Merge pull request #345 from The-OpenROAD-Project-staging/sta_statetable_mbff_regression

Restore statetable check in hasSequentials and add MBFF regression test

Author: maliberty

liberty/Liberty.cc

@@ -1489,7 +1489,8 @@ LibertyCell::outputPortSequential(LibertyPort *port)
 bool
 LibertyCell::hasSequentials() const
 {
-  return !sequentials_.empty();
+  return !sequentials_.empty()
+    || statetable_ != nullptr;
 }
 
 void
@@ -2477,10 +2478,8 @@ bool
 LibertyPort::less(const LibertyPort *port1,
                   const LibertyPort *port2)
 {
-  if (port1 == nullptr && port2 != nullptr)
-    return true;
-  if (port1 != nullptr && port2 == nullptr)
-    return false;
+  if (port1 == nullptr || port2 == nullptr)
+    return port1 == nullptr && port2 != nullptr;
   const std::string &name1 = port1->name();
   const std::string &name2 = port2->name();
   if (name1 == name2) {

liberty/test/cpp/TestLibertyStaCallbacks.cc

@@ -4308,4 +4308,52 @@ library(test_r11_ccs) {
   }() ));
 }
 
+// Regression: hasSequentials must return true for cells that define
+// sequential behavior via a statetable group (no ff/latch).
+// Multi-bit flip-flops (MBFFs) and clock-gated cells commonly use
+// statetable instead of ff/latch groups.  Without the statetable_
+// check in hasSequentials(), these cells are misclassified as
+// combinational — breaking power categorization, resizer guards,
+// and dbSta cell-type mapping.
+TEST_F(StaLibertyTest, HasSequentialsStatetableMBFF) {
+  const char *content = R"(
+library(test_mbff_statetable) {
+  delay_model : table_lookup ;
+  time_unit : "1ns" ;
+  voltage_unit : "1V" ;
+  current_unit : "1mA" ;
+  capacitive_load_unit(1, ff) ;
+  cell(MBFF2) {
+    area : 6.0 ;
+    pin(D0) { direction : input ; capacitance : 0.01 ; }
+    pin(D1) { direction : input ; capacitance : 0.01 ; }
+    pin(CLK) { direction : input ; capacitance : 0.01 ; clock : true ; }
+    pin(Q0) { direction : output ; function : "IQ0" ; }
+    pin(Q1) { direction : output ; function : "IQ1" ; }
+    statetable("D0 D1 CLK", "IQ0 IQ1") {
+      table : "- - ~R : - - : N N ,\
+               H - R  : - - : H N ,\
+               L - R  : - - : L N ,\
+               - H R  : - - : N H ,\
+               - L R  : - - : N L" ;
+    }
+  }
+}
+)";
+  LibertyLibrary *lib = writeAndReadLibReturn(sta_, content);
+  ASSERT_NE(lib, nullptr);
+  LibertyCell *mbff = lib->findLibertyCell("MBFF2");
+  ASSERT_NE(mbff, nullptr);
+
+  // The cell has no ff/latch group, so sequentials_ is empty.
+  EXPECT_TRUE(mbff->sequentials().empty());
+  // But it has a statetable, so it IS sequential.
+  EXPECT_NE(mbff->statetable(), nullptr);
+  // hasSequentials() must return true for statetable-only cells.
+  EXPECT_TRUE(mbff->hasSequentials())
+    << "MBFF2 uses statetable (no ff/latch) but hasSequentials() "
+       "returned false — statetable cells are misclassified as "
+       "combinational";
+}
+
 } // namespace sta