libgcc/config/epiphany/udivsi3.c

   1 /* Generic unsigned 32 bit division implementation.
   2    Copyright (C) 2009-2016 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
  39   /* Compute difference in number of bits in S0.  */
  40   u0.i = 0x40000000;
  41   u1b.i = u2b.i = u0.i;
  42   u1.i = a;
  43   u2.i = b;
  44   u1.i = a | u0.i;
  45   t = 0x4b800000 | ((a >> 23) & 0xffff);
  46   if (a >> 23)
  47     {
  48       u1.i = t;
  49       u1b.i = 0x4b800000;
  50     }
  51   u2.i = b | u0.i;
  52   t = 0x4b800000 | ((b >> 23) & 0xffff);
  53   if (b >> 23)
  54     {
  55       u2.i = t;
  56       u2b.i = 0x4b800000;
  57     }
  58   u1.f = u1.f - u1b.f;
  59   u2.f = u2.f - u2b.f;
  60   s1 = u1.i >> 23;
  61   s2 = u2.i >> 23;
  62   s0 = s1 - s2;
  63
  64   b <<= s0;
  65   d = b - 1;
  66
  67   r0 = 1 << s0;
  68   r1 = 0;
  69   t = a - b;
  70   if (t <= a)
  71     {
  72       a = t;
  73       r1 = r0;
  74     }
  75
  76 #define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t;
  77   switch (s0)
  78     {
  79     STEP (31)
  80     STEP (30)
  81     STEP (29)
  82     STEP (28)
  83     STEP (27)
  84     STEP (26)
  85     STEP (25)
  86     STEP (24)
  87     STEP (23)
  88     STEP (22)
  89     STEP (21)
  90     STEP (20)
  91     STEP (19)
  92     STEP (18)
  93     STEP (17)
  94     STEP (16)
  95     STEP (15)
  96     STEP (14)
  97     STEP (13)
  98     STEP (12)
  99     STEP (11)
 100     STEP (10)
 101     STEP (9)
 102     STEP (8)
 103     STEP (7)
 104     STEP (6)
 105     STEP (5)
 106     STEP (4)
 107     STEP (3)
 108     STEP (2)
 109     STEP (1)
 110     case 0: ;
 111     }
 112   r0 = r1 | (r0-1 & a);
 113   return r0;
 114 }