shithub: opus

ref: b3369d07bded3d20c60982d8e1fa124fb989a0bf
dir: /libcelt/entcode.c/

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "entcode.h"







int ec_ilog(ec_uint32 _v){
#if defined(EC_CLZ)
  return EC_CLZ0-EC_CLZ(_v);
#else
  /*On a Pentium M, this branchless version tested as the fastest on
     1,000,000,000 random 32-bit integers, edging out a similar version with
     branches, and a 256-entry LUT version.*/
  int ret;
  int m;
  ret=!!_v;
  m=!!(_v&0xFFFF0000)<<4;
  _v>>=m;
  ret|=m;
  m=!!(_v&0xFF00)<<3;
  _v>>=m;
  ret|=m;
  m=!!(_v&0xF0)<<2;
  _v>>=m;
  ret|=m;
  m=!!(_v&0xC)<<1;
  _v>>=m;
  ret|=m;
  ret+=!!(_v&0x2);
  return ret;
#endif
}