async.cc

   1 /*
   2  * Copyright (c) 2002 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: async.cc,v 1.7 2004/01/18 23:26:54 steve Exp $"
  21 #endif
  22
  23 # include "config.h"
  24
  25 # include  "functor.h"
  26 # include  "netlist.h"
  27 # include  <assert.h>
  28
  29 bool NetAssign::is_asynchronous()
  30 {
  31       return true;
  32 }
  33
  34 bool NetCondit::is_asynchronous()
  35 {
  36       return false;
  37 }
  38
  39 /*
  40  * NetEvWait statements come from statements of the form @(...) in the
  41  * Verilog source. These event waits are considered asynchronous if
  42  * all of the events in the list are ANYEDGE, and all the inputs to
  43  * the statement are included in the sensitivity list. If any of the
  44  * events are posedge or negedge, the statement is synchronous
  45  * (i.e. an edge-triggered flip-flop) and if any of the inputs are
  46  * unaccounted for in the sensitivity list then the statement is a
  47  * latch.
  48  */
  49 bool NetEvWait::is_asynchronous()
  50 {
  51         /* The "sense" set contains the set of Nexa that are in the
  52            sensitivity list. We also require that the events are all
  53            level sensitive, but the nex_async_ method takes care of
  54            that test. */
  55       NexusSet*sense = new NexusSet;
  56       for (unsigned idx = 0 ;  idx < nevents_ ;  idx += 1) {
  57             NexusSet*tmp = event(idx)->nex_async_();
  58             if (tmp == 0) {
  59                   delete sense;
  60                   return false;
  61             }
  62
  63             sense->add(*tmp);
  64             delete tmp;
  65       }
  66
  67       NexusSet*inputs = statement_->nex_input();
  68
  69       if (! sense->contains(*inputs)) {
  70             delete sense;
  71             delete inputs;
  72             return false;
  73       }
  74
  75       delete sense;
  76       delete inputs;
  77
  78         /* If it passes all the other tests, then this statement is
  79            asynchronous. */
  80       return true;
  81 }
  82
  83 bool NetProc::is_asynchronous()
  84 {
  85       return false;
  86 }
  87
  88 bool NetProcTop::is_asynchronous()
  89 {
  90       if (type_ == NetProcTop::KINITIAL)
  91             return false;
  92
  93       return statement_->is_asynchronous();
  94 }
  95
  96 /*
  97  * $Log: async.cc,v $
  98  * Revision 1.7  2004/01/18 23:26:54  steve
  99  *  The is_combinational function really need not recurse.
 100  *
 101  * Revision 1.6  2003/12/20 00:33:39  steve
 102  *  More thorough check that NetEvWait is asynchronous.
 103  *
 104  * Revision 1.5  2003/09/04 20:28:05  steve
 105  *  Support time0 resolution of combinational threads.
 106  *
 107  * Revision 1.4  2002/08/18 22:07:16  steve
 108  *  Detect temporaries in sequential block synthesis.
 109  *
 110  * Revision 1.3  2002/08/12 01:34:58  steve
 111  *  conditional ident string using autoconfig.
 112  *
 113  * Revision 1.2  2002/07/04 00:24:16  steve
 114  *  initial statements are not asynchronous.
 115  *
 116  * Revision 1.1  2002/06/30 02:21:31  steve
 117  *  Add structure for asynchronous logic synthesis.
 118  *
 119  */
 120