signbitd2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__
#ifndef _SIGNBITD2_H_
#define _SIGNBITD2_H_	1

#include <spu_intrinsics.h>

/*
 * FUNCTION
 *	vector unsigned long long _signbitd2(vector double x)
 *
 * DESCRIPTION
 *      The signbitd2 function returns a vector which contains either all ones 
 *      or all zeros, depending on the sign of the corresponding input vector 
 *      element.
 *
 *      Note that the signbit functions are not logically equivalent to 
 *      x < 0.0.  IEEE 754 floating point rules include a signed zero, so if
 *      the input value is –0.0, signbit will return non-zero, but the naive
 *      implementation will not.
 * 
 * RETURNS
 *      The function signbitf4 returns an unsigned int vector in which each
 *      element is defined as:
 *
 *        - ULLONG_MAX (0xFFFFFFFFFFFFFFFF)   if the sign bit is set for the 
 *                                            corresponding element of x
 *        - 0          (0x0000000000000000)   otherwise.
 *
 */
static __inline vector unsigned long long _signbitd2(vector double x)
{
  vec_uchar16 shuf = ((vec_uchar16){0, 1, 2, 3,  0, 1, 2, 3,  8, 9, 10, 11,  8, 9, 10, 11});
  vec_uint4 r = spu_rlmaska((vec_uint4)x,-31);
  return (vec_ullong2)spu_shuffle(r,r,shuf);
}
#endif /* _SIGNBITD2_H_ */
#endif /* __SPU__ */