libgcc/config/riscv/multi3.c

   1 /* Multiplication two double word integers for RISC-V.
   2
   3    Copyright (C) 2016-2017 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 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 #include "tconfig.h"
  27 #include "tsystem.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "libgcc_tm.h"
  31 #define LIBGCC2_UNITS_PER_WORD (__riscv_xlen / 8)
  32
  33 #include "libgcc2.h"
  34
  35 #if __riscv_xlen == 32
  36 /* Our RV64 64-bit routines are equivalent to our RV32 32-bit routines.  */
  37 # define __multi3 __muldi3
  38 #endif
  39
  40 DWtype
  41 __multi3 (DWtype u, DWtype v)
  42 {
  43   const DWunion uu = {.ll = u};
  44   const DWunion vv = {.ll = v};
  45   DWunion w;
  46   UWtype u_low = uu.s.low;
  47   UWtype v_low = vv.s.low;
  48   UWtype u_low_msb;
  49   UWtype w_low = 0;
  50   UWtype new_w_low;
  51   UWtype w_high = 0;
  52   UWtype w_high_tmp = 0;
  53   UWtype w_high_tmp2x;
  54   UWtype carry;
  55
  56   /* Calculate low half part of u and v, and get a UDWtype result just like
  57      what __umulsidi3 do.  */
  58   do
  59     {
  60       new_w_low = w_low + u_low;
  61       w_high_tmp2x = w_high_tmp << 1;
  62       w_high_tmp += w_high;
  63       if (v_low & 1)
  64         {
  65           carry = new_w_low < w_low;
  66           w_low = new_w_low;
  67           w_high = carry + w_high_tmp;
  68         }
  69       u_low_msb = (u_low >> ((sizeof (UWtype) * 8) - 1));
  70       v_low >>= 1;
  71       u_low <<= 1;
  72       w_high_tmp = u_low_msb | w_high_tmp2x;
  73     }
  74   while (v_low);
  75
  76   w.s.low = w_low;
  77   w.s.high = w_high;
  78
  79   if (uu.s.high)
  80     w.s.high = w.s.high + __muluw3(vv.s.low, uu.s.high);
  81
  82   if (vv.s.high)
  83     w.s.high += __muluw3(uu.s.low, vv.s.high);
  84
  85   return w.ll;
  86 }