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rsz: preserve buffers on hierarchical module boundaries in canRemoveBuffer #10985

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rsz: preserve buffers on hierarchical module boundaries in canRemoveBuffer #10985

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8 changes: 7 additions & 1 deletion src/rsz/src/Resizer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -2782,6 +2782,11 @@ bool Resizer::canRemoveBuffer(sta::Instance* buffer,
sta::Pin* output_pin = db_network_->findPin(buffer, output_port);
sta::Net* input_net = db_network_->net(input_pin);
sta::Net* output_net = db_network_->net(output_pin);
odb::dbModNet* input_modnet = db_network_->hierNet(input_pin);
odb::dbModNet* output_modnet = db_network_->hierNet(output_pin);
if (input_modnet != output_modnet) {
return false;
}
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odb::dbNet* input_db_net = db_network_->findFlatDbNet(input_net);
odb::dbNet* output_db_net = db_network_->findFlatDbNet(output_net);
if ((input_db_net != nullptr && input_db_net->isDoNotTouch())
Expand Down Expand Up @@ -2902,7 +2907,8 @@ bool Resizer::removeBuffer(sta::Instance* buffer)

sta_->disconnectPin(input_pin);
sta_->disconnectPin(output_pin);
if (survivor_modnet != nullptr && removed_modnet != nullptr) {
if (survivor_modnet != nullptr && removed_modnet != nullptr
&& survivor_modnet != removed_modnet) {
survivor_modnet->mergeModNet(removed_modnet);
} else if (survivor_modnet != nullptr) {
Comment on lines +2910 to 2913

@gemini-code-assist gemini-code-assist Bot Jul 25, 2026

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medium

If survivor_modnet == removed_modnet (and both are non-null), the current condition survivor_modnet != removed_modnet evaluates to false. This causes the execution to fall through to the else if (survivor_modnet != nullptr) branch, which will then execute survivor_modnet->connectTermsOf(db_removed). Since both nets are already part of the same hierarchical module net, calling connectTermsOf is redundant and potentially problematic.

Nesting the inequality check inside the if (survivor_modnet != nullptr && removed_modnet != nullptr) block avoids falling through to the else if branches when both modnets are identical.

  if (survivor_modnet != nullptr && removed_modnet != nullptr) {
    if (survivor_modnet != removed_modnet) {
      survivor_modnet->mergeModNet(removed_modnet);
    }
  } else if (survivor_modnet != nullptr) {

survivor_modnet->connectTermsOf(db_removed);
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