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rsz: add inverter-pair insertion to the Rebuffer DP #10597

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rsz: add inverter-pair insertion to the Rebuffer DP #10597

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3ef777d
rsz: add experimental inverter-pair insertion to Rebuffer DP
minjukim55 Jun 4, 2026
2378954
rsz: address inverter-pair review findings (drive-check, cap-order, g…
minjukim55 Jun 5, 2026
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6 changes: 6 additions & 0 deletions src/rsz/include/rsz/Resizer.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -215,6 +215,9 @@ class Resizer : public sta::dbStaState, public sta::dbNetworkObserver
sta::VertexSeq orderedLoadPinVertices();

void setDontUse(sta::LibertyCell* cell, bool dont_use);
void setInverterPairEnabled(bool enable);
bool isInverterPairEnabled() const { return inverter_pair_enabled_; }
const sta::LibertyCellSeq& inverterCells() const { return inverter_cells_; }
void resetDontUse();
bool dontUse(const sta::LibertyCell* cell);
bool isLinkCell(sta::LibertyCell* cell) const;
Expand Down Expand Up @@ -592,6 +595,7 @@ class Resizer : public sta::dbStaState, public sta::dbNetworkObserver
void findBuffers();
void findBuffersNoPruning();
void findFastBuffers();
void findInverters();
static MoveType moveTypeFromString(const std::string& str);
sta::LibertyCell* selectBufferCell(sta::LibertyCell* buffer_cell = nullptr);
void findTargetLoads();
Expand Down Expand Up @@ -933,6 +937,8 @@ class Resizer : public sta::dbStaState, public sta::dbNetworkObserver
sta::LibertyCellSeq buffer_cells_;
sta::LibertyCell* buffer_lowest_drive_ = nullptr;
std::unordered_set<sta::LibertyCell*> buffer_fast_sizes_;
sta::LibertyCellSeq inverter_cells_;
bool inverter_pair_enabled_ = false;
// Buffer list created by CTS kept here so that we use the
// exact same buffers when reparing clock nets.
sta::LibertyCellSeq clk_buffers_;
Expand Down
11 changes: 10 additions & 1 deletion src/rsz/src/BufferedNet.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,8 @@ BufferedNet::BufferedNet(const BufferedNetType type,
max_load_slew_ = min(ref->maxLoadSlew(), ref2->maxLoadSlew());

area_ = ref->area() + ref2->area();

parity_ = ref->parity();
}

// wire
Expand Down Expand Up @@ -181,6 +183,8 @@ BufferedNet::BufferedNet(const BufferedNetType type,
max_load_slew_ = ref->maxLoadSlew();

area_ = ref->area();

parity_ = ref->parity();
}

// via
Expand Down Expand Up @@ -208,6 +212,8 @@ BufferedNet::BufferedNet(const BufferedNetType type,
max_load_slew_ = ref->maxLoadSlew();

area_ = ref->area();

parity_ = ref->parity();
}

// buffer
Expand Down Expand Up @@ -237,6 +243,8 @@ BufferedNet::BufferedNet(const BufferedNetType type,
max_load_slew_ = resizer->maxInputSlew(input, corner);

area_ = ref->area() + buffer_cell_->area();

parity_ = buffer_cell->isInverter() ? (ref->parity() ^ 1) : ref->parity();
}

void BufferedNet::reportTree(const Resizer* resizer) const
Expand Down Expand Up @@ -1178,7 +1186,8 @@ bool BufferedNet::fitsEnvelope(Metrics target)
return maxLoadWireLength() <= target.max_load_wl && slack() >= target.slack
&& sta::fuzzyLessEqual(cap(), target.cap)
&& sta::fuzzyGreaterEqual(maxLoadSlew(), target.max_load_slew)
&& sta::fuzzyLessEqual(fanout(), target.fanout);
&& sta::fuzzyLessEqual(fanout(), target.fanout)
&& parity() == target.parity;
}

} // namespace rsz
9 changes: 8 additions & 1 deletion src/rsz/src/BufferedNet.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,9 @@ class BufferedNet
// repairNet
int maxLoadWireLength() const;

// Inverter count to loads, mod 2 (0 = polarity preserved).
int parity() const { return parity_; }

// Rebuffer
const sta::RiseFallBoth* slackTransition() const
{
Expand Down Expand Up @@ -222,6 +225,7 @@ class BufferedNet
float cap;
float max_load_slew;
float fanout;
int parity = 0;

Metrics withMaxLoadWl(int max_load_wl)
{
Expand Down Expand Up @@ -251,7 +255,8 @@ class BufferedNet
.slack = slack(),
.cap = cap(),
.max_load_slew = maxLoadSlew(),
.fanout = fanout()};
.fanout = fanout(),
.parity = parity()};
}

bool fitsEnvelope(Metrics target);
Expand Down Expand Up @@ -295,6 +300,8 @@ class BufferedNet
// Delay from driver pin to here
FixedDelay arrival_delay_ = FixedDelay::ZERO;

int8_t parity_ = 0;

const sta::Scene* corner_ = nullptr;
};

Expand Down
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