1  /* Multiplication two double word integers for RISC-V.
       2  
       3     Copyright (C) 2016-2023 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  }