truncf4.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__    
#ifndef _TRUNCF4_H_
#define _TRUNCF4_H_	1
    
#include <spu_intrinsics.h>
    
/*
 * FUNCTION
 *      vector float _truncf4(vector float x)
 *
 * DESCRIPTION
 *      The _truncf4 function truncates the elements of the input vector
 *      downwards (towards zero) to the nearest integer.
 *
 */
static __inline vector float _truncf4(vector float x) 
{
  vec_int4 exp;
  vec_uint4 or_mask, and_mask, mask;
  vec_float4 out;
    
  // Construct a mask to remove the fraction bits. The mask
  // depends on the exponent of the floating point
  // input value.
  exp = spu_sub(127, spu_and(spu_rlmask((vec_int4) x, -23), 0xFF));

  // Be sure to always preserve the sign bit
  or_mask = spu_rlmask(spu_cmpgt(exp, 0),-1);

  and_mask = spu_rlmask(spu_splats((unsigned int)0x7FFFFF), exp);
  mask = spu_or(spu_and(and_mask, spu_cmpgt(exp, -31)), or_mask);
    
  // Apply the mask and return the result.
    
  out = spu_andc(x, (vec_float4) (mask));
  return (out);
}
#endif /* _TRUNCF4_H_ */
#endif /* __SPU__ */