hweight.c 1.9 KB

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  1. // SPDX-License-Identifier: GPL-2.0
  2. #include <linux/export.h>
  3. #include <linux/bitops.h>
  4. #include <asm/types.h>
  5. /**
  6. * hweightN - returns the hamming weight of a N-bit word
  7. * @x: the word to weigh
  8. *
  9. * The Hamming Weight of a number is the total number of bits set in it.
  10. */
  11. unsigned int __sw_hweight32(unsigned int w)
  12. {
  13. #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  14. w -= (w >> 1) & 0x55555555;
  15. w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
  16. w = (w + (w >> 4)) & 0x0f0f0f0f;
  17. return (w * 0x01010101) >> 24;
  18. #else
  19. unsigned int res = w - ((w >> 1) & 0x55555555);
  20. res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  21. res = (res + (res >> 4)) & 0x0F0F0F0F;
  22. res = res + (res >> 8);
  23. return (res + (res >> 16)) & 0x000000FF;
  24. #endif
  25. }
  26. EXPORT_SYMBOL(__sw_hweight32);
  27. unsigned int __sw_hweight16(unsigned int w)
  28. {
  29. unsigned int res = w - ((w >> 1) & 0x5555);
  30. res = (res & 0x3333) + ((res >> 2) & 0x3333);
  31. res = (res + (res >> 4)) & 0x0F0F;
  32. return (res + (res >> 8)) & 0x00FF;
  33. }
  34. EXPORT_SYMBOL(__sw_hweight16);
  35. unsigned int __sw_hweight8(unsigned int w)
  36. {
  37. unsigned int res = w - ((w >> 1) & 0x55);
  38. res = (res & 0x33) + ((res >> 2) & 0x33);
  39. return (res + (res >> 4)) & 0x0F;
  40. }
  41. EXPORT_SYMBOL(__sw_hweight8);
  42. unsigned long __sw_hweight64(__u64 w)
  43. {
  44. #if BITS_PER_LONG == 32
  45. return __sw_hweight32((unsigned int)(w >> 32)) +
  46. __sw_hweight32((unsigned int)w);
  47. #elif BITS_PER_LONG == 64
  48. #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  49. w -= (w >> 1) & 0x5555555555555555ul;
  50. w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
  51. w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
  52. return (w * 0x0101010101010101ul) >> 56;
  53. #else
  54. __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
  55. res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
  56. res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
  57. res = res + (res >> 8);
  58. res = res + (res >> 16);
  59. return (res + (res >> 32)) & 0x00000000000000FFul;
  60. #endif
  61. #endif
  62. }
  63. EXPORT_SYMBOL(__sw_hweight64);