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Handle special case of net assigned to net. 

When nets are assigned directly to a net, we need to create a driver
to carry the strength. Normally, the implied drive of a continuous
assignment is carried by whatever gate the r-value expression ends
with, but with simble net-to-net assignment, there is no net so we
need to install a BUFZ to carry the assignment.
This commit is contained in:
Stephen Williams 2008-08-12 21:03:38 -07:00
parent 6051150c14
commit 3d1f363be8
1 changed files with 29 additions and 0 deletions
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29
elaborate.cc
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@ -128,13 +128,22 @@ void PGAssign::elaborate(Design*des, NetScope*scope) const
assert(lval && rval);
assert(rval->pin_count() == 1);
// Detect the case that the rvalue-expression is a simple
// expression. In this case, we will need to create a driver
// (later) to carry strengths.
bool need_driver_flag = false;
if (dynamic_cast<NetESignal*>(rval_expr))
need_driver_flag = true;
/* Cast the right side when needed. */
if ((lval->data_type() == IVL_VT_REAL &&
rval->data_type() != IVL_VT_REAL)) {
rval = cast_to_real(des, scope, rval);
need_driver_flag = false;
} else if ((lval->data_type() != IVL_VT_REAL &&
rval->data_type() == IVL_VT_REAL)) {
rval = cast_to_int(des, scope, rval, lval->vector_width());
need_driver_flag = false;
}
/* If the r-value insists on being smaller then the l-value
@ -158,6 +167,26 @@ void PGAssign::elaborate(Design*des, NetScope*scope) const
osig->data_type(rval->data_type());
connect(osig->pin(0), tmp->pin(0));
rval = osig;
need_driver_flag = false;
}
if (need_driver_flag) {
NetBUFZ*driver = new NetBUFZ(scope, scope->local_symbol(),
rval->vector_width());
driver->set_line(*this);
des->add_node(driver);
connect(rval->pin(0), driver->pin(1));
NetNet*tmp = new NetNet(scope, scope->local_symbol(),
NetNet::WIRE, rval->vector_width());
tmp->set_line(*this);
tmp->data_type(rval->data_type());
tmp->local_flag(true);
connect(driver->pin(0), tmp->pin(0));
rval = tmp;
}
/* Set the drive and delays for the r-val. */