[flang][driver] Add options for unparsing

This patch adds the following compiler frontend driver options:
  * -fdebug-unparse (f18 spelling: -funparse)
  * -fdebug-unparse-with-symbols (f18 spelling: -funparse-with-symbols)
The new driver will only accept the new spelling. `f18` will accept both
the original and the new spelling.

A new base class for frontend actions is added: `PrescanAndSemaAction`.
This is added to reduce code duplication that otherwise these new
options would lead to. Implementation from
  * `ParseSyntaxOnlyAction::ExecutionAction`
is moved to:
  * `PrescanAndSemaAction::BeginSourceFileAction`
This implementation is now shared between:
  * PrescanAndSemaAction
  * ParseSyntaxOnlyAction
  * DebugUnparseAction
  * DebugUnparseWithSymbolsAction

All tests that don't require other yet unimplemented options are
updated. This way `flang-new -fc1` is used instead of `f18` when
`FLANG_BUILD_NEW_DRIVER` is set to `On`. In order to facilitate this,
`%flang_fc1` is added in the LIT configuration (lit.cfg.py).

`asFortran` from f18.cpp is duplicated as `getBasicAsFortran` in
FrontendOptions.cpp. At this stage it's hard to find a good place to
share this method. I suggest that we revisit this once a switch from
`f18` to `flang-new` is complete.

Differential Revision: https://reviews.llvm.org/D96483

clang/include/clang/Driver/Options.td

@@ -4244,6 +4244,18 @@ def fopenacc : Flag<["-"], "fopenacc">, Group<f_Group>,
 
 }
 
+//===----------------------------------------------------------------------===//
+// FC1 Options
+//===----------------------------------------------------------------------===//
+let Flags = [FC1Option, FlangOnlyOption] in {
+
+def fdebug_unparse : Flag<["-"], "fdebug-unparse">, Group<Action_Group>,
+  HelpText<"Unparse and stop.">;
+def fdebug_unparse_with_symbols : Flag<["-"], "fdebug-unparse-with-symbols">, Group<Action_Group>,
+  HelpText<"Unparse and stop.">;
+
+}
+
 //===----------------------------------------------------------------------===//
 // CC1 Options
 //===----------------------------------------------------------------------===//

flang/include/flang/Frontend/FrontendActions.h

@@ -37,7 +37,23 @@ class PrintPreprocessedAction : public PrescanAction {
   void ExecuteAction() override;
 };
 
-class ParseSyntaxOnlyAction : public PrescanAction {
+//===----------------------------------------------------------------------===//
+// PrescanAndSema Actions
+//===----------------------------------------------------------------------===//
+class PrescanAndSemaAction : public FrontendAction {
+  void ExecuteAction() override = 0;
+  bool BeginSourceFileAction(CompilerInstance &ci) override;
+};
+
+class DebugUnparseWithSymbolsAction : public PrescanAndSemaAction {
+  void ExecuteAction() override;
+};
+
+class DebugUnparseAction : public PrescanAndSemaAction {
+  void ExecuteAction() override;
+};
+
+class ParseSyntaxOnlyAction : public PrescanAndSemaAction {
   void ExecuteAction() override;
 };
 

flang/include/flang/Frontend/FrontendOptions.h

@@ -9,6 +9,7 @@
 #define LLVM_FLANG_FRONTEND_FRONTENDOPTIONS_H
 
 #include "flang/Common/Fortran-features.h"
+#include "flang/Parser/unparse.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/MemoryBuffer.h"
 
@@ -32,6 +33,13 @@ enum ActionKind {
   /// Emit a .o file.
   EmitObj,
 
+  /// Parse, unparse the parse-tree and output a Fortran source file
+  DebugUnparse,
+
+  /// Parse, resolve the sybmols, unparse the parse-tree and then output a
+  /// Fortran source file
+  DebugUnparseWithSymbols,
+
   /// TODO: RunPreprocessor, EmitLLVM, EmitLLVMOnly,
   /// EmitCodeGenOnly, EmitAssembly, (...)
 };
@@ -40,6 +48,10 @@ enum ActionKind {
 /// \return True if the file extension should be processed as fixed form
 bool isFixedFormSuffix(llvm::StringRef suffix);
 
+// TODO: Find a more suitable location for this. Added for compability with
+// f18.cpp (this is equivalent to `asFortran` defined there).
+Fortran::parser::AnalyzedObjectsAsFortran getBasicAsFortran();
+
 /// \param suffix The file extension
 /// \return True if the file extension should be processed as free form
 bool isFreeFormSuffix(llvm::StringRef suffix);

flang/lib/Frontend/CMakeLists.txt

@@ -14,6 +14,7 @@ add_flang_library(flangFrontend
   LINK_LIBS
   FortranParser
   FortranSemantics
+  FortranEvaluate
   FortranCommon
   clangBasic
   clangDriver

flang/lib/Frontend/CompilerInvocation.cpp

@@ -110,6 +110,12 @@ static InputKind ParseFrontendArgs(FrontendOptions &opts,
     case clang::driver::options::OPT_emit_obj:
       opts.programAction_ = EmitObj;
       break;
+    case clang::driver::options::OPT_fdebug_unparse:
+      opts.programAction_ = DebugUnparse;
+      break;
+    case clang::driver::options::OPT_fdebug_unparse_with_symbols:
+      opts.programAction_ = DebugUnparseWithSymbols;
+      break;
 
       // TODO:
       // case calng::driver::options::OPT_emit_llvm:

flang/lib/Frontend/FrontendActions.cpp

@@ -9,10 +9,13 @@
 #include "flang/Frontend/FrontendActions.h"
 #include "flang/Common/default-kinds.h"
 #include "flang/Frontend/CompilerInstance.h"
+#include "flang/Frontend/FrontendOptions.h"
 #include "flang/Parser/parsing.h"
 #include "flang/Parser/provenance.h"
 #include "flang/Parser/source.h"
+#include "flang/Parser/unparse.h"
 #include "flang/Semantics/semantics.h"
+#include "flang/Semantics/unparse-with-symbols.h"
 
 using namespace Fortran::frontend;
 
@@ -49,6 +52,75 @@ bool PrescanAction::BeginSourceFileAction(CompilerInstance &c1) {
   return true;
 }
 
+bool PrescanAndSemaAction::BeginSourceFileAction(CompilerInstance &c1) {
+  CompilerInstance &ci = this->instance();
+
+  std::string currentInputPath{GetCurrentFileOrBufferName()};
+
+  Fortran::parser::Options parserOptions = ci.invocation().fortranOpts();
+
+  if (ci.invocation().frontendOpts().fortranForm_ == FortranForm::Unknown) {
+    // Switch between fixed and free form format based on the input file
+    // extension.
+    //
+    // Ideally we should have all Fortran options set before entering this
+    // method (i.e. before processing any specific input files). However, we
+    // can't decide between fixed and free form based on the file extension
+    // earlier than this.
+    parserOptions.isFixedForm = currentInput().IsFixedForm();
+  }
+
+  // Prescan. In case of failure, report and return.
+  ci.parsing().Prescan(currentInputPath, parserOptions);
+
+  if (ci.parsing().messages().AnyFatalError()) {
+    const unsigned diagID = ci.diagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error, "Could not scan %0");
+    ci.diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
+    ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+
+    return false;
+  }
+
+  // Parse. In case of failure, report and return.
+  ci.parsing().Parse(llvm::outs());
+
+  if (ci.parsing().messages().AnyFatalError()) {
+    unsigned diagID = ci.diagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error, "Could not parse %0");
+    ci.diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
+
+    ci.parsing().messages().Emit(
+        llvm::errs(), this->instance().allCookedSources());
+    return false;
+  }
+
+  // Report the diagnostics from parsing
+  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+
+  auto &parseTree{*ci.parsing().parseTree()};
+
+  // Prepare semantics
+  Fortran::semantics::Semantics semantics{ci.invocation().semanticsContext(),
+      parseTree, ci.parsing().cooked().AsCharBlock()};
+
+  // Run semantic checks
+  semantics.Perform();
+
+  // Report the diagnostics from the semantic checks
+  semantics.EmitMessages(ci.semaOutputStream());
+
+  if (semantics.AnyFatalError()) {
+    unsigned DiagID = ci.diagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error, "Semantic errors in %0");
+    ci.diagnostics().Report(DiagID) << GetCurrentFileOrBufferName();
+
+    return false;
+  }
+
+  return true;
+}
+
 void InputOutputTestAction::ExecuteAction() {
   CompilerInstance &ci = instance();
 
@@ -111,42 +183,25 @@ void PrintPreprocessedAction::ExecuteAction() {
   }
 }
 
-void ParseSyntaxOnlyAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void ParseSyntaxOnlyAction::ExecuteAction() {}
 
-  // Parse. In case of failure, report and return.
-  ci.parsing().Parse(llvm::outs());
+void DebugUnparseAction::ExecuteAction() {
+  auto &parseTree{instance().parsing().parseTree()};
+  Fortran::parser::AnalyzedObjectsAsFortran asFortran =
+      Fortran::frontend::getBasicAsFortran();
 
-  if (ci.parsing().messages().AnyFatalError()) {
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
-        clang::DiagnosticsEngine::Error, "Could not parse %0");
-    ci.diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
+  // TODO: Options should come from CompilerInvocation
+  Unparse(llvm::outs(), *parseTree,
+      /*encoding=*/Fortran::parser::Encoding::UTF_8,
+      /*capitalizeKeywords=*/true, /*backslashEscapes=*/false,
+      /*preStatement=*/nullptr, &asFortran);
+}
 
-    ci.parsing().messages().Emit(
-        llvm::errs(), this->instance().allCookedSources());
-    return;
-  }
+void DebugUnparseWithSymbolsAction::ExecuteAction() {
+  auto &parseTree{*instance().parsing().parseTree()};
 
-  // Report the diagnostics from parsing
-  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
-
-  auto &parseTree{*ci.parsing().parseTree()};
-
-  // Prepare semantics
-  Fortran::semantics::Semantics semantics{ci.invocation().semanticsContext(),
-      parseTree, ci.parsing().cooked().AsCharBlock()};
-
-  // Run semantic checks
-  semantics.Perform();
-
-  // Report the diagnostics from the semantic checks
-  semantics.EmitMessages(ci.semaOutputStream());
-
-  if (semantics.AnyFatalError()) {
-    unsigned DiagID = ci.diagnostics().getCustomDiagID(
-        clang::DiagnosticsEngine::Error, "Semantic errors in %0");
-    ci.diagnostics().Report(DiagID) << GetCurrentFileOrBufferName();
-  }
+  Fortran::semantics::UnparseWithSymbols(
+      llvm::outs(), parseTree, /*encoding=*/Fortran::parser::Encoding::UTF_8);
 }
 
 void EmitObjAction::ExecuteAction() {

flang/lib/Frontend/FrontendOptions.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Frontend/FrontendOptions.h"
+#include "flang/Evaluate/expression.h"
 
 using namespace Fortran::frontend;
 
@@ -25,6 +26,34 @@ bool Fortran::frontend::isFreeFormSuffix(llvm::StringRef suffix) {
       suffix == "f08" || suffix == "F08" || suffix == "f18" || suffix == "F18";
 }
 
+// TODO: This is a copy of `asFortran` from f18.cpp and is added here for
+// compatiblity. It doesn't really belong here, but I couldn't find a better
+// place. We should decide whether to add it to the Evaluate or Parse/Unparse
+// APIs or some dedicated utility library in the driver.
+Fortran::parser::AnalyzedObjectsAsFortran
+Fortran::frontend::getBasicAsFortran() {
+  return Fortran::parser::AnalyzedObjectsAsFortran{
+      [](llvm::raw_ostream &o, const Fortran::evaluate::GenericExprWrapper &x) {
+        if (x.v) {
+          x.v->AsFortran(o);
+        } else {
+          o << "(bad expression)";
+        }
+      },
+      [](llvm::raw_ostream &o,
+          const Fortran::evaluate::GenericAssignmentWrapper &x) {
+        if (x.v) {
+          x.v->AsFortran(o);
+        } else {
+          o << "(bad assignment)";
+        }
+      },
+      [](llvm::raw_ostream &o, const Fortran::evaluate::ProcedureRef &x) {
+        x.AsFortran(o << "CALL ");
+      },
+  };
+}
+
 InputKind FrontendOptions::GetInputKindForExtension(llvm::StringRef extension) {
   if (isFixedFormSuffix(extension) || isFreeFormSuffix(extension)) {
     return Language::Fortran;

flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp

@@ -37,6 +37,12 @@ static std::unique_ptr<FrontendAction> CreateFrontendBaseAction(
   case EmitObj:
     return std::make_unique<EmitObjAction>();
     break;
+  case DebugUnparse:
+    return std::make_unique<DebugUnparseAction>();
+    break;
+  case DebugUnparseWithSymbols:
+    return std::make_unique<DebugUnparseWithSymbolsAction>();
+    break;
   default:
     break;
     // TODO:

flang/lib/Parser/CMakeLists.txt

@@ -1,4 +1,3 @@
-
 add_flang_library(FortranParser
   Fortran-parsers.cpp
   char-buffer.cpp

flang/test/Flang-Driver/driver-help.f90

@@ -46,6 +46,9 @@
 ! HELP-FC1-NEXT: -D <macro>=<value>     Define <macro> to <value> (or 1 if <value> omitted)
 ! HELP-FC1-NEXT: -emit-obj Emit native object files
 ! HELP-FC1-NEXT: -E                     Only run the preprocessor
+! HELP-FC1-NEXT: -fdebug-unparse-with-symbols
+! HELP-FC1-NEXT:                        Unparse and stop.
+! HELP-FC1-NEXT: -fdebug-unparse        Unparse and stop.
 ! HELP-FC1-NEXT: -ffixed-form           Process source files in fixed form
 ! HELP-FC1-NEXT: -ffixed-line-length=<value>
 ! HELP-FC1-NEXT: Use <value> as character line width in fixed mode

flang/test/Parser/continuation-in-if.f

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
 ! CHECK: CALL foo("N","N")
 #ifdef transpose
       call foo('T',

flang/test/Parser/pp-dir-comments.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
 
 #define pmk
 #ifdef pmk // comment

flang/test/Semantics/canondo01.f90

@@ -1,5 +1,5 @@
 
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: end do
 
 SUBROUTINE sub00(a,b,n,m)

flang/test/Semantics/canondo02.f90

@@ -1,5 +1,5 @@
 
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: end do
 
 SUBROUTINE sub00(a,b,n,m)

flang/test/Semantics/canondo03.f90

@@ -1,5 +1,5 @@
 
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: 10 continue
 ! CHECK: end do
 

flang/test/Semantics/canondo04.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK-NOT: do [1-9]
 
 ! Figure out how to also execute this test.

flang/test/Semantics/canondo05.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! RUN: %f18 -fopenmp -funparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK-NOT: do *[1-9]
 

flang/test/Semantics/critical04.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK-NOT: Control flow escapes from CRITICAL
 
 subroutine test1(a, i)

flang/test/Semantics/defined-ops.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
 
 ! Check the analyzed form of a defined operator or assignment.
 

flang/test/Semantics/doconcurrent02.f90

@@ -1,6 +1,6 @@
 ! when the loops are not DO CONCURRENT
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK-NOT: image control statement not allowed in DO CONCURRENT
 ! CHECK-NOT: RETURN not allowed in DO CONCURRENT
 ! CHECK-NOT: call to impure procedure in DO CONCURRENT not allowed

flang/test/Semantics/doconcurrent03.f90

@@ -1,4 +1,4 @@
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Control flow escapes from DO CONCURRENT
 ! CHECK: branch into loop body from outside
 ! CHECK: the loop branched into

flang/test/Semantics/doconcurrent04.f90

@@ -1,5 +1,5 @@
 ! C1122 The index-name shall be a named scalar variable of type integer.
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Must have INTEGER type, but is REAL(4)
 
 subroutine do_concurrent_test1(n)

flang/test/Semantics/doconcurrent07.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK-NOT: exit from DO CONCURRENT construct
 
 subroutine do_concurrent_test1(n)

flang/test/Semantics/label02.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Label '0' is out of range
 ! CHECK: Label '100000' is out of range
 ! CHECK: Label '123456' is out of range

flang/test/Semantics/label03.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: DO loop doesn't properly nest
 ! CHECK: DO loop conflicts
 ! CHECK: Label '30' cannot be found

flang/test/Semantics/label04.f90

@@ -1,5 +1,5 @@
 
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: branch into loop body from outside
 ! CHECK: do 10 i = 1, m
 ! CHECK: the loop branched into

flang/test/Semantics/label05.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Label '50' was not found
 ! CHECK: Label '55' is not in scope
 ! CHECK: Label '70' is not a branch target

flang/test/Semantics/label06.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Label '10' is not in scope
 ! CHECK: Label '20' was not found
 ! CHECK: Label '30' is not a branch target

flang/test/Semantics/label07.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Label '30' is not a branch target
 ! CHECK: Control flow use of '30'
 ! CHECK: Label '10' is not in scope

flang/test/Semantics/label08.f90

@@ -1,5 +1,5 @@
 
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: CYCLE construct-name is not in scope
 ! CHECK: IF construct name unexpected
 ! CHECK: unnamed IF statement

flang/test/Semantics/label09.f90

@@ -1,4 +1,4 @@
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: Label '60' was not found
 
 subroutine s(a)

flang/test/Semantics/label10.f90

@@ -1,4 +1,4 @@
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: '60' not a FORMAT
 ! CHECK: data transfer use of '60'
 

flang/test/Semantics/label12.f90

@@ -1,4 +1,4 @@
-! RUN: not %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: expected end of statement
 
 subroutine s

flang/test/Semantics/label13.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse-with-symbols %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
 ! CHECK: branch into loop body from outside
 ! CHECK: the loop branched into
 

flang/test/Semantics/label15.f90

@@ -1,4 +1,4 @@
-! RUN: %f18 -funparse %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
 
 !CHECK-NOT: error:
 module mm

flang/test/lit.cfg.py

@@ -74,10 +74,15 @@ tools = [
 if config.include_flang_new_driver_test:
    tools.append(ToolSubst('%flang-new', command=FindTool('flang-new'), unresolved='fatal'))
    tools.append(ToolSubst('%flang', command=FindTool('flang-new'), unresolved='fatal'))
+   tools.append(ToolSubst('%flang_fc1', command=FindTool('flang-new'),
+    extra_args=['-fc1'], unresolved='fatal'))
 else:
    tools.append(ToolSubst('%flang', command=FindTool('f18'),
     extra_args=["-intrinsic-module-directory "+config.flang_intrinsic_modules_dir],
     unresolved='fatal'))
+   tools.append(ToolSubst('%flang_fc1', command=FindTool('f18'),
+    extra_args=["-intrinsic-module-directory "+config.flang_intrinsic_modules_dir],
+    unresolved='fatal'))
 
 if config.flang_standalone_build:
     llvm_config.add_tool_substitutions(tools, [config.flang_llvm_tools_dir])

flang/tools/f18/f18.cpp

@@ -540,9 +540,10 @@ int main(int argc, char *const argv[]) {
       options.instrumentedParse = true;
     } else if (arg == "-fdebug-no-semantics") {
       driver.debugNoSemantics = true;
-    } else if (arg == "-funparse") {
+    } else if (arg == "-funparse" || arg == "-fdebug-unparse") {
       driver.dumpUnparse = true;
-    } else if (arg == "-funparse-with-symbols") {
+    } else if (arg == "-funparse-with-symbols" ||
+        arg == "-fdebug-unparse-with-symbols") {
       driver.dumpUnparseWithSymbols = true;
     } else if (arg == "-funparse-typed-exprs-to-f18-fc") {
       driver.unparseTypedExprsToF18_FC = true;