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  1. #include "chess.h"
  2. #include "data.h"
  3. /* last modified 02/16/14 */
  4. /*
  5.  *******************************************************************************
  6.  *                                                                             *
  7.  *   This group of procedures provide the three basic bitboard operators,      *
  8.  *   MSB(x) that determines the Most Significant Bit, LSB(x) that determines   *
  9.  *   the Least Significant Bit, and PopCnt(x) which returns the number of one  *
  10.  *   bits set in the word.                                                     *
  11.  *                                                                             *
  12.  *   We prefer to use hardware facilities (such as intel BSF/BSR) when they    *
  13.  *   are available, otherwise we resort to C and table lookups to do this in   *
  14.  *   the most efficient way possible.                                          *
  15.  *                                                                             *
  16.  *******************************************************************************
  17.  */
  18. #if !defined(INLINEASM)
  19. int MSB(uint64_t arg1) {
  20.   if (arg1 >> 48)
  21.     return msb[arg1 >> 48] + 48;
  22.   if (arg1 >> 32 & 65535)
  23.     return msb[arg1 >> 32 & 65535] + 32;
  24.   if (arg1 >> 16 & 65535)
  25.     return msb[arg1 >> 16 & 65535] + 16;
  26.   return msb[arg1 & 65535];
  27. }
  28.  
  29. int LSB(uint64_t arg1) {
  30.   if (arg1 & 65535)
  31.     return lsb[arg1 & 65535];
  32.   if (arg1 >> 16 & 65535)
  33.     return lsb[arg1 >> 16 & 65535] + 16;
  34.   if (arg1 >> 32 & 65535)
  35.     return lsb[arg1 >> 32 & 65535] + 32;
  36.   return lsb[arg1 >> 48] + 48;
  37. }
  38.  
  39. int PopCnt(uint64_t arg1) {
  40.   int c = 1;
  41.   while (arg1 &= arg1 - 1)
  42.     c++;
  43.   return c;
  44. }
  45. #endif
  46.