newlib/newlib/libm/machine/spu/headers/ldexp.h

/*
  (C) Copyright 2001,2006,
  International Business Machines Corporation,
  Sony Computer Entertainment, Incorporated,
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    * 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
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    * 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 _LDEXP_H_
#define _LDEXP_H_	1

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

/* ldexp computes x * 2^exp. This function variant computes the result
 * and handles overflow, underflow, and denorms by breaking the problem
 * into:
 *      exp = MAX(exp, -2044)
 *      exp = MIN(exp,  2046)
 *      e1 = exp / 2
 *      e2 = exp - e1;
 * x * 2^e1 * 2^e2
 */
static __inline double _ldexp(double x, int exp)
{
  vec_int4 e, e1, e2;
  vec_int4 min = VEC_SPLAT_S32(-2044);
  vec_int4 max = VEC_SPLAT_S32(2046);
  vec_uint4 cmp_min, cmp_max;
  vec_uint4 shift = VEC_LITERAL(vec_uint4, 20, 32, 20, 32);
  vec_double2 f1, f2;
  vec_double2 in, out;

  in = spu_promote(x, 0);
  e = spu_promote(exp, 0);

  /* Clamp the specified exponent to the range -2044 to 2046.
   */
  cmp_min = spu_cmpgt(e, min);
  cmp_max = spu_cmpgt(e, max);
  e = spu_sel(min, e, cmp_min);
  e = spu_sel(e, max, cmp_max);

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

  return (spu_extract(out, 0));
}

#endif /* _LDEXP_H_ */