clzdi2.c revision 1.3
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) 22extern si_int __clzsi2(si_int); 23#endif 24 25/* Precondition: a != 0 */ 26 27COMPILER_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