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latch en=1 tags 

Signed-off-by: James Cherry <cherry@parallaxsw.com>
This commit is contained in:
James Cherry 2026-03-06 18:10:20 -07:00
parent d8c0e9285b
commit 12c811a492
2 changed files with 90 additions and 59 deletions
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147
search/Latches.cc
View File

@ -323,6 +323,10 @@ Latches::latchOutArrival(const Path *data_path,
ArcDelay &arc_delay,
Arrival &q_arrival)
{
q_tag = nullptr;
arc_delay = 0.0;
q_arrival = 0.0;
Scene *scene = data_path->scene(this);
Sdc *sdc = scene->sdc();
const Mode *mode = scene->mode();
@ -337,83 +341,110 @@ Latches::latchOutArrival(const Path *data_path,
// Latch enable may be missing if library is malformed.
switch (state) {
case LatchEnableState::closed:
// Latch is disabled by constant enable.
// Latch is always closed because enable is constant.
break;
case LatchEnableState::open: {
// Latch is always open because enable is constant.
ExceptionPath *excpt = exceptionTo(data_path, nullptr);
if (!(excpt && excpt->isFalse())) {
arc_delay = search_->deratedDelay(data_vertex, d_q_arc, d_q_edge,
false, min_max, dcalc_ap, sdc);
q_arrival = data_path->arrival() + arc_delay;
q_tag = data_path->tag(this);
// Copy the data tag but remove the drprClkPath.
// Levelization does not traverse latch D->Q edges, so in some cases
// level(Q) < level(D)
// Note that
// level(crprClkPath(data)) < level(D)
// The danger is that
// level(crprClkPath(data)) == level(Q)
// or some other downstream vertex.
// This can lead to data races when finding arrivals at the same level
// use multiple threads.
// Kill the crprClklPath to be safe.
const ClkInfo *data_clk_info = data_path->clkInfo(this);
const ClkInfo *q_clk_info =
search_->findClkInfo(scene,
data_clk_info->clkEdge(),
data_clk_info->clkSrc(),
data_clk_info->isPropagated(),
data_clk_info->genClkSrc(),
data_clk_info->isGenClkSrcPath(),
data_clk_info->pulseClkSense(),
data_clk_info->insertion(),
data_clk_info->latency(),
data_clk_info->uncertainties(),
min_max, nullptr);
q_tag = search_->findTag(scene, d_q_arc->toEdge()->asRiseFall(),
min_max, q_clk_info, false,
nullptr, false, data_path->tag(this)->states(),
false, nullptr);
}
}
break;
}
case LatchEnableState::enabled: {
const MinMax *tgt_min_max = data_path->tgtClkMinMax(this);
VertexPathIterator enable_iter(enable_vertex, scene, tgt_min_max,
enable_rf, this);
while (enable_iter.hasNext()) {
Path *enable_path = enable_iter.next();
const ClkInfo *en_clk_info = enable_path->clkInfo(this);
const ClockEdge *en_clk_edge = en_clk_info->clkEdge();
if (enable_path->isClock(this)) {
ExceptionPath *excpt = exceptionTo(data_path, en_clk_edge);
// D->Q is disabled when if there is a path delay -to D or EN clk.
if (!(excpt && (excpt->isFalse()
|| excpt->isPathDelay()))) {
Path *disable_path = latchEnableOtherPath(enable_path);
Delay borrow, time_given_to_startpoint;
Arrival adjusted_data_arrival;
Required required;
latchRequired(data_path, enable_path, disable_path,
required, borrow, adjusted_data_arrival,
time_given_to_startpoint);
if (delayGreater(borrow, 0.0, this)) {
// Latch is transparent when data arrives.
arc_delay = search_->deratedDelay(data_vertex, d_q_arc, d_q_edge,
false, min_max, dcalc_ap, sdc);
q_arrival = adjusted_data_arrival + arc_delay;
// Tag switcheroo - data passing thru gets latch enable tag.
// States and path ap come from Q, everything else from enable.
Path *crpr_clk_path = crprActive(mode) ? enable_path : nullptr;
const ClkInfo *q_clk_info =
search_->findClkInfo(en_clk_info->scene(),
en_clk_edge,
en_clk_info->clkSrc(),
en_clk_info->isPropagated(),
en_clk_info->genClkSrc(),
en_clk_info->isGenClkSrcPath(),
en_clk_info->pulseClkSense(),
en_clk_info->insertion(),
en_clk_info->latency(),
en_clk_info->uncertainties(),
min_max, crpr_clk_path);
const RiseFall *q_rf = d_q_arc->toEdge()->asRiseFall();
ExceptionStateSet *states = nullptr;
// Latch data pin is a valid exception -from pin.
if (sdc->exceptionFromStates(data_path->pin(this),
data_path->transition(this),
nullptr, nullptr, // clk below
MinMax::max(), states)
// -from enable non-filter exceptions apply.
&& sdc->exceptionFromStates(enable_vertex->pin(),
enable_rf,
en_clk_edge->clock(),
en_clk_edge->transition(),
MinMax::max(), false, states))
q_tag = search_->findTag(enable_path->tag(this)->scene(),
q_rf, MinMax::max(), q_clk_info, false,
nullptr, false, states, true, nullptr);
}
return;
}
}
const ClkInfo *en_clk_info = enable_path->clkInfo(this);
const ClockEdge *en_clk_edge = en_clk_info->clkEdge();
if (enable_path->isClock(this)) {
ExceptionPath *excpt = exceptionTo(data_path, en_clk_edge);
// D->Q is disabled when if there is a path delay -to D or EN clk.
if (!(excpt && (excpt->isFalse()
|| excpt->isPathDelay()))) {
Path *disable_path = latchEnableOtherPath(enable_path);
Delay borrow, time_given_to_startpoint;
Arrival adjusted_data_arrival;
Required required;
latchRequired(data_path, enable_path, disable_path,
required, borrow, adjusted_data_arrival,
time_given_to_startpoint);
if (delayGreater(borrow, 0.0, this)) {
// Latch is transparent when data arrives.
arc_delay = search_->deratedDelay(data_vertex, d_q_arc, d_q_edge,
false, min_max, dcalc_ap, sdc);
q_arrival = adjusted_data_arrival + arc_delay;
// Tag switcheroo - data passing thru gets latch enable tag.
// States and path ap come from Q, everything else from enable.
Path *crpr_clk_path = crprActive(mode) ? enable_path : nullptr;
const ClkInfo *q_clk_info =
search_->findClkInfo(scene,
en_clk_edge,
en_clk_info->clkSrc(),
en_clk_info->isPropagated(),
en_clk_info->genClkSrc(),
en_clk_info->isGenClkSrcPath(),
en_clk_info->pulseClkSense(),
en_clk_info->insertion(),
en_clk_info->latency(),
en_clk_info->uncertainties(),
min_max, crpr_clk_path);
ExceptionStateSet *states = nullptr;
// Latch data pin is a valid exception -from pin.
if (sdc->exceptionFromStates(data_path->pin(this),
data_path->transition(this),
nullptr, nullptr, // clk below
MinMax::max(), states)
// -from enable non-filter exceptions apply.
&& sdc->exceptionFromStates(enable_vertex->pin(),
enable_rf,
en_clk_edge->clock(),
en_clk_edge->transition(),
MinMax::max(), false, states))
q_tag = search_->findTag(scene, d_q_arc->toEdge()->asRiseFall(),
MinMax::max(), q_clk_info, false,
nullptr, false, states, true, nullptr);
}
return;
}
}
}
// No enable path found.
}
break;
}
}
}
ExceptionPath *

2
search/Search.cc
View File

@ -3654,7 +3654,7 @@ RequiredVisitor::visitFromToPath(const Pin *,
const MinMax *min_max)
{
// Don't propagate required times through latch D->Q edges.
if (edge->role() != TimingRole::latchDtoQ()) {
if (!edge->role()->isLatchDtoQ()) {
debugPrint(debug_, "search", 3, " %s -> %s %s",
from_rf->shortName(),
to_rf->shortName(),