pad_to_width.cc

   1 /*
   2  * Copyright (c) 1999-2005 Stephen Williams (steve@icarus.com)
   3  *
   4  *    This source code is free software; you can redistribute it
   5  *    and/or modify it in source code form under the terms of the GNU
   6  *    General Public License as published by the Free Software
   7  *    Foundation; either version 2 of the License, or (at your option)
   8  *    any later version.
   9  *
  10  *    This program is distributed in the hope that it will be useful,
  11  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *    GNU General Public License for more details.
  14  *
  15  *    You should have received a copy of the GNU General Public License
  16  *    along with this program; if not, write to the Free Software
  17  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  18  */
  19 #ifdef HAVE_CVS_IDENT
  20 #ident "$Id: pad_to_width.cc,v 1.20 2005/12/22 15:43:47 steve Exp $"
  21 #endif
  22
  23 # include "config.h"
  24
  25 # include  "netlist.h"
  26 # include  "netmisc.h"
  27
  28
  29 /*
  30  * This function transforms an expression by padding the high bits
  31  * with V0 until the expression has the desired width. This may mean
  32  * not transforming the expression at all, if it is already wide
  33  * enough.
  34  */
  35 NetExpr*pad_to_width(NetExpr*expr, unsigned wid)
  36 {
  37       if (wid <= expr->expr_width())
  38             return expr;
  39
  40         /* If the expression is a const, then replace it with a wider
  41            const. This is a more efficient result. */
  42       if (NetEConst*tmp = dynamic_cast<NetEConst*>(expr)) {
  43             verinum oval = pad_to_width(tmp->value(), wid);
  44             tmp = new NetEConst(oval);
  45             delete expr;
  46             return tmp;
  47       }
  48
  49       NetESelect*tmp = new NetESelect(expr, 0, wid);
  50       tmp->set_line(*expr);
  51       tmp->cast_signed(expr->has_sign());
  52       return tmp;
  53 }
  54
  55 /*
  56  * Pad a NetNet to the desired vector width by concatenating a
  57  * NetConst of constant zeros. Use a NetConcat node to do the
  58  * concatenation.
  59  */
  60 NetNet*pad_to_width(Design*des, NetNet*net, unsigned wid)
  61 {
  62       NetScope*scope = net->scope();
  63
  64       if (net->vector_width() >= wid)
  65             return net;
  66
  67         // Make the NetConcat and connect the input net to the lsb input.
  68       NetConcat*cc = new NetConcat(scope, scope->local_symbol(), wid, 2);
  69       des->add_node(cc);
  70       connect(cc->pin(1), net->pin(0));
  71
  72         // Make a NetConst of the desired width and connect in to the
  73         // lsb input of the NetConcat.
  74       verinum pad(verinum::V0, wid - net->vector_width());
  75       NetConst*con = new NetConst(scope, scope->local_symbol(), pad);
  76       des->add_node(con);
  77       connect(cc->pin(2), con->pin(0));
  78
  79         // Make a NetNet for the NetConst to NetConcat link.
  80       NetNet*tmp = new NetNet(scope, scope->local_symbol(),
  81                                NetNet::WIRE, wid - net->vector_width());
  82       tmp->data_type( net->data_type() );
  83       tmp->local_flag(true);
  84       connect(cc->pin(2), tmp->pin(0));
  85
  86         // Create a NetNet of the output width and connect it to the
  87         // NetConcat node output pin.
  88       tmp = new NetNet(scope, scope->local_symbol(),
  89                        NetNet::WIRE, wid);
  90       tmp->data_type( net->data_type() );
  91       tmp->local_flag(true);
  92       connect(cc->pin(0), tmp->pin(0));
  93
  94       return tmp;
  95 }
  96
  97 NetNet*pad_to_width_signed(Design*des, NetNet*net, unsigned wid)
  98 {
  99       NetScope*scope = net->scope();
 100
 101       if (net->vector_width() >= wid)
 102             return net;
 103
 104       NetSignExtend*se
 105             = new NetSignExtend(scope, scope->local_symbol(), wid);
 106       se->set_line(*net);
 107       des->add_node(se);
 108
 109       NetNet*tmp = new NetNet(scope, scope->local_symbol(), NetNet::WIRE, wid);
 110       tmp->set_line(*net);
 111       tmp->local_flag(true);
 112       tmp->data_type(net->data_type());
 113       tmp->set_signed(true);
 114
 115       connect(tmp->pin(0), se->pin(0));
 116       connect(se->pin(1), net->pin(0));
 117
 118       return tmp;
 119 }
 120
 121 NetNet*crop_to_width(Design*des, NetNet*net, unsigned wid)
 122 {
 123       NetScope*scope = net->scope();
 124
 125       if (net->vector_width() <= wid)
 126             return net;
 127
 128       NetPartSelect*ps = new NetPartSelect(net, 0, wid, NetPartSelect::VP);
 129       des->add_node(ps);
 130       ps->set_line(*net);
 131
 132       NetNet*tmp = new NetNet(scope, scope->local_symbol(),
 133                               NetNet::WIRE, wid);
 134       tmp->data_type(net->data_type());
 135       tmp->local_flag(true);
 136       tmp->set_line(*tmp);
 137       connect(ps->pin(0), tmp->pin(0));
 138
 139       return tmp;
 140 }
 141
 142 /*
 143  * $Log: pad_to_width.cc,v $
 144  * Revision 1.20  2005/12/22 15:43:47  steve
 145  *  pad_to_width handles signed expressions.
 146  *
 147  * Revision 1.19  2005/07/07 16:22:49  steve
 148  *  Generalize signals to carry types.
 149  *
 150  * Revision 1.18  2005/05/24 01:44:28  steve
 151  *  Do sign extension of structuran nets.
 152  *
 153  * Revision 1.17  2005/04/24 23:44:02  steve
 154  *  Update DFF support to new data flow.
 155  *
 156  * Revision 1.16  2005/01/12 03:17:37  steve
 157  *  Properly pad vector widths in pgassign.
 158  *
 159  * Revision 1.15  2004/02/18 17:11:57  steve
 160  *  Use perm_strings for named langiage items.
 161  *
 162  * Revision 1.14  2003/03/06 00:28:42  steve
 163  *  All NetObj objects have lex_string base names.
 164  *
 165  * Revision 1.13  2003/01/27 05:09:17  steve
 166  *  Spelling fixes.
 167  *
 168  * Revision 1.12  2003/01/26 21:15:59  steve
 169  *  Rework expression parsing and elaboration to
 170  *  accommodate real/realtime values and expressions.
 171  *
 172  * Revision 1.11  2002/08/12 01:35:00  steve
 173  *  conditional ident string using autoconfig.
 174  *
 175  * Revision 1.10  2002/05/25 16:43:22  steve
 176  *  Better padding of constants.
 177  *
 178  * Revision 1.9  2001/10/28 01:14:53  steve
 179  *  NetObj constructor finally requires a scope.
 180  *
 181  * Revision 1.8  2001/07/25 03:10:49  steve
 182  *  Create a config.h.in file to hold all the config
 183  *  junk, and support gcc 3.0. (Stephan Boettcher)
 184  */
 185