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elab_lval.cc
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elab_lval.cc
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/*
* Copyright (c) 2000 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
* General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CVS_IDENT
#ident "$Id: elab_lval.cc,v 1.29 2004/10/04 01:10:52 steve Exp $"
#endif
# include "config.h"
# include "PExpr.h"
# include "netlist.h"
# include "netmisc.h"
# include <iostream>
/*
* These methods generate a NetAssign_ object for the l-value of the
* assignment. This is common code for the = and <= statements.
*
* What gets generated depends on the structure of the l-value. If the
* l-value is a simple name (i.e., foo <= <value>) the the NetAssign_
* is created the width of the foo reg and connected to all the
* bits.
*
* If there is a part select (i.e., foo[3:1] <= <value>) the NetAssign_
* is made only as wide as it needs to be (3 bits in this example) and
* connected to the correct bits of foo. A constant bit select is a
* special case of the part select.
*
* If the bit-select is non-constant (i.e., foo[<expr>] = <value>) the
* NetAssign_ is made wide enough to connect to all the bits of foo,
* then the mux expression is elaborated and attached to the
* NetAssign_ node as a b_mux value. The target must interpret the
* presence of a bmux value as taking a single bit and assigning it to
* the bit selected by the bmux expression.
*
* If the l-value expression is non-trivial, but can be fully
* evaluated at compile time (meaning any bit selects are constant)
* then elaboration will make a single NetAssign_ that connects to a
* synthetic reg that in turn connects to all the proper pins of the
* l-value.
*
* This last case can turn up in statements like: {a, b[1]} = c;
* rather then create a NetAssign_ for each item in the concatenation,
* elaboration makes a single NetAssign_ and connects it up properly.
*/
/*
* The default interpretation of an l-value to a procedural assignment
* is to try to make a net elaboration, and see if the result is
* suitable for assignment.
*/
NetAssign_* PExpr::elaborate_lval(Design*des, NetScope*scope) const
{
NetNet*ll = 0;
if (ll == 0) {
cerr << get_line() << ": Assignment l-value too complex."
<< endl;
return 0;
}
NetAssign_*lv = new NetAssign_(ll);
return lv;
}
/*
* Concatenation expressions can appear as l-values. Handle them here.
*
* If adjacent l-values in the concatenation are not bit selects, then
* merge them into a single NetAssign_ object. This can happen is code
* like ``{ ...a, b, ...}''. As long as "a" and "b" do not have bit
* selects (or the bit selects are constant) we can merge the
* NetAssign_ objects.
*
* Be careful to get the bit order right. In the expression ``{a, b}''
* a is the MSB and b the LSB. Connect the LSB to the low pins of the
* NetAssign_ object.
*/
NetAssign_* PEConcat::elaborate_lval(Design*des, NetScope*scope) const
{
if (repeat_) {
cerr << get_line() << ": error: Repeat concatenations make "
"no sense in l-value expressions. I refuse." << endl;
des->errors += 1;
return 0;
}
NetAssign_*res = 0;
for (unsigned idx = 0 ; idx < parms_.count() ; idx += 1) {
if (parms_[idx] == 0) {
cerr << get_line() << ": error: Empty expressions "
<< "not allowed in concatenations." << endl;
des->errors += 1;
continue;
}
NetAssign_*tmp = parms_[idx]->elaborate_lval(des, scope);
/* If the l-value doesn't elaborate, the error was
already detected and printed. We just skip it and let
the compiler catch more errors. */
if (tmp == 0)
continue;
assert(tmp);
/* Link the new l-value to the previous one. */
NetAssign_*last = tmp;
while (last->more)
last = last->more;
last->more = res;
res = tmp;
}
return res;
}
/*
* Handle the ident as an l-value. This includes bit and part selects
* of that ident.
*/
NetAssign_* PEIdent::elaborate_lval(Design*des, NetScope*scope) const
{
NetNet* reg = 0;
NetMemory* mem = 0;
NetVariable* var = 0;
const NetExpr*par = 0;
NetEvent* eve = 0;
symbol_search(des, scope, path_, reg, mem, var, par, eve);
if (mem) {
return elaborate_mem_lval_(des, scope, mem);
}
if (var) {
NetAssign_*cur = new NetAssign_(var);
return cur;
}
if (reg == 0) {
cerr << get_line() << ": error: Could not find variable ``"
<< path_ << "'' in ``" << scope->name() <<
"''" << endl;
des->errors += 1;
return 0;
}
assert(reg);
/* Get the signal referenced by the identifier, and make sure
it is a register. (Wires are not allows in this context. */
if (reg->type() != NetNet::REG) {
cerr << get_line() << ": error: " << path_ <<
" is not a reg/integer/time in " << scope->name() <<
"." << endl;
cerr << reg->get_line() << ": : " << path_ <<
" is declared here as " << reg->type() << "." << endl;
des->errors += 1;
return 0;
}
long msb, lsb;
NetExpr*mux;
if (msb_ && lsb_) {
/* This handles part selects. In this case, there are
two bit select expressions, and both must be
constant. Evaluate them and pass the results back to
the caller. */
verinum*vl = lsb_->eval_const(des, scope);
if (vl == 0) {
cerr << lsb_->get_line() << ": error: "
"Part select expressions must be constant."
<< endl;
cerr << lsb_->get_line() << ": : This lsb expression "
"violates the rule: " << *lsb_ << endl;
des->errors += 1;
return 0;
}
verinum*vm = msb_->eval_const(des, scope);
if (vm == 0) {
cerr << msb_->get_line() << ": error: "
"Part select expressions must be constant."
<< endl;
cerr << msb_->get_line() << ": : This msb expression "
"violates the rule: " << *msb_ << endl;
des->errors += 1;
return 0;
}
msb = vm->as_long();
lsb = vl->as_long();
mux = 0;
} else if (msb_) {
/* If there is only a single select expression, it is a
bit select. Evaluate the constant value and treat it
as a part select with a bit width of 1. If the
expression it not constant, then return the
expression as a mux. */
assert(lsb_ == 0);
verinum*v = msb_->eval_const(des, scope);
if (v == 0) {
NetExpr*m = msb_->elaborate_expr(des, scope);
assert(m);
msb = 0;
lsb = 0;
mux = m;
} else {
msb = v->as_long();
lsb = v->as_long();
mux = 0;
}
} else {
/* No select expressions, so presume a part select the
width of the register. */
assert(msb_ == 0);
assert(lsb_ == 0);
msb = reg->msb();
lsb = reg->lsb();
mux = 0;
}
NetAssign_*lv;
if (mux) {
/* If there is a non-constant bit select, make a
NetAssign_ to the target reg and attach a
bmux to select the target bit. */
lv = new NetAssign_(reg);
lv->set_bmux(mux);
} else {
/* If the bit/part select is constant, then make the
NetAssign_ only as wide as it needs to be and connect
only to the selected bits of the reg. */
unsigned loff = reg->sb_to_idx(lsb);
unsigned moff = reg->sb_to_idx(msb);
unsigned wid = moff - loff + 1;
if (moff < loff) {
cerr << get_line() << ": error: part select "
<< reg->name() << "[" << msb<<":"<<lsb<<"]"
<< " is reversed." << endl;
des->errors += 1;
return 0;
}
/* If the part select extends beyond the extreme of the
variable, then report an error. Note that loff is
converted to normalized form so is relative the
variable pins. */
if ((wid + loff) > reg->pin_count()) {
cerr << get_line() << ": error: bit/part select "
<< reg->name() << "[" << msb<<":"<<lsb<<"]"
<< " is out of range." << endl;
des->errors += 1;
return 0;
}
lv = new NetAssign_(reg);
lv->set_part(loff, wid);
assert(moff < reg->pin_count());
}
return lv;
}
NetAssign_* PEIdent::elaborate_mem_lval_(Design*des, NetScope*scope,
NetMemory*mem) const
{
if (msb_ == 0) {
cerr << get_line() << ": error: Assign to memory \""
<< mem->name() << "\" requires a word select index."
<< endl;
des->errors += 1;
return 0;
}
if (msb_ && lsb_) {
cerr << get_line() << ": error: Cannot use part select on "
<< "memory \"" << mem->name() << ".\"" << endl;
des->errors += 1;
return 0;
}
assert(msb_ && !lsb_);
NetExpr*ix = msb_->elaborate_expr(des, scope);
if (ix == 0)
return 0;
/* Evaluate the memory index expression down as must as
possible. Ideally, we can get it down to a constant. */
if (! dynamic_cast<NetEConst*>(ix)) {
NetExpr*tmp = ix->eval_tree();
if (tmp) {
tmp->set_line(*ix);
delete ix;
ix = tmp;
}
}
NetAssign_*lv = new NetAssign_(mem);
lv->set_bmux(ix);
lv->set_part(0, mem->width());
return lv;
}
NetAssign_* PENumber::elaborate_lval(Design*des, NetScope*) const
{
cerr << get_line() << ": error: Constant values not allowed "
<< "in l-value expressions." << endl;
des->errors += 1;
return 0;
}
/*
* $Log: elab_lval.cc,v $
* Revision 1.29 2004/10/04 01:10:52 steve
* Clean up spurious trailing white space.
*
* Revision 1.28 2004/08/28 14:59:44 steve
* More detailed error message about bad variable.
*
* Revision 1.27 2003/09/19 03:30:05 steve
* Fix name search in elab_lval.
*
* Revision 1.26 2003/01/27 05:09:17 steve
* Spelling fixes.
*
* Revision 1.25 2003/01/26 21:15:58 steve
* Rework expression parsing and elaboration to
* accommodate real/realtime values and expressions.
*
* Revision 1.24 2003/01/19 00:35:39 steve
* Detect null arguments to concatenation operator.
*
* Revision 1.23 2002/11/21 23:27:51 steve
* Precalculate indices to l-value arrays.
*
* Revision 1.22 2002/11/21 18:15:40 steve
* Fix const test of msb in assignment l-values.
*
* Revision 1.21 2002/11/02 01:10:49 steve
* Detect memories without work index in l-value.
*
* Revision 1.20 2002/08/12 01:34:58 steve
* conditional ident string using autoconfig.
*
* Revision 1.19 2002/06/04 05:38:44 steve
* Add support for memory words in l-value of
* blocking assignments, and remove the special
* NetAssignMem class.
*
* Revision 1.18 2002/03/09 04:02:26 steve
* Constant expressions are not l-values for task ports.
*
* Revision 1.17 2001/12/03 04:47:14 steve
* Parser and pform use hierarchical names as hname_t
* objects instead of encoded strings.
*
* Revision 1.16 2001/11/08 05:15:50 steve
* Remove string paths from PExpr elaboration.
*
* Revision 1.15 2001/11/07 04:01:59 steve
* eval_const uses scope instead of a string path.
*
* Revision 1.14 2001/08/25 23:50:02 steve
* Change the NetAssign_ class to refer to the signal
* instead of link into the netlist. This is faster
* and uses less space. Make the NetAssignNB carry
* the delays instead of the NetAssign_ lval objects.
*
* Change the vvp code generator to support multiple
* l-values, i.e. concatenations of part selects.
*
* Revision 1.13 2001/07/25 03:10:48 steve
* Create a config.h.in file to hold all the config
* junk, and support gcc 3.0. (Stephan Boettcher)
*
* Revision 1.12 2001/02/09 03:16:48 steve
* Report bit/part select out of range errors. (PR#133)
*
* Revision 1.11 2001/01/10 03:13:23 steve
* Build task outputs as lval instead of nets. (PR#98)
*
* Revision 1.10 2001/01/06 06:31:58 steve
* declaration initialization for time variables.
*
* Revision 1.9 2001/01/06 02:29:36 steve
* Support arrays of integers.
*
* Revision 1.8 2000/12/12 06:14:51 steve
* sorry for concatenated memories in l-values. (PR#76)
*
* Revision 1.7 2000/12/01 02:55:37 steve
* Detect part select errors on l-values.
*
* Revision 1.6 2000/10/31 17:49:02 steve
* Support time variables.
*
* Revision 1.5 2000/10/26 17:09:46 steve
* Fix handling of errors in behavioral lvalues. (PR#28)
*
* Revision 1.4 2000/09/10 15:43:59 steve
* Some error checking.
*
* Revision 1.3 2000/09/10 03:59:59 steve
* Agressively merge NetAssign_ within concatenations.
*
* Revision 1.2 2000/09/10 02:18:16 steve
* elaborate complex l-values
*
* Revision 1.1 2000/09/09 15:21:26 steve
* move lval elaboration to PExpr virtual methods.
*
*/