lib/muldi3.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  */
   4
   5 #include <linux/export.h>
   6 #include <linux/libgcc.h>
   7
   8 #define W_TYPE_SIZE 32
   9
  10 #define __ll_B ((unsigned long) 1 << (W_TYPE_SIZE / 2))
  11 #define __ll_lowpart(t) ((unsigned long) (t) & (__ll_B - 1))
  12 #define __ll_highpart(t) ((unsigned long) (t) >> (W_TYPE_SIZE / 2))
  13
  14 /* If we still don't have umul_ppmm, define it using plain C.  */
  15 #if !defined(umul_ppmm)
  16 #define umul_ppmm(w1, w0, u, v)                                         \
  17         do {                                                            \
  18                 unsigned long __x0, __x1, __x2, __x3;                   \
  19                 unsigned short __ul, __vl, __uh, __vh;                  \
  20                                                                         \
  21                 __ul = __ll_lowpart(u);                                 \
  22                 __uh = __ll_highpart(u);                                \
  23                 __vl = __ll_lowpart(v);                                 \
  24                 __vh = __ll_highpart(v);                                \
  25                                                                         \
  26                 __x0 = (unsigned long) __ul * __vl;                     \
  27                 __x1 = (unsigned long) __ul * __vh;                     \
  28                 __x2 = (unsigned long) __uh * __vl;                     \
  29                 __x3 = (unsigned long) __uh * __vh;                     \
  30                                                                         \
  31                 __x1 += __ll_highpart(__x0); /* this can't give carry */\
  32                 __x1 += __x2; /* but this indeed can */                 \
  33                 if (__x1 < __x2) /* did we get it? */                   \
  34                 __x3 += __ll_B; /* yes, add it in the proper pos */     \
  35                                                                         \
  36                 (w1) = __x3 + __ll_highpart(__x1);                      \
  37                 (w0) = __ll_lowpart(__x1) * __ll_B + __ll_lowpart(__x0);\
  38         } while (0)
  39 #endif
  40
  41 #if !defined(__umulsidi3)
  42 #define __umulsidi3(u, v) ({                            \
  43         DWunion __w;                                    \
  44         umul_ppmm(__w.s.high, __w.s.low, u, v);         \
  45         __w.ll;                                         \
  46         })
  47 #endif
  48
  49 long long notrace __muldi3(long long u, long long v)
  50 {
  51         const DWunion uu = {.ll = u};
  52         const DWunion vv = {.ll = v};
  53         DWunion w = {.ll = __umulsidi3(uu.s.low, vv.s.low)};
  54
  55         w.s.high += ((unsigned long) uu.s.low * (unsigned long) vv.s.high
  56                 + (unsigned long) uu.s.high * (unsigned long) vv.s.low);
  57
  58         return w.ll;
  59 }
  60 EXPORT_SYMBOL(__muldi3);