llvm-project/compiler-rt/lib/builtins/moddi3.c

/*===-- moddi3.c - Implement __moddi3 -------------------------------------===
 *
 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.
 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 *
 * ===----------------------------------------------------------------------===
 *
 * This file implements __moddi3 for the compiler_rt library.
 *
 * ===----------------------------------------------------------------------===
 */

#include "int_lib.h"

/* Returns: a % b */

COMPILER_RT_ABI 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 */
  du_int r;
  __udivmoddi4(a, b, &r);
  return ((di_int)r ^ s) - s; /* negate if s == -1 */
}