[flang][driver] Add support for the "-init-only" option

[stuartellis]

Summary

Adding the -init-only option and corresponding frontend action to
generate a diagnostic.

-init-only vs -test-io:
-init-only ignores the input (it never calls the prescanner)
-test-io is similar to -init-only, but does read and print the input
without calling the prescanner.

This patch also adds a Driver test to check this action.

[AMDChirag]

LGTM. I'll let someone else take a look too.

[awarzynski]

Hi @stuartellis ,

Thank you for preparing this! This looks good to me, but I would appreciate a comment somewhere (e.g. in the commit message) comparing -init-only and -test-io. Essentially, both options are for testing purposes only. IMHO, we should only require one of them (I would be in favor of -init-only), but it's a bit tricky with input files being managed by the prescanner rather than the driver. So for the time being I would keep both, but just make it clear that:

• -init-only ignores the input (because it never calls the prescanner)
• -test-io is similar to -init-only, but does read and print the input without calling the prescanner.

Please let me know if any of this is unclear!

clang/include/clang/Driver/Options.td

5743

[nit] Remove empty line

flang/include/flang/Frontend/FrontendOptions.h

77

[Nit] Whenever possible, we've been adopting names from Clang (hopefully, this way it will be easier for developers to switch between the drivers). So, in this case, it would be InitOnly rather than InitializationOnly: https://github.com/llvm/llvm-project/blob/main/clang/lib/Frontend/CompilerInvocation.cpp#L2385.

flang/test/Driver/init-only.f90

3

Missing ! REQUIRES: new-flang-driver.

[stuartellis]

Address review comments
Renaming InitializationOnly to InitOnly
Add missing line in init-only.f90
Updating commit message with init-only/test-io comparison

clang/include/clang/Driver/Options.td

 def Eonly : Flag<["-"], "Eonly">,
   HelpText<"Just run preprocessor, no output (for timings)">;
 def dump_raw_tokens : Flag<["-"], "dump-raw-tokens">,
   HelpText<"Lex file in raw mode and dump raw tokens">;
 def analyze : Flag<["-"], "analyze">,
   HelpText<"Run static analysis engine">;
 def dump_tokens : Flag<["-"], "dump-tokens">,
   HelpText<"Run preprocessor, dump internal rep of tokens">;
-def init_only : Flag<["-"], "init-only">,
-  HelpText<"Only execute frontend initialization">;
 def fixit : Flag<["-"], "fixit">,
   HelpText<"Apply fix-it advice to the input source">;
 def fixit_EQ : Joined<["-"], "fixit=">,
   HelpText<"Apply fix-it advice creating a file with the given suffix">;
 def print_preamble : Flag<["-"], "print-preamble">,
   HelpText<"Print the \"preamble\" of a file, which is a candidate for implicit"
            " precompiled headers.">;
 def emit_html : Flag<["-"], "emit-html">,

 //===----------------------------------------------------------------------===//
 // Frontend Options - cc1 + fc1
 //===----------------------------------------------------------------------===//
 let Flags = [CC1Option, FC1Option, NoDriverOption] in {
 let Group = Action_Group in {
 
 def emit_obj : Flag<["-"], "emit-obj">,
   HelpText<"Emit native object files">;
+def init_only : Flag<["-"], "init-only">,
+  HelpText<"Only execute frontend initialization">;
 
 } // let Group = Action_Group
 } // let Flags = [CC1Option, FC1Option, NoDriverOption]
 
 //===----------------------------------------------------------------------===//
 // cc1as-only Options
 //===----------------------------------------------------------------------===//
 
 let Flags = [CC1AsOption, NoDriverOption] in {

flang/include/flang/Frontend/FrontendActions.h

 class InputOutputTestAction : public FrontendAction {
   void ExecuteAction() override;
 };
 
 class EmitObjAction : public FrontendAction {
   void ExecuteAction() override;
 };
 
+class InitOnlyAction : public FrontendAction {
+  void ExecuteAction() override;
+};
+
 //===----------------------------------------------------------------------===//
 // Prescan Actions
 //===----------------------------------------------------------------------===//
 class PrescanAction : public FrontendAction {
   void ExecuteAction() override = 0;
   bool BeginSourceFileAction(CompilerInstance &ci) override;
 };
 

flang/include/flang/Frontend/FrontendOptions.h

enum ActionKind {
 
   /// Parse, run semantics and then output the pre-FIR tree
   DebugPreFIRTree,
 
   /// `-fget-definition`
   GetDefinition,
 
   /// Parse, run semantics and then dump symbol sources map
-  GetSymbolsSources
+  GetSymbolsSources,
+
+  /// Only execute frontend initialization
+  InitOnly
 
   /// TODO: RunPreprocessor, EmitLLVM, EmitLLVMOnly,
   /// EmitCodeGenOnly, EmitAssembly, (...)
 };
 
 /// \param suffix The file extension
 /// \return True if the file extension should be processed as fixed form
 bool isFixedFormSuffix(llvm::StringRef suffix);

flang/lib/Frontend/CompilerInvocation.cpp

case clang::driver::options::OPT_fdebug_pre_fir_tree:
       opts.programAction_ = DebugPreFIRTree;
       break;
     case clang::driver::options::OPT_fget_symbols_sources:
       opts.programAction_ = GetSymbolsSources;
       break;
     case clang::driver::options::OPT_fget_definition:
       opts.programAction_ = GetDefinition;
       break;
+    case clang::driver::options::OPT_init_only:
+      opts.programAction_ = InitOnly;
+      break;
 
       // TODO:
-      // case calng::driver::options::OPT_emit_llvm:
+      // case clang::driver::options::OPT_emit_llvm:
       // case clang::driver::options::OPT_emit_llvm_only:
       // case clang::driver::options::OPT_emit_codegen_only:
       // case clang::driver::options::OPT_emit_module:
       // (...)
     }
 
     // Parse the values provided with `-fget-definition` (there should be 3
     // integers)

flang/lib/Frontend/FrontendActions.cpp

 }
 
 void EmitObjAction::ExecuteAction() {
   CompilerInstance &ci = this->instance();
   unsigned DiagID = ci.diagnostics().getCustomDiagID(
       clang::DiagnosticsEngine::Error, "code-generation is not available yet");
   ci.diagnostics().Report(DiagID);
 }
+
+void InitOnlyAction::ExecuteAction() {
+  CompilerInstance &ci = this->instance();
+  unsigned DiagID =
+      ci.diagnostics().getCustomDiagID(clang::DiagnosticsEngine::Warning,
+          "Use `-init-only` for testing purposes only");
+  ci.diagnostics().Report(DiagID);
+}

flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp

case DebugPreFIRTree:
     return std::make_unique<DebugPreFIRTreeAction>();
     break;
   case GetDefinition:
     return std::make_unique<GetDefinitionAction>();
     break;
   case GetSymbolsSources:
     return std::make_unique<GetSymbolsSourcesAction>();
     break;
+  case InitOnly:
+    return std::make_unique<InitOnlyAction>();
+    break;
   default:
     break;
     // TODO:
     // case RunPreprocessor:
     // case ParserSyntaxOnly:
     // case EmitLLVM:
     // case EmitLLVMOnly:
     // case EmitCodeGenOnly:

flang/test/Driver/driver-help.f90

 ! HELP-FC1-NEXT: -fintrinsic-modules-path <dir>
 ! HELP-FC1-NEXT:                        Specify where to find the compiled intrinsic modules
 ! HELP-FC1-NEXT: -flarge-sizes          Use INTEGER(KIND=8) for the result type in size-related intrinsics
 ! HELP-FC1-NEXT: -flogical-abbreviations Enable logical abbreviations
 ! HELP-FC1-NEXT: -fopenacc              Enable OpenACC
 ! HELP-FC1-NEXT: -fopenmp               Parse OpenMP pragmas and generate parallel code.
 ! HELP-FC1-NEXT: -fxor-operator         Enable .XOR. as a synonym of .NEQV.
 ! HELP-FC1-NEXT: -help                  Display available options
+! HELP-FC1-NEXT: -init-only             Only execute frontend initialization
 ! HELP-FC1-NEXT: -I <dir>               Add directory to the end of the list of include search paths
 ! HELP-FC1-NEXT: -module-dir <dir>      Put MODULE files in <dir>
 ! HELP-FC1-NEXT: -module-suffix <suffix> Use <suffix> as the suffix for module files (the default value is `.mod`)
 ! HELP-FC1-NEXT: -nocpp                 Disable predefined and command line preprocessor macros
 ! HELP-FC1-NEXT: -o <file>              Write output to <file>
 ! HELP-FC1-NEXT: -pedantic              Warn on language extensions
 ! HELP-FC1-NEXT: -std=<value>           Language standard to compile for
 ! HELP-FC1-NEXT: -test-io               Run the InputOuputTest action. Use for development and testing only.
 ! HELP-FC1-NEXT: -U <macro>             Undefine macro <macro>
 ! HELP-FC1-NEXT: --version              Print version information
 ! HELP-FC1-NEXT: -W<warning>            Enable the specified warning
 
 !---------------
 ! EXPECTED ERROR
 !---------------
 ! ERROR: error: unknown argument '-helps'; did you mean '-help'

flang/test/Driver/init-only.f90

+! Verify that -init-only flag generates a diagnostic as expected
+
+! REQUIRES: new-flang-driver
+
+! RUN: %flang_fc1 -init-only 2>&1 | FileCheck %s
+
+! CHECK: warning: Use `-init-only` for testing purposes only