compiler-rt/lib/builtins/divmodti4.c

   1 //===-- divmodti4.c - Implement __divmodti4 -------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements __divmodti4 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 #ifdef CRT_HAS_128BIT
  16
  17 // Returns: a / b, *rem = a % b
  18
  19 COMPILER_RT_ABI ti_int __divmodti4(ti_int a, ti_int b, ti_int *rem) {
  20   const int bits_in_tword_m1 = (int)(sizeof(ti_int) * CHAR_BIT) - 1;
  21   ti_int s_a = a >> bits_in_tword_m1;                   // s_a = a < 0 ? -1 : 0
  22   ti_int s_b = b >> bits_in_tword_m1;                   // s_b = b < 0 ? -1 : 0
  23   a = (tu_int)(a ^ s_a) - s_a;                          // negate if s_a == -1
  24   b = (tu_int)(b ^ s_b) - s_b;                          // negate if s_b == -1
  25   s_b ^= s_a;                                           // sign of quotient
  26   tu_int r;
  27   ti_int q = (__udivmodti4(a, b, &r) ^ s_b) - s_b;      // negate if s_b == -1
  28   *rem = (r ^ s_a) - s_a;                               // negate if s_a == -1
  29   return q;
  30 }
  31
  32 #endif // CRT_HAS_128BIT