newlib-cygwin/newlib/libm/machine/spu/headers/logbf4.h

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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__

#ifndef _LOGBF4_H_
#define _LOGBF4_H_	1

#include <spu_intrinsics.h>
#include <vec_types.h>

/*
 * FUNCTION
 *	vector float _logbf4(vector float x)
 *
 * DESCRIPTION
 *  The _logbf4 function returns a vector float that contains the exponent
 *  of the corresponding elements of the input vector x. The exponent is
 *  defined by:
 *    x = frac * FLT_RADIX^exp, with frac in [1, FLT_RADIX).
 *
 *  Special Cases:
 *    x = 0,  result is undefined.
 *    x = NaN, result is NaN.
 *    x = infinity, +infinity is returned.
 *
 */
static __inline vector float _logbf4(vector float x)
{
  vec_uint4 lzero     = (vector unsigned int) {0, 0, 0, 0};
  vec_uint4 exp_mask  = (vector unsigned int) {0xFF, 0xFF, 0xFF, 0xFF};
  vec_int4  exp_shift = (vector signed int) { -23,  -23,  -23,  -23};
  vec_int4  exp_bias  = (vector signed int) {-127, -127, -127, -127};
  vec_uint4 sign_mask = (vector unsigned int) {0x80000000, 0x80000000,
		                                       0x80000000, 0x80000000};
  vec_uint4 linf      = (vector unsigned int) {0x7F800000, 0x7F800000,
		                                       0x7F800000, 0x7F800000};
  vec_uint4 lminf     = (vector unsigned int) {0xFF800000, 0xFF800000,
		                                       0xFF800000, 0xFF800000};
  vec_uint4 exp;
  vec_uint4 xabs;
  vec_float4 exp_unbias;


  xabs = spu_andc((vec_uint4)x, sign_mask);

  exp  = spu_and(spu_rlmask((vec_uint4)x, exp_shift), exp_mask);
  exp_unbias = spu_convtf(spu_add((vec_int4)exp, exp_bias), 0);

  /* Zero */
  exp_unbias = spu_sel(exp_unbias, (vec_float4)lminf, (vec_uint4)spu_cmpeq(xabs, lzero));

  /* NaN */
  exp_unbias = spu_sel(exp_unbias, x, (vec_uint4)spu_cmpgt(xabs, linf));

  /* Infinite */
  exp_unbias = spu_sel(exp_unbias, (vec_float4)linf, (vec_uint4)spu_cmpeq(xabs, linf));

  return (exp_unbias);
}

#endif /* _LOGBF4_H_ */

#endif /* __SPU__ */