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Handle wait with constant-false expression.

This commit is contained in:
steve 2004-05-25 03:42:58 +00:00
parent 559f73c135
commit 55ba131997
1 changed files with 36 additions and 12 deletions
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48
elaborate.cc
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@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CVS_IDENT
#ident "$Id: elaborate.cc,v 1.300 2004/03/08 00:47:44 steve Exp $"
#ident "$Id: elaborate.cc,v 1.301 2004/05/25 03:42:58 steve Exp $"
#endif
# include "config.h"
@ -2022,8 +2022,8 @@ NetProc* PEventStatement::elaborate_wait(Design*des, NetScope*scope,
}
// If the condition expression is more then 1 bits, then
// generate a comparison operator to get the result down to
// one bit. Turn <e> into |<e>;
// generate a reduction operator to get the result down to
// one bit. In other words, Turn <e> into |<e>;
if (expr->expr_width() < 1) {
cerr << get_line() << ": internal error: "
@ -2037,30 +2037,51 @@ NetProc* PEventStatement::elaborate_wait(Design*des, NetScope*scope,
expr = cmp;
}
assert(expr->expr_width() == 1);
expr = new NetEBComp('N', expr, new NetEConst(verinum(verinum::V1)));
NetExpr*tmp = expr->eval_tree();
if (tmp) {
delete expr;
expr = tmp;
}
/* Detect the unusual case that the wait expression is
constant. Constant true is OK (it becomes transparent) but
constant false is almost certainly not what is intended. */
assert(expr->expr_width() == 1);
if (NetEConst*ce = dynamic_cast<NetEConst*>(expr)) {
verinum val = ce->value();
assert(val.len() == 1);
/* Constant true -- wait(1) <s1> reduces to <s1>. */
if (val[0] == verinum::V1) {
delete expr;
assert(enet);
return enet;
}
/* Otherwise, false. wait(0) blocks permanently. */
cerr << get_line() << ": warning: wait expression is "
<< "constant false." << endl;
cerr << get_line() << ": : The statement will "
<< "block permanently." << endl;
/* Create an event wait and an otherwise unreferenced
event variable to force a perpetual wait. */
NetEvent*wait_event = new NetEvent(scope->local_symbol());
scope->add_event(wait_event);
NetEvWait*wait = new NetEvWait(0);
wait->add_event(wait_event);
wait->set_line(*this);
delete expr;
delete enet;
return wait;
}
/* Invert the sense of the test with an exclusive NOR. In
other words, if this adjusted expression returns TRUE, then
wait. */
assert(expr->expr_width() == 1);
expr = new NetEBComp('N', expr, new NetEConst(verinum(verinum::V1)));
NetExpr*tmp = expr->eval_tree();
if (tmp) {
delete expr;
expr = tmp;
}
NetEvent*wait_event = new NetEvent(scope->local_symbol());
@ -2102,7 +2123,7 @@ NetProc* PEventStatement::elaborate_wait(Design*des, NetScope*scope,
if (enet == 0)
return loop;
/* Create a sequential block to conbine the wait loop and the
/* Create a sequential block to combine the wait loop and the
delayed statement. */
NetBlock*block = new NetBlock(NetBlock::SEQU, 0);
block->append(loop);
@ -2679,6 +2700,9 @@ Design* elaborate(list<perm_string>roots)
/*
* $Log: elaborate.cc,v $
* Revision 1.301 2004/05/25 03:42:58 steve
* Handle wait with constant-false expression.
*
* Revision 1.300 2004/03/08 00:47:44 steve
* primitive ports can bind bi name.
*