lib/builtins/divsi3.c

   1 /* ===-- divsi3.c - Implement __divsi3 -------------------------------------===
   2  *
   3  *                     The LLVM Compiler Infrastructure
   4  *
   5  * This file is dual licensed under the MIT and the University of Illinois Open
   6  * Source Licenses. See LICENSE.TXT for details.
   7  *
   8  * ===----------------------------------------------------------------------===
   9  *
  10  * This file implements __divsi3 for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 /* Returns: a / b */
  18
  19 ARM_EABI_FNALIAS(idiv, divsi3)
  20
  21 COMPILER_RT_ABI si_int
  22 __divsi3(si_int a, si_int b)
  23 {
  24     const int bits_in_word_m1 = (int)(sizeof(si_int) * CHAR_BIT) - 1;
  25     si_int s_a = a >> bits_in_word_m1;           /* s_a = a < 0 ? -1 : 0 */
  26     si_int s_b = b >> bits_in_word_m1;           /* s_b = b < 0 ? -1 : 0 */
  27     a = (a ^ s_a) - s_a;                         /* negate if s_a == -1 */
  28     b = (b ^ s_b) - s_b;                         /* negate if s_b == -1 */
  29     s_a ^= s_b;                                  /* sign of quotient */
  30     /*
  31      * On CPUs without unsigned hardware division support,
  32      *  this calls __udivsi3 (notice the cast to su_int).
  33      * On CPUs with unsigned hardware division support,
  34      *  this uses the unsigned division instruction.
  35      */
  36     return ((su_int)a/(su_int)b ^ s_a) - s_a;    /* negate if s_a == -1 */
  37 }