ffsdi2.c 939 B

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  1. /* ===-- ffsdi2.c - Implement __ffsdi2 -------------------------------------===
  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 __ffsdi2 for the compiler_rt library.
  11. *
  12. * ===----------------------------------------------------------------------===
  13. */
  14. #include "int_lib.h"
  15. /* Returns: the index of the least significant 1-bit in a, or
  16. * the value zero if a is zero. The least significant bit is index one.
  17. */
  18. COMPILER_RT_ABI si_int
  19. __ffsdi2(di_int a)
  20. {
  21. dwords x;
  22. x.all = a;
  23. if (x.s.low == 0)
  24. {
  25. if (x.s.high == 0)
  26. return 0;
  27. return __builtin_ctz(x.s.high) + (1 + sizeof(si_int) * CHAR_BIT);
  28. }
  29. return __builtin_ctz(x.s.low) + 1;
  30. }