1  /* Generic unsigned 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  unsigned int __udivsi3 (unsigned int a, unsigned int b);
      29  
      30  unsigned int
      31  __udivsi3 (unsigned int a, unsigned int b)
      32  {
      33    unsigned int d, t, s0, s1, s2, r0, r1;
      34    fu u0, u1, u2,  u1b, u2b;
      35  
      36    if (b > a)
      37      return 0;
      38    if ((int) b < 0)
      39      return 1;
      40  
      41    /* Assuming B is nonzero, compute S0 such that 0 <= S0,
      42       (B << S0+1) does not overflow,
      43       A < 4.01 * (B << S0), with S0 chosen as small as possible
      44       without taking to much time calculating.  */
      45  #ifdef CONVERT_UNSIGNED
      46    u0.f = a;
      47    u1.f = b;
      48  #else /* !CONVERT_UNSIGNED */
      49    u0.f = (int) a;
      50    u1.f = (int) b;
      51  #ifdef CONCISE
      52    if ((int) a < 0)
      53      u0.i = (a >> 8) - 0x00800000 + 0x3f800000 + (31 << 23);
      54  #else /* To use flag setting / cmove, this can be written as:  */
      55   {
      56    unsigned c = 0xff800000 - 0x4f000000;
      57    t = (int)a >> 8;
      58    if (t >= c)
      59      u0.i = (t - c);
      60   }
      61  #endif
      62  #endif /* !CONVERT_UNSIGNED */
      63    s0 = u0.i + 1 /* Compensate for rounding errors.  */
      64  	    - 0x00800000 /* adjust by one */ ;
      65    s0 = s0 - u1.i;
      66    s0 = (int)s0 >= 0 ? s0 : 0;
      67    s0 >>= 23;
      68  
      69    b <<= s0;
      70    r1 = 0;
      71  
      72    r0 = 1 << s0;
      73    a = ((t=a) - b);
      74    if (a <= t)
      75      {
      76        r1 += r0;
      77        a = ((t=a) - b);
      78        if (a <= t)
      79  	do {
      80  	  r1 += r0;
      81  	  a = ((t=a) - b);
      82  	} while (a <= t);
      83      }
      84    a += b;
      85    d = b - 1;
      86  
      87  #define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t;
      88    switch (s0)
      89      {
      90      STEP (31)
      91      STEP (30)
      92      STEP (29)
      93      STEP (28)
      94      STEP (27)
      95      STEP (26)
      96      STEP (25)
      97      STEP (24)
      98      STEP (23)
      99      STEP (22)
     100      STEP (21)
     101      STEP (20)
     102      STEP (19)
     103      STEP (18)
     104      STEP (17)
     105      STEP (16)
     106      STEP (15)
     107      STEP (14)
     108      STEP (13)
     109      STEP (12)
     110      STEP (11)
     111      STEP (10)
     112      STEP (9)
     113      STEP (8)
     114      STEP (7)
     115      STEP (6)
     116      STEP (5)
     117      STEP (4)
     118      STEP (3)
     119      STEP (2)
     120      STEP (1)
     121      case 0: ;
     122      }
     123    r0 = r1 | (r0-1 & a);
     124    return r0;
     125  }