compiler-rt/lib/builtins/divmodsi4.c

   1 //===-- divmodsi4.c - Implement __divmodsi4
   2 //--------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements __divmodsi4 for the compiler_rt library.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "int_lib.h"
  15
  16 // Returns: a / b, *rem = a % b
  17
  18 COMPILER_RT_ABI si_int __divmodsi4(si_int a, si_int b, si_int *rem) {
  19   const int bits_in_word_m1 = (int)(sizeof(si_int) * CHAR_BIT) - 1;
  20   si_int s_a = a >> bits_in_word_m1;                    // s_a = a < 0 ? -1 : 0
  21   si_int s_b = b >> bits_in_word_m1;                    // s_b = b < 0 ? -1 : 0
  22   a = (a ^ s_a) - s_a;                                  // negate if s_a == -1
  23   b = (b ^ s_b) - s_b;                                  // negate if s_b == -1
  24   s_b ^= s_a;                                           // sign of quotient
  25   su_int r;
  26   si_int q = (__udivmodsi4(a, b, &r) ^ s_b) - s_b;      // negate if s_b == -1
  27   *rem = (r ^ s_a) - s_a;                               // negate if s_a == -1
  28   return q;
  29 }