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Eliminate zero inputs to xor.

This commit is contained in:
steve 2000-10-06 21:26:34 +00:00
parent 02bee9358c
commit 20d07a7366
1 changed files with 54 additions and 1 deletions
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55
cprop.cc
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@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: cprop.cc,v 1.15 2000/08/02 14:48:01 steve Exp $"
#ident "$Id: cprop.cc,v 1.16 2000/10/06 21:26:34 steve Exp $"
#endif
# include "netlist.h"
@ -222,6 +222,56 @@ void cprop_functor::lpm_logic(Design*des, NetLogic*obj)
count += 1;
return;
case NetLogic::XOR: {
unsigned top = obj->pin_count();
unsigned idx = 1;
while (idx < top) {
if (! link_drivers_constant(obj->pin(idx))) {
idx += 1;
continue;
}
if (driven_value(obj->pin(idx)) == verinum::V0) {
obj->pin(idx).unlink();
top -= 1;
if (idx < top) {
connect(obj->pin(idx), obj->pin(top));
obj->pin(top).unlink();
}
} else {
idx += 1;
}
}
if (top == 2) {
NetLogic*tmp = new NetLogic(obj->name(), top,
NetLogic::BUF);
des->add_node(tmp);
tmp->pin(0).drive0(obj->pin(0).drive0());
tmp->pin(0).drive1(obj->pin(0).drive1());
connect(obj->pin(0), tmp->pin(0));
connect(obj->pin(1), tmp->pin(1));
delete obj;
count += 1;
return;
}
if (top < obj->pin_count()) {
NetLogic*tmp = new NetLogic(obj->name(), top,
NetLogic::XOR);
des->add_node(tmp);
tmp->pin(0).drive0(obj->pin(0).drive0());
tmp->pin(0).drive1(obj->pin(0).drive1());
for (unsigned idx = 0 ; idx < top ; idx += 1)
connect(tmp->pin(idx), obj->pin(idx));
delete obj;
count += 1;
return;
}
}
default:
break;
}
@ -378,6 +428,9 @@ void cprop(Design*des)
/*
* $Log: cprop.cc,v $
* Revision 1.16 2000/10/06 21:26:34 steve
* Eliminate zero inputs to xor.
*
* Revision 1.15 2000/08/02 14:48:01 steve
* use bufif0 if z is in true case of mux.
*