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      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 #if !defined(__clang__) && (defined(__sparc64__) || defined(__mips64) || defined(__riscv__))
     20 /* gcc resolves __builtin_clz -> __clzdi2 leading to infinite recursion */
     21 #define __builtin_clz(a) __clzsi2(a)
     22 extern si_int __clzsi2(si_int);
     23 #endif
     24 
     25 /* Precondition: a != 0 */
     26 
     27 COMPILER_RT_ABI si_int
     28 __clzdi2(di_int a)
     29 {
     30     dwords x;
     31     x.all = a;
     32     const si_int f = -(x.s.high == 0);
     33     return __builtin_clz((x.s.high & ~f) | (x.s.low & f)) +
     34            (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
     35 }
     36