ctzdi2.c 836 B

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  1. /* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===
  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 __ctzdi2 for the compiler_rt library.
  11. *
  12. * ===----------------------------------------------------------------------===
  13. */
  14. #include "int_lib.h"
  15. /* Returns: the number of trailing 0-bits */
  16. /* Precondition: a != 0 */
  17. COMPILER_RT_ABI si_int
  18. __ctzdi2(di_int a)
  19. {
  20. dwords x;
  21. x.all = a;
  22. const si_int f = -(x.s.low == 0);
  23. return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
  24. (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
  25. }