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Fix constant CA delays to support two/three values.

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This patch fixes the code generator to correctly create three value
constant delays. It also fixes a bug in the compiler related to the
precalculation of the high-Z delay when only two delays are given.
Previously if was using a pointer not a value comparison to find
the minimum value.

Variable delays should work when one or three values are given.
For the two value case we need to do a comparison at run time and
that will require changing the compiler/run time interface so that
can only go into the V0.10 branch. This patch can be applied to
both development and V0.9. I have added a sorry message and an
assert for this case. I will add the variable two delay case at a
later time. We also do not support mixing constant and variable
delays on a single statement. That is a much bigger change and
can wait until someone asks for it.
(cherry picked from commit b1cb80b32e)
This commit is contained in:
Cary R
2009-04-05 13:58:22 -07:00
committed by Stephen Williams
parent 682e54841c
commit ec809c9137
4 changed files with 38 additions and 15 deletions
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PDelays.cc
+20 -6
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@@ -119,6 +119,20 @@ static NetExpr* make_delay_nets(Design*des, NetScope*scope, NetExpr*expr)
return expr;
}
static NetExpr* calc_decay_time(NetExpr *rise, NetExpr *fall)
{
NetEConst *c_rise = dynamic_cast<NetEConst*>(rise);
NetEConst *c_fall = dynamic_cast<NetEConst*>(fall);
if (c_rise && c_fall) {
if (c_rise->value() < c_fall->value()) return rise;
else return fall;
}
cerr << fall->get_fileline() << ": sorry: can not calculate the "
<< "decay time from " << *rise << " and " << *fall << endl;
return 0;
}
void PDelays::eval_delays(Design*des, NetScope*scope,
NetExpr*&rise_time,
NetExpr*&fall_time,
@@ -140,14 +154,14 @@ void PDelays::eval_delays(Design*des, NetScope*scope,
if (delay_[2]) {
decay_time = calculate_val(des, scope, delay_[2]);
if (as_nets_flag)
decay_time = make_delay_nets(des, scope, decay_time);
if (as_nets_flag)
decay_time = make_delay_nets(des, scope,
decay_time);
} else {
if (rise_time < fall_time)
decay_time = rise_time;
else
decay_time = fall_time;
// If this is zero then we need to do the min()
// at run time.
decay_time = calc_decay_time(rise_time, fall_time);
}
} else {
assert(delay_[2] == 0);