lib/builtins/clzdi2.c

   1 /* ===-- clzdi2.c - Implement __clzdi2 -------------------------------------===
   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 __clzdi2 for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 /* Returns: the number of leading 0-bits */
  18
  19 /* Precondition: a != 0 */
  20
  21 COMPILER_RT_ABI si_int
  22 __clzdi2(di_int a)
  23 {
  24     dwords x;
  25     x.all = a;
  26     const si_int f = -(x.s.high == 0);
  27     return __builtin_clz((x.s.high & ~f) | (x.s.low & f)) +
  28            (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
  29 }