truncd2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__
#ifndef _TRUNCD2_H_
#define _TRUNCD2_H_	1

#include <spu_intrinsics.h>

/*
 * FUNCTION
 *      vector double _truncd2(vector double x)
 *
 * DESCRIPTION
 *      The _truncd2 function truncates the elements of the input vector
 *      downwards (towards zero) to the nearest integer.
 *
 */
static __inline vector double _truncd2(vector double in)
{
  vec_uchar16 splat_hi = (vec_uchar16) { 0,1,2,3,0,1,2,3, 8,9,10,11, 8,9,10,11 };
  vec_int4 exp, shift;
  vec_uint4 sign = (vec_uint4) { 0x80000000, 0, 0x80000000, 0 };
  vec_uint4 or_mask, and_mask, mask;
  vec_double2 in_hi, out;

  /* Construct a mask to remove the fraction bits. The mask
   * depends on the exponent of the floating point
   * input value.
   */
  in_hi = spu_shuffle(in, in, splat_hi);
  exp = spu_and(spu_rlmask((vec_int4)in_hi, -20), 0x7FF);

  shift = spu_sub(((vec_int4) { 1023, 1043, 1023, 1043 }), exp);
  or_mask = spu_andc(spu_cmpgt(shift, 0), sign);

  and_mask = spu_rlmask(((vec_uint4) { 0xFFFFF, -1, 0xFFFFF, -1 }), shift);
  mask = spu_or(spu_and(and_mask, spu_cmpgt(shift, -32)), or_mask);

  /* Apply the mask and return the result.
   */
  out = spu_andc(in, (vec_double2)(mask));

  return (out);
}


#endif /* _TRUNCD2_H_ */
#endif /* __SPU__ */