llvm-project/compiler-rt/lib/builtins/modti3.c

//===-- modti3.c - Implement __modti3 -------------------------------------===//
//
// 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 __modti3 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//

#include "int_lib.h"

#ifdef CRT_HAS_128BIT

// Returns: a % b

COMPILER_RT_ABI ti_int __modti3(ti_int a, ti_int b) {
  const int bits_in_tword_m1 = (int)(sizeof(ti_int) * CHAR_BIT) - 1;
  ti_int s = b >> bits_in_tword_m1; // s = b < 0 ? -1 : 0
  b = (b ^ s) - s;                  // negate if s == -1
  s = a >> bits_in_tword_m1;        // s = a < 0 ? -1 : 0
  a = (a ^ s) - s;                  // negate if s == -1
  tu_int r;
  __udivmodti4(a, b, &r);
  return ((ti_int)r ^ s) - s; // negate if s == -1
}

#endif // CRT_HAS_128BIT