popcountti2.c 1.8 KB

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  1. /* ===-- popcountti2.c - Implement __popcountti2 ----------------------------===
  2. *
  3. * The LLVM Compiler Infrastructure
  4. *
  5. * This file is dual licensed under the MIT and the University of Illinois Open
  6. * Source Licenses. See LICENSE.TXT for details.
  7. *
  8. * ===----------------------------------------------------------------------===
  9. *
  10. * This file implements __popcountti2 for the compiler_rt library.
  11. *
  12. * ===----------------------------------------------------------------------===
  13. */
  14. #include "int_lib.h"
  15. #ifdef CRT_HAS_128BIT
  16. /* Returns: count of 1 bits */
  17. COMPILER_RT_ABI si_int
  18. __popcountti2(ti_int a)
  19. {
  20. tu_int x3 = (tu_int)a;
  21. x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) |
  22. 0x5555555555555555uLL));
  23. /* Every 2 bits holds the sum of every pair of bits (64) */
  24. x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL))
  25. + (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL));
  26. /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) */
  27. x3 = (x3 + (x3 >> 4))
  28. & (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL);
  29. /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) */
  30. du_int x2 = (du_int)(x3 + (x3 >> 64));
  31. /* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) */
  32. su_int x = (su_int)(x2 + (x2 >> 32));
  33. /* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) */
  34. x = x + (x >> 16);
  35. /* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) */
  36. /* Upper 16 bits are garbage */
  37. return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */
  38. }
  39. #endif /* CRT_HAS_128BIT */