[ExportVerilog] Add lowering option to not emit version comment (#4811)

docs/VerilogGeneration.md

@@ -116,10 +116,12 @@ The current set of "style" Lowering Options is:
      For a namehint with "\_" prefix, if the term size is greater than `wireSpillingNamehintTermLimit`
      (default=3), then the expression is spilled.
  * `emitWireInPorts` (default=`false`). Emits `wire` in port lists rather than
-  relying on 'default_nettype'. For instance, instead of `input a` this option
-  would emit that port as `input wire a`.
-* `emitBindComments` (default=`false`). Emits a comment wherever an instance or
-  interface instance is not printed, because it was emitted as a bind elsewhere.
+   relying on 'default_nettype'. For instance, instead of `input a` this option
+   would emit that port as `input wire a`.
+ * `emitBindComments` (default=`false`). Emits a comment wherever an instance or
+   interface instance is not printed, because it was emitted as a bind elsewhere.
+ * `omitVersionComment` (default=`false`). Avoids emitting a version comment
+   (e.g. `// Generated by CIRCT ...`) at the top of each verilog file.
 
 The current set of "lint warnings fix" Lowering Options is:
 

include/circt/Support/LoweringOptions.h

@@ -151,6 +151,9 @@ struct LoweringOptions {
   /// If true, emit a comment wherever an instance wasn't printed, because
   /// it's emitted elsewhere as a bind.
   bool emitBindComments = false;
+
+  /// If true, do not emit a version comment at the top of each verilog file.
+  bool omitVersionComment = false;
 };
 } // namespace circt
 

lib/Conversion/ExportVerilog/ExportVerilog.cpp

@@ -5144,7 +5144,7 @@ void SharedEmitterState::collectOpsForFile(const FileInfo &file,
                                            EmissionList &thingsToEmit,
                                            bool emitHeader) {
   // Include the version string comment when the file is verilog.
-  if (file.isVerilog)
+  if (file.isVerilog && !options.omitVersionComment)
     thingsToEmit.emplace_back(circt::getCirctVersionComment());
 
   // If we're emitting replicated ops, keep track of where we are in the list.

lib/Support/LoweringOptions.cpp

@@ -113,6 +113,8 @@ void LoweringOptions::parse(StringRef text, ErrorHandlerT errorHandler) {
       emitWireInPorts = true;
     } else if (option == "emitBindComments") {
       emitBindComments = true;
+    } else if (option == "omitVersionComment") {
+      omitVersionComment = true;
     } else {
       errorHandler(llvm::Twine("unknown style option \'") + option + "\'");
       // We continue parsing options after a failure.
@@ -164,6 +166,8 @@ std::string LoweringOptions::toString() const {
     options += "emitWireInPorts,";
   if (emitBindComments)
     options += "emitBindComments,";
+  if (omitVersionComment)
+    options += "omitVersionComment,";
 
   // Remove a trailing comma if present.
   if (!options.empty()) {

test/Conversion/ExportVerilog/version-comment.mlir

@@ -0,0 +1,19 @@
+// RUN: circt-opt %s -export-verilog --split-input-file | FileCheck %s
+
+module {
+// CHECK-LABEL: Generated
+// CHECK-NEXT: module Foo(
+hw.module @Foo(%a: i1 loc("")) -> () {
+  hw.output
+}
+}
+
+// -----
+
+module attributes {circt.loweringOptions = "omitVersionComment"}{
+// CHECK-NOT: Generated
+// CHECK-LABEL: module Bar(
+hw.module @Bar() -> () {
+  hw.output
+}
+}