[circt-verilog-lsp-server] Add Verilog Language Server

This is a first PR to add a Language Server Protocol (LSP) implementation
for Verilog/SystemVerilog using the slang frontend. This enables IDE features
like syntax error checking and diagnostics.

The server is built as circt-verilog-lsp-server and integrates with CIRCT's
existing Verilog import capabilities. It leverages MLIR's LSP server support
libraries for the protocol implementation.

cmake/modules/SlangCompilerOptions.cmake

@@ -0,0 +1,30 @@
+# slang uses exceptions
+set(LLVM_REQUIRES_EH ON)
+set(LLVM_REQUIRES_RTTI ON)
+
+# For ABI compatibility, define the DEBUG macro in debug builds. Slang sets this
+# internally. If we don't set this here as well, header-defined things like the
+# destructor of `Driver`, which is generated in ImportVerilog's compilation
+# unit, will destroy a different set of fields than what was potentially built
+# or modified by code compiled in the Slang compilation unit.
+add_compile_definitions($<$<CONFIG:Debug>:DEBUG>)
+
+# Disable some compiler warnings caused by slang headers such that the
+# `ImportVerilog` build doesn't spew out a ton of warnings that are not related
+# to CIRCT.
+if (MSVC)
+  # No idea what to put here
+else ()
+  # slang uses exceptions; we intercept these in ImportVerilog
+  add_compile_options(-fexceptions)
+  add_compile_options(-frtti)
+  # slang has some classes with virtual funcs but non-virtual destructor.
+  add_compile_options(-Wno-non-virtual-dtor)
+  # some other warnings we've seen
+  add_compile_options(-Wno-c++98-compat-extra-semi)
+  add_compile_options(-Wno-ctad-maybe-unsupported)
+  add_compile_options(-Wno-cast-qual)
+  # visitor switch statements cover all cases but have default
+  add_compile_options(-Wno-covered-switch-default)
+endif ()
+

include/circt/Tools/circt-verilog-lsp-server/CirctVerilogLspServerMain.h

@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Main entry function for circt-verilog-lsp-server for when built as standalone
+// binary.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CIRCT_TOOLS_CIRCT_VERILOG_LSP_SERVER_CIRCTVERILOGLSPSERVERMAIN_H
+#define CIRCT_TOOLS_CIRCT_VERILOG_LSP_SERVER_CIRCTVERILOGLSPSERVERMAIN_H
+#include "mlir/Support/LLVM.h"
+#include "llvm/ADT/StringRef.h"
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+namespace llvm {
+struct LogicalResult;
+} // namespace llvm
+
+namespace mlir {
+namespace lsp {
+class JSONTransport;
+} // namespace lsp
+} // namespace mlir
+
+namespace circt {
+namespace lsp {
+struct VerilogServerOptions {
+  VerilogServerOptions(const std::vector<std::string> &libDirs)
+      : libDirs(libDirs) {}
+  /// Additional list of RTL directories to search.
+  const std::vector<std::string> &libDirs;
+};
+// namespace lsp
+
+/// Implementation for tools like `circt-verilog-lsp-server`.
+llvm::LogicalResult
+CirctVerilogLspServerMain(const VerilogServerOptions &options,
+                          mlir::lsp::JSONTransport &transport);
+
+} // namespace lsp
+} // namespace circt
+
+#endif // CIRCT_TOOLS_CIRCT_VERILOG_LSP_SERVER_CIRCTVERILOGLSPSERVERMAIN_H

lib/Conversion/ImportVerilog/CMakeLists.txt

@@ -1,32 +1,4 @@
-# slang uses exceptions
-set(LLVM_REQUIRES_EH ON)
-set(LLVM_REQUIRES_RTTI ON)
-
-# For ABI compatibility, define the DEBUG macro in debug builds. Slang sets this
-# internally. If we don't set this here as well, header-defined things like the
-# destructor of `Driver`, which is generated in ImportVerilog's compilation
-# unit, will destroy a different set of fields than what was potentially built
-# or modified by code compiled in the Slang compilation unit.
-add_compile_definitions($<$<CONFIG:Debug>:DEBUG>)
-
-# Disable some compiler warnings caused by slang headers such that the
-# `ImportVerilog` build doesn't spew out a ton of warnings that are not related
-# to CIRCT.
-if (MSVC)
-  # No idea what to put here
-else ()
-  # slang uses exceptions; we intercept these in ImportVerilog
-  add_compile_options(-fexceptions)
-  add_compile_options(-frtti)
-  # slang has some classes with virtual funcs but non-virtual destructor.
-  add_compile_options(-Wno-non-virtual-dtor)
-  # some other warnings we've seen
-  add_compile_options(-Wno-c++98-compat-extra-semi)
-  add_compile_options(-Wno-ctad-maybe-unsupported)
-  add_compile_options(-Wno-cast-qual)
-  # visitor switch statements cover all cases but have default
-  add_compile_options(-Wno-covered-switch-default)
-endif ()
+include(SlangCompilerOptions)
 
 add_circt_translation_library(CIRCTImportVerilog
   Expressions.cpp

lib/Tools/CMakeLists.txt

@@ -1,3 +1,7 @@
 add_subdirectory(circt-bmc)
 add_subdirectory(circt-lec)
 add_subdirectory(rtgtool)
+
+if(CIRCT_SLANG_FRONTEND_ENABLED)
+  add_subdirectory(circt-verilog-lsp-server)
+endif()

lib/Tools/circt-verilog-lsp-server/CMakeLists.txt

@@ -0,0 +1,14 @@
+add_subdirectory(VerilogServerImpl)
+
+add_circt_library(CIRCTVerilogLspServerLib
+  CirctVerilogLspServerMain.cpp
+  LSPServer.cpp
+  LSPUtils.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/circt/Tools/crct-verilog-lsp-server
+
+  LINK_LIBS PUBLIC
+  CIRCTVerilogLspServerImpl
+  MLIRLspServerSupportLib
+)

lib/Tools/circt-verilog-lsp-server/CirctVerilogLspServerMain.cpp

@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "circt/Tools/circt-verilog-lsp-server/CirctVerilogLspServerMain.h"
+#include "LSPServer.h"
+#include "VerilogServer.h"
+#include "mlir/Tools/lsp-server-support/Transport.h"
+
+using namespace mlir;
+using namespace mlir::lsp;
+
+llvm::LogicalResult circt::lsp::CirctVerilogLspServerMain(
+    const circt::lsp::VerilogServerOptions &options,
+    mlir::lsp::JSONTransport &transport) {
+  circt::lsp::VerilogServer server(options);
+  return circt::lsp::runVerilogLSPServer(server, transport);
+}

lib/Tools/circt-verilog-lsp-server/LSPServer.cpp

@@ -0,0 +1,163 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "LSPServer.h"
+#include "VerilogServer.h"
+#include "mlir/Tools/lsp-server-support/Protocol.h"
+#include "mlir/Tools/lsp-server-support/Transport.h"
+#include <optional>
+
+#define DEBUG_TYPE "circt-verilog-lsp-server"
+
+using namespace mlir;
+using namespace mlir::lsp;
+
+//===----------------------------------------------------------------------===//
+// LSPServer
+//===----------------------------------------------------------------------===//
+
+namespace {
+struct LSPServer {
+  LSPServer(circt::lsp::VerilogServer &server, JSONTransport &transport)
+      : server(server), transport(transport) {}
+
+  //===--------------------------------------------------------------------===//
+  // Initialization
+  //===--------------------------------------------------------------------===//
+
+  void onInitialize(const InitializeParams &params,
+                    Callback<llvm::json::Value> reply);
+  void onInitialized(const InitializedParams &params);
+  void onShutdown(const NoParams &params, Callback<std::nullptr_t> reply);
+
+  //===--------------------------------------------------------------------===//
+  // Document Change
+  //===--------------------------------------------------------------------===//
+
+  void onDocumentDidOpen(const DidOpenTextDocumentParams &params);
+  void onDocumentDidClose(const DidCloseTextDocumentParams &params);
+  void onDocumentDidChange(const DidChangeTextDocumentParams &params);
+
+  //===--------------------------------------------------------------------===//
+  // Fields
+  //===--------------------------------------------------------------------===//
+
+  circt::lsp::VerilogServer &server;
+  JSONTransport &transport;
+
+  /// An outgoing notification used to send diagnostics to the client when they
+  /// are ready to be processed.
+  OutgoingNotification<PublishDiagnosticsParams> publishDiagnostics;
+
+  /// Used to indicate that the 'shutdown' request was received from the
+  /// Language Server client.
+  bool shutdownRequestReceived = false;
+};
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// Initialization
+//===----------------------------------------------------------------------===//
+
+void LSPServer::onInitialize(const InitializeParams &params,
+                             Callback<llvm::json::Value> reply) {
+  // Send a response with the capabilities of this server.
+  llvm::json::Object serverCaps{
+      {"textDocumentSync",
+       llvm::json::Object{
+           {"openClose", true},
+           {"change", (int)TextDocumentSyncKind::Incremental},
+           {"save", true},
+       }}};
+
+  llvm::json::Object result{
+      {{"serverInfo", llvm::json::Object{{"name", "circt-verilog-lsp-server"},
+                                         {"version", "0.0.1"}}},
+       {"capabilities", std::move(serverCaps)}}};
+  reply(std::move(result));
+}
+void LSPServer::onInitialized(const InitializedParams &) {}
+void LSPServer::onShutdown(const NoParams &, Callback<std::nullptr_t> reply) {
+  shutdownRequestReceived = true;
+  reply(nullptr);
+}
+
+//===----------------------------------------------------------------------===//
+// Document Change
+//===----------------------------------------------------------------------===//
+
+void LSPServer::onDocumentDidOpen(const DidOpenTextDocumentParams &params) {
+  PublishDiagnosticsParams diagParams(params.textDocument.uri,
+                                      params.textDocument.version);
+  server.addDocument(params.textDocument.uri, params.textDocument.text,
+                     params.textDocument.version, diagParams.diagnostics);
+
+  // Publish any recorded diagnostics.
+  publishDiagnostics(diagParams);
+}
+
+void LSPServer::onDocumentDidClose(const DidCloseTextDocumentParams &params) {
+  std::optional<int64_t> version =
+      server.removeDocument(params.textDocument.uri);
+  if (!version)
+    return;
+
+  // Empty out the diagnostics shown for this document. This will clear out
+  // anything currently displayed by the client for this document (e.g. in the
+  // "Problems" pane of VSCode).
+  publishDiagnostics(
+      PublishDiagnosticsParams(params.textDocument.uri, *version));
+}
+
+void LSPServer::onDocumentDidChange(const DidChangeTextDocumentParams &params) {
+  PublishDiagnosticsParams diagParams(params.textDocument.uri,
+                                      params.textDocument.version);
+  server.updateDocument(params.textDocument.uri, params.contentChanges,
+                        params.textDocument.version, diagParams.diagnostics);
+
+  // Publish any recorded diagnostics.
+  publishDiagnostics(diagParams);
+}
+
+//===----------------------------------------------------------------------===//
+// Entry Point
+//===----------------------------------------------------------------------===//
+
+LogicalResult circt::lsp::runVerilogLSPServer(VerilogServer &server,
+                                              JSONTransport &transport) {
+  LSPServer lspServer(server, transport);
+  MessageHandler messageHandler(transport);
+
+  // Initialization
+  messageHandler.method("initialize", &lspServer, &LSPServer::onInitialize);
+  messageHandler.notification("initialized", &lspServer,
+                              &LSPServer::onInitialized);
+  messageHandler.method("shutdown", &lspServer, &LSPServer::onShutdown);
+
+  // Document Changes
+  messageHandler.notification("textDocument/didOpen", &lspServer,
+                              &LSPServer::onDocumentDidOpen);
+  messageHandler.notification("textDocument/didClose", &lspServer,
+                              &LSPServer::onDocumentDidClose);
+  messageHandler.notification("textDocument/didChange", &lspServer,
+                              &LSPServer::onDocumentDidChange);
+
+  // Diagnostics
+  lspServer.publishDiagnostics =
+      messageHandler.outgoingNotification<PublishDiagnosticsParams>(
+          "textDocument/publishDiagnostics");
+
+  // Run the main loop of the transport.
+  if (llvm::Error error = transport.run(messageHandler)) {
+    Logger::error("Transport error: {0}", error);
+    llvm::consumeError(std::move(error));
+    return failure();
+  }
+
+  return success(lspServer.shutdownRequestReceived);
+}

lib/Tools/circt-verilog-lsp-server/LSPServer.h

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIB_CIRCT_TOOLS_CIRCT_VERILOG_LSP_LSPSERVER_H
+#define LIB_CIRCT_TOOLS_CIRCT_VERILOG_LSP_LSPSERVER_H
+
+#include <memory>
+
+namespace llvm {
+struct LogicalResult;
+} // namespace llvm
+namespace mlir {
+namespace lsp {
+class JSONTransport;
+} // namespace lsp
+} // namespace mlir
+
+namespace circt {
+namespace lsp {
+class VerilogServer;
+
+/// Run the main loop of the LSP server using the given Verilog server and
+/// transport.
+llvm::LogicalResult runVerilogLSPServer(VerilogServer &server,
+                                        mlir::lsp::JSONTransport &transport);
+
+} // namespace lsp
+} // namespace circt
+
+#endif // LIB_CIRCT_TOOLS_CIRCT_VERILOG_LSP_LSPSERVER_H

lib/Tools/circt-verilog-lsp-server/LSPUtils.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains utilities for CIRCT Verilog LSP server.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LSPUtils.h"
+#include "mlir/Tools/lsp-server-support/Logging.h"
+
+void circt::lsp::Logger::error(Twine message) {
+  mlir::lsp::Logger::error("{}", message);
+}
+
+void circt::lsp::Logger::info(Twine message) {
+  mlir::lsp::Logger::info("{}", message);
+}
+
+void circt::lsp::Logger::debug(Twine message) {
+  mlir::lsp::Logger::debug("{}", message);
+}