ldexpd2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__

#ifndef _LDEXPD2_H_
#define _LDEXPD2_H_	1

#include <spu_intrinsics.h>

/*
 * FUNCTION
 *      vector double _ldexpd2(vector double x, vector signed long long exp)
 *
 * DESCRIPTION
 *      The _ldexpd2 function Computes x * 2^exp for each of the two elements 
 *      of x using the corresponding elements of exp.
 *
 */
static __inline vector double _ldexpd2(vector double x, vector signed long long llexp)
{
  vec_uchar16 odd_to_even = ((vec_uchar16) { 4,5,6,7,     0x80,0x80,0x80,0x80, 
                                             12,13,14,15, 0x80,0x80,0x80,0x80 });
  vec_uchar16 dup_even = ((vec_uchar16) { 0,1,2,3,    0,1,2,3,
                                          8,9,10,11,  8,9,10,11});
  vec_int4 exp;
  vec_uint4 exphi;
  vec_int4 e1, e2;
  vec_int4 min = spu_splats(-2044);
  vec_int4 max = spu_splats(2046);
  vec_uint4 cmp_min, cmp_max;
  vec_uint4 shift = (vec_uint4) { 20, 32, 20, 32 };
  vec_double2 f1, f2;
  vec_double2 out;

  exp = (vec_int4)spu_shuffle(llexp, llexp, odd_to_even);

  exphi = (vec_uint4)spu_shuffle(llexp, llexp, dup_even);

  /* Clamp the specified exponent to the range -2044 to 2046.
   */

  cmp_min = spu_cmpgt(exp, min);
  cmp_max = spu_cmpgt(exp, max);
  exp = spu_sel(min, exp, cmp_min);
  exp = spu_sel(exp, max, cmp_max);

  /* Generate the factors f1 = 2^e1 and f2 = 2^e2
   */
  e1 = spu_rlmaska(exp, -1);
  e2 = spu_sub(exp, e1);

  f1 = (vec_double2)spu_sl(spu_add(e1, 1023), shift);
  f2 = (vec_double2)spu_sl(spu_add(e2, 1023), shift);

  /* Compute the product x * 2^e1 * 2^e2
   */
  out = spu_mul(spu_mul(x, f1), f2);

  return (out);
}

#endif /* _LDEXPD2_H_ */
#endif /* __SPU__ */