lib/ctzti2.c

   1 /* ===-- ctzti2.c - Implement __ctzti2 -------------------------------------===
   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 __ctzti2 for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 #if __x86_64
  18
  19 /* Returns: the number of trailing 0-bits */
  20
  21 /* Precondition: a != 0 */
  22
  23 si_int
  24 __ctzti2(ti_int a)
  25 {
  26     twords x;
  27     x.all = a;
  28     const di_int f = -(x.s.low == 0);
  29     return __builtin_ctzll((x.s.high & f) | (x.s.low & ~f)) +
  30               ((si_int)f & ((si_int)(sizeof(di_int) * CHAR_BIT)));
  31 }
  32
  33 #endif