lib/clzti2.c

   1 /* ===-- clzti2.c - Implement __clzti2 -------------------------------------===
   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 __clzti2 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 leading 0-bits */
  20
  21 /* Precondition: a != 0 */
  22
  23 si_int
  24 __clzti2(ti_int a)
  25 {
  26     twords x;
  27     x.all = a;
  28     const di_int f = -(x.s.high == 0);
  29     return __builtin_clzll((x.s.high & ~f) | (x.s.low & f)) +
  30            ((si_int)f & ((si_int)(sizeof(di_int) * CHAR_BIT)));
  31 }
  32
  33 #endif /* __x86_64 */