Support selecting bits from parameters.
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steve
parent
c7107dc973
commit
7f8f0eb65a
78
elab_expr.cc
78
elab_expr.cc
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@ -17,7 +17,7 @@
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#if !defined(WINNT) && !defined(macintosh)
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#ident "$Id: elab_expr.cc,v 1.55 2002/04/25 05:04:31 steve Exp $"
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#ident "$Id: elab_expr.cc,v 1.56 2002/04/27 02:38:04 steve Exp $"
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#endif
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# include "config.h"
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@ -401,10 +401,57 @@ NetExpr* PEIdent::elaborate_expr(Design*des, NetScope*scope,
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tmp = new NetEParam(des, scope, path_);
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if (msb_ && lsb_) {
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cerr << get_line() << ": error: part select of "
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<< "parameter " << path_ << " in " << scope->name()
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<< " is illegal." << endl;
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des->errors += 1;
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/* If the parameter has a part select, we support
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it by pulling the right bits out and making a
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sized unsigned constant. This code assumes the
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lsb of a parameter is 0 and the msb is the
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width of the parameter. */
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verinum*lsn = lsb_->eval_const(des, scope);
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verinum*msn = msb_->eval_const(des, scope);
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if ((lsn == 0) || (msn == 0)) {
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cerr << get_line() << ": error: "
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"Part select expresions must be "
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"constant expressions." << endl;
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des->errors += 1;
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return 0;
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}
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long lsb = lsn->as_long();
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long msb = msn->as_long();
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if ((lsb < 0) || (msb < lsb)) {
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cerr << get_line() << ": error: invalid part "
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<< "select: " << path_
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<< "["<<msb<<":"<<lsb<<"]" << endl;
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des->errors += 1;
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return 0;
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}
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NetEConst*le = dynamic_cast<NetEConst*>(tmp);
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assert(le);
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verinum result (verinum::V0, msb-lsb+1, true);
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verinum exl = le->value();
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/* Pull the bits from the parameter, one at a
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time. If the bit is within the range, simply
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copy it to the result. If the bit is outside
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the range, we sign extend signed unsized
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numbers, zero extend unsigned unsigned numbers,
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and X extend sized numbers. */
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for (long idx = lsb ; idx <= msb ; idx += 1) {
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if (idx < exl.len())
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result.set(idx-lsb, exl.get(idx));
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else if (exl.has_len())
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result.set(idx-lsb, verinum::Vx);
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else if (exl.has_sign())
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result.set(idx-lsb, exl.get(exl.len()-1));
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else
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result.set(idx-lsb, verinum::V0);
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}
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delete tmp;
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tmp = new NetEConst(result);
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} else if (msb_) {
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/* Handle the case where a parameter has a bit
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@ -785,6 +832,9 @@ NetExpr* PEUnary::elaborate_expr(Design*des, NetScope*scope, bool) const
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/*
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* $Log: elab_expr.cc,v $
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* Revision 1.56 2002/04/27 02:38:04 steve
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* Support selecting bits from parameters.
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*
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* Revision 1.55 2002/04/25 05:04:31 steve
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* Evaluate constant bit select of constants.
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*
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@ -807,23 +857,5 @@ NetExpr* PEUnary::elaborate_expr(Design*des, NetScope*scope, bool) const
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*
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* Revision 1.49 2002/01/11 05:25:45 steve
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* The stime system function is 32bits.
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*
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* Revision 1.48 2001/12/31 00:08:14 steve
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* Support $signed cast of expressions.
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*
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* Revision 1.47 2001/12/29 20:41:30 steve
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* Allow escaped $ in identifiers.
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*
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* Revision 1.46 2001/12/03 04:47:14 steve
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* Parser and pform use hierarchical names as hname_t
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* objects instead of encoded strings.
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*
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* Revision 1.45 2001/11/19 02:54:12 steve
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* Handle division and modulus by zero while
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* evaluating run-time constants.
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*
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* Revision 1.44 2001/11/19 01:54:14 steve
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* Port close cropping behavior from mcrgb
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* Move window array reset to libmc.
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*/
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@ -386,8 +386,25 @@ changes in inputs until the thread that changed the inputs yields
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execution.
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$Id: ieee1364-notes.txt,v 1.10 2002/03/31 01:54:13 steve Exp $
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* BIT AND PART SELECTS OF PARAMTERS
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Bit and part selects are supposed to only be supported on vector nets
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and variables (wires, regs, etc.) However, it is common for Verilog
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compilers to also support bit and part select on parameters. Icarus
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Verilog also chooses to support bit and part selects on parameter
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names, but we need to define what that means.
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A bit or a part select on a parameter expression returns an unsigned
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value with a defined size. The parameter value is considered be a
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constant vector of bits foo[X:0]. That is, zero based. The bit and
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part selects operate from that assumption.
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$Id: ieee1364-notes.txt,v 1.11 2002/04/27 02:38:04 steve Exp $
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$Log: ieee1364-notes.txt,v $
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Revision 1.11 2002/04/27 02:38:04 steve
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Support selecting bits from parameters.
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Revision 1.10 2002/03/31 01:54:13 steve
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Notes about scheduling
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