \
    (!defined(__VFP_FP__) && (defined(__arm__) || defined(__thumb__))))

typedef union
{
  double value;
  struct
  {
    u_int32_t msw;
    u_int32_t lsw;
  } parts;
} ieee_double_shape_type;

#else

typedef union
{
  double value;
  struct
  {
    u_int32_t lsw;
    u_int32_t msw;
  } parts;
} ieee_double_shape_type;

#endif

/* Get two 32 bit ints from a double.  */

#define EXTRACT_WORDS(ix0,ix1,d)				\
do {								\
  ieee_double_shape_type ew_u;					\
  ew_u.value = (d);						\
  (ix0) = ew_u.parts.msw;					\
  (ix1) = ew_u.parts.lsw;					\
} while (0)

/* Get the more significant 32 bit int from a double.  */

#define GET_HIGH_WORD(i,d)					\
do {								\
  ieee_double_shape_type gh_u;					\
  gh_u.value = (d);						\
  (i) = gh_u.parts.msw;						\
} while (0)

/* Get the less significant 32 bit int from a double.  */

#define GET_LOW_WORD(i,d)					\
do {								\
  ieee_double_shape_type gl_u;					\
  gl_u.value = (d);						\
  (i) = gl_u.parts.lsw;						\
} while (0)

/* Set a double from two 32 bit ints.  */

#define INSERT_WORDS(d,ix0,ix1)					\
do {								\
  ieee_double_shape_type iw_u;					\
  iw_u.parts.msw = (ix0);					\
  iw_u.parts.lsw = (ix1);					\
  (d) = iw_u.value;						\
} while (0)

/* Set the more significant 32 bits of a double from an int.  */

#define SET_HIGH_WORD(d,v)					\
do {								\
  ieee_double_shape_type sh_u;					\
  sh_u.value = (d);						\
  sh_u.parts.msw = (v);						\
  (d) = sh_u.value;						\
} while (0)

/* Set the less significant 32 bits of a double from an int.  */

#define SET_LOW_WORD(d,v)					\
do {								\
  ieee_double_shape_type sl_u;					\
  sl_u.value = (d);						\
  sl_u.parts.lsw = (v);						\
  (d) = sl_u.value;						\
} while (0)

/* A union which permits us to convert between a float and a 32 bit
   int.  */

typedef union
{
  float value;
  u_int32_t word;
} ieee_float_shape_type;

/* Get a 32 bit int from a float.  */

#define GET_FLOAT_WORD(i,d)					\
do {								\
  ieee_float_shape_type gf_u;					\
  gf_u.value = (d);						\
  (i) = gf_u.word;						\
} while (0)

/* Set a float from a 32 bit int.  */

#define SET_FLOAT_WORD(d,i)					\
do {								\
  ieee_float_shape_type sf_u;					\
  sf_u.word = (i);						\
  (d) = sf_u.value;						\
} while (0)

/* ieee style elementary functions */
extern double __ieee754_sqrt (double) attribute_hidden;
extern double __ieee754_acos (double) attribute_hidden;
extern double __ieee754_acosh (double) attribute_hidden;
extern double __ieee754_log (double) attribute_hidden;
extern double __ieee754_log2 (double) attribute_hidden;
extern double __ieee754_atanh (double) attribute_hidden;
extern double __ieee754_asin (double) attribute_hidden;
extern double __ieee754_atan2 (double,double) attribute_hidden;
extern double __ieee754_exp (double) attribute_hidden;
extern double __ieee754_cosh (double) attribute_hidden;
extern double __ieee754_fmod (double,double) attribute_hidden;
extern double __ieee754_pow (double,double) attribute_hidden;
extern double __ieee754_lgamma_r (double,int *) attribute_hidden;
/*extern double __ieee754_gamma_r (double,int *) attribute_hidden;*/
extern double __ieee754_lgamma (double) attribute_hidden;
/*extern double __ieee754_gamma (double) attribute_hidden;*/
extern double __ieee754_log10 (double) attribute_hidden;
extern double __ieee754_sinh (double) attribute_hidden;
extern double __ieee754_hypot (double,double) attribute_hidden;
extern double __ieee754_j0 (double) attribute_hidden;
extern double __ieee754_j1 (double) attribute_hidden;
extern double __ieee754_y0 (double) attribute_hidden;
extern double __ieee754_y1 (double) attribute_hidden;
extern double __ieee754_jn (int,double) attribute_hidden;
extern double __ieee754_yn (int,double) attribute_hidden;
extern double __ieee754_remainder (double,double) attribute_hidden;
extern int    __ieee754_rem_pio2 (double,double*) attribute_hidden;
extern double __ieee754_scalb (double,double) attribute_hidden;

/* fdlibm kernel function */
#ifndef _IEEE_LIBM
extern double __kernel_standard (double,double,int) attribute_hidden;
#endif
extern double __kernel_sin (double,double,int) attribute_hidden;
extern double __kernel_cos (double,double) attribute_hidden;
extern double __kernel_tan (double,double,int) attribute_hidden;
extern int    __kernel_rem_pio2 (double*,double*,int,int,int,const int*) attribute_hidden;

/*
 * math_opt_barrier(x): safely load x, even if it was manipulated
 * by non-floationg point operations. This macro returns the value of x.
 * This ensures compiler does not (ab)use its knowledge about x value
 * and don't optimize future operations. Example:
 * float x;
 * SET_FLOAT_WORD(x, 0x80000001); // sets a bit pattern
 * y = math_opt_barrier(x); // "compiler, do not cheat!"
 * y = y * y; // compiler can't optimize, must use real multiply insn
 *
 * math_force_eval(x): force expression x to be evaluated.
 * Useful if otherwise compiler may eliminate the expression
 * as unused. This macro returns no value.
 * Example: "void fn(float f) { f = f * f; }"
 *   versus "void fn(float f) { f = f * f; math_force_eval(f); }"
 *
 * Currently, math_force_eval(x) stores x into
 * a floating point register or memory *of the appropriate size*.
 * There is no guarantee this will not change.
 */
#if defined(__i386__)
#define math_opt_barrier(x) ({ \
	__typeof(x) __x = (x); \
	/* "t": load x into top-of-stack fpreg */ \
	__asm ("" : "=t" (__x) : "0" (__x)); \
	__x; \
})
#define math_force_eval(x) do {	\
	__typeof(x) __x = (x); \
	if (sizeof(__x) <= sizeof(double)) \
		/* "m": store x into a memory location */ \
		__asm __volatile ("" : : "m" (__x)); \
	else /* long double */ \
		/* "f": load x into (any) fpreg */ \
		__asm __volatile ("" : : "f" (__x)); \
} while (0)
#endif

#if defined(__x86_64__)
#define math_opt_barrier(x) ({ \
	__typeof(x) __x = (x); \
	if (sizeof(__x) <= sizeof(double)) \
		/* "x": load into XMM SSE register */ \
		__asm ("" : "=x" (__x) : "0" (__x)); \
	else /* long double */ \
		/* "t": load x into top-of-stack fpreg */ \
		__asm ("" : "=t" (__x) : "0" (__x)); \
	__x; \
})
#define math_force_eval(x) do { \
	__typeof(x) __x = (x); \
	if (sizeof(__x) <= sizeof(double)) \
		/* "x": load into XMM SSE register */ \
		__asm __volatile ("" : : "x" (__x)); \
	else /* long double */ \
		/* "f": load x into (any) fpreg */ \
		__asm __volatile ("" : : "f" (__x)); \
} while (0)
#endif

/* Default implementations force store to a memory location */
#ifndef math_opt_barrier
#define math_opt_barrier(x) ({ __typeof(x) __x = (x); __asm ("" : "+m" (__x)); __x; })
#endif
#ifndef math_force_eval
#define math_force_eval(x)  do { __typeof(x) __x = (x); __asm __volatile ("" : : "m" (__x)); } while (0)
#endif


#endif /* _MATH_PRIVATE_H_ */