Subversion Repositories openrisc_2011-10-31

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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__
#ifndef _SCALBNF4_H_
#define _SCALBNF4_H_	1
 
#include <spu_intrinsics.h>
 
/*
 * FUNCTION
 *	vector float _scalbnf4(vector float x, vector signed int exp)
 *
 * DESCRIPTION
 *      The _scalbnf4 function returns a vector containing each element of x 
 *      multiplied by 2^n computed efficiently.  This function is computed 
 *      without the assistance of any floating point operations and as such 
 *      does not set any floating point exceptions.
 *
 *      Special Cases:
 *	  - if the exponent is 0, then x is either 0 or a subnormal, and the
 *          result will be returned as 0.
 *        - if the result if underflows, it will be returned as 0.
 *        - if the result overflows, it will be returned as FLT_MAX.
 *
 */
static __inline vector float _scalbnf4(vector float x, vector signed int exp)
{
  vec_int4 x_exp;
  vec_uint4 zero;
  vec_uint4 overflow;
  vec_uint4 exp_mask = (vec_uint4)spu_splats(0x7F800000);
  vec_float4 out;
 
  /* Extract exponent from x. If the exponent is 0, then
   * x is either 0 or a denorm and x*2^exp is a zero.
   */
  x_exp = spu_and(spu_rlmask((vec_int4)x, -23), 0xFF);
  zero = spu_cmpeq(x_exp, 0);
 
  /* Compute the expected exponent and determine if the 
   * result is within range.
   */
  x_exp = spu_add(exp, x_exp);
 
  /* Check for zero or overflow of result.
   * Note: set high bit of flags = 0, since we have to
   * return -0 when x = -0
   */
  zero     = spu_rlmask(spu_orc(zero, spu_cmpgt(x_exp, 0)), -1);
  overflow = spu_rlmask(spu_cmpgt(x_exp, 255), -1);
 
  /* Merge the expect exponent with x's mantissa. Zero the
   * result if underflow and force to max if overflow.
   */
  out = spu_sel(x, (vec_float4)spu_rl(x_exp, 23), exp_mask);
  out = spu_andc(out, (vec_float4)zero);
  out = spu_or(out, (vec_float4)overflow);
 
  return out;
}
 
#endif /* _SCALBNF4_H_ */
#endif /* __SPU__ */