lib/ctzdi2.c

//===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements __ctzdi2 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//

#include "int_lib.h"

// Returns: the number of trailing 0-bits

// Precondition: a != 0

si_int
__ctzdi2(di_int a)
{
    dwords x;
    x.all = a;
    const si_int f = -(x.low == 0);
    return __builtin_ctz((x.high & f) | (x.low & ~f)) +
              (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
}