lib/ffsti2.c

   1 /* ===-- ffsti2.c - Implement __ffsti2 -------------------------------------===
   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 __ffsti2 for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 #if __x86_64
  18
  19 /* Returns: the index of the least significant 1-bit in a, or
  20  * the value zero if a is zero. The least significant bit is index one.
  21  */
  22
  23 si_int
  24 __ffsti2(ti_int a)
  25 {
  26     twords x;
  27     x.all = a;
  28     if (x.s.low == 0)
  29     {
  30         if (x.s.high == 0)
  31             return 0;
  32         return __builtin_ctzll(x.s.high) + (1 + sizeof(di_int) * CHAR_BIT);
  33     }
  34     return __builtin_ctzll(x.s.low) + 1;
  35 }
  36
  37 #endif /* __x86_64 */