374 lines
11 KiB
C++
374 lines
11 KiB
C++
/*
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* Copyright (c) 2000 Stephen Williams (steve@icarus.com)
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*
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* This source code is free software; you can redistribute it
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* and/or modify it in source code form under the terms of the GNU
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* General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#ifdef HAVE_CVS_IDENT
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#ident "$Id: elab_lval.cc,v 1.20 2002/08/12 01:34:58 steve Exp $"
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#endif
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# include "config.h"
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# include "PExpr.h"
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# include "netlist.h"
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# include <iostream>
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/*
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* These methods generate a NetAssign_ object for the l-value of the
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* assignemnt. This is common code for the = and <= statements.
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*
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* What gets generated depends on the structure of the l-value. If the
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* l-value is a simple name (i.e. foo <= <value>) the the NetAssign_
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* is created the width of the foo reg and connected to all the
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* bits.
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*
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* If there is a part select (i.e. foo[3:1] <= <value>) the NetAssign_
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* is made only as wide as it needs to be (3 bits in this example) and
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* connected to the correct bits of foo. A constant bit select is a
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* special case of the part select.
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*
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* If the bit-select is non-constant (i.e. foo[<expr>] = <value>) the
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* NetAssign_ is made wide enough to connect to all the bits of foo,
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* then the mux expression is elaborated and attached to the
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* NetAssign_ node as a b_mux value. The target must interpret the
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* presense of a bmux value as taking a single bit and assigning it to
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* the bit selected by the bmux expression.
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*
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* If the l-value expression is non-trivial, but can be fully
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* evaluated at compile time (meaning any bit selects are constant)
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* then elaboration will make a single NetAssign_ that connects to a
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* synthetic reg that in turn connects to all the proper pins of the
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* l-value.
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*
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* This last case can turn up in statements like: {a, b[1]} = c;
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* rather then create a NetAssign_ for each item in the contatenation,
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* elaboration makes a single NetAssign_ and connects it up properly.
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*/
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/*
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* The default interpretation of an l-value to a procedural assignment
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* is to try to make a net elaboration, and see if the result is
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* suitable for assignment.
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*/
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NetAssign_* PExpr::elaborate_lval(Design*des, NetScope*scope) const
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{
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NetNet*ll = 0;
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if (ll == 0) {
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cerr << get_line() << ": Assignment l-value too complex."
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<< endl;
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return 0;
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}
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NetAssign_*lv = new NetAssign_(ll);
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return lv;
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}
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/*
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* Concatenation expressions can appear as l-values. Handle them here.
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*
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* If adjacent l-values in the concatenation are not bit selects, then
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* merge them into a single NetAssign_ object. This can happen is code
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* like ``{ ...a, b, ...}''. As long as "a" and "b" do not have bit
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* selects (or the bit selects are constant) we can merge the
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* NetAssign_ objects.
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*
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* Be careful to get the bit order right. In the expression ``{a, b}''
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* a is the MSB and b the LSB. Connect the LSB to the low pins of the
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* NetAssign_ object.
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*/
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NetAssign_* PEConcat::elaborate_lval(Design*des, NetScope*scope) const
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{
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if (repeat_) {
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cerr << get_line() << ": error: Repeat concatenations make "
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"no sense in l-value expressions. I refuse." << endl;
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des->errors += 1;
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return 0;
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}
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NetAssign_*res = 0;
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for (unsigned idx = 0 ; idx < parms_.count() ; idx += 1) {
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NetAssign_*tmp = parms_[idx]->elaborate_lval(des, scope);
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/* If the l-value doesn't elaborate, the error was
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already detected and printed. We just skip it and let
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the compiler catch more errors. */
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if (tmp == 0)
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continue;
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assert(tmp);
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/* Link the new l-value to the previous one. */
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NetAssign_*last = tmp;
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while (last->more)
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last = last->more;
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last->more = res;
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res = tmp;
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}
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return res;
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}
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/*
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* Handle the ident as an l-value. This includes bit and part selects
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* of that ident.
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*/
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NetAssign_* PEIdent::elaborate_lval(Design*des, NetScope*scope) const
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{
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/* Get the signal referenced by the identifier, and make sure
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it is a register. (Wires are not allows in this context. */
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NetNet*reg = des->find_signal(scope, path_);
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if (reg == 0) {
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NetMemory*mem = des->find_memory(scope, path_);
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if (mem != 0)
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return elaborate_mem_lval_(des, scope, mem);
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cerr << get_line() << ": error: Could not find variable ``"
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<< path_ << "'' in ``" << scope->name() <<
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"''" << endl;
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des->errors += 1;
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return 0;
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}
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assert(reg);
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if (reg->type() != NetNet::REG) {
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cerr << get_line() << ": error: " << path_ <<
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" is not a reg/integer/time in " << scope->name() <<
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"." << endl;
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des->errors += 1;
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return 0;
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}
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long msb, lsb;
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NetExpr*mux;
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if (msb_ && lsb_) {
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/* This handles part selects. In this case, there are
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two bit select expressions, and both must be
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constant. Evaluate them and pass the results back to
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the caller. */
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verinum*vl = lsb_->eval_const(des, scope);
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if (vl == 0) {
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cerr << lsb_->get_line() << ": error: "
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"Part select expressions must be constant: "
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<< *lsb_;
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des->errors += 1;
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return 0;
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}
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verinum*vm = msb_->eval_const(des, scope);
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if (vl == 0) {
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cerr << msb_->get_line() << ": error: "
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"Part select expressions must be constant: "
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<< *msb_;
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des->errors += 1;
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return 0;
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}
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msb = vm->as_long();
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lsb = vl->as_long();
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mux = 0;
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} else if (msb_) {
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/* If there is only a single select expression, it is a
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bit select. Evaluate the constant value and treat it
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as a part select with a bit width of 1. If the
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expression it not constant, then return the
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expression as a mux. */
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assert(lsb_ == 0);
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verinum*v = msb_->eval_const(des, scope);
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if (v == 0) {
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NetExpr*m = msb_->elaborate_expr(des, scope);
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assert(m);
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msb = 0;
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lsb = 0;
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mux = m;
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} else {
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msb = v->as_long();
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lsb = v->as_long();
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mux = 0;
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}
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} else {
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/* No select expressions, so presume a part select the
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width of the register. */
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assert(msb_ == 0);
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assert(lsb_ == 0);
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msb = reg->msb();
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lsb = reg->lsb();
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mux = 0;
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}
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NetAssign_*lv;
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if (mux) {
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/* If there is a non-constant bit select, make a
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NetAssign_ to the target reg and attach a
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bmux to select the target bit. */
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lv = new NetAssign_(reg);
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lv->set_bmux(mux);
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} else {
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/* If the bit/part select is constant, then make the
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NetAssign_ only as wide as it needs to be and connect
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only to the selected bits of the reg. */
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unsigned loff = reg->sb_to_idx(lsb);
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unsigned moff = reg->sb_to_idx(msb);
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unsigned wid = moff - loff + 1;
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if (moff < loff) {
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cerr << get_line() << ": error: part select "
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<< reg->name() << "[" << msb<<":"<<lsb<<"]"
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<< " is reversed." << endl;
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des->errors += 1;
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return 0;
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}
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/* If the part select extends beyond the extreme of the
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variable, then report an error. Note that loff is
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converted to normalized form so is relative the
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variable pins. */
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if ((wid + loff) > reg->pin_count()) {
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cerr << get_line() << ": error: bit/part select "
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<< reg->name() << "[" << msb<<":"<<lsb<<"]"
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<< " is out of range." << endl;
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des->errors += 1;
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return 0;
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}
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lv = new NetAssign_(reg);
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lv->set_part(loff, wid);
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assert(moff < reg->pin_count());
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}
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return lv;
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}
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NetAssign_* PEIdent::elaborate_mem_lval_(Design*des, NetScope*scope,
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NetMemory*mem) const
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{
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assert(msb_ && !lsb_);
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NetExpr*ix = msb_->elaborate_expr(des, scope);
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if (ix == 0)
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return 0;
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NetAssign_*lv = new NetAssign_(mem);
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lv->set_bmux(ix);
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lv->set_part(0, mem->width());
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return lv;
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}
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NetAssign_* PENumber::elaborate_lval(Design*des, NetScope*) const
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{
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cerr << get_line() << ": error: Constant values not allowed "
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<< "in l-value expressions." << endl;
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des->errors += 1;
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return 0;
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}
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/*
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* $Log: elab_lval.cc,v $
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* Revision 1.20 2002/08/12 01:34:58 steve
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* conditional ident string using autoconfig.
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*
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* Revision 1.19 2002/06/04 05:38:44 steve
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* Add support for memory words in l-value of
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* blocking assignments, and remove the special
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* NetAssignMem class.
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*
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* Revision 1.18 2002/03/09 04:02:26 steve
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* Constant expressions are not l-values for task ports.
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*
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* Revision 1.17 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 1.16 2001/11/08 05:15:50 steve
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* Remove string paths from PExpr elaboration.
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*
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* Revision 1.15 2001/11/07 04:01:59 steve
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* eval_const uses scope instead of a string path.
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*
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* Revision 1.14 2001/08/25 23:50:02 steve
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* Change the NetAssign_ class to refer to the signal
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* instead of link into the netlist. This is faster
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* and uses less space. Make the NetAssignNB carry
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* the delays instead of the NetAssign_ lval objects.
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*
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* Change the vvp code generator to support multiple
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* l-values, i.e. concatenations of part selects.
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*
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* Revision 1.13 2001/07/25 03:10:48 steve
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* Create a config.h.in file to hold all the config
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* junk, and support gcc 3.0. (Stephan Boettcher)
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*
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* Revision 1.12 2001/02/09 03:16:48 steve
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* Report bit/part select out of range errors. (PR#133)
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*
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* Revision 1.11 2001/01/10 03:13:23 steve
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* Build task outputs as lval instead of nets. (PR#98)
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*
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* Revision 1.10 2001/01/06 06:31:58 steve
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* declaration initialization for time variables.
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*
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* Revision 1.9 2001/01/06 02:29:36 steve
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* Support arrays of integers.
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*
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* Revision 1.8 2000/12/12 06:14:51 steve
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* sorry for concatenated memories in l-values. (PR#76)
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*
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* Revision 1.7 2000/12/01 02:55:37 steve
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* Detect part select errors on l-values.
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*
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* Revision 1.6 2000/10/31 17:49:02 steve
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* Support time variables.
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*
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* Revision 1.5 2000/10/26 17:09:46 steve
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* Fix handling of errors in behavioral lvalues. (PR#28)
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*
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* Revision 1.4 2000/09/10 15:43:59 steve
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* Some error checking.
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*
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* Revision 1.3 2000/09/10 03:59:59 steve
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* Agressively merge NetAssign_ within concatenations.
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*
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* Revision 1.2 2000/09/10 02:18:16 steve
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* elaborate complex l-values
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*
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* Revision 1.1 2000/09/09 15:21:26 steve
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* move lval elaboration to PExpr virtual methods.
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*
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*/
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