iverilog/tgt-vhdl/lpm.cc

/*
 *  VHDL code generation for LPM devices.
 *
 *  Copyright (C) 2008  Nick Gasson (nick@nickg.me.uk)
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "vhdl_target.h"

#include <iostream>
#include <cassert>

static int draw_binop_lpm(vhdl_arch *arch, ivl_lpm_t lpm, vhdl_binop_t op)
{
   vhdl_expr *lhs = nexus_to_var_ref(arch->get_scope(), ivl_lpm_data(lpm, 0));
   if (NULL == lhs)
      return 1;

   vhdl_expr *rhs = nexus_to_var_ref(arch->get_scope(), ivl_lpm_data(lpm, 1));
   if (NULL == rhs)
      return 1;

   vhdl_var_ref *out = nexus_to_var_ref(arch->get_scope(), ivl_lpm_q(lpm, 0));
   if (NULL == out)
      return 1;

   vhdl_type *result_type = new vhdl_type(*lhs->get_type());
   vhdl_expr *expr = new vhdl_binop_expr(lhs, op, rhs, result_type);

   if (op == VHDL_BINOP_MULT) {
      // Need to resize the output to the desired size,
      // as this does not happen automatically in VHDL
      
      unsigned out_width = ivl_lpm_width(lpm);
      vhdl_fcall *resize =
         new vhdl_fcall("Resize", vhdl_type::nsigned(out_width));
      resize->add_expr(expr);
      resize->add_expr(new vhdl_const_int(out_width));
      
      expr = resize;
   }

   arch->add_stmt(new vhdl_cassign_stmt(out, expr));
      
   return 0;
}

int draw_part_select_lpm(vhdl_arch *arch, ivl_lpm_t lpm)
{
   vhdl_var_ref *selfrom = nexus_to_var_ref(arch->get_scope(), ivl_lpm_data(lpm, 0));
   if (NULL == selfrom)
      return 1;

   vhdl_expr *off = NULL;
   ivl_nexus_t base = ivl_lpm_data(lpm, 1);
   if (base != NULL)
      off = nexus_to_var_ref(arch->get_scope(), base);
   else
      off = new vhdl_const_int(ivl_lpm_base(lpm));
   
   if (NULL == off)
      return 1;

   vhdl_var_ref *out = nexus_to_var_ref(arch->get_scope(), ivl_lpm_q(lpm, 0));
   if (NULL == out)
      return 1;

   // Array indexes must be integers
   vhdl_type integer(VHDL_TYPE_INTEGER);
   off = off->cast(&integer);

   selfrom->set_slice(off);
   arch->add_stmt(new vhdl_cassign_stmt(out, selfrom));
   
   return 0;
}

int draw_lpm(vhdl_arch *arch, ivl_lpm_t lpm)
{
   switch (ivl_lpm_type(lpm)) {
   case IVL_LPM_ADD:
      return draw_binop_lpm(arch, lpm, VHDL_BINOP_ADD);
   case IVL_LPM_SUB:
      return draw_binop_lpm(arch, lpm, VHDL_BINOP_SUB);
   case IVL_LPM_MULT:
      return draw_binop_lpm(arch, lpm, VHDL_BINOP_MULT);
   case IVL_LPM_PART_VP:
      return draw_part_select_lpm(arch, lpm);
   default:
      error("Unsupported LPM type: %d", ivl_lpm_type(lpm));
      return 1;
   }
}