[firtool] Move 1st DropName to after CSE. Delete 2nd DropName pass. (#…

…4928)

This reduces entire execution time by 2~3%.

tools/firtool/firtool.cpp

@@ -525,14 +525,13 @@ static LogicalResult processBuffer(
 
   pm.nest<firrtl::CircuitOp>().addPass(firrtl::createLowerIntrinsicsPass());
 
-  // TODO: Move this to the O1 pipeline.
-  pm.nest<firrtl::CircuitOp>().nest<firrtl::FModuleOp>().addPass(
-      firrtl::createDropNamesPass(preserveMode));
-
   if (!disableOptimization)
     pm.nest<firrtl::CircuitOp>().nest<firrtl::FModuleOp>().addPass(
         createCSEPass());
 
+  pm.nest<firrtl::CircuitOp>().nest<firrtl::FModuleOp>().addPass(
+      firrtl::createDropNamesPass(preserveMode));
+
   pm.nest<firrtl::CircuitOp>().addPass(firrtl::createInjectDUTHierarchyPass());
 
   pm.nest<firrtl::CircuitOp>().nest<firrtl::FModuleOp>().addPass(
@@ -639,9 +638,6 @@ static LogicalResult processBuffer(
   pm.nest<firrtl::CircuitOp>().addPass(
       firrtl::createBlackBoxReaderPass(blackBoxRoot));
 
-  pm.nest<firrtl::CircuitOp>().nest<firrtl::FModuleOp>().addPass(
-      firrtl::createDropNamesPass(preserveMode));
-
   // Run SymbolDCE as late as possible, but before InnerSymbolDCE. This is for
   // hierpathop's and just for general cleanup.
   pm.addNestedPass<firrtl::CircuitOp>(mlir::createSymbolDCEPass());