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Comments about xor evaluation.

This commit is contained in:
steve 2002-02-03 00:06:28 +00:00
parent 54dab22042
commit 78bb3d6f09
1 changed files with 10 additions and 5 deletions
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15
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 1.31 2001/12/31 01:56:08 steve Exp $"
#ident "$Id: cprop.cc,v 1.32 2002/02/03 00:06:28 steve Exp $"
#endif
# include "config.h"
@ -583,7 +583,10 @@ void cprop_functor::lpm_logic(Design*des, NetLogic*obj)
unsigned idx = 1;
/* Eliminate all the 0 inputs. They have no effect
on the output of an XOR gate. */
on the output of an XOR gate. The eliminate works
by unlinking the current input and relinking the
last input to this position. It's like bubbling
all the 0 inputs to the end. */
while (idx < top) {
if (! link_drivers_constant(obj->pin(idx))) {
idx += 1;
@ -651,7 +654,7 @@ void cprop_functor::lpm_logic(Design*des, NetLogic*obj)
}
/* If all the inputs were eliminated, then replace
the gate with a constant 0 and I am done. */
the gate with a constant value and I am done. */
if (top == 1) {
verinum::V out = obj->type()==NetLogic::XNOR
? verinum::V1
@ -887,7 +890,7 @@ void cprop_dc_functor::lpm_const(Design*des, NetConst*obj)
return;
// Look for signals that have NetESignal nodes attached to
// them. If I find any, this this constant is used by a
// them. If I find any, then this constant is used by a
// behavioral expression somewhere.
for (unsigned idx = 0 ; idx < obj->pin_count() ; idx += 1) {
Nexus*nex = obj->pin(idx).nexus();
@ -920,7 +923,6 @@ void cprop_dc_functor::lpm_const(Design*des, NetConst*obj)
}
}
// Done. Delete me.
delete obj;
}
@ -942,6 +944,9 @@ void cprop(Design*des)
/*
* $Log: cprop.cc,v $
* Revision 1.32 2002/02/03 00:06:28 steve
* Comments about xor evaluation.
*
* Revision 1.31 2001/12/31 01:56:08 steve
* Get sense of 1-bit == operator right.
*