runtime/lib/moddi3.c

/*===-- moddi3.c - Implement __moddi3 -------------------------------------===
 *
 *                    The LLVM Compiler Infrastructure
 *
 * This file is distributed under the University of Illinois Open Source
 * License. See LICENSE.TXT for details.
 *
 * ===----------------------------------------------------------------------===
 *
 * This file implements __moddi3 for the compiler_rt library.
 *
 * ===----------------------------------------------------------------------===
 */

#include "int_lib.h"

du_int __udivmoddi4(du_int a, du_int b, du_int* rem);

/* Returns: a % b */

di_int
__moddi3(di_int a, di_int b)
{
    const int bits_in_dword_m1 = (int)(sizeof(di_int) * CHAR_BIT) - 1;
    di_int s = b >> bits_in_dword_m1;  /* s = b < 0 ? -1 : 0 */
    b = (b ^ s) - s;                   /* negate if s == -1 */
    s = a >> bits_in_dword_m1;         /* s = a < 0 ? -1 : 0 */
    a = (a ^ s) - s;                   /* negate if s == -1 */
    di_int r;
    __udivmoddi4(a, b, (du_int*)&r);
    return (r ^ s) - s;                /* negate if s == -1 */
}