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ctzdi2.c revision 1.1 
      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 
     15 #include "int_lib.h"
     16 
     17 /* Returns: the number of trailing 0-bits  */
     18 
     19 /* Precondition: a != 0 */
     20 
     21 COMPILER_RT_ABI si_int
     22 __ctzdi2(di_int a)
     23 {
     24     dwords x;
     25     x.all = a;
     26     const si_int f = -(x.s.low == 0);
     27     return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
     28               (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
     29 }
     30