fmin.h

Newlib 嵌入式 C库 标准实现代码

/*
  (C) Copyright 2001,2006,
  International Business Machines Corporation,
  Sony Computer Entertainment, Incorporated,
  Toshiba Corporation,

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  modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.
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  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
    * Neither the names of the copyright holders nor the names of their
  contributors may be used to endorse or promote products derived from this
  software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
  OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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*/
#ifndef _FMIN_H_
#define _FMIN_H_	1

#include <spu_intrinsics.h>
#include "headers/vec_literal.h"

/* Return the minimum numeric value of their arguments. If one argument
 * is a NaN, fmin returns the other value. If both are NaNs, then a NaN
 * is returned.
 *
 * Notes:
 * 1) Double precision denorms equate to zero so two denorms compare
 *    equal thereby making the following true for two denorm inputs
 *    fmin(a, b) != fmin(b, a);
 */

static __inline double _fmin(double x, double y)
{
  vec_uint4 nan_x, selector, abs_x, gt, eq;
  vec_uint4 sign = VEC_LITERAL(vec_uint4, 0x80000000, 0, 0x80000000, 0);
  vec_uint4 infinity = VEC_LITERAL(vec_uint4, 0x7FF00000, 0, 0x7FF00000, 0);
  vec_double2 vx, vy, diff, min;

  vx = spu_promote(x, 0);
  vy = spu_promote(y, 0);

  /* If x is a NaN, then select y as min
   */
  abs_x = spu_andc((vec_uint4)vx, sign);
  gt = spu_cmpgt(abs_x, infinity);
  eq = spu_cmpeq(abs_x, infinity);

  nan_x = spu_or(gt, spu_and(eq, spu_rlqwbyte(gt, 4)));

  diff = spu_sub(vy, vx);
  selector = spu_orc(nan_x, spu_cmpgt((vec_int4)diff, -1));
  selector = spu_maskw(spu_extract(selector, 0));

  min = spu_sel(vx, vy, (vec_ullong2)selector);

  return (spu_extract(min, 0));
}
#endif /* _FMIN_H_ */