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Handle X values in constant == nets.

This commit is contained in:
steve 2003-04-25 05:06:32 +00:00
parent 6df92f7cca
commit 65c8722d72
1 changed files with 37 additions and 3 deletions
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40
cprop.cc
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@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CVS_IDENT
#ident "$Id: cprop.cc,v 1.43 2003/03/06 00:28:41 steve Exp $"
#ident "$Id: cprop.cc,v 1.44 2003/04/25 05:06:32 steve Exp $"
#endif
# include "config.h"
@ -155,6 +155,9 @@ void cprop_functor::lpm_compare_eq_(Design*des, NetCompare*obj)
{
NetScope*scope = obj->scope();
unsigned const_count = 0;
bool unknown_flag = false;
/* First, look for the case where constant bits on matching A
and B inputs are different. This this is so, the device can
be completely eliminated and replaced with a constant 0. */
@ -164,8 +167,21 @@ void cprop_functor::lpm_compare_eq_(Design*des, NetCompare*obj)
continue;
if (! obj->pin_DataB(idx).nexus()->drivers_constant())
continue;
if (obj->pin_DataA(idx).nexus()->driven_value() ==
obj->pin_DataB(idx).nexus()->driven_value())
const_count += 1;
verinum::V abit = obj->pin_DataA(idx).nexus()->driven_value();
verinum::V bbit = obj->pin_DataB(idx).nexus()->driven_value();
if ((abit == verinum::V0) && (bbit == verinum::V0))
continue;
if ((abit == verinum::V1) && (bbit == verinum::V1))
continue;
unknown_flag = true;
if ((abit == verinum::Vz) || (abit == verinum::Vx))
continue;
if ((bbit == verinum::Vz) || (bbit == verinum::Vx))
continue;
NetConst*zero = new NetConst(scope, obj->name(), verinum::V0);
@ -176,6 +192,21 @@ void cprop_functor::lpm_compare_eq_(Design*des, NetCompare*obj)
return;
}
/* If all the inputs are constant, then at this point the
result is either V1 or Vx. */
if (const_count == obj->width()) {
NetConst*val = new NetConst(scope, obj->name(),
unknown_flag
? verinum::Vx
: verinum::V1);
connect(val->pin(0), obj->pin_AEB());
delete obj;
des->add_node(val);
count += 1;
return;
}
/* Still may need the gate. Run through the inputs again, and
look for pairs of constants. Those inputs can be removed. */
@ -996,6 +1027,9 @@ void cprop(Design*des)
/*
* $Log: cprop.cc,v $
* Revision 1.44 2003/04/25 05:06:32 steve
* Handle X values in constant == nets.
*
* Revision 1.43 2003/03/06 00:28:41 steve
* All NetObj objects have lex_string base names.
*