[flang][driver] Add print function name Plugin example

[stuartellis]

Summary

Replacing Hello World example Plugin with one that counts and prints the names of
functions and subroutines.
This involves changing the PluginParseTreeAction Plugin base class to
inherit from PrescanAndSemaAction class to get access to the Parse Tree
so that the Plugin can walk it.
Additionally, there are tests of this new Plugin to check it prints the correct
things in different circumstances.

Depends on: D106137

[awarzynski]

Thank you for working on this @stuartellis ! This plugin is going to be a great reference example for walking the parse tree.

I have a couple of suggestions:

• I think that you can replace flangHelloWorldPlugin with flangPrintFunctionNames. The former becomes uninteresting when compared to the latter :)
• Could you add more tests? More on this below.

Ideas for extra tests:

• function + subroutine calls (these should not be taken into account, right?)
• functions within INTERFACE s
• external vs internal functions and subroutines

I know that @kiranchandramohan used the visitor API before, so perhaps he'll have another suggestion.

flang/examples/PrintFlangFunctionNames/CMakeLists.txt

6

FIXME

flang/examples/PrintFlangFunctionNames/PrintFlangFunctionNames.cpp

58

FIXME

flang/test/Driver/plugin-print-fns.f90

29

FIXME

[kiranchandramohan]

I think using Function and Subroutine Statement in the Post statement will cause to include function interface specification and miss cases like module procedures.

https://www.ibm.com/docs/en/xl-fortran-aix/16.1.0?topic=attributes-module-procedure-fortran-2008

[stuartellis]

Address review comments
Extending testing to different types of functions/subroutines
Removing flangHelloWorldPlugin

[awarzynski]

Thank you for addressing my comments @stuartellis ! I've left a couple of comments inline. I would be tempted to further split the test file into multiple files:

• one test file to show that function and subroutine definitions are counted as expected (count should be != 0)
• one test file to show that function/subroutine calls are ignored (with count == 0, if possible)
• one test file to show that interfaces are not taken into account (with count == 0, if possible)
• one test file with a misspelled plugin name

Also, the tests should probably be located in flang/test/examples rather than flang/test/Driver.

flang/examples/PrintFlangFunctionNames/PrintFlangFunctionNames.cpp

68

Non-public data members should be named with leading miniscule (lower-case) letters, internal camelCase capitalization, and a trailing underscore, e.g. DoubleEntryBookkeepingSystem myLedger_;.

https://github.com/llvm/llvm-project/blob/main/flang/docs/C%2B%2Bstyle.md#naming

flang/test/Driver/plugin-print-fns.f90

10–14

Could you move this test to a separate file? It's orthogonal to other things being tested here and IMO it makes sense to keep it separate. Basically, I would split the testing as follows:

• test for expected output to verify that the plugin works as expected when _everything is fine_
• test for diagnostics to verify that any abnormal behavior is reported in a sane way.

Otherwise, different tests blend with each other. And by moving them to separate files, you can give the test files a bit more accurate/descriptive names, e.g.:

• functions_and_subroutines.f90
• invalid_plugin_name.f90

[kiranchandramohan]

LGTM. I have one comment.

flang/examples/PrintFlangFunctionNames/PrintFlangFunctionNames.cpp

61

Nit: Do you want to count this along with Subroutines or as a separate category? If you are not counting then it might be OK to skip it completely.

There are also statement functions. How will you count them? If not counting then feel free to skip.
https://docs.oracle.com/cd/E19957-01/805-4939/6j4m0vnb9/index.html

[stuartellis]

Addressing review comments:
Split test into multiple files

[stuartellis]

I have split up the test and moved them into a new flang/text/Examples directory, but kept one test in the flang/test/Drivers directory, which doesn't reference the example plugin, for testing the incorrect plugin name Error diagnostic.

I have chosen for this plugin to skip counting/printing of Statement Functions or Module Procedures, which would be dealt with through StmtFunctionStmt and MpSubprogramStmt nodes respectively. I have adjusted the comment in the Plugin to make note of this.

[awarzynski]

With the latest update, the tests make it clear what is supported. Thank you, LGTM!

flang/examples/CMakeLists.txt

 # This test is not run by default as it requires input.
 add_executable(external-hello-world
   external-hello.cpp
 )
 
 target_link_libraries(external-hello-world
   FortranRuntime
 )
 
 add_subdirectory(HelloWorld)
+add_subdirectory(PrintFlangFunctionNames)

flang/examples/PrintFlangFunctionNames/CMakeLists.txt

+add_llvm_library(
+    flangPrintFunctionNames
+    MODULE
+    PrintFlangFunctionNames.cpp
+)
 No newline at end of file

flang/examples/PrintFlangFunctionNames/PrintFlangFunctionNames.cpp

+//===-- PrintFlangFunctionNames.cpp ---------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Small example Flang plugin which walks the Parse Tree using a visitor struct
+// that has Post functions for FunctionStmt and SubroutineStmt to count and
+// print out the names of the functions and subroutines
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Frontend/CompilerInstance.h"
+#include "flang/Frontend/FrontendActions.h"
+#include "flang/Frontend/FrontendPluginRegistry.h"
+#include "flang/Parser/dump-parse-tree.h"
+#include "flang/Parser/parsing.h"
+
+using namespace Fortran::frontend;
+
+class PrintFunctionNamesAction : public PluginParseTreeAction {
+
+  // Visitor struct that defines Pre/Post functions for different types of nodes
+  struct ParseTreeVisitor {
+    template <typename A> bool Pre(const A &) { return true; }
+    template <typename A> void Post(const A &) {}
+
+    void Post(const Fortran::parser::FunctionStmt &f) {
+      llvm::outs() << "Function:\t"
+                   << std::get<Fortran::parser::Name>(f.t).ToString() << "\n";
+      fcounter++;
+    }
+    void Post(const Fortran::parser::SubroutineStmt &s) {
+      llvm::outs() << "Subroutine:\t"
+                   << std::get<Fortran::parser::Name>(s.t).ToString() << "\n";
+      scounter++;
+    }
+
+    int fcounter{0};
+    int scounter{0};
+  };
+
+  void ExecuteAction() override {
+    auto &parseTree{instance().parsing().parseTree()};
+
+    ParseTreeVisitor visitor;
+    Fortran::parser::Walk(parseTree, visitor);
+
+    llvm::outs() << "\n====   Functions: " << visitor.fcounter << " ====\n";
+    llvm::outs() << "==== Subroutines: " << visitor.scounter << " ====\n";
+  }
+};
+
+static FrontendPluginRegistry::Add<PrintFunctionNamesAction> X(
+    "print-fns", "Print Function names");
 No newline at end of file

flang/include/flang/Frontend/FrontendActions.h

struct MeasurementVisitor {
   }
   size_t objects{0}, bytes{0};
 };
 
 //===----------------------------------------------------------------------===//
 // Custom Consumer Actions
 //===----------------------------------------------------------------------===//
 
-class PluginParseTreeAction : public FrontendAction {
-  void ExecuteAction() override;
-};
-
 class InputOutputTestAction : public FrontendAction {
   void ExecuteAction() override;
 };
 
 class EmitObjAction : public FrontendAction {
   void ExecuteAction() override;
 };
 

 class GetSymbolsSourcesAction : public PrescanAndSemaAction {
   void ExecuteAction() override;
 };
 
 class ParseSyntaxOnlyAction : public PrescanAndSemaAction {
   void ExecuteAction() override;
 };
 
+class PluginParseTreeAction : public PrescanAndSemaAction {
+  void ExecuteAction() override;
+};
+
 } // namespace Fortran::frontend
 
 #endif // LLVM_FLANG_FRONTEND_FRONTENDACTIONS_H

flang/test/CMakeLists.txt

 
 if (FLANG_INCLUDE_TESTS)
   if (FLANG_GTEST_AVAIL)
     list(APPEND FLANG_TEST_DEPENDS FlangUnitTests)
   endif()
 endif()
 
 if (FLANG_BUILD_EXAMPLES)
-  list(APPEND FLANG_TEST_DEPENDS flangHelloWorldPlugin)
+  list(APPEND FLANG_TEST_DEPENDS 
+    flangHelloWorldPlugin 
+    flangPrintFunctionNames
+    )
 endif ()
 
 add_custom_target(flang-test-depends DEPENDS ${FLANG_TEST_DEPENDS})
 
 add_lit_testsuite(check-flang "Running the Flang regression tests"
   ${CMAKE_CURRENT_BINARY_DIR}
   PARAMS ${FLANG_TEST_PARAMS}
   DEPENDS ${FLANG_TEST_DEPENDS}

flang/test/Driver/plugin-print-fns.f90

+! Check that the Flang Print Function Names example plugin prints out and counts the function and subroutine names
+! This requires that the examples are built (FLANG_BUILD_EXAMPLES=ON)
+
+! REQUIRES: new-flang-driver, plugins, examples, shell
+
+! RUN: %flang_fc1 -load %llvmshlibdir/flangPrintFunctionNames%pluginext -plugin print-fns %s 2>&1 | FileCheck %s
+
+!------------------------------------------------
+! EXPECTED OUTPUT: Print names & num of each type
+!------------------------------------------------
+! CHECK: Function: func1
+! CHECK-NEXT: Function: func2
+! CHECK-NEXT: Subroutine: routine
+! CHECK-EMPTY:
+! CHECK-NEXT: ==== Functions: 2 ====
+! CHECK-NEXT: ==== Subroutines: 1 ====
+
+!--------------------------
+! INPUT
+!--------------------------
+function func1()
+end function func1
+
+function func2()
+end function func2
+
+subroutine routine()
+end subroutine routine
 No newline at end of file