rsz: add user_function_class filter to swappable cells

Signed-off-by: Arthur Koucher <[email protected]>

src/rsz/include/rsz/Resizer.hh

@@ -477,7 +477,6 @@ class Resizer : public dbStaState
 
   void resizePreamble();
   LibertyCellSeq getSwappableCells(LibertyCell* source_cell);
-  bool footprintsMatch(LibertyCell* source, LibertyCell* target);
 
   // Resize drvr_pin instance to target slew.
   // Return 1 if resized.

src/rsz/src/Resizer.cc

@@ -1014,15 +1014,32 @@ void Resizer::resizePreamble()
 // Filter equivalent cells based on the following liberty attributes:
 // - Footprint (Optional - Honored if enforced by user): Cells with the
 //   same footprint have the same layout boundary.
+// - User Function Class (Optional - Honored if found): Cells with the
+//   same user_function_class are electrically compatible.
 LibertyCellSeq Resizer::getSwappableCells(LibertyCell* source_cell)
 {
   LibertyCellSeq swappable_cells;
   LibertyCellSeq* equiv_cells = sta_->equivCells(source_cell);
 
   if (equiv_cells) {
     for (LibertyCell* equiv_cell : *equiv_cells) {
-      if (match_cell_footprint_ && !footprintsMatch(source_cell, equiv_cell)) {
-        continue;
+      if (match_cell_footprint_) {
+        const bool footprints_match = sta::stringEqIf(source_cell->footprint(),
+                                                      equiv_cell->footprint());
+        if (!footprints_match) {
+          continue;
+        }
+      }
+
+      if (source_cell->userFunctionClass()) {
+        // Don't use stringEqIf to avoid a reduntant nullptr check.
+        // Here, we assume that the equivalent cell will also have
+        // a user_function_class attribute.
+        const bool user_function_classes_match = sta::stringEqual(
+            source_cell->userFunctionClass(), equiv_cell->userFunctionClass());
+        if (!user_function_classes_match) {
+          continue;
+        }
       }
 
       swappable_cells.push_back(equiv_cell);
@@ -1032,11 +1049,6 @@ LibertyCellSeq Resizer::getSwappableCells(LibertyCell* source_cell)
   return swappable_cells;
 }
 
-bool Resizer::footprintsMatch(LibertyCell* source, LibertyCell* target)
-{
-  return sta::stringEqIf(source->footprint(), target->footprint());
-}
-
 void Resizer::checkLibertyForAllCorners()
 {
   for (Corner* corner : *sta_->corners()) {