_ Git - BearSSL/blob - src/int/i32_div32.c

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #include "inner.h"
  26
  27 /* see inner.h */
  28 uint32_t
  29 br_divrem(uint32_t hi, uint32_t lo, uint32_t d, uint32_t *r)
  30 {
  31         /* TODO: optimize this */
  32         uint32_t q;
  33         uint32_t ch, cf;
  34         int k;
  35
  36         q = 0;
  37         ch = EQ(hi, d);
  38         hi = MUX(ch, 0, hi);
  39         for (k = 31; k > 0; k --) {
  40                 int j;
  41                 uint32_t w, ctl, hi2, lo2;
  42
  43                 j = 32 - k;
  44                 w = (hi << j) | (lo >> k);
  45                 ctl = GE(w, d) | (hi >> k);
  46                 hi2 = (w - d) >> j;
  47                 lo2 = lo - (d << k);
  48                 hi = MUX(ctl, hi2, hi);
  49                 lo = MUX(ctl, lo2, lo);
  50                 q |= ctl << k;
  51         }
  52         cf = GE(lo, d) | hi;
  53         q |= cf;
  54         *r = MUX(cf, lo - d, lo);
  55         return q;
  56 }