lib/muldi3.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, see the file COPYING, or write
  14  * to the Free Software Foundation, Inc.
  15  */
  16
  17 #include <linux/export.h>
  18 #include <linux/libgcc.h>
  19
  20 #define W_TYPE_SIZE 32
  21
  22 #define __ll_B ((unsigned long) 1 << (W_TYPE_SIZE / 2))
  23 #define __ll_lowpart(t) ((unsigned long) (t) & (__ll_B - 1))
  24 #define __ll_highpart(t) ((unsigned long) (t) >> (W_TYPE_SIZE / 2))
  25
  26 /* If we still don't have umul_ppmm, define it using plain C.  */
  27 #if !defined(umul_ppmm)
  28 #define umul_ppmm(w1, w0, u, v)                                         \
  29         do {                                                            \
  30                 unsigned long __x0, __x1, __x2, __x3;                   \
  31                 unsigned short __ul, __vl, __uh, __vh;                  \
  32                                                                         \
  33                 __ul = __ll_lowpart(u);                                 \
  34                 __uh = __ll_highpart(u);                                \
  35                 __vl = __ll_lowpart(v);                                 \
  36                 __vh = __ll_highpart(v);                                \
  37                                                                         \
  38                 __x0 = (unsigned long) __ul * __vl;                     \
  39                 __x1 = (unsigned long) __ul * __vh;                     \
  40                 __x2 = (unsigned long) __uh * __vl;                     \
  41                 __x3 = (unsigned long) __uh * __vh;                     \
  42                                                                         \
  43                 __x1 += __ll_highpart(__x0); /* this can't give carry */\
  44                 __x1 += __x2; /* but this indeed can */                 \
  45                 if (__x1 < __x2) /* did we get it? */                   \
  46                 __x3 += __ll_B; /* yes, add it in the proper pos */     \
  47                                                                         \
  48                 (w1) = __x3 + __ll_highpart(__x1);                      \
  49                 (w0) = __ll_lowpart(__x1) * __ll_B + __ll_lowpart(__x0);\
  50         } while (0)
  51 #endif
  52
  53 #if !defined(__umulsidi3)
  54 #define __umulsidi3(u, v) ({                            \
  55         DWunion __w;                                    \
  56         umul_ppmm(__w.s.high, __w.s.low, u, v);         \
  57         __w.ll;                                         \
  58         })
  59 #endif
  60
  61 long long notrace __muldi3(long long u, long long v)
  62 {
  63         const DWunion uu = {.ll = u};
  64         const DWunion vv = {.ll = v};
  65         DWunion w = {.ll = __umulsidi3(uu.s.low, vv.s.low)};
  66
  67         w.s.high += ((unsigned long) uu.s.low * (unsigned long) vv.s.high
  68                 + (unsigned long) uu.s.high * (unsigned long) vv.s.low);
  69
  70         return w.ll;
  71 }
  72 EXPORT_SYMBOL(__muldi3);