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Allow ternary result to be padded to result width.

This commit is contained in:
steve 2000-05-03 21:21:36 +00:00
parent ed5e587cf1
commit 0a70a8a954
1 changed files with 46 additions and 6 deletions
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52
elab_net.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: elab_net.cc,v 1.32 2000/05/02 03:13:31 steve Exp $"
#ident "$Id: elab_net.cc,v 1.33 2000/05/03 21:21:36 steve Exp $"
#endif
# include "PExpr.h"
@ -1221,7 +1221,17 @@ NetNet* PENumber::elaborate_net(Design*des, const string&path,
/*
* Elaborate the ternary operator in a netlist by creating a LPM_MUX
* with width matching the result, size == 2 and 1 select input.
* with width matching the result, size == 2 and 1 select input. These
* expressions come from code like:
*
* res = test ? a : b;
*
* The res has the width requested of this method, and the a and b
* expressions have their own similar widths. The test expression is
* only a single bit wide. The output from this function is a NetNet
* object the width of the <res> expression and connected to the
* Result pins of the LPM_MUX device. Any width not covered by the
* width of the mux is padded with a NetConst device.
*/
NetNet* PETernary::elaborate_net(Design*des, const string&path,
unsigned width,
@ -1241,22 +1251,49 @@ NetNet* PETernary::elaborate_net(Design*des, const string&path,
}
assert(tru_sig->pin_count() == fal_sig->pin_count());
assert(width == tru_sig->pin_count());
if (width == 0)
width = tru_sig->pin_count();
assert(width >= tru_sig->pin_count());
assert(expr_sig->pin_count() == 1);
/* This is the width of the LPM_MUX device that I'm about to
create. It may be smaller then the desired output, but I'll
handle padding below.
Create a NetNet object wide enough to hold the result. */
unsigned dwidth = tru_sig->pin_count();
NetNet*sig = new NetNet(scope, des->local_symbol(path), NetNet::WIRE,
tru_sig->pin_count());
width);
sig->local_flag(true);
NetMux*mux = new NetMux(des->local_symbol(path), width, 2, 1);
/* Make the device and connect its outputs to the osig and
inputs to the tru and false case nets. Also connect the
selector bit to the sel input. */
NetMux*mux = new NetMux(des->local_symbol(path), dwidth, 2, 1);
connect(mux->pin_Sel(0), expr_sig->pin(0));
for (unsigned idx = 0 ; idx < width ; idx += 1) {
for (unsigned idx = 0 ; idx < dwidth ; idx += 1) {
connect(mux->pin_Result(idx), sig->pin(idx));
connect(mux->pin_Data(idx,0), fal_sig->pin(idx));
connect(mux->pin_Data(idx,1), tru_sig->pin(idx));
}
/* If the device is too narrow to fill out the desired result,
pad with zeros by creating a NetConst device. */
if (dwidth < width) {
verinum vpad (verinum::V0, width-dwidth);
NetConst*pad = new NetConst(des->local_symbol(path), vpad);
des->add_node(pad);
for (unsigned idx = dwidth ; idx < width ; idx += 1)
connect(sig->pin(idx), pad->pin(idx-dwidth));
}
des->add_node(mux);
return sig;
@ -1410,6 +1447,9 @@ NetNet* PEUnary::elaborate_net(Design*des, const string&path,
/*
* $Log: elab_net.cc,v $
* Revision 1.33 2000/05/03 21:21:36 steve
* Allow ternary result to be padded to result width.
*
* Revision 1.32 2000/05/02 03:13:31 steve
* Move memories to the NetScope object.
*