[Macros] Infer in-process plugin server in swift-frontend

Not all driver can send '-in-process-plugin-server-path'. To keep
existing '-plugin-path' working, infer default server path in the
frontend.

Author: rintaro

include/swift/Frontend/Frontend.h

@@ -250,6 +250,12 @@ class CompilerInvocation {
   /// If we haven't explicitly passed -blocklist-paths, set it to the default value.
   void setDefaultBlocklistsIfNecessary();
 
+  /// If we haven't explicitly passed '-in-process-plugin-server-path', infer
+  /// it as a default value.
+  ///
+  /// FIXME: Remove this after all the clients start sending it.
+  void setDefaultInProcessPluginServerPathIfNecessary();
+
   /// Computes the runtime resource path relative to the given Swift
   /// executable.
   static void computeRuntimeResourcePathFromExecutablePath(

lib/Frontend/CompilerInvocation.cpp

@@ -187,6 +187,37 @@ void CompilerInvocation::setDefaultBlocklistsIfNecessary() {
   }
 }
 
+void CompilerInvocation::setDefaultInProcessPluginServerPathIfNecessary() {
+  if (!SearchPathOpts.InProcessPluginServerPath.empty())
+    return;
+  if (FrontendOpts.MainExecutablePath.empty())
+    return;
+
+  // '/usr/bin/swift'
+  SmallString<64> serverLibPath{FrontendOpts.MainExecutablePath};
+  llvm::sys::path::remove_filename(serverLibPath); // remove 'swift'
+
+#if defined(_WIN32)
+  // Windows: usr\bin\SwiftInProcPluginServer.dll
+  llvm::sys::path::append(serverLibPath, "SwiftInProcPluginServer.dll");
+
+#elif defined(__APPLE__)
+  // Darwin: usr/lib/swift/host/libSwiftInProcPluginServer.dylib
+  llvm::sys::path::remove_filename(serverLibPath); // remove 'bin'
+  llvm::sys::path::append(serverLibPath, "lib", "swift", "host");
+  llvm::sys::path::append(serverLibPath, "libSwiftInProcPluginServer.dylib");
+
+#else
+  // Other: usr/lib/swift/host/libSwiftInProcPluginServer.so
+  llvm::sys::path::remove_filename(serverLibPath); // remove 'bin'
+  llvm::sys::path::append(serverLibPath, "lib", "swift", "host");
+  llvm::sys::path::append(serverLibPath, "libSwiftInProcPluginServer.so");
+
+#endif
+
+  SearchPathOpts.InProcessPluginServerPath = serverLibPath.str();
+}
+
 static void updateRuntimeLibraryPaths(SearchPathOptions &SearchPathOpts,
                                       const FrontendOptions &FrontendOpts,
                                       const LangOptions &LangOpts) {
@@ -3532,6 +3563,7 @@ bool CompilerInvocation::parseArgs(
   updateRuntimeLibraryPaths(SearchPathOpts, FrontendOpts, LangOpts);
   setDefaultPrebuiltCacheIfNecessary();
   setDefaultBlocklistsIfNecessary();
+  setDefaultInProcessPluginServerPathIfNecessary();
 
   // Now that we've parsed everything, setup some inter-option-dependent state.
   setIRGenOutputOptsFromFrontendOptions(IRGenOpts, FrontendOpts);

test/lit.cfg

@@ -1272,9 +1272,6 @@ if run_vendor == 'apple':
         config.resource_dir_opt = "-resource-dir %s" % new_resource_dir
         lit_config.note('Using freestanding resource dir: ' + new_resource_dir)
 
-    config.swift_in_process_plugin_server_path = make_path(config.swift_lib_dir, 'swift', 'host', 'libSwiftInProcPluginServer.dylib')
-    config.swift_test_options += " -in-process-plugin-server-path %s" % shell_quote(config.swift_in_process_plugin_server_path)
-
     # Auto-linking does not work when stdlib is built with LTO, because linked
     # libraries are discovered too late (after optimizations are applied), and
     # ld64 hits an assert and crashes, or worse, deadlocks. Until ld64 fixes
@@ -1625,9 +1622,6 @@ elif run_os in ['windows-msvc']:
         config.target_msvc_runtime_opt += ' -D_DLL'
     config.target_env_prefix = ''
 
-    config.swift_in_process_plugin_server_path = make_path(config.swift_bin_dir, 'SwiftInProcPluginServer.dll')
-    config.swift_test_options += " -in-process-plugin-server-path %s" % shell_quote(config.swift_in_process_plugin_server_path)
-
     config.target_build_swift =                                                  \
             ('%r -target %s %s %s %s %s %s -libc %s' %                           \
                     (config.swiftc, config.variant_triple,                       \
@@ -1759,9 +1753,6 @@ elif (run_os in ['linux-gnu', 'linux-gnueabihf', 'freebsd', 'openbsd', 'windows-
     config.target_runtime = "native"
     config.target_swift_autolink_extract = inferSwiftBinary("swift-autolink-extract")
 
-    config.swift_in_process_plugin_server_path = make_path(config.swift_lib_dir, 'swift', 'host', 'libSwiftInProcPluginServer.so')
-    config.swift_test_options += " -in-process-plugin-server-path %s" % shell_quote(config.swift_in_process_plugin_server_path)
-
     libdispatch_artifact_dir = config.libdispatch_build_path
     libdispatch_swift_module_dir = make_path(libdispatch_artifact_dir, 'src', 'swift', 'swift')
     libdispatch_source_dir = make_path(config.swift_src_root, os.pardir, 'swift-corelibs-libdispatch')

tools/swift-ide-test/swift-ide-test.cpp

@@ -4576,6 +4576,7 @@ int main(int argc, char *argv[]) {
     InitInvok.getSearchPathOptions().PluginSearchOpts.emplace_back(
         PluginSearchOption::PluginPath{path});
   }
+  InitInvok.setDefaultInProcessPluginServerPathIfNecessary();
 
   // Process the clang arguments last and allow them to override previously
   // set options.