1  /* Generic signed 32 bit division implementation.
       2     Copyright (C) 2009-2023 Free Software Foundation, Inc.
       3     Contributed by Embecosm on behalf of Adapteva, Inc.
       4  
       5  This file is part of GCC.
       6  
       7  This file is free software; you can redistribute it and/or modify it
       8  under the terms of the GNU General Public License as published by the
       9  Free Software Foundation; either version 3, or (at your option) any
      10  later version.
      11  
      12  This file is distributed in the hope that it will be useful, but
      13  WITHOUT ANY WARRANTY; without even the implied warranty of
      14  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      15  General Public License for more details.
      16  
      17  Under Section 7 of GPL version 3, you are granted additional
      18  permissions described in the GCC Runtime Library Exception, version
      19  3.1, as published by the Free Software Foundation.
      20  
      21  You should have received a copy of the GNU General Public License and
      22  a copy of the GCC Runtime Library Exception along with this program;
      23  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      24  <http://www.gnu.org/licenses/>.  */
      25  
      26  typedef union { unsigned int i; float f; } fu;
      27  
      28  /* Although the semantics of the function ask for signed / unsigned inputs,
      29     for the actual implementation we use unsigned numbers.  */
      30  unsigned int __divsi3 (unsigned int a, unsigned int b);
      31  
      32  unsigned int
      33  __divsi3 (unsigned int a, unsigned int b)
      34  {
      35    unsigned int sign = (int) (a ^ b) >> 31;
      36    unsigned int d, t, s0, s1, s2, r0, r1;
      37    fu u0, u1, u2, u1b, u2b;
      38  
      39    a = abs (a);
      40    b = abs (b);
      41  
      42    if (b > a)
      43      return 0;
      44  
      45    /* Compute difference in number of bits in S0.  */
      46    u0.i = 0x40000000;
      47    u1b.i = u2b.i = u0.i;
      48    u1.i = a;
      49    u2.i = b;
      50    u1.i = a | u0.i;
      51    t = 0x4b800000 | ((a >> 23) & 0xffff);
      52    if (a >> 23)
      53      {
      54        u1.i = t;
      55        u1b.i = 0x4b800000;
      56      }
      57    u2.i = b | u0.i;
      58    t = 0x4b800000 | ((b >> 23) & 0xffff);
      59    if (b >> 23)
      60      {
      61        u2.i = t;
      62        u2b.i = 0x4b800000;
      63      }
      64    u1.f = u1.f - u1b.f;
      65    u2.f = u2.f - u2b.f;
      66    s1 = u1.i >> 23;
      67    s2 = u2.i >> 23;
      68    s0 = s1 - s2;
      69  
      70    b <<= s0;
      71    d = b - 1;
      72  
      73    r0 = 1 << s0;
      74    r1 = 0;
      75    t = a - b;
      76    if (t <= a)
      77      {
      78        a = t;
      79        r1 = r0;
      80      }
      81  
      82  #define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t;
      83    switch (s0)
      84      {
      85      STEP (31)
      86      STEP (30)
      87      STEP (29)
      88      STEP (28)
      89      STEP (27)
      90      STEP (26)
      91      STEP (25)
      92      STEP (24)
      93      STEP (23)
      94      STEP (22)
      95      STEP (21)
      96      STEP (20)
      97      STEP (19)
      98      STEP (18)
      99      STEP (17)
     100      STEP (16)
     101      STEP (15)
     102      STEP (14)
     103      STEP (13)
     104      STEP (12)
     105      STEP (11)
     106      STEP (10)
     107      STEP (9)
     108      STEP (8)
     109      STEP (7)
     110      STEP (6)
     111      STEP (5)
     112      STEP (4)
     113      STEP (3)
     114      STEP (2)
     115      STEP (1)
     116      case 0: ;
     117      }
     118    r0 = r1 | (r0-1 & a);
     119    return (r0 ^ sign) - sign;
     120  }