floord2.h

Newlib 嵌入式 C库 标准实现代码

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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__

#ifndef _FLOORD2_H_
#define _FLOORD2_H_	1

#include <spu_intrinsics.h>


/*
 * FUNCTION
 *	vector double _floord2(vector double x)
 *
 * DESCRIPTION
 *	The _floord2 function rounds the elements of an vector double
 *      input vector downwards to their nearest integer representable
 *      as a double. 
 *
 */
static __inline vector double _floord2(vector double in)
{
  vec_uchar16 swap_words = (vec_uchar16) { 4,5,6,7, 0,1,2,3, 12,13,14,15, 8,9,10,11 };
  vec_uchar16 splat_hi = (vec_uchar16)   { 0,1,2,3, 0,1,2,3, 8,9,10,11,   8,9,10,11 };
  vec_uint4 one = (vec_uint4) { 0, 1, 0, 1 };
  vec_int4 exp, shift;
  vec_uint4 mask, mask_1, frac_mask, addend, insert, pos, equal0;
  vec_ullong2 sign = spu_splats(0x8000000000000000ULL);
  vec_double2 in_hi, out;
  vec_double2 minus_one = spu_splats(-1.0);

  /* This function generates the following component
   * based upon the inputs.
   *
   *   mask = bits of the input that need to be replaced.
   *   insert = value of the bits that need to be replaced
   *   addend = value to be added to perform function.
   *
   * These are applied as follows:.
   *
   *   out = ((in & mask) | insert) + addend
   */
  in_hi = spu_shuffle(in, in, splat_hi);
  pos = spu_cmpgt((vec_int4)in_hi, -1);
  exp = spu_and(spu_rlmask((vec_int4)in_hi, -20), 0x7FF);
  shift = spu_sub(((vec_int4) { 1023, 1043, 1023, 1043 } ), exp);

  /* clamp shift to the range 0 to -31.
   */
  shift = spu_sel(spu_splats(-32), spu_andc(shift, (vec_int4)spu_cmpgt(shift, 0)), spu_cmpgt(shift, -32));

  frac_mask = spu_rlmask(((vec_uint4) { 0xFFFFF, -1, 0xFFFFF, -1 } ), shift);
  mask = spu_orc(frac_mask, spu_cmpgt(exp, 0x3FE));

  /* addend = ((in & mask) && (in >= 0)) ? mask+1 : 0
   */
  mask_1 = spu_addx(mask, one, spu_rlqwbyte(spu_genc(mask, one), 4));

  equal0 = spu_cmpeq(spu_and((vec_uint4)in, mask), 0);
  addend = spu_andc(spu_andc(mask_1, pos), spu_and(equal0, spu_shuffle(equal0, equal0, swap_words)));

  insert = spu_andc(spu_andc((vec_uint4)minus_one, pos), 
		    spu_cmpgt((vec_uint4)spu_add(exp, -1), 1022));

  in = spu_sel(in, (vec_double2)insert, spu_andc((vec_ullong2)mask, sign));
  out = (vec_double2)spu_addx((vec_uint4)in, addend, spu_rlqwbyte(spu_genc((vec_uint4)in, addend), 4));

  return (out);
}

#endif /* _FLOORD2_H_ */
#endif /* __SPU__ */