diff --git a/flang/include/flang/Frontend/.clang-tidy b/flang/include/flang/Frontend/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/include/flang/Frontend/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/include/flang/Frontend/CompilerInstance.h b/flang/include/flang/Frontend/CompilerInstance.h
--- a/flang/include/flang/Frontend/CompilerInstance.h
+++ b/flang/include/flang/Frontend/CompilerInstance.h
@@ -5,8 +5,8 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-#ifndef LLVM_FLANG_FRONTEND_COMPILERINSTANCE_H
-#define LLVM_FLANG_FRONTEND_COMPILERINSTANCE_H
+#ifndef FORTRAN_FRONTEND_COMPILERINSTANCE_H
+#define FORTRAN_FRONTEND_COMPILERINSTANCE_H
 
 #include "flang/Frontend/CompilerInvocation.h"
 #include "flang/Frontend/FrontendAction.h"
@@ -37,43 +37,43 @@
 class CompilerInstance {
 
   /// The options used in this compiler instance.
-  std::shared_ptr<CompilerInvocation> invocation_;
+  std::shared_ptr<CompilerInvocation> invocation;
 
   /// Flang file  manager.
-  std::shared_ptr<Fortran::parser::AllSources> allSources_;
+  std::shared_ptr<Fortran::parser::AllSources> allSources;
 
-  std::shared_ptr<Fortran::parser::AllCookedSources> allCookedSources_;
+  std::shared_ptr<Fortran::parser::AllCookedSources> allCookedSources;
 
-  std::shared_ptr<Fortran::parser::Parsing> parsing_;
+  std::shared_ptr<Fortran::parser::Parsing> parsing;
 
-  std::unique_ptr<Fortran::semantics::Semantics> semantics_;
+  std::unique_ptr<Fortran::semantics::Semantics> semantics;
 
-  std::unique_ptr<Fortran::semantics::RuntimeDerivedTypeTables> rtTyTables_;
+  std::unique_ptr<Fortran::semantics::RuntimeDerivedTypeTables> rtTyTables;
 
   /// The stream for diagnostics from Semantics
-  llvm::raw_ostream *semaOutputStream_ = &llvm::errs();
+  llvm::raw_ostream *semaOutputStream = &llvm::errs();
 
   /// The stream for diagnostics from Semantics if owned, otherwise nullptr.
-  std::unique_ptr<llvm::raw_ostream> ownedSemaOutputStream_;
+  std::unique_ptr<llvm::raw_ostream> ownedSemaOutputStream;
 
   /// The diagnostics engine instance.
-  llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diagnostics_;
+  llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diagnostics;
 
   /// Holds information about the output file.
   struct OutputFile {
-    std::string filename_;
+    std::string filename;
     OutputFile(std::string inputFilename)
-        : filename_(std::move(inputFilename)) {}
+        : filename(std::move(inputFilename)) {}
   };
 
   /// The list of active output files.
-  std::list<OutputFile> outputFiles_;
+  std::list<OutputFile> outputFiles;
 
   /// Holds the output stream provided by the user. Normally, users of
   /// CompilerInstance will call CreateOutputFile to obtain/create an output
   /// stream. If they want to provide their own output stream, this field will
   /// facilitate this. It is optional and will normally be just a nullptr.
-  std::unique_ptr<llvm::raw_pwrite_stream> outputStream_;
+  std::unique_ptr<llvm::raw_pwrite_stream> outputStream;
 
 public:
   explicit CompilerInstance();
@@ -83,26 +83,26 @@
   /// @name Compiler Invocation
   /// {
 
-  CompilerInvocation &invocation() {
-    assert(invocation_ && "Compiler instance has no invocation!");
-    return *invocation_;
+  CompilerInvocation &getInvocation() {
+    assert(invocation && "Compiler instance has no invocation!");
+    return *invocation;
   };
 
   /// Replace the current invocation.
-  void set_invocation(std::shared_ptr<CompilerInvocation> value);
+  void setInvocation(std::shared_ptr<CompilerInvocation> value);
 
   /// }
   /// @name File manager
   /// {
 
   /// Return the current allSources.
-  Fortran::parser::AllSources &allSources() const { return *allSources_; }
+  Fortran::parser::AllSources &getAllSources() const { return *allSources; }
 
-  bool HasAllSources() const { return allSources_ != nullptr; }
+  bool hasAllSources() const { return allSources != nullptr; }
 
-  parser::AllCookedSources &allCookedSources() {
-    assert(allCookedSources_ && "Compiler instance has no AllCookedSources!");
-    return *allCookedSources_;
+  parser::AllCookedSources &getAllCookedSources() {
+    assert(allCookedSources && "Compiler instance has no AllCookedSources!");
+    return *allCookedSources;
   };
 
   /// }
@@ -110,36 +110,38 @@
   /// {
 
   /// Return parsing to be used by Actions.
-  Fortran::parser::Parsing &parsing() const { return *parsing_; }
+  Fortran::parser::Parsing &getParsing() const { return *parsing; }
 
   /// }
   /// @name Semantic analysis
   /// {
 
   /// Replace the current stream for verbose output.
-  void set_semaOutputStream(llvm::raw_ostream &Value);
+  void setSemaOutputStream(llvm::raw_ostream &value);
 
   /// Replace the current stream for verbose output.
-  void set_semaOutputStream(std::unique_ptr<llvm::raw_ostream> Value);
+  void setSemaOutputStream(std::unique_ptr<llvm::raw_ostream> value);
 
   /// Get the current stream for verbose output.
-  llvm::raw_ostream &semaOutputStream() { return *semaOutputStream_; }
+  llvm::raw_ostream &getSemaOutputStream() { return *semaOutputStream; }
 
-  Fortran::semantics::Semantics &semantics() { return *semantics_; }
-  const Fortran::semantics::Semantics &semantics() const { return *semantics_; }
+  Fortran::semantics::Semantics &getSemantics() { return *semantics; }
+  const Fortran::semantics::Semantics &getSemantics() const {
+    return *semantics;
+  }
 
-  void SetSemantics(std::unique_ptr<Fortran::semantics::Semantics> semantics) {
-    semantics_ = std::move(semantics);
+  void setSemantics(std::unique_ptr<Fortran::semantics::Semantics> sema) {
+    semantics = std::move(sema);
   }
 
   void setRtTyTables(
       std::unique_ptr<Fortran::semantics::RuntimeDerivedTypeTables> tables) {
-    rtTyTables_ = std::move(tables);
+    rtTyTables = std::move(tables);
   }
 
   Fortran::semantics::RuntimeDerivedTypeTables &getRtTyTables() {
-    assert(rtTyTables_ && "Missing runtime derived type tables!");
-    return *rtTyTables_;
+    assert(rtTyTables && "Missing runtime derived type tables!");
+    return *rtTyTables;
   }
 
   /// }
@@ -150,47 +152,47 @@
   /// CompilerInvocation object.
   /// \param act - The action to execute.
   /// \return - True on success.
-  bool ExecuteAction(FrontendAction &act);
+  bool executeAction(FrontendAction &act);
 
   /// }
   /// @name Forwarding Methods
   /// {
 
-  clang::DiagnosticOptions &GetDiagnosticOpts() {
-    return invocation_->GetDiagnosticOpts();
+  clang::DiagnosticOptions &getDiagnosticOpts() {
+    return invocation->getDiagnosticOpts();
   }
-  const clang::DiagnosticOptions &GetDiagnosticOpts() const {
-    return invocation_->GetDiagnosticOpts();
+  const clang::DiagnosticOptions &getDiagnosticOpts() const {
+    return invocation->getDiagnosticOpts();
   }
 
-  FrontendOptions &frontendOpts() { return invocation_->frontendOpts(); }
-  const FrontendOptions &frontendOpts() const {
-    return invocation_->frontendOpts();
+  FrontendOptions &getFrontendOpts() { return invocation->getFrontendOpts(); }
+  const FrontendOptions &getFrontendOpts() const {
+    return invocation->getFrontendOpts();
   }
 
   PreprocessorOptions &preprocessorOpts() {
-    return invocation_->preprocessorOpts();
+    return invocation->getPreprocessorOpts();
   }
   const PreprocessorOptions &preprocessorOpts() const {
-    return invocation_->preprocessorOpts();
+    return invocation->getPreprocessorOpts();
   }
 
   /// }
   /// @name Diagnostics Engine
   /// {
 
-  bool HasDiagnostics() const { return diagnostics_ != nullptr; }
+  bool hasDiagnostics() const { return diagnostics != nullptr; }
 
   /// Get the current diagnostics engine.
-  clang::DiagnosticsEngine &diagnostics() const {
-    assert(diagnostics_ && "Compiler instance has no diagnostics!");
-    return *diagnostics_;
+  clang::DiagnosticsEngine &getDiagnostics() const {
+    assert(diagnostics && "Compiler instance has no diagnostics!");
+    return *diagnostics;
   }
 
-  clang::DiagnosticConsumer &GetDiagnosticClient() const {
-    assert(diagnostics_ && diagnostics_->getClient() &&
+  clang::DiagnosticConsumer &getDiagnosticClient() const {
+    assert(diagnostics && diagnostics->getClient() &&
         "Compiler instance has no diagnostic client!");
-    return *diagnostics_->getClient();
+    return *diagnostics->getClient();
   }
 
   /// {
@@ -198,7 +200,7 @@
   /// {
 
   /// Clear the output file list.
-  void ClearOutputFiles(bool eraseFiles);
+  void clearOutputFiles(bool eraseFiles);
 
   /// Create the default output file (based on the invocation's options) and
   /// add it to the list of tracked output files. If the name of the output
@@ -211,7 +213,7 @@
   /// \param extension  The extension to use for output names derived from
   ///                   \p baseInput.
   /// \return           Null on error, ostream for the output file otherwise
-  std::unique_ptr<llvm::raw_pwrite_stream> CreateDefaultOutputFile(
+  std::unique_ptr<llvm::raw_pwrite_stream> createDefaultOutputFile(
       bool binary = true, llvm::StringRef baseInput = "",
       llvm::StringRef extension = "");
 
@@ -221,7 +223,7 @@
   /// \param outputPath   The path to the output file.
   /// \param binary       The mode to open the file in.
   /// \return             Null on error, ostream for the output file otherwise
-  llvm::Expected<std::unique_ptr<llvm::raw_pwrite_stream>> CreateOutputFileImpl(
+  llvm::Expected<std::unique_ptr<llvm::raw_pwrite_stream>> createOutputFileImpl(
       llvm::StringRef outputPath, bool binary);
 
 public:
@@ -244,33 +246,33 @@
   /// DiagnosticsEngine object.
   ///
   /// \return The new object on success, or null on failure.
-  static clang::IntrusiveRefCntPtr<clang::DiagnosticsEngine> CreateDiagnostics(
+  static clang::IntrusiveRefCntPtr<clang::DiagnosticsEngine> createDiagnostics(
       clang::DiagnosticOptions *opts,
       clang::DiagnosticConsumer *client = nullptr, bool shouldOwnClient = true);
-  void CreateDiagnostics(
+  void createDiagnostics(
       clang::DiagnosticConsumer *client = nullptr, bool shouldOwnClient = true);
 
   /// }
   /// @name Output Stream Methods
   /// {
-  void set_outputStream(std::unique_ptr<llvm::raw_pwrite_stream> outStream) {
-    outputStream_ = std::move(outStream);
+  void setOutputStream(std::unique_ptr<llvm::raw_pwrite_stream> outStream) {
+    outputStream = std::move(outStream);
   }
 
-  bool IsOutputStreamNull() { return (outputStream_ == nullptr); }
+  bool isOutputStreamNull() { return (outputStream == nullptr); }
 
   // Allow the frontend compiler to write in the output stream.
-  void WriteOutputStream(const std::string &message) {
-    *outputStream_ << message;
+  void writeOutputStream(const std::string &message) {
+    *outputStream << message;
   }
 
   /// Get the user specified output stream.
-  llvm::raw_pwrite_stream &GetOutputStream() {
-    assert(outputStream_ &&
+  llvm::raw_pwrite_stream &getOutputStream() {
+    assert(outputStream &&
         "Compiler instance has no user-specified output stream!");
-    return *outputStream_;
+    return *outputStream;
   }
 };
 
 } // end namespace Fortran::frontend
-#endif // LLVM_FLANG_FRONTEND_COMPILERINSTANCE_H
+#endif // FORTRAN_FRONTEND_COMPILERINSTANCE_H
diff --git a/flang/include/flang/Frontend/CompilerInvocation.h b/flang/include/flang/Frontend/CompilerInvocation.h
--- a/flang/include/flang/Frontend/CompilerInvocation.h
+++ b/flang/include/flang/Frontend/CompilerInvocation.h
@@ -5,8 +5,8 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-#ifndef LLVM_FLANG_FRONTEND_COMPILERINVOCATION_H
-#define LLVM_FLANG_FRONTEND_COMPILERINVOCATION_H
+#ifndef FORTRAN_FRONTEND_COMPILERINVOCATION_H
+#define FORTRAN_FRONTEND_COMPILERINVOCATION_H
 
 #include "flang/Frontend/FrontendOptions.h"
 #include "flang/Frontend/PreprocessorOptions.h"
@@ -24,30 +24,30 @@
 ///
 /// When errors are encountered, return false and, if Diags is non-null,
 /// report the error(s).
-bool ParseDiagnosticArgs(clang::DiagnosticOptions &opts,
+bool parseDiagnosticArgs(clang::DiagnosticOptions &opts,
     llvm::opt::ArgList &args, bool defaultDiagColor = true);
 
 class CompilerInvocationBase {
 public:
   /// Options controlling the diagnostic engine.
-  llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagnosticOpts_;
+  llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagnosticOpts;
   /// Options for the preprocessor.
-  std::shared_ptr<Fortran::frontend::PreprocessorOptions> preprocessorOpts_;
+  std::shared_ptr<Fortran::frontend::PreprocessorOptions> preprocessorOpts;
 
   CompilerInvocationBase();
   CompilerInvocationBase(const CompilerInvocationBase &x);
   ~CompilerInvocationBase();
 
-  clang::DiagnosticOptions &GetDiagnosticOpts() {
-    return *diagnosticOpts_.get();
+  clang::DiagnosticOptions &getDiagnosticOpts() {
+    return *diagnosticOpts.get();
   }
-  const clang::DiagnosticOptions &GetDiagnosticOpts() const {
-    return *diagnosticOpts_.get();
+  const clang::DiagnosticOptions &getDiagnosticOpts() const {
+    return *diagnosticOpts.get();
   }
 
-  PreprocessorOptions &preprocessorOpts() { return *preprocessorOpts_; }
-  const PreprocessorOptions &preprocessorOpts() const {
-    return *preprocessorOpts_;
+  PreprocessorOptions &getPreprocessorOpts() { return *preprocessorOpts; }
+  const PreprocessorOptions &getPreprocessorOpts() const {
+    return *preprocessorOpts;
   }
 };
 
@@ -55,43 +55,43 @@
   /// Options for the frontend driver
   // TODO: Merge with or translate to parserOpts_. We shouldn't need two sets of
   // options.
-  FrontendOptions frontendOpts_;
+  FrontendOptions frontendOpts;
 
   /// Options for Flang parser
-  // TODO: Merge with or translate to frontendOpts_. We shouldn't need two sets
+  // TODO: Merge with or translate to frontendOpts. We shouldn't need two sets
   // of options.
-  Fortran::parser::Options parserOpts_;
+  Fortran::parser::Options parserOpts;
 
   /// Options controlling the target.
-  Fortran::frontend::TargetOptions targetOpts_;
+  Fortran::frontend::TargetOptions targetOpts;
 
   // Semantics context
-  std::unique_ptr<Fortran::semantics::SemanticsContext> semanticsContext_;
+  std::unique_ptr<Fortran::semantics::SemanticsContext> semanticsContext;
 
   /// Semantic options
-  // TODO: Merge with or translate to frontendOpts_. We shouldn't need two sets
+  // TODO: Merge with or translate to frontendOpts. We shouldn't need two sets
   // of options.
-  std::string moduleDir_ = ".";
+  std::string moduleDir = ".";
 
-  std::string moduleFileSuffix_ = ".mod";
+  std::string moduleFileSuffix = ".mod";
 
-  bool debugModuleDir_ = false;
+  bool debugModuleDir = false;
 
-  bool warnAsErr_ = false;
+  bool warnAsErr = false;
 
   /// This flag controls the unparsing and is used to decide whether to print out
   /// the semantically analyzed version of an object or expression or the plain
   /// version that does not include any information from semantic analysis.
-  bool useAnalyzedObjectsForUnparse_ = true;
+  bool useAnalyzedObjectsForUnparse = true;
 
   // Fortran Dialect options
-  Fortran::common::IntrinsicTypeDefaultKinds defaultKinds_;
+  Fortran::common::IntrinsicTypeDefaultKinds defaultKinds;
 
-  bool EnableConformanceChecks_ = false;
+  bool enableConformanceChecks = false;
 
   /// Used in e.g. unparsing to dump the analyzed rather than the original
   /// parse-tree objects.
-  Fortran::parser::AnalyzedObjectsAsFortran AsFortran_{
+  Fortran::parser::AnalyzedObjectsAsFortran asFortran{
       [](llvm::raw_ostream &o, const Fortran::evaluate::GenericExprWrapper &x) {
         if (x.v) {
           x.v->AsFortran(o);
@@ -115,102 +115,106 @@
 public:
   CompilerInvocation() = default;
 
-  FrontendOptions &frontendOpts() { return frontendOpts_; }
-  const FrontendOptions &frontendOpts() const { return frontendOpts_; }
+  FrontendOptions &getFrontendOpts() { return frontendOpts; }
+  const FrontendOptions &getFrontendOpts() const { return frontendOpts; }
 
-  Fortran::parser::Options &fortranOpts() { return parserOpts_; }
-  const Fortran::parser::Options &fortranOpts() const { return parserOpts_; }
+  Fortran::parser::Options &getFortranOpts() { return parserOpts; }
+  const Fortran::parser::Options &getFortranOpts() const { return parserOpts; }
 
-  TargetOptions &targetOpts() { return targetOpts_; }
-  const TargetOptions &targetOpts() const { return targetOpts_; }
+  TargetOptions &getTargetOpts() { return targetOpts; }
+  const TargetOptions &getTargetOpts() const { return targetOpts; }
 
-  Fortran::semantics::SemanticsContext &semanticsContext() {
-    return *semanticsContext_;
+  Fortran::semantics::SemanticsContext &getSemanticsContext() {
+    return *semanticsContext;
   }
-  const Fortran::semantics::SemanticsContext &semanticsContext() const {
-    return *semanticsContext_;
+  const Fortran::semantics::SemanticsContext &getSemanticsContext() const {
+    return *semanticsContext;
   }
 
-  std::string &moduleDir() { return moduleDir_; }
-  const std::string &moduleDir() const { return moduleDir_; }
+  std::string &getModuleDir() { return moduleDir; }
+  const std::string &getModuleDir() const { return moduleDir; }
 
-  std::string &moduleFileSuffix() { return moduleFileSuffix_; }
-  const std::string &moduleFileSuffix() const { return moduleFileSuffix_; }
+  std::string &getModuleFileSuffix() { return moduleFileSuffix; }
+  const std::string &getModuleFileSuffix() const { return moduleFileSuffix; }
 
-  bool &debugModuleDir() { return debugModuleDir_; }
-  const bool &debugModuleDir() const { return debugModuleDir_; }
+  bool &getDebugModuleDir() { return debugModuleDir; }
+  const bool &getDebugModuleDir() const { return debugModuleDir; }
 
-  bool &warnAsErr() { return warnAsErr_; }
-  const bool &warnAsErr() const { return warnAsErr_; }
+  bool &getWarnAsErr() { return warnAsErr; }
+  const bool &getWarnAsErr() const { return warnAsErr; }
 
-  bool &useAnalyzedObjectsForUnparse() { return useAnalyzedObjectsForUnparse_; }
-  const bool &useAnalyzedObjectsForUnparse() const {
-    return useAnalyzedObjectsForUnparse_;
+  bool &getUseAnalyzedObjectsForUnparse() {
+    return useAnalyzedObjectsForUnparse;
+  }
+  const bool &getUseAnalyzedObjectsForUnparse() const {
+    return useAnalyzedObjectsForUnparse;
   }
 
-  bool &enableConformanceChecks() { return EnableConformanceChecks_; }
-  const bool &enableConformanceChecks() const {
-    return EnableConformanceChecks_;
+  bool &getEnableConformanceChecks() { return enableConformanceChecks; }
+  const bool &getEnableConformanceChecks() const {
+    return enableConformanceChecks;
   }
 
-  Fortran::parser::AnalyzedObjectsAsFortran &asFortran() { return AsFortran_; }
-  const Fortran::parser::AnalyzedObjectsAsFortran &asFortran() const {
-    return AsFortran_;
+  Fortran::parser::AnalyzedObjectsAsFortran &getAsFortran() {
+    return asFortran;
+  }
+  const Fortran::parser::AnalyzedObjectsAsFortran &getAsFortran() const {
+    return asFortran;
   }
 
-  Fortran::common::IntrinsicTypeDefaultKinds &defaultKinds() {
-    return defaultKinds_;
+  Fortran::common::IntrinsicTypeDefaultKinds &getDefaultKinds() {
+    return defaultKinds;
   }
-  const Fortran::common::IntrinsicTypeDefaultKinds &defaultKinds() const {
-    return defaultKinds_;
+  const Fortran::common::IntrinsicTypeDefaultKinds &getDefaultKinds() const {
+    return defaultKinds;
   }
 
   /// Create a compiler invocation from a list of input options.
   /// \returns true on success.
   /// \returns false if an error was encountered while parsing the arguments
   /// \param [out] res - The resulting invocation.
-  static bool CreateFromArgs(CompilerInvocation &res,
+  static bool createFromArgs(CompilerInvocation &res,
       llvm::ArrayRef<const char *> commandLineArgs,
       clang::DiagnosticsEngine &diags);
 
   // Enables the std=f2018 conformance check
-  void set_EnableConformanceChecks() { EnableConformanceChecks_ = true; }
+  void setEnableConformanceChecks() { enableConformanceChecks = true; }
 
   /// Useful setters
-  void SetModuleDir(std::string &moduleDir) { moduleDir_ = moduleDir; }
+  void setModuleDir(std::string &dir) { moduleDir = dir; }
 
-  void SetModuleFileSuffix(const char *moduleFileSuffix) {
-    moduleFileSuffix_ = std::string(moduleFileSuffix);
+  void setModuleFileSuffix(const char *suffix) {
+    moduleFileSuffix = std::string(suffix);
   }
 
-  void SetDebugModuleDir(bool flag) { debugModuleDir_ = flag; }
+  void setDebugModuleDir(bool flag) { debugModuleDir = flag; }
 
-  void SetWarnAsErr(bool flag) { warnAsErr_ = flag; }
+  void setWarnAsErr(bool flag) { warnAsErr = flag; }
 
-  void SetUseAnalyzedObjectsForUnparse(bool flag) {
-    useAnalyzedObjectsForUnparse_ = flag;
+  void setUseAnalyzedObjectsForUnparse(bool flag) {
+    useAnalyzedObjectsForUnparse = flag;
   }
 
   /// Set the Fortran options to predefined defaults.
   // TODO: We should map frontendOpts_ to parserOpts_ instead. For that, we
   // need to extend frontendOpts_ first. Next, we need to add the corresponding
   // compiler driver options in libclangDriver.
-  void SetDefaultFortranOpts();
+  void setDefaultFortranOpts();
 
   /// Set the default predefinitions.
-  void SetDefaultPredefinitions();
+  void setDefaultPredefinitions();
 
   /// Collect the macro definitions from preprocessorOpts_ and prepare them for
   /// the parser (i.e. copy into parserOpts_)
-  void CollectMacroDefinitions();
+  void collectMacroDefinitions();
 
   /// Set the Fortran options to user-specified values.
   /// These values are found in the preprocessor options.
-  void SetFortranOpts();
+  void setFortranOpts();
 
   /// Set the Semantic Options
-  void SetSemanticsOpts(Fortran::parser::AllCookedSources &);
+  void setSemanticsOpts(Fortran::parser::AllCookedSources &);
 };
 
 } // end namespace Fortran::frontend
-#endif // LLVM_FLANG_FRONTEND_COMPILERINVOCATION_H
+#endif // FORTRAN_FRONTEND_COMPILERINVOCATION_H
diff --git a/flang/include/flang/Frontend/FrontendAction.h b/flang/include/flang/Frontend/FrontendAction.h
--- a/flang/include/flang/Frontend/FrontendAction.h
+++ b/flang/include/flang/Frontend/FrontendAction.h
@@ -11,8 +11,8 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTEND_FRONTENDACTION_H
-#define LLVM_FLANG_FRONTEND_FRONTENDACTION_H
+#ifndef FORTRAN_FRONTEND_FRONTENDACTION_H
+#define FORTRAN_FRONTEND_FRONTENDACTION_H
 
 #include "flang/Frontend/FrontendOptions.h"
 #include "llvm/Support/Error.h"
@@ -22,8 +22,8 @@
 
 /// Abstract base class for actions which can be performed by the frontend.
 class FrontendAction {
-  FrontendInputFile currentInput_;
-  CompilerInstance *instance_;
+  FrontendInputFile currentInput;
+  CompilerInstance *instance;
 
 protected:
   /// @name Implementation Action Interface
@@ -31,54 +31,54 @@
 
   /// Callback to run the program action, using the initialized
   /// compiler instance.
-  virtual void ExecuteAction() = 0;
+  virtual void executeAction() = 0;
 
   /// Callback at the end of processing a single input, to determine
   /// if the output files should be erased or not.
   ///
   /// By default it returns true if a compiler error occurred.
-  virtual bool ShouldEraseOutputFiles();
+  virtual bool shouldEraseOutputFiles();
 
   /// Callback at the start of processing a single input.
   ///
   /// \return True on success; on failure ExecutionAction() and
   /// EndSourceFileAction() will not be called.
-  virtual bool BeginSourceFileAction() { return true; }
+  virtual bool beginSourceFileAction() { return true; }
 
   /// @}
 
 public:
-  FrontendAction() : instance_(nullptr) {}
+  FrontendAction() : instance(nullptr) {}
   virtual ~FrontendAction() = default;
 
   /// @name Compiler Instance Access
   /// @{
 
-  CompilerInstance &instance() const {
-    assert(instance_ && "Compiler instance not registered!");
-    return *instance_;
+  CompilerInstance &getInstance() const {
+    assert(instance && "Compiler instance not registered!");
+    return *instance;
   }
 
-  void set_instance(CompilerInstance *value) { instance_ = value; }
+  void setInstance(CompilerInstance *value) { instance = value; }
 
   /// @}
   /// @name Current File Information
   /// @{
 
-  const FrontendInputFile &currentInput() const { return currentInput_; }
+  const FrontendInputFile &getCurrentInput() const { return currentInput; }
 
-  llvm::StringRef GetCurrentFile() const {
-    assert(!currentInput_.IsEmpty() && "No current file!");
-    return currentInput_.file();
+  llvm::StringRef getCurrentFile() const {
+    assert(!currentInput.isEmpty() && "No current file!");
+    return currentInput.getFile();
   }
 
-  llvm::StringRef GetCurrentFileOrBufferName() const {
-    assert(!currentInput_.IsEmpty() && "No current file!");
-    return currentInput_.IsFile()
-        ? currentInput_.file()
-        : currentInput_.buffer()->getBufferIdentifier();
+  llvm::StringRef getCurrentFileOrBufferName() const {
+    assert(!currentInput.isEmpty() && "No current file!");
+    return currentInput.isFile()
+        ? currentInput.getFile()
+        : currentInput.getBuffer()->getBufferIdentifier();
   }
-  void set_currentInput(const FrontendInputFile &currentInput);
+  void setCurrentInput(const FrontendInputFile &currentIntput);
 
   /// @}
   /// @name Public Action Interface
@@ -92,30 +92,30 @@
   /// action may store and use this object.
   /// \param input - The input filename and kind.
   /// \return True on success; on failure the compilation of this file should
-  bool BeginSourceFile(CompilerInstance &ci, const FrontendInputFile &input);
+  bool beginSourceFile(CompilerInstance &ci, const FrontendInputFile &input);
 
   /// Run the action.
-  llvm::Error Execute();
+  llvm::Error execute();
 
   /// Perform any per-file post processing, deallocate per-file
   /// objects, and run statistics and output file cleanup code.
-  void EndSourceFile();
+  void endSourceFile();
 
   /// @}
 protected:
   // Prescan the current input file. Return False if fatal errors are reported,
   // True otherwise.
-  bool RunPrescan();
+  bool runPrescan();
   // Parse the current input file. Return False if fatal errors are reported,
   // True otherwise.
-  bool RunParse();
+  bool runParse();
   // Run semantic checks for the current input file. Return False if fatal
   // errors are reported, True otherwise.
-  bool RunSemanticChecks();
+  bool runSemanticChecks();
   // Generate run-time type information for derived types. This may lead to new
   // semantic errors. Return False if fatal errors are reported, True
   // otherwise.
-  bool GenerateRtTypeTables();
+  bool generateRtTypeTables();
 
   // Report fatal semantic errors. Return True if present, false otherwise.
   bool reportFatalSemanticErrors();
@@ -136,4 +136,4 @@
 
 } // namespace Fortran::frontend
 
-#endif // LLVM_FLANG_FRONTEND_FRONTENDACTION_H
+#endif // FORTRAN_FRONTEND_FRONTENDACTION_H
diff --git a/flang/include/flang/Frontend/FrontendActions.h b/flang/include/flang/Frontend/FrontendActions.h
--- a/flang/include/flang/Frontend/FrontendActions.h
+++ b/flang/include/flang/Frontend/FrontendActions.h
@@ -6,8 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTEND_FRONTENDACTIONS_H
-#define LLVM_FLANG_FRONTEND_FRONTENDACTIONS_H
+#ifndef FORTRAN_FRONTEND_FRONTENDACTIONS_H
+#define FORTRAN_FRONTEND_FRONTENDACTIONS_H
 
 #include "flang/Frontend/FrontendAction.h"
 #include "flang/Parser/parsing.h"
@@ -37,51 +37,51 @@
 //===----------------------------------------------------------------------===//
 
 class InputOutputTestAction : public FrontendAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class InitOnlyAction : public FrontendAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 //===----------------------------------------------------------------------===//
 // Prescan Actions
 //===----------------------------------------------------------------------===//
 class PrescanAction : public FrontendAction {
-  void ExecuteAction() override = 0;
-  bool BeginSourceFileAction() override;
+  void executeAction() override = 0;
+  bool beginSourceFileAction() override;
 };
 
 class PrintPreprocessedAction : public PrescanAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpProvenanceAction : public PrescanAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpParsingLogAction : public PrescanAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugMeasureParseTreeAction : public PrescanAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 //===----------------------------------------------------------------------===//
 // PrescanAndParse Actions
 //===----------------------------------------------------------------------===//
 class PrescanAndParseAction : public FrontendAction {
-  void ExecuteAction() override = 0;
-  bool BeginSourceFileAction() override;
+  void executeAction() override = 0;
+  bool beginSourceFileAction() override;
 };
 
 class DebugUnparseNoSemaAction : public PrescanAndParseAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpParseTreeNoSemaAction : public PrescanAndParseAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 //===----------------------------------------------------------------------===//
@@ -92,48 +92,48 @@
 //===----------------------------------------------------------------------===//
 class PrescanAndSemaAction : public FrontendAction {
 
-  void ExecuteAction() override = 0;
-  bool BeginSourceFileAction() override;
+  void executeAction() override = 0;
+  bool beginSourceFileAction() override;
 };
 
 class DebugUnparseWithSymbolsAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugUnparseAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpSymbolsAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpParseTreeAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugDumpPFTAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class DebugPreFIRTreeAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class GetDefinitionAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class GetSymbolsSourcesAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class ParseSyntaxOnlyAction : public PrescanAndSemaAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 class PluginParseTreeAction : public PrescanAndSemaAction {
-  void ExecuteAction() override = 0;
+  void executeAction() override = 0;
 
 public:
   Fortran::parser::Parsing &getParsing();
@@ -160,12 +160,12 @@
 //===----------------------------------------------------------------------===//
 class PrescanAndSemaDebugAction : public FrontendAction {
 
-  void ExecuteAction() override = 0;
-  bool BeginSourceFileAction() override;
+  void executeAction() override = 0;
+  bool beginSourceFileAction() override;
 };
 
 class DebugDumpAllAction : public PrescanAndSemaDebugAction {
-  void ExecuteAction() override;
+  void executeAction() override;
 };
 
 //===----------------------------------------------------------------------===//
@@ -191,10 +191,10 @@
 /// tree to an MLIR module.
 class CodeGenAction : public FrontendAction {
 
-  void ExecuteAction() override;
+  void executeAction() override;
   /// Runs prescan, parsing, sema and lowers to MLIR.
-  bool BeginSourceFileAction() override;
-  void SetUpTargetMachine();
+  bool beginSourceFileAction() override;
+  void setUpTargetMachine();
 
 protected:
   CodeGenAction(BackendActionTy act) : action{act} {};
@@ -210,11 +210,11 @@
 
   /// Generates an LLVM IR module from CodeGenAction::mlirModule and saves it
   /// in CodeGenAction::llvmModule.
-  void GenerateLLVMIR();
+  void generateLLVMIR();
 
   BackendActionTy action;
 
-  std::unique_ptr<llvm::TargetMachine> TM;
+  std::unique_ptr<llvm::TargetMachine> tm;
   /// }
 public:
   ~CodeGenAction() override;
@@ -247,4 +247,4 @@
 
 } // namespace Fortran::frontend
 
-#endif // LLVM_FLANG_FRONTEND_FRONTENDACTIONS_H
+#endif // FORTRAN_FRONTEND_FRONTENDACTIONS_H
diff --git a/flang/include/flang/Frontend/FrontendOptions.h b/flang/include/flang/Frontend/FrontendOptions.h
--- a/flang/include/flang/Frontend/FrontendOptions.h
+++ b/flang/include/flang/Frontend/FrontendOptions.h
@@ -5,15 +5,14 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-#ifndef LLVM_FLANG_FRONTEND_FRONTENDOPTIONS_H
-#define LLVM_FLANG_FRONTEND_FRONTENDOPTIONS_H
+#ifndef FORTRAN_FRONTEND_FRONTENDOPTIONS_H
+#define FORTRAN_FRONTEND_FRONTENDOPTIONS_H
 
 #include "flang/Common/Fortran-features.h"
 #include "flang/Parser/characters.h"
 #include "flang/Parser/unparse.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/MemoryBuffer.h"
-
 #include <cstdint>
 #include <string>
 
@@ -106,7 +105,7 @@
 
 /// \param suffix The file extension
 /// \return True if the file should be preprocessed
-bool mustBePreprocessed(llvm::StringRef suffix);
+bool isToBePreprocessed(llvm::StringRef suffix);
 
 enum class Language : uint8_t {
   Unknown,
@@ -134,76 +133,75 @@
 /// The kind of a file that we've been handed as an input.
 class InputKind {
 private:
-  Language lang_;
+  Language lang;
 
 public:
   /// The input file format.
   enum Format { Source, ModuleMap, Precompiled };
 
-  constexpr InputKind(Language l = Language::Unknown) : lang_(l) {}
+  constexpr InputKind(Language l = Language::Unknown) : lang(l) {}
 
-  Language GetLanguage() const { return static_cast<Language>(lang_); }
+  Language getLanguage() const { return static_cast<Language>(lang); }
 
   /// Is the input kind fully-unknown?
-  bool IsUnknown() const { return lang_ == Language::Unknown; }
+  bool isUnknown() const { return lang == Language::Unknown; }
 };
 
 /// An input file for the front end.
 class FrontendInputFile {
   /// The file name, or "-" to read from standard input.
-  std::string file_;
+  std::string file;
 
   /// The input, if it comes from a buffer rather than a file. This object
   /// does not own the buffer, and the caller is responsible for ensuring
   /// that it outlives any users.
-  const llvm::MemoryBuffer *buffer_ = nullptr;
+  const llvm::MemoryBuffer *buffer = nullptr;
 
   /// The kind of input, atm it contains language
-  InputKind kind_;
+  InputKind kind;
 
   /// Is this input file in fixed-form format? This is simply derived from the
   /// file extension and should not be altered by consumers. For input from
   /// stdin this is never modified.
-  bool isFixedForm_ = false;
+  bool isFixedForm = false;
 
   /// Must this file be preprocessed? Note that in Flang the preprocessor is
   /// always run. This flag is used to control whether predefined and command
   /// line preprocessor macros are enabled or not. In practice, this is
   /// sufficient to implement gfortran`s logic controlled with `-cpp/-nocpp`.
-  unsigned mustBePreprocessed_ : 1;
+  unsigned mustBePreprocessed : 1;
 
 public:
   FrontendInputFile() = default;
-  FrontendInputFile(llvm::StringRef file, InputKind kind)
-      : file_(file.str()), kind_(kind) {
+  FrontendInputFile(llvm::StringRef file, InputKind inKind)
+      : file(file.str()), kind(inKind) {
 
     // Based on the extension, decide whether this is a fixed or free form
     // file.
     auto pathDotIndex{file.rfind(".")};
     std::string pathSuffix{file.substr(pathDotIndex + 1)};
-    isFixedForm_ = isFixedFormSuffix(pathSuffix);
-    mustBePreprocessed_ = mustBePreprocessed(pathSuffix);
+    isFixedForm = isFixedFormSuffix(pathSuffix);
+    mustBePreprocessed = isToBePreprocessed(pathSuffix);
   }
 
-  FrontendInputFile(const llvm::MemoryBuffer *buffer, InputKind kind)
-      : buffer_(buffer), kind_(kind) {}
+  FrontendInputFile(const llvm::MemoryBuffer *memBuf, InputKind inKind)
+      : buffer(memBuf), kind(inKind) {}
 
-  InputKind kind() const { return kind_; }
+  InputKind getKind() const { return kind; }
 
-  bool IsEmpty() const { return file_.empty() && buffer_ == nullptr; }
-  bool IsFile() const { return !IsBuffer(); }
-  bool IsBuffer() const { return buffer_ != nullptr; }
-  bool IsFixedForm() const { return isFixedForm_; }
-  bool MustBePreprocessed() const { return mustBePreprocessed_; }
+  bool isEmpty() const { return file.empty() && buffer == nullptr; }
+  bool isFile() const { return (buffer == nullptr); }
+  bool getIsFixedForm() const { return isFixedForm; }
+  bool getMustBePreprocessed() const { return mustBePreprocessed; }
 
-  llvm::StringRef file() const {
-    assert(IsFile());
-    return file_;
+  llvm::StringRef getFile() const {
+    assert(isFile());
+    return file;
   }
 
-  const llvm::MemoryBuffer *buffer() const {
-    assert(IsBuffer() && "Requested buffer_, but it is empty!");
-    return buffer_;
+  const llvm::MemoryBuffer *getBuffer() const {
+    assert(buffer && "Requested buffer, but it is empty!");
+    return buffer;
   }
 };
 
@@ -265,7 +263,7 @@
   std::vector<std::string> plugins;
 
   /// The name of the action to run when using a plugin action.
-  std::string ActionName;
+  std::string actionName;
 
   /// A list of arguments to forward to LLVM's option processing; this
   /// should only be used for debugging and experimental features.
@@ -280,8 +278,8 @@
   ///
   /// \return The input kind for the extension, or Language::Unknown if the
   /// extension is not recognized.
-  static InputKind GetInputKindForExtension(llvm::StringRef extension);
+  static InputKind getInputKindForExtension(llvm::StringRef extension);
 };
 } // namespace Fortran::frontend
 
-#endif // LLVM_FLANG_FRONTEND_FRONTENDOPTIONS_H
+#endif // FORTRAN_FRONTEND_FRONTENDOPTIONS_H
diff --git a/flang/include/flang/Frontend/FrontendPluginRegistry.h b/flang/include/flang/Frontend/FrontendPluginRegistry.h
--- a/flang/include/flang/Frontend/FrontendPluginRegistry.h
+++ b/flang/include/flang/Frontend/FrontendPluginRegistry.h
@@ -10,8 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef FLANG_FRONTEND_FRONTENDPLUGINREGISTRY_H
-#define FLANG_FRONTEND_FRONTENDPLUGINREGISTRY_H
+#ifndef FORTRAN_FRONTEND_FRONTENDPLUGINREGISTRY_H
+#define FORTRAN_FRONTEND_FRONTENDPLUGINREGISTRY_H
 
 #include "flang/Frontend/FrontendActions.h"
 #include "llvm/Support/Registry.h"
@@ -23,4 +23,4 @@
 
 } // namespace Fortran::frontend
 
-#endif // FLANG_FRONTEND_FRONTENDPLUGINREGISTRY_H
+#endif // FORTRAN_FRONTEND_FRONTENDPLUGINREGISTRY_H
diff --git a/flang/include/flang/Frontend/PreprocessorOptions.h b/flang/include/flang/Frontend/PreprocessorOptions.h
--- a/flang/include/flang/Frontend/PreprocessorOptions.h
+++ b/flang/include/flang/Frontend/PreprocessorOptions.h
@@ -12,8 +12,8 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_PREPROCESSOROPTIONS_H
-#define LLVM_FLANG_PREPROCESSOROPTIONS_H
+#ifndef FORTRAN_FRONTEND_PREPROCESSOROPTIONS_H
+#define FORTRAN_FRONTEND_PREPROCESSOROPTIONS_H
 
 #include "llvm/ADT/StringRef.h"
 
@@ -63,4 +63,4 @@
 
 } // namespace Fortran::frontend
 
-#endif // LLVM_FLANG_PREPROCESSOROPTIONS_H
+#endif // FORTRAN_FRONTEND_PREPROCESSOROPTIONS_H
diff --git a/flang/include/flang/Frontend/TargetOptions.h b/flang/include/flang/Frontend/TargetOptions.h
--- a/flang/include/flang/Frontend/TargetOptions.h
+++ b/flang/include/flang/Frontend/TargetOptions.h
@@ -11,8 +11,8 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_TARGETOPTIONS_H
-#define LLVM_FLANG_TARGETOPTIONS_H
+#ifndef FORTRAN_FRONTEND_TARGETOPTIONS_H
+#define FORTRAN_FRONTEND_TARGETOPTIONS_H
 
 namespace Fortran::frontend {
 
diff --git a/flang/include/flang/Frontend/TextDiagnostic.h b/flang/include/flang/Frontend/TextDiagnostic.h
--- a/flang/include/flang/Frontend/TextDiagnostic.h
+++ b/flang/include/flang/Frontend/TextDiagnostic.h
@@ -12,8 +12,8 @@
 // TODO: If expanding, consider sharing the implementation with Clang.
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTEND_TEXTDIAGNOSTIC_H
-#define LLVM_FLANG_FRONTEND_TEXTDIAGNOSTIC_H
+#ifndef FORTRAN_FRONTEND_TEXTDIAGNOSTIC_H
+#define FORTRAN_FRONTEND_TEXTDIAGNOSTIC_H
 
 #include "clang/Basic/Diagnostic.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
@@ -46,7 +46,7 @@
   /// \param os Where the message is printed
   /// \param level The diagnostic level (e.g. error or warning)
   /// \param showColors Enable colorizing of the message.
-  static void PrintDiagnosticLevel(llvm::raw_ostream &os,
+  static void printDiagnosticLevel(llvm::raw_ostream &os,
       clang::DiagnosticsEngine::Level level, bool showColors);
 
   /// Pretty-print a diagnostic message to a llvm::raw_ostream.
@@ -61,7 +61,7 @@
   /// \param isSupplemental true if this is a continuation note diagnostic
   /// \param message The text actually printed
   /// \param showColors Enable colorizing of the message.
-  static void PrintDiagnosticMessage(llvm::raw_ostream &os, bool isSupplemental,
+  static void printDiagnosticMessage(llvm::raw_ostream &os, bool isSupplemental,
       llvm::StringRef message, bool showColors);
 };
 
diff --git a/flang/include/flang/Frontend/TextDiagnosticBuffer.h b/flang/include/flang/Frontend/TextDiagnosticBuffer.h
--- a/flang/include/flang/Frontend/TextDiagnosticBuffer.h
+++ b/flang/include/flang/Frontend/TextDiagnosticBuffer.h
@@ -12,8 +12,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTEND_TEXTDIAGNOSTICBUFFER_H
-#define LLVM_FLANG_FRONTEND_TEXTDIAGNOSTICBUFFER_H
+#ifndef FORTRAN_FRONTEND_TEXTDIAGNOSTICBUFFER_H
+#define FORTRAN_FRONTEND_TEXTDIAGNOSTICBUFFER_H
 
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/SourceLocation.h"
@@ -31,22 +31,22 @@
       std::vector<std::pair<clang::DiagnosticsEngine::Level, size_t>>;
 
 private:
-  DiagList errors_, warnings_, remarks_, notes_;
+  DiagList errors, warnings, remarks, notes;
 
   /// All diagnostics in the order in which they were generated. That order
   /// likely doesn't correspond to user input order, but at least it keeps
   /// notes in the right places. Each pair is a diagnostic level and an index
   /// into the corresponding DiagList above.
-  DiagnosticsLevelAndIndexPairs all_;
+  DiagnosticsLevelAndIndexPairs all;
 
 public:
   void HandleDiagnostic(clang::DiagnosticsEngine::Level diagLevel,
       const clang::Diagnostic &info) override;
 
   /// Flush the buffered diagnostics to a given diagnostic engine.
-  void FlushDiagnostics(clang::DiagnosticsEngine &diags) const;
+  void flushDiagnostics(clang::DiagnosticsEngine &diags) const;
 };
 
 } // namespace Fortran::frontend
 
-#endif // LLVM_CLANG_FRONTEND_TEXTDIAGNOSTICBUFFER_H
+#endif // FORTRAN_FRONTEND_TEXTDIAGNOSTICBUFFER_H
diff --git a/flang/include/flang/Frontend/TextDiagnosticPrinter.h b/flang/include/flang/Frontend/TextDiagnosticPrinter.h
--- a/flang/include/flang/Frontend/TextDiagnosticPrinter.h
+++ b/flang/include/flang/Frontend/TextDiagnosticPrinter.h
@@ -13,8 +13,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTEND_TEXTDIAGNOSTICPRINTER_H
-#define LLVM_FLANG_FRONTEND_TEXTDIAGNOSTICPRINTER_H
+#ifndef FORTRAN_FRONTEND_TEXTDIAGNOSTICPRINTER_H
+#define FORTRAN_FRONTEND_TEXTDIAGNOSTICPRINTER_H
 
 #include "clang/Basic/Diagnostic.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
@@ -32,11 +32,11 @@
 class TextDiagnostic;
 
 class TextDiagnosticPrinter : public clang::DiagnosticConsumer {
-  raw_ostream &os_;
-  llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagOpts_;
+  raw_ostream &os;
+  llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagOpts;
 
   /// A string to prefix to error messages.
-  std::string prefix_;
+  std::string prefix;
 
 public:
   TextDiagnosticPrinter(raw_ostream &os, clang::DiagnosticOptions *diags);
@@ -44,7 +44,7 @@
 
   /// Set the diagnostic printer prefix string, which will be printed at the
   /// start of any diagnostics. If empty, no prefix string is used.
-  void set_prefix(std::string value) { prefix_ = std::move(value); }
+  void setPrefix(std::string value) { prefix = std::move(value); }
 
   void HandleDiagnostic(clang::DiagnosticsEngine::Level level,
       const clang::Diagnostic &info) override;
diff --git a/flang/include/flang/FrontendTool/.clang-tidy b/flang/include/flang/FrontendTool/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/include/flang/FrontendTool/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/include/flang/FrontendTool/Utils.h b/flang/include/flang/FrontendTool/Utils.h
--- a/flang/include/flang/FrontendTool/Utils.h
+++ b/flang/include/flang/FrontendTool/Utils.h
@@ -11,8 +11,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_FLANG_FRONTENDTOOL_UTILS_H
-#define LLVM_FLANG_FRONTENDTOOL_UTILS_H
+#ifndef FORTRAN_FRONTEND_FRONTENDTOOL_UTILS_H
+#define FORTRAN_FRONTEND_FRONTENDTOOL_UTILS_H
 
 namespace Fortran::frontend {
 
@@ -22,8 +22,8 @@
 /// compiler invocation object in the given compiler instance.
 ///
 /// \return - True on success.
-bool ExecuteCompilerInvocation(CompilerInstance *flang);
+bool executeCompilerInvocation(CompilerInstance *flang);
 
 } // end namespace Fortran::frontend
 
-#endif // LLVM_FLANG_FRONTENDTOOL_UTILS_H
+#endif // FORTRAN_FRONTEND_FRONTENDTOOL_UTILS_H
diff --git a/flang/lib/Frontend/.clang-tidy b/flang/lib/Frontend/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/lib/Frontend/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/lib/Frontend/CompilerInstance.cpp b/flang/lib/Frontend/CompilerInstance.cpp
--- a/flang/lib/Frontend/CompilerInstance.cpp
+++ b/flang/lib/Frontend/CompilerInstance.cpp
@@ -22,33 +22,32 @@
 using namespace Fortran::frontend;
 
 CompilerInstance::CompilerInstance()
-    : invocation_(new CompilerInvocation()),
-      allSources_(new Fortran::parser::AllSources()),
-      allCookedSources_(new Fortran::parser::AllCookedSources(*allSources_)),
-      parsing_(new Fortran::parser::Parsing(*allCookedSources_)) {
+    : invocation(new CompilerInvocation()),
+      allSources(new Fortran::parser::AllSources()),
+      allCookedSources(new Fortran::parser::AllCookedSources(*allSources)),
+      parsing(new Fortran::parser::Parsing(*allCookedSources)) {
   // TODO: This is a good default during development, but ultimately we should
   // give the user the opportunity to specify this.
-  allSources_->set_encoding(Fortran::parser::Encoding::UTF_8);
+  allSources->set_encoding(Fortran::parser::Encoding::UTF_8);
 }
 
 CompilerInstance::~CompilerInstance() {
-  assert(outputFiles_.empty() && "Still output files in flight?");
+  assert(outputFiles.empty() && "Still output files in flight?");
 }
 
-void CompilerInstance::set_invocation(
+void CompilerInstance::setInvocation(
     std::shared_ptr<CompilerInvocation> value) {
-  invocation_ = std::move(value);
+  invocation = std::move(value);
 }
 
-void CompilerInstance::set_semaOutputStream(raw_ostream &Value) {
-  ownedSemaOutputStream_.release();
-  semaOutputStream_ = &Value;
+void CompilerInstance::setSemaOutputStream(raw_ostream &value) {
+  ownedSemaOutputStream.release();
+  semaOutputStream = &value;
 }
 
-void CompilerInstance::set_semaOutputStream(
-    std::unique_ptr<raw_ostream> Value) {
-  ownedSemaOutputStream_.swap(Value);
-  semaOutputStream_ = ownedSemaOutputStream_.get();
+void CompilerInstance::setSemaOutputStream(std::unique_ptr<raw_ostream> value) {
+  ownedSemaOutputStream.swap(value);
+  semaOutputStream = ownedSemaOutputStream.get();
 }
 
 // Helper method to generate the path of the output file. The following logic
@@ -59,8 +58,9 @@
 //    the input file (i.e. inputFilename + extension)
 // 3. If the output file is not specified and the input file is `-`, then set
 //    the output file to `-` as well.
-static std::string GetOutputFilePath(llvm::StringRef outputFilename,
-    llvm::StringRef inputFilename, llvm::StringRef extension) {
+static std::string getOutputFilePath(llvm::StringRef outputFilename,
+                                     llvm::StringRef inputFilename,
+                                     llvm::StringRef extension) {
 
   // Output filename _is_ specified. Just use that.
   if (!outputFilename.empty())
@@ -78,35 +78,35 @@
 }
 
 std::unique_ptr<llvm::raw_pwrite_stream>
-CompilerInstance::CreateDefaultOutputFile(
-    bool binary, llvm::StringRef baseName, llvm::StringRef extension) {
+CompilerInstance::createDefaultOutputFile(bool binary, llvm::StringRef baseName,
+                                          llvm::StringRef extension) {
 
   // Get the path of the output file
   std::string outputFilePath =
-      GetOutputFilePath(frontendOpts().outputFile, baseName, extension);
+      getOutputFilePath(getFrontendOpts().outputFile, baseName, extension);
 
   // Create the output file
   llvm::Expected<std::unique_ptr<llvm::raw_pwrite_stream>> os =
-      CreateOutputFileImpl(outputFilePath, binary);
+      createOutputFileImpl(outputFilePath, binary);
 
   // If successful, add the file to the list of tracked output files and
   // return.
   if (os) {
-    outputFiles_.emplace_back(OutputFile(outputFilePath));
+    outputFiles.emplace_back(OutputFile(outputFilePath));
     return std::move(*os);
   }
 
   // If unsuccessful, issue an error and return Null
-  unsigned DiagID = diagnostics().getCustomDiagID(
+  unsigned diagID = getDiagnostics().getCustomDiagID(
       clang::DiagnosticsEngine::Error, "unable to open output file '%0': '%1'");
-  diagnostics().Report(DiagID)
+  getDiagnostics().Report(diagID)
       << outputFilePath << llvm::errorToErrorCode(os.takeError()).message();
   return nullptr;
 }
 
 llvm::Expected<std::unique_ptr<llvm::raw_pwrite_stream>>
-CompilerInstance::CreateOutputFileImpl(
-    llvm::StringRef outputFilePath, bool binary) {
+CompilerInstance::createOutputFileImpl(llvm::StringRef outputFilePath,
+                                       bool binary) {
 
   // Creates the file descriptor for the output file
   std::unique_ptr<llvm::raw_fd_ostream> os;
@@ -128,47 +128,48 @@
   return std::make_unique<llvm::buffer_unique_ostream>(std::move(os));
 }
 
-void CompilerInstance::ClearOutputFiles(bool eraseFiles) {
-  for (OutputFile &of : outputFiles_)
-    if (!of.filename_.empty() && eraseFiles)
-      llvm::sys::fs::remove(of.filename_);
+void CompilerInstance::clearOutputFiles(bool eraseFiles) {
+  for (OutputFile &of : outputFiles)
+    if (!of.filename.empty() && eraseFiles)
+      llvm::sys::fs::remove(of.filename);
 
-  outputFiles_.clear();
+  outputFiles.clear();
 }
 
-bool CompilerInstance::ExecuteAction(FrontendAction &act) {
-  auto &invoc = this->invocation();
+bool CompilerInstance::executeAction(FrontendAction &act) {
+  auto &invoc = this->getInvocation();
 
   // Set some sane defaults for the frontend.
-  invoc.SetDefaultFortranOpts();
+  invoc.setDefaultFortranOpts();
   // Update the fortran options based on user-based input.
-  invoc.SetFortranOpts();
+  invoc.setFortranOpts();
   // Set the encoding to read all input files in based on user input.
-  allSources_->set_encoding(invoc.fortranOpts().encoding);
+  allSources->set_encoding(invoc.getFortranOpts().encoding);
   // Create the semantics context and set semantic options.
-  invoc.SetSemanticsOpts(*this->allCookedSources_);
+  invoc.setSemanticsOpts(*this->allCookedSources);
 
   // Run the frontend action `act` for every input file.
-  for (const FrontendInputFile &fif : frontendOpts().inputs) {
-    if (act.BeginSourceFile(*this, fif)) {
-      if (llvm::Error err = act.Execute()) {
+  for (const FrontendInputFile &fif : getFrontendOpts().inputs) {
+    if (act.beginSourceFile(*this, fif)) {
+      if (llvm::Error err = act.execute()) {
         consumeError(std::move(err));
       }
-      act.EndSourceFile();
+      act.endSourceFile();
     }
   }
-  return !diagnostics().getClient()->getNumErrors();
+  return !getDiagnostics().getClient()->getNumErrors();
 }
 
-void CompilerInstance::CreateDiagnostics(
-    clang::DiagnosticConsumer *client, bool shouldOwnClient) {
-  diagnostics_ =
-      CreateDiagnostics(&GetDiagnosticOpts(), client, shouldOwnClient);
+void CompilerInstance::createDiagnostics(clang::DiagnosticConsumer *client,
+                                         bool shouldOwnClient) {
+  diagnostics =
+      createDiagnostics(&getDiagnosticOpts(), client, shouldOwnClient);
 }
 
 clang::IntrusiveRefCntPtr<clang::DiagnosticsEngine>
-CompilerInstance::CreateDiagnostics(clang::DiagnosticOptions *opts,
-    clang::DiagnosticConsumer *client, bool shouldOwnClient) {
+CompilerInstance::createDiagnostics(clang::DiagnosticOptions *opts,
+                                    clang::DiagnosticConsumer *client,
+                                    bool shouldOwnClient) {
   clang::IntrusiveRefCntPtr<clang::DiagnosticIDs> diagID(
       new clang::DiagnosticIDs());
   clang::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diags(
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -37,12 +37,12 @@
 // Initialization.
 //===----------------------------------------------------------------------===//
 CompilerInvocationBase::CompilerInvocationBase()
-    : diagnosticOpts_(new clang::DiagnosticOptions()),
-      preprocessorOpts_(new PreprocessorOptions()) {}
+    : diagnosticOpts(new clang::DiagnosticOptions()),
+      preprocessorOpts(new PreprocessorOptions()) {}
 
 CompilerInvocationBase::CompilerInvocationBase(const CompilerInvocationBase &x)
-    : diagnosticOpts_(new clang::DiagnosticOptions(x.GetDiagnosticOpts())),
-      preprocessorOpts_(new PreprocessorOptions(x.preprocessorOpts())) {}
+    : diagnosticOpts(new clang::DiagnosticOptions(x.getDiagnosticOpts())),
+      preprocessorOpts(new PreprocessorOptions(x.getPreprocessorOpts())) {}
 
 CompilerInvocationBase::~CompilerInvocationBase() = default;
 
@@ -59,31 +59,33 @@
     Colors_On,
     Colors_Off,
     Colors_Auto
-  } ShowColors = defaultColor ? Colors_Auto : Colors_Off;
+  } showColors = defaultColor ? Colors_Auto : Colors_Off;
 
   for (auto *a : args) {
-    const llvm::opt::Option &O = a->getOption();
-    if (O.matches(clang::driver::options::OPT_fcolor_diagnostics)) {
-      ShowColors = Colors_On;
-    } else if (O.matches(clang::driver::options::OPT_fno_color_diagnostics)) {
-      ShowColors = Colors_Off;
-    } else if (O.matches(clang::driver::options::OPT_fdiagnostics_color_EQ)) {
+    const llvm::opt::Option &opt = a->getOption();
+    if (opt.matches(clang::driver::options::OPT_fcolor_diagnostics)) {
+      showColors = Colors_On;
+    } else if (opt.matches(clang::driver::options::OPT_fno_color_diagnostics)) {
+      showColors = Colors_Off;
+    } else if (opt.matches(clang::driver::options::OPT_fdiagnostics_color_EQ)) {
       llvm::StringRef value(a->getValue());
       if (value == "always")
-        ShowColors = Colors_On;
+        showColors = Colors_On;
       else if (value == "never")
-        ShowColors = Colors_Off;
+        showColors = Colors_Off;
       else if (value == "auto")
-        ShowColors = Colors_Auto;
+        showColors = Colors_Auto;
     }
   }
 
-  return ShowColors == Colors_On ||
-      (ShowColors == Colors_Auto && llvm::sys::Process::StandardErrHasColors());
+  return showColors == Colors_On ||
+         (showColors == Colors_Auto &&
+          llvm::sys::Process::StandardErrHasColors());
 }
 
-bool Fortran::frontend::ParseDiagnosticArgs(clang::DiagnosticOptions &opts,
-    llvm::opt::ArgList &args, bool defaultDiagColor) {
+bool Fortran::frontend::parseDiagnosticArgs(clang::DiagnosticOptions &opts,
+                                            llvm::opt::ArgList &args,
+                                            bool defaultDiagColor) {
   opts.ShowColors = parseShowColorsArgs(args, defaultDiagColor);
 
   return true;
@@ -94,7 +96,7 @@
 ///
 /// \param [in] opts The target options instance to update
 /// \param [in] args The list of input arguments (from the compiler invocation)
-static void ParseTargetArgs(TargetOptions &opts, llvm::opt::ArgList &args) {
+static void parseTargetArgs(TargetOptions &opts, llvm::opt::ArgList &args) {
   if (const llvm::opt::Arg *a =
           args.getLastArg(clang::driver::options::OPT_triple))
     opts.triple = a->getValue();
@@ -110,8 +112,8 @@
     opts.needProvenanceRangeToCharBlockMappings = true;
 }
 
-static bool ParseFrontendArgs(FrontendOptions &opts, llvm::opt::ArgList &args,
-    clang::DiagnosticsEngine &diags) {
+static bool parseFrontendArgs(FrontendOptions &opts, llvm::opt::ArgList &args,
+                              clang::DiagnosticsEngine &diags) {
   unsigned numErrorsBefore = diags.getNumErrors();
 
   // By default the frontend driver creates a ParseSyntaxOnly action.
@@ -243,7 +245,7 @@
   if (const llvm::opt::Arg *a =
           args.getLastArg(clang::driver::options::OPT_plugin)) {
     opts.programAction = PluginAction;
-    opts.ActionName = a->getValue();
+    opts.actionName = a->getValue();
   }
 
   opts.outputFile = args.getLastArgValue(clang::driver::options::OPT_o);
@@ -254,19 +256,19 @@
   InputKind dashX(Language::Unknown);
   if (const llvm::opt::Arg *a =
           args.getLastArg(clang::driver::options::OPT_x)) {
-    llvm::StringRef XValue = a->getValue();
+    llvm::StringRef xValue = a->getValue();
     // Principal languages.
-    dashX = llvm::StringSwitch<InputKind>(XValue)
+    dashX = llvm::StringSwitch<InputKind>(xValue)
                 .Case("f90", Language::Fortran)
                 .Default(Language::Unknown);
 
     // Some special cases cannot be combined with suffixes.
-    if (dashX.IsUnknown())
-      dashX = llvm::StringSwitch<InputKind>(XValue)
+    if (dashX.isUnknown())
+      dashX = llvm::StringSwitch<InputKind>(xValue)
                   .Case("ir", Language::LLVM_IR)
                   .Default(Language::Unknown);
 
-    if (dashX.IsUnknown())
+    if (dashX.isUnknown())
       diags.Report(clang::diag::err_drv_invalid_value)
           << a->getAsString(args) << a->getValue();
   }
@@ -280,10 +282,10 @@
     inputs.push_back("-");
   for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
     InputKind ik = dashX;
-    if (ik.IsUnknown()) {
-      ik = FrontendOptions::GetInputKindForExtension(
+    if (ik.isUnknown()) {
+      ik = FrontendOptions::getInputKindForExtension(
           llvm::StringRef(inputs[i]).rsplit('.').second);
-      if (ik.IsUnknown())
+      if (ik.isUnknown())
         ik = Language::Unknown;
       if (i == 0)
         dashX = ik;
@@ -449,23 +451,23 @@
     diags.Report(diagID);
   }
   if (moduleDirList.size() == 1)
-    res.SetModuleDir(moduleDirList[0]);
+    res.setModuleDir(moduleDirList[0]);
 
   // -fdebug-module-writer option
   if (args.hasArg(clang::driver::options::OPT_fdebug_module_writer)) {
-    res.SetDebugModuleDir(true);
+    res.setDebugModuleDir(true);
   }
 
   // -module-suffix
   if (const auto *moduleSuffix =
           args.getLastArg(clang::driver::options::OPT_module_suffix)) {
-    res.SetModuleFileSuffix(moduleSuffix->getValue());
+    res.setModuleFileSuffix(moduleSuffix->getValue());
   }
 
   // -f{no-}analyzed-objects-for-unparse
-  res.SetUseAnalyzedObjectsForUnparse(
-      args.hasFlag(clang::driver::options::OPT_fanalyzed_objects_for_unparse,
-          clang::driver::options::OPT_fno_analyzed_objects_for_unparse, true));
+  res.setUseAnalyzedObjectsForUnparse(args.hasFlag(
+      clang::driver::options::OPT_fanalyzed_objects_for_unparse,
+      clang::driver::options::OPT_fno_analyzed_objects_for_unparse, true));
 
   return diags.getNumErrors() == numErrorsBefore;
 }
@@ -482,7 +484,7 @@
   if (args.hasArg(clang::driver::options::OPT_W_Joined)) {
     if (args.getLastArgValue(clang::driver::options::OPT_W_Joined)
             .equals("error")) {
-      res.SetWarnAsErr(true);
+      res.setWarnAsErr(true);
     } else {
       const unsigned diagID =
           diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
@@ -502,13 +504,13 @@
 
   // -fdefault* family
   if (args.hasArg(clang::driver::options::OPT_fdefault_real_8)) {
-    res.defaultKinds().set_defaultRealKind(8);
-    res.defaultKinds().set_doublePrecisionKind(16);
+    res.getDefaultKinds().set_defaultRealKind(8);
+    res.getDefaultKinds().set_doublePrecisionKind(16);
   }
   if (args.hasArg(clang::driver::options::OPT_fdefault_integer_8)) {
-    res.defaultKinds().set_defaultIntegerKind(8);
-    res.defaultKinds().set_subscriptIntegerKind(8);
-    res.defaultKinds().set_sizeIntegerKind(8);
+    res.getDefaultKinds().set_defaultIntegerKind(8);
+    res.getDefaultKinds().set_subscriptIntegerKind(8);
+    res.getDefaultKinds().set_sizeIntegerKind(8);
   }
   if (args.hasArg(clang::driver::options::OPT_fdefault_double_8)) {
     if (!args.hasArg(clang::driver::options::OPT_fdefault_real_8)) {
@@ -520,24 +522,24 @@
       diags.Report(diagID);
     }
     // https://gcc.gnu.org/onlinedocs/gfortran/Fortran-Dialect-Options.html
-    res.defaultKinds().set_doublePrecisionKind(8);
+    res.getDefaultKinds().set_doublePrecisionKind(8);
   }
   if (args.hasArg(clang::driver::options::OPT_flarge_sizes))
-    res.defaultKinds().set_sizeIntegerKind(8);
+    res.getDefaultKinds().set_sizeIntegerKind(8);
 
   // -fopenmp and -fopenacc
   if (args.hasArg(clang::driver::options::OPT_fopenacc)) {
-    res.frontendOpts().features.Enable(
+    res.getFrontendOpts().features.Enable(
         Fortran::common::LanguageFeature::OpenACC);
   }
   if (args.hasArg(clang::driver::options::OPT_fopenmp)) {
-    res.frontendOpts().features.Enable(
+    res.getFrontendOpts().features.Enable(
         Fortran::common::LanguageFeature::OpenMP);
   }
 
   // -pedantic
   if (args.hasArg(clang::driver::options::OPT_pedantic)) {
-    res.set_EnableConformanceChecks();
+    res.setEnableConformanceChecks();
   }
   // -std=f2018 (currently this implies -pedantic)
   // TODO: Set proper options when more fortran standards
@@ -546,7 +548,7 @@
     auto standard = args.getLastArgValue(clang::driver::options::OPT_std_EQ);
     // We only allow f2018 as the given standard
     if (standard.equals("f2018")) {
-      res.set_EnableConformanceChecks();
+      res.setEnableConformanceChecks();
     } else {
       const unsigned diagID =
           diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
@@ -557,8 +559,8 @@
   return diags.getNumErrors() == numErrorsBefore;
 }
 
-bool CompilerInvocation::CreateFromArgs(CompilerInvocation &res,
-    llvm::ArrayRef<const char *> commandLineArgs,
+bool CompilerInvocation::createFromArgs(
+    CompilerInvocation &res, llvm::ArrayRef<const char *> commandLineArgs,
     clang::DiagnosticsEngine &diags) {
 
   bool success = true;
@@ -569,7 +571,7 @@
   // NOTE: Like in Clang, it would be nice to use option marshalling
   // for this so that the entire logic for setting-up the triple is in one
   // place.
-  res.targetOpts().triple =
+  res.getTargetOpts().triple =
       llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple());
 
   // Parse the arguments
@@ -598,23 +600,23 @@
     success = false;
   }
 
-  success &= ParseFrontendArgs(res.frontendOpts(), args, diags);
-  ParseTargetArgs(res.targetOpts(), args);
-  parsePreprocessorArgs(res.preprocessorOpts(), args);
+  success &= parseFrontendArgs(res.getFrontendOpts(), args, diags);
+  parseTargetArgs(res.getTargetOpts(), args);
+  parsePreprocessorArgs(res.getPreprocessorOpts(), args);
   success &= parseSemaArgs(res, args, diags);
   success &= parseDialectArgs(res, args, diags);
   success &= parseDiagArgs(res, args, diags);
-  res.frontendOpts_.llvmArgs =
+  res.frontendOpts.llvmArgs =
       args.getAllArgValues(clang::driver::options::OPT_mllvm);
 
-  res.frontendOpts_.mlirArgs =
+  res.frontendOpts.mlirArgs =
       args.getAllArgValues(clang::driver::options::OPT_mmlir);
 
   return success;
 }
 
-void CompilerInvocation::CollectMacroDefinitions() {
-  auto &ppOpts = this->preprocessorOpts();
+void CompilerInvocation::collectMacroDefinitions() {
+  auto &ppOpts = this->getPreprocessorOpts();
 
   for (unsigned i = 0, n = ppOpts.macros.size(); i != n; ++i) {
     llvm::StringRef macro = ppOpts.macros[i].first;
@@ -626,8 +628,8 @@
 
     // For an #undef'd macro, we only care about the name.
     if (isUndef) {
-      parserOpts_.predefinitions.emplace_back(
-          macroName.str(), std::optional<std::string>{});
+      parserOpts.predefinitions.emplace_back(macroName.str(),
+                                             std::optional<std::string>{});
       continue;
     }
 
@@ -636,16 +638,16 @@
       macroBody = "1";
     else {
       // Note: GCC drops anything following an end-of-line character.
-      llvm::StringRef::size_type End = macroBody.find_first_of("\n\r");
-      macroBody = macroBody.substr(0, End);
+      llvm::StringRef::size_type end = macroBody.find_first_of("\n\r");
+      macroBody = macroBody.substr(0, end);
     }
-    parserOpts_.predefinitions.emplace_back(
+    parserOpts.predefinitions.emplace_back(
         macroName, std::optional<std::string>(macroBody.str()));
   }
 }
 
-void CompilerInvocation::SetDefaultFortranOpts() {
-  auto &fortranOptions = fortranOpts();
+void CompilerInvocation::setDefaultFortranOpts() {
+  auto &fortranOptions = getFortranOpts();
 
   std::vector<std::string> searchDirectories{"."s};
   fortranOptions.searchDirectories = searchDirectories;
@@ -660,9 +662,9 @@
 // TODO: When expanding this method, consider creating a dedicated API for
 // this. Also at some point we will need to differentiate between different
 // targets and add dedicated predefines for each.
-void CompilerInvocation::SetDefaultPredefinitions() {
-  auto &fortranOptions = fortranOpts();
-  const auto &frontendOptions = frontendOpts();
+void CompilerInvocation::setDefaultPredefinitions() {
+  auto &fortranOptions = getFortranOpts();
+  const auto &frontendOptions = getFrontendOpts();
 
   // Populate the macro list with version numbers and other predefinitions.
   fortranOptions.predefinitions.emplace_back("__flang__", "1");
@@ -684,11 +686,11 @@
   }
 }
 
-void CompilerInvocation::SetFortranOpts() {
-  auto &fortranOptions = fortranOpts();
-  const auto &frontendOptions = frontendOpts();
-  const auto &preprocessorOptions = preprocessorOpts();
-  auto &moduleDirJ = moduleDir();
+void CompilerInvocation::setFortranOpts() {
+  auto &fortranOptions = getFortranOpts();
+  const auto &frontendOptions = getFrontendOpts();
+  const auto &preprocessorOptions = getPreprocessorOpts();
+  auto &moduleDirJ = getModuleDir();
 
   if (frontendOptions.fortranForm != FortranForm::Unknown) {
     fortranOptions.isFixedForm =
@@ -725,22 +727,22 @@
   if (frontendOptions.needProvenanceRangeToCharBlockMappings)
     fortranOptions.needProvenanceRangeToCharBlockMappings = true;
 
-  if (enableConformanceChecks()) {
+  if (getEnableConformanceChecks()) {
     fortranOptions.features.WarnOnAllNonstandard();
   }
 }
 
-void CompilerInvocation::SetSemanticsOpts(
+void CompilerInvocation::setSemanticsOpts(
     Fortran::parser::AllCookedSources &allCookedSources) {
-  const auto &fortranOptions = fortranOpts();
+  const auto &fortranOptions = getFortranOpts();
 
-  semanticsContext_ = std::make_unique<semantics::SemanticsContext>(
-      defaultKinds(), fortranOptions.features, allCookedSources);
+  semanticsContext = std::make_unique<semantics::SemanticsContext>(
+      getDefaultKinds(), fortranOptions.features, allCookedSources);
 
-  semanticsContext_->set_moduleDirectory(moduleDir())
+  semanticsContext->set_moduleDirectory(getModuleDir())
       .set_searchDirectories(fortranOptions.searchDirectories)
       .set_intrinsicModuleDirectories(fortranOptions.intrinsicModuleDirectories)
-      .set_warnOnNonstandardUsage(enableConformanceChecks())
-      .set_warningsAreErrors(warnAsErr())
-      .set_moduleFileSuffix(moduleFileSuffix());
+      .set_warnOnNonstandardUsage(getEnableConformanceChecks())
+      .set_warningsAreErrors(getWarnAsErr())
+      .set_moduleFileSuffix(getModuleFileSuffix());
 }
diff --git a/flang/lib/Frontend/FrontendAction.cpp b/flang/lib/Frontend/FrontendAction.cpp
--- a/flang/lib/Frontend/FrontendAction.cpp
+++ b/flang/lib/Frontend/FrontendAction.cpp
@@ -19,110 +19,111 @@
 
 LLVM_INSTANTIATE_REGISTRY(FrontendPluginRegistry)
 
-void FrontendAction::set_currentInput(const FrontendInputFile &currentInput) {
-  this->currentInput_ = currentInput;
+void FrontendAction::setCurrentInput(const FrontendInputFile &input) {
+  this->currentInput = input;
 }
 
 // Call this method if BeginSourceFile fails.
 // Deallocate compiler instance, input and output descriptors
-static void BeginSourceFileCleanUp(FrontendAction &fa, CompilerInstance &ci) {
-  ci.ClearOutputFiles(/*EraseFiles=*/true);
-  fa.set_currentInput(FrontendInputFile());
-  fa.set_instance(nullptr);
+static void beginSourceFileCleanUp(FrontendAction &fa, CompilerInstance &ci) {
+  ci.clearOutputFiles(/*EraseFiles=*/true);
+  fa.setCurrentInput(FrontendInputFile());
+  fa.setInstance(nullptr);
 }
 
-bool FrontendAction::BeginSourceFile(
-    CompilerInstance &ci, const FrontendInputFile &realInput) {
+bool FrontendAction::beginSourceFile(CompilerInstance &ci,
+                                     const FrontendInputFile &realInput) {
 
   FrontendInputFile input(realInput);
 
   // Return immediately if the input file does not exist or is not a file. Note
   // that we cannot check this for input from stdin.
-  if (input.file() != "-") {
-    if (!llvm::sys::fs::is_regular_file(input.file())) {
+  if (input.getFile() != "-") {
+    if (!llvm::sys::fs::is_regular_file(input.getFile())) {
       // Create an diagnostic ID to report
       unsigned diagID;
-      if (llvm::vfs::getRealFileSystem()->exists(input.file())) {
-        ci.diagnostics().Report(clang::diag::err_fe_error_reading)
-            << input.file();
-        diagID = ci.diagnostics().getCustomDiagID(
+      if (llvm::vfs::getRealFileSystem()->exists(input.getFile())) {
+        ci.getDiagnostics().Report(clang::diag::err_fe_error_reading)
+            << input.getFile();
+        diagID = ci.getDiagnostics().getCustomDiagID(
             clang::DiagnosticsEngine::Error, "%0 is not a regular file");
       } else {
-        diagID = ci.diagnostics().getCustomDiagID(
+        diagID = ci.getDiagnostics().getCustomDiagID(
             clang::DiagnosticsEngine::Error, "%0 does not exist");
       }
 
       // Report the diagnostic and return
-      ci.diagnostics().Report(diagID) << input.file();
-      BeginSourceFileCleanUp(*this, ci);
+      ci.getDiagnostics().Report(diagID) << input.getFile();
+      beginSourceFileCleanUp(*this, ci);
       return false;
     }
   }
 
-  assert(!instance_ && "Already processing a source file!");
-  assert(!realInput.IsEmpty() && "Unexpected empty filename!");
-  set_currentInput(realInput);
-  set_instance(&ci);
+  assert(!instance && "Already processing a source file!");
+  assert(!realInput.isEmpty() && "Unexpected empty filename!");
+  setCurrentInput(realInput);
+  setInstance(&ci);
 
-  if (!ci.HasAllSources()) {
-    BeginSourceFileCleanUp(*this, ci);
+  if (!ci.hasAllSources()) {
+    beginSourceFileCleanUp(*this, ci);
     return false;
   }
 
-  auto &invoc = ci.invocation();
+  auto &invoc = ci.getInvocation();
 
   // Include command-line and predefined preprocessor macros. Use either:
   //  * `-cpp/-nocpp`, or
   //  * the file extension (if the user didn't express any preference)
   // to decide whether to include them or not.
-  if ((invoc.preprocessorOpts().macrosFlag == PPMacrosFlag::Include) ||
-      (invoc.preprocessorOpts().macrosFlag == PPMacrosFlag::Unknown &&
-          currentInput().MustBePreprocessed())) {
-    invoc.SetDefaultPredefinitions();
-    invoc.CollectMacroDefinitions();
+  if ((invoc.getPreprocessorOpts().macrosFlag == PPMacrosFlag::Include) ||
+      (invoc.getPreprocessorOpts().macrosFlag == PPMacrosFlag::Unknown &&
+       getCurrentInput().getMustBePreprocessed())) {
+    invoc.setDefaultPredefinitions();
+    invoc.collectMacroDefinitions();
   }
 
   // Decide between fixed and free form (if the user didn't express any
   // preference, use the file extension to decide)
-  if (invoc.frontendOpts().fortranForm == FortranForm::Unknown) {
-    invoc.fortranOpts().isFixedForm = currentInput().IsFixedForm();
+  if (invoc.getFrontendOpts().fortranForm == FortranForm::Unknown) {
+    invoc.getFortranOpts().isFixedForm = getCurrentInput().getIsFixedForm();
   }
 
-  if (!BeginSourceFileAction()) {
-    BeginSourceFileCleanUp(*this, ci);
+  if (!beginSourceFileAction()) {
+    beginSourceFileCleanUp(*this, ci);
     return false;
   }
 
   return true;
 }
 
-bool FrontendAction::ShouldEraseOutputFiles() {
-  return instance().diagnostics().hasErrorOccurred();
+bool FrontendAction::shouldEraseOutputFiles() {
+  return getInstance().getDiagnostics().hasErrorOccurred();
 }
 
-llvm::Error FrontendAction::Execute() {
-  ExecuteAction();
+llvm::Error FrontendAction::execute() {
+  executeAction();
 
   return llvm::Error::success();
 }
 
-void FrontendAction::EndSourceFile() {
-  CompilerInstance &ci = instance();
+void FrontendAction::endSourceFile() {
+  CompilerInstance &ci = getInstance();
 
   // Cleanup the output streams, and erase the output files if instructed by the
   // FrontendAction.
-  ci.ClearOutputFiles(/*EraseFiles=*/ShouldEraseOutputFiles());
+  ci.clearOutputFiles(/*EraseFiles=*/shouldEraseOutputFiles());
 
-  set_instance(nullptr);
-  set_currentInput(FrontendInputFile());
+  setInstance(nullptr);
+  setCurrentInput(FrontendInputFile());
 }
 
-bool FrontendAction::RunPrescan() {
-  CompilerInstance &ci = this->instance();
-  std::string currentInputPath{GetCurrentFileOrBufferName()};
-  Fortran::parser::Options parserOptions = ci.invocation().fortranOpts();
+bool FrontendAction::runPrescan() {
+  CompilerInstance &ci = this->getInstance();
+  std::string currentInputPath{getCurrentFileOrBufferName()};
+  Fortran::parser::Options parserOptions = ci.getInvocation().getFortranOpts();
 
-  if (ci.invocation().frontendOpts().fortranForm == FortranForm::Unknown) {
+  if (ci.getInvocation().getFrontendOpts().fortranForm ==
+      FortranForm::Unknown) {
     // Switch between fixed and free form format based on the input file
     // extension.
     //
@@ -130,41 +131,41 @@
     // 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();
+    parserOptions.isFixedForm = getCurrentInput().getIsFixedForm();
   }
 
   // Prescan. In case of failure, report and return.
-  ci.parsing().Prescan(currentInputPath, parserOptions);
+  ci.getParsing().Prescan(currentInputPath, parserOptions);
 
   return !reportFatalScanningErrors();
 }
 
-bool FrontendAction::RunParse() {
-  CompilerInstance &ci = this->instance();
+bool FrontendAction::runParse() {
+  CompilerInstance &ci = this->getInstance();
 
   // Parse. In case of failure, report and return.
-  ci.parsing().Parse(llvm::outs());
+  ci.getParsing().Parse(llvm::outs());
 
   if (reportFatalParsingErrors()) {
     return false;
   }
 
-  // Report the diagnostics from parsing
-  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+  // Report the diagnostics from getParsing
+  ci.getParsing().messages().Emit(llvm::errs(), ci.getAllCookedSources());
 
   return true;
 }
 
-bool FrontendAction::RunSemanticChecks() {
-  CompilerInstance &ci = this->instance();
-  std::optional<parser::Program> &parseTree{ci.parsing().parseTree()};
+bool FrontendAction::runSemanticChecks() {
+  CompilerInstance &ci = this->getInstance();
+  std::optional<parser::Program> &parseTree{ci.getParsing().parseTree()};
   assert(parseTree && "Cannot run semantic checks without a parse tree!");
 
   // Prepare semantics
-  ci.SetSemantics(std::make_unique<Fortran::semantics::Semantics>(
-      ci.invocation().semanticsContext(), *parseTree,
-      ci.invocation().debugModuleDir()));
-  auto &semantics = ci.semantics();
+  ci.setSemantics(std::make_unique<Fortran::semantics::Semantics>(
+      ci.getInvocation().getSemanticsContext(), *parseTree,
+      ci.getInvocation().getDebugModuleDir()));
+  auto &semantics = ci.getSemantics();
 
   // Run semantic checks
   semantics.Perform();
@@ -174,16 +175,16 @@
   }
 
   // Report the diagnostics from the semantic checks
-  semantics.EmitMessages(ci.semaOutputStream());
+  semantics.EmitMessages(ci.getSemaOutputStream());
 
   return true;
 }
 
-bool FrontendAction::GenerateRtTypeTables() {
-  instance().setRtTyTables(
+bool FrontendAction::generateRtTypeTables() {
+  getInstance().setRtTyTables(
       std::make_unique<Fortran::semantics::RuntimeDerivedTypeTables>(
           BuildRuntimeDerivedTypeTables(
-              instance().invocation().semanticsContext())));
+              getInstance().getInvocation().getSemanticsContext())));
 
   // The runtime derived type information table builder may find additional
   // semantic errors. Report them.
@@ -196,28 +197,28 @@
 
 template <unsigned N>
 bool FrontendAction::reportFatalErrors(const char (&message)[N]) {
-  if (!instance_->parsing().messages().empty() &&
-      (instance_->invocation().warnAsErr() ||
-          instance_->parsing().messages().AnyFatalError())) {
-    const unsigned diagID = instance_->diagnostics().getCustomDiagID(
+  if (!instance->getParsing().messages().empty() &&
+      (instance->getInvocation().getWarnAsErr() ||
+       instance->getParsing().messages().AnyFatalError())) {
+    const unsigned diagID = instance->getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, message);
-    instance_->diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
-    instance_->parsing().messages().Emit(
-        llvm::errs(), instance_->allCookedSources());
+    instance->getDiagnostics().Report(diagID) << getCurrentFileOrBufferName();
+    instance->getParsing().messages().Emit(llvm::errs(),
+                                           instance->getAllCookedSources());
     return true;
   }
   return false;
 }
 
 bool FrontendAction::reportFatalSemanticErrors() {
-  auto &diags = instance_->diagnostics();
-  auto &sema = instance_->semantics();
-
-  if (instance_->semantics().AnyFatalError()) {
-    unsigned DiagID = diags.getCustomDiagID(
-        clang::DiagnosticsEngine::Error, "Semantic errors in %0");
-    diags.Report(DiagID) << GetCurrentFileOrBufferName();
-    sema.EmitMessages(instance_->semaOutputStream());
+  auto &diags = instance->getDiagnostics();
+  auto &sema = instance->getSemantics();
+
+  if (instance->getSemantics().AnyFatalError()) {
+    unsigned diagID = diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
+                                            "Semantic errors in %0");
+    diags.Report(diagID) << getCurrentFileOrBufferName();
+    sema.EmitMessages(instance->getSemaOutputStream());
 
     return true;
   }
diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -30,6 +30,7 @@
 #include "mlir/IR/Dialect.h"
 #include "mlir/Pass/PassManager.h"
 #include "mlir/Target/LLVMIR/ModuleTranslation.h"
+#include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticFrontend.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
@@ -42,7 +43,6 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Target/TargetMachine.h"
-#include <clang/Basic/Diagnostic.h>
 #include <memory>
 
 using namespace Fortran::frontend;
@@ -51,46 +51,46 @@
 // Custom BeginSourceFileAction
 //===----------------------------------------------------------------------===//
 
-bool PrescanAction::BeginSourceFileAction() { return RunPrescan(); }
+bool PrescanAction::beginSourceFileAction() { return runPrescan(); }
 
-bool PrescanAndParseAction::BeginSourceFileAction() {
-  return RunPrescan() && RunParse();
+bool PrescanAndParseAction::beginSourceFileAction() {
+  return runPrescan() && runParse();
 }
 
-bool PrescanAndSemaAction::BeginSourceFileAction() {
-  return RunPrescan() && RunParse() && RunSemanticChecks() &&
-      GenerateRtTypeTables();
+bool PrescanAndSemaAction::beginSourceFileAction() {
+  return runPrescan() && runParse() && runSemanticChecks() &&
+         generateRtTypeTables();
 }
 
-bool PrescanAndSemaDebugAction::BeginSourceFileAction() {
+bool PrescanAndSemaDebugAction::beginSourceFileAction() {
   // This is a "debug" action for development purposes. To facilitate this, the
   // semantic checks are made to succeed unconditionally to prevent this action
   // from exiting early (i.e. in the presence of semantic errors). We should
   // never do this in actions intended for end-users or otherwise regular
   // compiler workflows!
-  return RunPrescan() && RunParse() && (RunSemanticChecks() || true) &&
-      (GenerateRtTypeTables() || true);
+  return runPrescan() && runParse() && (runSemanticChecks() || true) &&
+         (generateRtTypeTables() || true);
 }
 
-bool CodeGenAction::BeginSourceFileAction() {
+bool CodeGenAction::beginSourceFileAction() {
   llvmCtx = std::make_unique<llvm::LLVMContext>();
 
   // If the input is an LLVM file, just parse it and return.
-  if (this->currentInput().kind().GetLanguage() == Language::LLVM_IR) {
+  if (this->getCurrentInput().getKind().getLanguage() == Language::LLVM_IR) {
     llvm::SMDiagnostic err;
-    llvmModule = llvm::parseIRFile(currentInput().file(), err, *llvmCtx);
+    llvmModule = llvm::parseIRFile(getCurrentInput().getFile(), err, *llvmCtx);
 
     return (nullptr != llvmModule);
   }
 
   // Otherwise, generate an MLIR module from the input Fortran source
-  assert(currentInput().kind().GetLanguage() == Language::Fortran &&
+  assert(getCurrentInput().getKind().getLanguage() == Language::Fortran &&
          "Invalid input type - expecting a Fortran file");
-  bool res = RunPrescan() && RunParse() && RunSemanticChecks();
+  bool res = runPrescan() && runParse() && runSemanticChecks();
   if (!res)
     return res;
 
-  CompilerInstance &ci = this->instance();
+  CompilerInstance &ci = this->getInstance();
 
   // Load the MLIR dialects required by Flang
   mlir::DialectRegistry registry;
@@ -100,28 +100,29 @@
 
   // Create a LoweringBridge
   const common::IntrinsicTypeDefaultKinds &defKinds =
-      ci.invocation().semanticsContext().defaultKinds();
+      ci.getInvocation().getSemanticsContext().defaultKinds();
   fir::KindMapping kindMap(mlirCtx.get(),
       llvm::ArrayRef<fir::KindTy>{fir::fromDefaultKinds(defKinds)});
-  lower::LoweringBridge lb = Fortran::lower::LoweringBridge::create(*mlirCtx,
-      defKinds, ci.invocation().semanticsContext().intrinsics(),
-      ci.parsing().allCooked(), ci.invocation().targetOpts().triple, kindMap);
+  lower::LoweringBridge lb = Fortran::lower::LoweringBridge::create(
+      *mlirCtx, defKinds, ci.getInvocation().getSemanticsContext().intrinsics(),
+      ci.getParsing().allCooked(), ci.getInvocation().getTargetOpts().triple,
+      kindMap);
 
   // Create a parse tree and lower it to FIR
-  Fortran::parser::Program &parseTree{*ci.parsing().parseTree()};
-  lb.lower(parseTree, ci.invocation().semanticsContext());
+  Fortran::parser::Program &parseTree{*ci.getParsing().parseTree()};
+  lb.lower(parseTree, ci.getInvocation().getSemanticsContext());
   mlirModule = std::make_unique<mlir::ModuleOp>(lb.getModule());
 
-  // Run the default passes.
+  // run the default passes.
   mlir::PassManager pm(mlirCtx.get(), mlir::OpPassManager::Nesting::Implicit);
   pm.enableVerifier(/*verifyPasses=*/true);
   pm.addPass(std::make_unique<Fortran::lower::VerifierPass>());
 
   if (mlir::failed(pm.run(*mlirModule))) {
-    unsigned diagID =
-        ci.diagnostics().getCustomDiagID(clang::DiagnosticsEngine::Error,
-            "verification of lowering to FIR failed");
-    ci.diagnostics().Report(diagID);
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error,
+        "verification of lowering to FIR failed");
+    ci.getDiagnostics().Report(diagID);
     return false;
   }
 
@@ -131,66 +132,66 @@
 //===----------------------------------------------------------------------===//
 // Custom ExecuteAction
 //===----------------------------------------------------------------------===//
-void InputOutputTestAction::ExecuteAction() {
-  CompilerInstance &ci = instance();
+void InputOutputTestAction::executeAction() {
+  CompilerInstance &ci = getInstance();
 
   // Create a stream for errors
   std::string buf;
-  llvm::raw_string_ostream error_stream{buf};
+  llvm::raw_string_ostream errorStream{buf};
 
   // Read the input file
-  Fortran::parser::AllSources &allSources{ci.allSources()};
-  std::string path{GetCurrentFileOrBufferName()};
+  Fortran::parser::AllSources &allSources{ci.getAllSources()};
+  std::string path{getCurrentFileOrBufferName()};
   const Fortran::parser::SourceFile *sf;
   if (path == "-")
-    sf = allSources.ReadStandardInput(error_stream);
+    sf = allSources.ReadStandardInput(errorStream);
   else
-    sf = allSources.Open(path, error_stream, std::optional<std::string>{"."s});
+    sf = allSources.Open(path, errorStream, std::optional<std::string>{"."s});
   llvm::ArrayRef<char> fileContent = sf->content();
 
   // Output file descriptor to receive the contents of the input file.
   std::unique_ptr<llvm::raw_ostream> os;
 
   // Copy the contents from the input file to the output file
-  if (!ci.IsOutputStreamNull()) {
+  if (!ci.isOutputStreamNull()) {
     // An output stream (outputStream_) was set earlier
-    ci.WriteOutputStream(fileContent.data());
+    ci.writeOutputStream(fileContent.data());
   } else {
     // No pre-set output stream - create an output file
-    os = ci.CreateDefaultOutputFile(
-        /*binary=*/true, GetCurrentFileOrBufferName(), "txt");
+    os = ci.createDefaultOutputFile(
+        /*binary=*/true, getCurrentFileOrBufferName(), "txt");
     if (!os)
       return;
     (*os) << fileContent.data();
   }
 }
 
-void PrintPreprocessedAction::ExecuteAction() {
+void PrintPreprocessedAction::executeAction() {
   std::string buf;
   llvm::raw_string_ostream outForPP{buf};
 
   // Format or dump the prescanner's output
-  CompilerInstance &ci = this->instance();
-  if (ci.invocation().preprocessorOpts().noReformat) {
-    ci.parsing().DumpCookedChars(outForPP);
+  CompilerInstance &ci = this->getInstance();
+  if (ci.getInvocation().getPreprocessorOpts().noReformat) {
+    ci.getParsing().DumpCookedChars(outForPP);
   } else {
-    ci.parsing().EmitPreprocessedSource(
-        outForPP, !ci.invocation().preprocessorOpts().noLineDirectives);
+    ci.getParsing().EmitPreprocessedSource(
+        outForPP, !ci.getInvocation().getPreprocessorOpts().noLineDirectives);
   }
 
-  // Print diagnostics from the prescanner
-  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+  // Print getDiagnostics from the prescanner
+  ci.getParsing().messages().Emit(llvm::errs(), ci.getAllCookedSources());
 
   // If a pre-defined output stream exists, dump the preprocessed content there
-  if (!ci.IsOutputStreamNull()) {
+  if (!ci.isOutputStreamNull()) {
     // Send the output to the pre-defined output buffer.
-    ci.WriteOutputStream(outForPP.str());
+    ci.writeOutputStream(outForPP.str());
     return;
   }
 
   // Create a file and save the preprocessed output there
-  std::unique_ptr<llvm::raw_pwrite_stream> os{ci.CreateDefaultOutputFile(
-      /*Binary=*/true, /*InFile=*/GetCurrentFileOrBufferName())};
+  std::unique_ptr<llvm::raw_pwrite_stream> os{ci.createDefaultOutputFile(
+      /*Binary=*/true, /*InFile=*/getCurrentFileOrBufferName())};
   if (!os) {
     return;
   }
@@ -198,46 +199,47 @@
   (*os) << outForPP.str();
 }
 
-void DebugDumpProvenanceAction::ExecuteAction() {
-  this->instance().parsing().DumpProvenance(llvm::outs());
+void DebugDumpProvenanceAction::executeAction() {
+  this->getInstance().getParsing().DumpProvenance(llvm::outs());
 }
 
-void ParseSyntaxOnlyAction::ExecuteAction() {
-}
+void ParseSyntaxOnlyAction::executeAction() {}
 
-void DebugUnparseNoSemaAction::ExecuteAction() {
-  auto &invoc = this->instance().invocation();
-  auto &parseTree{instance().parsing().parseTree()};
+void DebugUnparseNoSemaAction::executeAction() {
+  auto &invoc = this->getInstance().getInvocation();
+  auto &parseTree{getInstance().getParsing().parseTree()};
 
   // TODO: Options should come from CompilerInvocation
   Unparse(llvm::outs(), *parseTree,
-      /*encoding=*/Fortran::parser::Encoding::UTF_8,
-      /*capitalizeKeywords=*/true, /*backslashEscapes=*/false,
-      /*preStatement=*/nullptr,
-      invoc.useAnalyzedObjectsForUnparse() ? &invoc.asFortran() : nullptr);
+          /*encoding=*/Fortran::parser::Encoding::UTF_8,
+          /*capitalizeKeywords=*/true, /*backslashEscapes=*/false,
+          /*preStatement=*/nullptr,
+          invoc.getUseAnalyzedObjectsForUnparse() ? &invoc.getAsFortran()
+                                                  : nullptr);
 }
 
-void DebugUnparseAction::ExecuteAction() {
-  auto &invoc = this->instance().invocation();
-  auto &parseTree{instance().parsing().parseTree()};
+void DebugUnparseAction::executeAction() {
+  auto &invoc = this->getInstance().getInvocation();
+  auto &parseTree{getInstance().getParsing().parseTree()};
 
-  CompilerInstance &ci = this->instance();
-  auto os{ci.CreateDefaultOutputFile(
-      /*Binary=*/false, /*InFile=*/GetCurrentFileOrBufferName())};
+  CompilerInstance &ci = this->getInstance();
+  auto os{ci.createDefaultOutputFile(
+      /*Binary=*/false, /*InFile=*/getCurrentFileOrBufferName())};
 
   // TODO: Options should come from CompilerInvocation
   Unparse(*os, *parseTree,
-      /*encoding=*/Fortran::parser::Encoding::UTF_8,
-      /*capitalizeKeywords=*/true, /*backslashEscapes=*/false,
-      /*preStatement=*/nullptr,
-      invoc.useAnalyzedObjectsForUnparse() ? &invoc.asFortran() : nullptr);
+          /*encoding=*/Fortran::parser::Encoding::UTF_8,
+          /*capitalizeKeywords=*/true, /*backslashEscapes=*/false,
+          /*preStatement=*/nullptr,
+          invoc.getUseAnalyzedObjectsForUnparse() ? &invoc.getAsFortran()
+                                                  : nullptr);
 
   // Report fatal semantic errors
   reportFatalSemanticErrors();
 }
 
-void DebugUnparseWithSymbolsAction::ExecuteAction() {
-  auto &parseTree{*instance().parsing().parseTree()};
+void DebugUnparseWithSymbolsAction::executeAction() {
+  auto &parseTree{*getInstance().getParsing().parseTree()};
 
   Fortran::semantics::UnparseWithSymbols(
       llvm::outs(), parseTree, /*encoding=*/Fortran::parser::Encoding::UTF_8);
@@ -246,38 +248,38 @@
   reportFatalSemanticErrors();
 }
 
-void DebugDumpSymbolsAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugDumpSymbolsAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   if (!ci.getRtTyTables().schemata) {
-    unsigned DiagID =
-        ci.diagnostics().getCustomDiagID(clang::DiagnosticsEngine::Error,
-            "could not find module file for __fortran_type_info");
-    ci.diagnostics().Report(DiagID);
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error,
+        "could not find module file for __fortran_type_info");
+    ci.getDiagnostics().Report(diagID);
     llvm::errs() << "\n";
     return;
   }
 
   // Dump symbols
-  ci.semantics().DumpSymbols(llvm::outs());
+  ci.getSemantics().DumpSymbols(llvm::outs());
 }
 
-void DebugDumpAllAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugDumpAllAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   // Dump parse tree
-  auto &parseTree{instance().parsing().parseTree()};
+  auto &parseTree{getInstance().getParsing().parseTree()};
   llvm::outs() << "========================";
   llvm::outs() << " Flang: parse tree dump ";
   llvm::outs() << "========================\n";
-  Fortran::parser::DumpTree(
-      llvm::outs(), parseTree, &ci.invocation().asFortran());
+  Fortran::parser::DumpTree(llvm::outs(), parseTree,
+                            &ci.getInvocation().getAsFortran());
 
   if (!ci.getRtTyTables().schemata) {
-    unsigned DiagID =
-        ci.diagnostics().getCustomDiagID(clang::DiagnosticsEngine::Error,
-            "could not find module file for __fortran_type_info");
-    ci.diagnostics().Report(DiagID);
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error,
+        "could not find module file for __fortran_type_info");
+    ci.getDiagnostics().Report(diagID);
     llvm::errs() << "\n";
     return;
   }
@@ -286,50 +288,52 @@
   llvm::outs() << "=====================";
   llvm::outs() << " Flang: symbols dump ";
   llvm::outs() << "=====================\n";
-  ci.semantics().DumpSymbols(llvm::outs());
+  ci.getSemantics().DumpSymbols(llvm::outs());
 }
 
-void DebugDumpParseTreeNoSemaAction::ExecuteAction() {
-  auto &parseTree{instance().parsing().parseTree()};
+void DebugDumpParseTreeNoSemaAction::executeAction() {
+  auto &parseTree{getInstance().getParsing().parseTree()};
 
   // Dump parse tree
   Fortran::parser::DumpTree(
-      llvm::outs(), parseTree, &this->instance().invocation().asFortran());
+      llvm::outs(), parseTree,
+      &this->getInstance().getInvocation().getAsFortran());
 }
 
-void DebugDumpParseTreeAction::ExecuteAction() {
-  auto &parseTree{instance().parsing().parseTree()};
+void DebugDumpParseTreeAction::executeAction() {
+  auto &parseTree{getInstance().getParsing().parseTree()};
 
   // Dump parse tree
   Fortran::parser::DumpTree(
-      llvm::outs(), parseTree, &this->instance().invocation().asFortran());
+      llvm::outs(), parseTree,
+      &this->getInstance().getInvocation().getAsFortran());
 
   // Report fatal semantic errors
   reportFatalSemanticErrors();
 }
 
-void DebugMeasureParseTreeAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugMeasureParseTreeAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   // Parse. In case of failure, report and return.
-  ci.parsing().Parse(llvm::outs());
+  ci.getParsing().Parse(llvm::outs());
 
-  if (!ci.parsing().messages().empty() &&
-      (ci.invocation().warnAsErr() ||
-          ci.parsing().messages().AnyFatalError())) {
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
+  if (!ci.getParsing().messages().empty() &&
+      (ci.getInvocation().getWarnAsErr() ||
+       ci.getParsing().messages().AnyFatalError())) {
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "Could not parse %0");
-    ci.diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
+    ci.getDiagnostics().Report(diagID) << getCurrentFileOrBufferName();
 
-    ci.parsing().messages().Emit(
-        llvm::errs(), this->instance().allCookedSources());
+    ci.getParsing().messages().Emit(llvm::errs(),
+                                    this->getInstance().getAllCookedSources());
     return;
   }
 
-  // Report the diagnostics from parsing
-  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+  // Report the getDiagnostics from parsing
+  ci.getParsing().messages().Emit(llvm::errs(), ci.getAllCookedSources());
 
-  auto &parseTree{*ci.parsing().parseTree()};
+  auto &parseTree{*ci.getParsing().parseTree()};
 
   // Measure the parse tree
   MeasurementVisitor visitor;
@@ -339,61 +343,61 @@
                << " total bytes.\n";
 }
 
-void DebugPreFIRTreeAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugPreFIRTreeAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
   // Report and exit if fatal semantic errors are present
   if (reportFatalSemanticErrors()) {
     return;
   }
 
-  auto &parseTree{*ci.parsing().parseTree()};
+  auto &parseTree{*ci.getParsing().parseTree()};
 
   // Dump pre-FIR tree
   if (auto ast{Fortran::lower::createPFT(
-          parseTree, ci.invocation().semanticsContext())}) {
+          parseTree, ci.getInvocation().getSemanticsContext())}) {
     Fortran::lower::dumpPFT(llvm::outs(), *ast);
   } else {
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "Pre FIR Tree is NULL.");
-    ci.diagnostics().Report(diagID);
+    ci.getDiagnostics().Report(diagID);
   }
 }
 
-void DebugDumpParsingLogAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugDumpParsingLogAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
-  ci.parsing().Parse(llvm::errs());
-  ci.parsing().DumpParsingLog(llvm::outs());
+  ci.getParsing().Parse(llvm::errs());
+  ci.getParsing().DumpParsingLog(llvm::outs());
 }
 
-void GetDefinitionAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void GetDefinitionAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   // Report and exit if fatal semantic errors are present
   if (reportFatalSemanticErrors()) {
     return;
   }
 
-  parser::AllCookedSources &cs = ci.allCookedSources();
-  unsigned diagID = ci.diagnostics().getCustomDiagID(
+  parser::AllCookedSources &cs = ci.getAllCookedSources();
+  unsigned diagID = ci.getDiagnostics().getCustomDiagID(
       clang::DiagnosticsEngine::Error, "Symbol not found");
 
-  auto gdv = ci.invocation().frontendOpts().getDefVals;
+  auto gdv = ci.getInvocation().getFrontendOpts().getDefVals;
   auto charBlock{cs.GetCharBlockFromLineAndColumns(
       gdv.line, gdv.startColumn, gdv.endColumn)};
   if (!charBlock) {
-    ci.diagnostics().Report(diagID);
+    ci.getDiagnostics().Report(diagID);
     return;
   }
 
   llvm::outs() << "String range: >" << charBlock->ToString() << "<\n";
 
-  auto *symbol{ci.invocation()
-                   .semanticsContext()
+  auto *symbol{ci.getInvocation()
+                   .getSemanticsContext()
                    .FindScope(*charBlock)
                    .FindSymbol(*charBlock)};
   if (!symbol) {
-    ci.diagnostics().Report(diagID);
+    ci.getDiagnostics().Report(diagID);
     return;
   }
 
@@ -414,15 +418,15 @@
                << "-" << sourceInfo->second.column << "\n";
 }
 
-void GetSymbolsSourcesAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void GetSymbolsSourcesAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   // Report and exit if fatal semantic errors are present
   if (reportFatalSemanticErrors()) {
     return;
   }
 
-  ci.semantics().DumpSymbolsSources(llvm::outs());
+  ci.getSemantics().DumpSymbolsSources(llvm::outs());
 }
 
 //===----------------------------------------------------------------------===//
@@ -434,10 +438,10 @@
 #include "flang/Tools/CLOptions.inc"
 
 // Lower the previously generated MLIR module into an LLVM IR module
-void CodeGenAction::GenerateLLVMIR() {
+void CodeGenAction::generateLLVMIR() {
   assert(mlirModule && "The MLIR module has not been generated yet.");
 
-  CompilerInstance &ci = this->instance();
+  CompilerInstance &ci = this->getInstance();
 
   fir::support::loadDialects(*mlirCtx);
   fir::support::registerLLVMTranslation(*mlirCtx);
@@ -452,11 +456,11 @@
   fir::createMLIRToLLVMPassPipeline(pm);
   mlir::applyPassManagerCLOptions(pm);
 
-  // Run the pass manager
+  // run the pass manager
   if (!mlir::succeeded(pm.run(*mlirModule))) {
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "Lowering to LLVM IR failed");
-    ci.diagnostics().Report(diagID);
+    ci.getDiagnostics().Report(diagID);
   }
 
   // Translate to LLVM IR
@@ -465,20 +469,21 @@
       *mlirModule, *llvmCtx, moduleName ? *moduleName : "FIRModule");
 
   if (!llvmModule) {
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "failed to create the LLVM module");
-    ci.diagnostics().Report(diagID);
+    ci.getDiagnostics().Report(diagID);
     return;
   }
 }
 
-void CodeGenAction::SetUpTargetMachine() {
-  CompilerInstance &ci = this->instance();
+void CodeGenAction::setUpTargetMachine() {
+  CompilerInstance &ci = this->getInstance();
 
   // Set the triple based on the CompilerInvocation set-up
-  const std::string &theTriple = ci.invocation().targetOpts().triple;
+  const std::string &theTriple = ci.getInvocation().getTargetOpts().triple;
   if (llvmModule->getTargetTriple() != theTriple) {
-    ci.diagnostics().Report(clang::diag::warn_fe_override_module) << theTriple;
+    ci.getDiagnostics().Report(clang::diag::warn_fe_override_module)
+        << theTriple;
     llvmModule->setTargetTriple(theTriple);
   }
 
@@ -489,31 +494,31 @@
   assert(theTarget && "Failed to create Target");
 
   // Create `TargetMachine`
-  TM.reset(theTarget->createTargetMachine(theTriple, /*CPU=*/"",
+  tm.reset(theTarget->createTargetMachine(theTriple, /*CPU=*/"",
                                           /*Features=*/"",
                                           llvm::TargetOptions(), llvm::None));
-  assert(TM && "Failed to create TargetMachine");
-  llvmModule->setDataLayout(TM->createDataLayout());
+  assert(tm && "Failed to create TargetMachine");
+  llvmModule->setDataLayout(tm->createDataLayout());
 }
 
 static std::unique_ptr<llvm::raw_pwrite_stream>
-GetOutputStream(CompilerInstance &ci, llvm::StringRef inFile,
+getOutputStream(CompilerInstance &ci, llvm::StringRef inFile,
                 BackendActionTy action) {
   switch (action) {
   case BackendActionTy::Backend_EmitAssembly:
-    return ci.CreateDefaultOutputFile(
+    return ci.createDefaultOutputFile(
         /*Binary=*/false, inFile, /*extension=*/"s");
   case BackendActionTy::Backend_EmitLL:
-    return ci.CreateDefaultOutputFile(
+    return ci.createDefaultOutputFile(
         /*Binary=*/false, inFile, /*extension=*/"ll");
   case BackendActionTy::Backend_EmitMLIR:
-    return ci.CreateDefaultOutputFile(
+    return ci.createDefaultOutputFile(
         /*Binary=*/false, inFile, /*extension=*/"mlir");
   case BackendActionTy::Backend_EmitBC:
-    return ci.CreateDefaultOutputFile(
+    return ci.createDefaultOutputFile(
         /*Binary=*/true, inFile, /*extension=*/"bc");
   case BackendActionTy::Backend_EmitObj:
-    return ci.CreateDefaultOutputFile(
+    return ci.createDefaultOutputFile(
         /*Binary=*/true, inFile, /*extension=*/"o");
   }
 
@@ -524,12 +529,12 @@
 /// module.
 ///
 /// \param [in] diags Diagnostics engine for reporting errors
-/// \param [in] TM Target machine to aid the code-gen pipeline set-up
+/// \param [in] tm Target machine to aid the code-gen pipeline set-up
 /// \param [in] act Backend act to run (assembly vs machine-code generation)
 /// \param [in] llvmModule LLVM module to lower to assembly/machine-code
 /// \param [out] os Output stream to emit the generated code to
 static void GenerateMachineCodeOrAssemblyImpl(clang::DiagnosticsEngine &diags,
-                                              llvm::TargetMachine &TM,
+                                              llvm::TargetMachine &tm,
                                               BackendActionTy act,
                                               llvm::Module &llvmModule,
                                               llvm::raw_pwrite_stream &os) {
@@ -540,20 +545,20 @@
   // Set-up the pass manager, i.e create an LLVM code-gen pass pipeline.
   // Currently only the legacy pass manager is supported.
   // TODO: Switch to the new PM once it's available in the backend.
-  llvm::legacy::PassManager CodeGenPasses;
-  CodeGenPasses.add(
-      createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
+  llvm::legacy::PassManager codeGenPasses;
+  codeGenPasses.add(
+      createTargetTransformInfoWrapperPass(tm.getTargetIRAnalysis()));
 
   llvm::Triple triple(llvmModule.getTargetTriple());
-  std::unique_ptr<llvm::TargetLibraryInfoImpl> TLII =
+  std::unique_ptr<llvm::TargetLibraryInfoImpl> tLII =
       std::make_unique<llvm::TargetLibraryInfoImpl>(triple);
-  assert(TLII && "Failed to create TargetLibraryInfo");
-  CodeGenPasses.add(new llvm::TargetLibraryInfoWrapperPass(*TLII));
+  assert(tLII && "Failed to create TargetLibraryInfo");
+  codeGenPasses.add(new llvm::TargetLibraryInfoWrapperPass(*tLII));
 
   llvm::CodeGenFileType cgft = (act == BackendActionTy::Backend_EmitAssembly)
                                    ? llvm::CodeGenFileType::CGFT_AssemblyFile
                                    : llvm::CodeGenFileType::CGFT_ObjectFile;
-  if (TM.addPassesToEmitFile(CodeGenPasses, os, nullptr, cgft)) {
+  if (tm.addPassesToEmitFile(codeGenPasses, os, nullptr, cgft)) {
     unsigned diagID =
         diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
                               "emission of this file type is not supported");
@@ -562,120 +567,120 @@
   }
 
   // Run the passes
-  CodeGenPasses.run(llvmModule);
+  codeGenPasses.run(llvmModule);
 }
 
 /// Generate LLVM byte code file from the input LLVM module.
 ///
-/// \param [in] TM Target machine to aid the code-gen pipeline set-up
+/// \param [in] tm Target machine to aid the code-gen pipeline set-up
 /// \param [in] llvmModule LLVM module to lower to assembly/machine-code
 /// \param [out] os Output stream to emit the generated code to
-static void GenerateLLVMBCImpl(llvm::TargetMachine &TM,
+static void GenerateLLVMBCImpl(llvm::TargetMachine &tm,
                                llvm::Module &llvmModule,
                                llvm::raw_pwrite_stream &os) {
   // Set-up the pass manager
-  llvm::ModulePassManager MPM;
-  llvm::ModuleAnalysisManager MAM;
-  llvm::PassBuilder PB(&TM);
-  PB.registerModuleAnalyses(MAM);
-  MPM.addPass(llvm::BitcodeWriterPass(os));
-
-  // Run the passes
-  MPM.run(llvmModule, MAM);
+  llvm::ModulePassManager mPM;
+  llvm::ModuleAnalysisManager mAM;
+  llvm::PassBuilder pB(&tm);
+  pB.registerModuleAnalyses(mAM);
+  mPM.addPass(llvm::BitcodeWriterPass(os));
+
+  // run the passes
+  mPM.run(llvmModule, mAM);
 }
 
-void CodeGenAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void CodeGenAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
   // If the output stream is a file, generate it and define the corresponding
   // output stream. If a pre-defined output stream is available, we will use
   // that instead.
   //
   // NOTE: `os` is a smart pointer that will be destroyed at the end of this
-  // method. However, it won't be written to until `CodeGenPasses` is
-  // destroyed. By defining `os` before `CodeGenPasses`, we make sure that the
+  // method. However, it won't be written to until `codeGenPasses` is
+  // destroyed. By defining `os` before `codeGenPasses`, we make sure that the
   // output stream won't be destroyed before it is written to. This only
   // applies when an output file is used (i.e. there is no pre-defined output
   // stream).
-  // TODO: Revisit once the new PM is ready (i.e. when `CodeGenPasses` is
+  // TODO: Revisit once the new PM is ready (i.e. when `codeGenPasses` is
   // updated to use it).
   std::unique_ptr<llvm::raw_pwrite_stream> os;
-  if (ci.IsOutputStreamNull()) {
-    os = GetOutputStream(ci, GetCurrentFileOrBufferName(), action);
+  if (ci.isOutputStreamNull()) {
+    os = getOutputStream(ci, getCurrentFileOrBufferName(), action);
 
     if (!os) {
-      unsigned diagID = ci.diagnostics().getCustomDiagID(
+      unsigned diagID = ci.getDiagnostics().getCustomDiagID(
           clang::DiagnosticsEngine::Error, "failed to create the output file");
-      ci.diagnostics().Report(diagID);
+      ci.getDiagnostics().Report(diagID);
       return;
     }
   }
 
   if (action == BackendActionTy::Backend_EmitMLIR) {
-    mlirModule->print(ci.IsOutputStreamNull() ? *os : ci.GetOutputStream());
+    mlirModule->print(ci.isOutputStreamNull() ? *os : ci.getOutputStream());
     return;
   }
 
-  // Generate an LLVM module if it's not already present (it will already be
+  // generate an LLVM module if it's not already present (it will already be
   // present if the input file is an LLVM IR/BC file).
   if (!llvmModule)
-    GenerateLLVMIR();
+    generateLLVMIR();
 
   if (action == BackendActionTy::Backend_EmitLL) {
-    llvmModule->print(ci.IsOutputStreamNull() ? *os : ci.GetOutputStream(),
+    llvmModule->print(ci.isOutputStreamNull() ? *os : ci.getOutputStream(),
                       /*AssemblyAnnotationWriter=*/nullptr);
     return;
   }
 
-  SetUpTargetMachine();
+  setUpTargetMachine();
   if (action == BackendActionTy::Backend_EmitBC) {
-    GenerateLLVMBCImpl(*TM, *llvmModule, *os);
+    GenerateLLVMBCImpl(*tm, *llvmModule, *os);
     return;
   }
 
   if (action == BackendActionTy::Backend_EmitAssembly ||
       action == BackendActionTy::Backend_EmitObj) {
     GenerateMachineCodeOrAssemblyImpl(
-        ci.diagnostics(), *TM, action, *llvmModule,
-        ci.IsOutputStreamNull() ? *os : ci.GetOutputStream());
+        ci.getDiagnostics(), *tm, action, *llvmModule,
+        ci.isOutputStreamNull() ? *os : ci.getOutputStream());
     return;
   }
 }
 
-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);
+void InitOnlyAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
+  unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+      clang::DiagnosticsEngine::Warning,
+      "Use `-init-only` for testing purposes only");
+  ci.getDiagnostics().Report(diagID);
 }
 
-void PluginParseTreeAction::ExecuteAction() {}
+void PluginParseTreeAction::executeAction() {}
 
-void DebugDumpPFTAction::ExecuteAction() {
-  CompilerInstance &ci = this->instance();
+void DebugDumpPFTAction::executeAction() {
+  CompilerInstance &ci = this->getInstance();
 
-  if (auto ast = Fortran::lower::createPFT(
-          *ci.parsing().parseTree(), ci.semantics().context())) {
+  if (auto ast = Fortran::lower::createPFT(*ci.getParsing().parseTree(),
+                                           ci.getSemantics().context())) {
     Fortran::lower::dumpPFT(llvm::outs(), *ast);
     return;
   }
 
-  unsigned DiagID = ci.diagnostics().getCustomDiagID(
+  unsigned diagID = ci.getDiagnostics().getCustomDiagID(
       clang::DiagnosticsEngine::Error, "Pre FIR Tree is NULL.");
-  ci.diagnostics().Report(DiagID);
+  ci.getDiagnostics().Report(diagID);
 }
 
 Fortran::parser::Parsing &PluginParseTreeAction::getParsing() {
-  return instance().parsing();
+  return getInstance().getParsing();
 }
 
 std::unique_ptr<llvm::raw_pwrite_stream>
 PluginParseTreeAction::createOutputFile(llvm::StringRef extension = "") {
 
-  std::unique_ptr<llvm::raw_pwrite_stream> OS{
-      instance().CreateDefaultOutputFile(
-          /*Binary=*/false, /*InFile=*/GetCurrentFileOrBufferName(),
+  std::unique_ptr<llvm::raw_pwrite_stream> os{
+      getInstance().createDefaultOutputFile(
+          /*Binary=*/false, /*InFile=*/getCurrentFileOrBufferName(),
           extension)};
-  return OS;
+  return os;
 }
diff --git a/flang/lib/Frontend/FrontendOptions.cpp b/flang/lib/Frontend/FrontendOptions.cpp
--- a/flang/lib/Frontend/FrontendOptions.cpp
+++ b/flang/lib/Frontend/FrontendOptions.cpp
@@ -25,13 +25,13 @@
       suffix == "F08" || suffix == "f18" || suffix == "F18";
 }
 
-bool Fortran::frontend::mustBePreprocessed(llvm::StringRef suffix) {
+bool Fortran::frontend::isToBePreprocessed(llvm::StringRef suffix) {
   return suffix == "F" || suffix == "FOR" || suffix == "fpp" ||
       suffix == "FPP" || suffix == "F90" || suffix == "F95" ||
       suffix == "F03" || suffix == "F08" || suffix == "F18";
 }
 
-InputKind FrontendOptions::GetInputKindForExtension(llvm::StringRef extension) {
+InputKind FrontendOptions::getInputKindForExtension(llvm::StringRef extension) {
   if (isFixedFormSuffix(extension) || isFreeFormSuffix(extension)) {
     return Language::Fortran;
   }
diff --git a/flang/lib/Frontend/TextDiagnostic.cpp b/flang/lib/Frontend/TextDiagnostic.cpp
--- a/flang/lib/Frontend/TextDiagnostic.cpp
+++ b/flang/lib/Frontend/TextDiagnostic.cpp
@@ -30,8 +30,10 @@
 
 TextDiagnostic::~TextDiagnostic() {}
 
-/*static*/ void TextDiagnostic::PrintDiagnosticLevel(llvm::raw_ostream &os,
-    clang::DiagnosticsEngine::Level level, bool showColors) {
+/*static*/ void
+TextDiagnostic::printDiagnosticLevel(llvm::raw_ostream &os,
+                                     clang::DiagnosticsEngine::Level level,
+                                     bool showColors) {
   if (showColors) {
     // Print diagnostic category in bold and color
     switch (level) {
@@ -82,8 +84,10 @@
 }
 
 /*static*/
-void TextDiagnostic::PrintDiagnosticMessage(llvm::raw_ostream &os,
-    bool isSupplemental, llvm::StringRef message, bool showColors) {
+void TextDiagnostic::printDiagnosticMessage(llvm::raw_ostream &os,
+                                            bool isSupplemental,
+                                            llvm::StringRef message,
+                                            bool showColors) {
   if (showColors && !isSupplemental) {
     // Print primary diagnostic messages in bold and without color.
     os.changeColor(savedColor, true);
diff --git a/flang/lib/Frontend/TextDiagnosticBuffer.cpp b/flang/lib/Frontend/TextDiagnosticBuffer.cpp
--- a/flang/lib/Frontend/TextDiagnosticBuffer.cpp
+++ b/flang/lib/Frontend/TextDiagnosticBuffer.cpp
@@ -30,44 +30,44 @@
   default:
     llvm_unreachable("Diagnostic not handled during diagnostic buffering!");
   case clang::DiagnosticsEngine::Note:
-    all_.emplace_back(level, notes_.size());
-    notes_.emplace_back(info.getLocation(), std::string(buf.str()));
+    all.emplace_back(level, notes.size());
+    notes.emplace_back(info.getLocation(), std::string(buf.str()));
     break;
   case clang::DiagnosticsEngine::Warning:
-    all_.emplace_back(level, warnings_.size());
-    warnings_.emplace_back(info.getLocation(), std::string(buf.str()));
+    all.emplace_back(level, warnings.size());
+    warnings.emplace_back(info.getLocation(), std::string(buf.str()));
     break;
   case clang::DiagnosticsEngine::Remark:
-    all_.emplace_back(level, remarks_.size());
-    remarks_.emplace_back(info.getLocation(), std::string(buf.str()));
+    all.emplace_back(level, remarks.size());
+    remarks.emplace_back(info.getLocation(), std::string(buf.str()));
     break;
   case clang::DiagnosticsEngine::Error:
   case clang::DiagnosticsEngine::Fatal:
-    all_.emplace_back(level, errors_.size());
-    errors_.emplace_back(info.getLocation(), std::string(buf.str()));
+    all.emplace_back(level, errors.size());
+    errors.emplace_back(info.getLocation(), std::string(buf.str()));
     break;
   }
 }
 
-void TextDiagnosticBuffer::FlushDiagnostics(
-    clang::DiagnosticsEngine &Diags) const {
-  for (const auto &i : all_) {
-    auto Diag = Diags.Report(Diags.getCustomDiagID(i.first, "%0"));
+void TextDiagnosticBuffer::flushDiagnostics(
+    clang::DiagnosticsEngine &diags) const {
+  for (const auto &i : all) {
+    auto diag = diags.Report(diags.getCustomDiagID(i.first, "%0"));
     switch (i.first) {
     default:
       llvm_unreachable("Diagnostic not handled during diagnostic flushing!");
     case clang::DiagnosticsEngine::Note:
-      Diag << notes_[i.second].second;
+      diag << notes[i.second].second;
       break;
     case clang::DiagnosticsEngine::Warning:
-      Diag << warnings_[i.second].second;
+      diag << warnings[i.second].second;
       break;
     case clang::DiagnosticsEngine::Remark:
-      Diag << remarks_[i.second].second;
+      diag << remarks[i.second].second;
       break;
     case clang::DiagnosticsEngine::Error:
     case clang::DiagnosticsEngine::Fatal:
-      Diag << errors_[i.second].second;
+      diag << errors[i.second].second;
       break;
     }
   }
diff --git a/flang/lib/Frontend/TextDiagnosticPrinter.cpp b/flang/lib/Frontend/TextDiagnosticPrinter.cpp
--- a/flang/lib/Frontend/TextDiagnosticPrinter.cpp
+++ b/flang/lib/Frontend/TextDiagnosticPrinter.cpp
@@ -19,9 +19,9 @@
 
 using namespace Fortran::frontend;
 
-TextDiagnosticPrinter::TextDiagnosticPrinter(
-    raw_ostream &os, clang::DiagnosticOptions *diags)
-    : os_(os), diagOpts_(diags) {}
+TextDiagnosticPrinter::TextDiagnosticPrinter(raw_ostream &diagOs,
+                                             clang::DiagnosticOptions *diags)
+    : os(diagOs), diagOpts(diags) {}
 
 TextDiagnosticPrinter::~TextDiagnosticPrinter() {}
 
@@ -35,21 +35,22 @@
   llvm::SmallString<100> outStr;
   info.FormatDiagnostic(outStr);
 
-  llvm::raw_svector_ostream DiagMessageStream(outStr);
+  llvm::raw_svector_ostream diagMessageStream(outStr);
 
-  if (!prefix_.empty())
-    os_ << prefix_ << ": ";
+  if (!prefix.empty())
+    os << prefix << ": ";
 
   // We only emit diagnostics in contexts that lack valid source locations.
   assert(!info.getLocation().isValid() &&
       "Diagnostics with valid source location are not supported");
 
-  Fortran::frontend::TextDiagnostic::PrintDiagnosticLevel(
-      os_, level, diagOpts_->ShowColors);
-  Fortran::frontend::TextDiagnostic::PrintDiagnosticMessage(os_,
+  Fortran::frontend::TextDiagnostic::printDiagnosticLevel(os, level,
+                                                          diagOpts->ShowColors);
+  Fortran::frontend::TextDiagnostic::printDiagnosticMessage(
+      os,
       /*IsSupplemental=*/level == clang::DiagnosticsEngine::Note,
-      DiagMessageStream.str(), diagOpts_->ShowColors);
+      diagMessageStream.str(), diagOpts->ShowColors);
 
-  os_.flush();
+  os.flush();
   return;
 }
diff --git a/flang/lib/FrontendTool/.clang-tidy b/flang/lib/FrontendTool/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/lib/FrontendTool/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
--- a/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -14,20 +14,21 @@
 #include "flang/Frontend/CompilerInstance.h"
 #include "flang/Frontend/FrontendActions.h"
 #include "flang/Frontend/FrontendPluginRegistry.h"
+
+#include "mlir/IR/MLIRContext.h"
+#include "mlir/Pass/PassManager.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/BuryPointer.h"
 #include "llvm/Support/CommandLine.h"
-#include "mlir/IR/MLIRContext.h"
-#include "mlir/Pass/PassManager.h"
 
 namespace Fortran::frontend {
 
-static std::unique_ptr<FrontendAction> CreateFrontendAction(
+static std::unique_ptr<FrontendAction> createFrontendAction(
     CompilerInstance &ci) {
 
-  switch (ci.frontendOpts().programAction) {
+  switch (ci.getFrontendOpts().programAction) {
   case InputOutputTest:
     return std::make_unique<InputOutputTestAction>();
   case PrintPreprocessedInput:
@@ -77,14 +78,14 @@
   case PluginAction: {
     for (const FrontendPluginRegistry::entry &plugin :
         FrontendPluginRegistry::entries()) {
-      if (plugin.getName() == ci.frontendOpts().ActionName) {
+      if (plugin.getName() == ci.getFrontendOpts().actionName) {
         std::unique_ptr<PluginParseTreeAction> p(plugin.instantiate());
         return std::move(p);
       }
     }
-    unsigned diagID = ci.diagnostics().getCustomDiagID(
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "unable to find plugin '%0'");
-    ci.diagnostics().Report(diagID) << ci.frontendOpts().ActionName;
+    ci.getDiagnostics().Report(diagID) << ci.getFrontendOpts().actionName;
     return nullptr;
   }
   }
@@ -92,9 +93,9 @@
   llvm_unreachable("Invalid program action!");
 }
 
-bool ExecuteCompilerInvocation(CompilerInstance *flang) {
+bool executeCompilerInvocation(CompilerInstance *flang) {
   // Honor -help.
-  if (flang->frontendOpts().showHelp) {
+  if (flang->getFrontendOpts().showHelp) {
     clang::driver::getDriverOptTable().printHelp(llvm::outs(),
         "flang-new -fc1 [options] file...", "LLVM 'Flang' Compiler",
         /*Include=*/clang::driver::options::FC1Option,
@@ -104,61 +105,61 @@
   }
 
   // Honor -version.
-  if (flang->frontendOpts().showVersion) {
+  if (flang->getFrontendOpts().showVersion) {
     llvm::cl::PrintVersionMessage();
     return true;
   }
 
   // Load any requested plugins.
-  for (const std::string &Path : flang->frontendOpts().plugins) {
-    std::string Error;
+  for (const std::string &path : flang->getFrontendOpts().plugins) {
+    std::string error;
     if (llvm::sys::DynamicLibrary::LoadLibraryPermanently(
-            Path.c_str(), &Error)) {
-      unsigned diagID = flang->diagnostics().getCustomDiagID(
+            path.c_str(), &error)) {
+      unsigned diagID = flang->getDiagnostics().getCustomDiagID(
           clang::DiagnosticsEngine::Error, "unable to load plugin '%0': '%1'");
-      flang->diagnostics().Report(diagID) << Path << Error;
+      flang->getDiagnostics().Report(diagID) << path << error;
     }
   }
 
   // Honor -mllvm. This should happen AFTER plugins have been loaded!
-  if (!flang->frontendOpts().llvmArgs.empty()) {
-    unsigned numArgs = flang->frontendOpts().llvmArgs.size();
+  if (!flang->getFrontendOpts().llvmArgs.empty()) {
+    unsigned numArgs = flang->getFrontendOpts().llvmArgs.size();
     auto args = std::make_unique<const char *[]>(numArgs + 2);
     args[0] = "flang (LLVM option parsing)";
 
     for (unsigned i = 0; i != numArgs; ++i)
-      args[i + 1] = flang->frontendOpts().llvmArgs[i].c_str();
+      args[i + 1] = flang->getFrontendOpts().llvmArgs[i].c_str();
 
     args[numArgs + 1] = nullptr;
     llvm::cl::ParseCommandLineOptions(numArgs + 1, args.get());
   }
 
   // Honor -mmlir. This should happen AFTER plugins have been loaded!
-  if (!flang->frontendOpts().mlirArgs.empty()) {
+  if (!flang->getFrontendOpts().mlirArgs.empty()) {
     mlir::registerMLIRContextCLOptions();
     mlir::registerPassManagerCLOptions();
-    unsigned numArgs = flang->frontendOpts().mlirArgs.size();
+    unsigned numArgs = flang->getFrontendOpts().mlirArgs.size();
     auto args = std::make_unique<const char *[]>(numArgs + 2);
     args[0] = "flang (MLIR option parsing)";
 
     for (unsigned i = 0; i != numArgs; ++i)
-      args[i + 1] = flang->frontendOpts().mlirArgs[i].c_str();
+      args[i + 1] = flang->getFrontendOpts().mlirArgs[i].c_str();
 
     args[numArgs + 1] = nullptr;
     llvm::cl::ParseCommandLineOptions(numArgs + 1, args.get());
   }
 
   // If there were errors in processing arguments, don't do anything else.
-  if (flang->diagnostics().hasErrorOccurred()) {
+  if (flang->getDiagnostics().hasErrorOccurred()) {
     return false;
   }
 
   // Create and execute the frontend action.
-  std::unique_ptr<FrontendAction> act(CreateFrontendAction(*flang));
+  std::unique_ptr<FrontendAction> act(createFrontendAction(*flang));
   if (!act)
     return false;
 
-  bool success = flang->ExecuteAction(*act);
+  bool success = flang->executeAction(*act);
   return success;
 }
 
diff --git a/flang/tools/flang-driver/.clang-tidy b/flang/tools/flang-driver/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/tools/flang-driver/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/tools/flang-driver/driver.cpp b/flang/tools/flang-driver/driver.cpp
--- a/flang/tools/flang-driver/driver.cpp
+++ b/flang/tools/flang-driver/driver.cpp
@@ -29,15 +29,15 @@
 // main frontend method. Lives inside fc1_main.cpp
 extern int fc1_main(llvm::ArrayRef<const char *> argv, const char *argv0);
 
-std::string GetExecutablePath(const char *argv0) {
+std::string getExecutablePath(const char *argv0) {
   // This just needs to be some symbol in the binary
-  void *p = (void *)(intptr_t)GetExecutablePath;
+  void *p = (void *)(intptr_t)getExecutablePath;
   return llvm::sys::fs::getMainExecutable(argv0, p);
 }
 
 // This lets us create the DiagnosticsEngine with a properly-filled-out
 // DiagnosticOptions instance
-static clang::DiagnosticOptions *CreateAndPopulateDiagOpts(
+static clang::DiagnosticOptions *createAndPopulateDiagOpts(
     llvm::ArrayRef<const char *> argv) {
   auto *diagOpts = new clang::DiagnosticOptions;
 
@@ -49,12 +49,12 @@
       argv.slice(1), missingArgIndex, missingArgCount,
       /*FlagsToInclude=*/clang::driver::options::FlangOption);
 
-  (void)Fortran::frontend::ParseDiagnosticArgs(*diagOpts, args);
+  (void)Fortran::frontend::parseDiagnosticArgs(*diagOpts, args);
 
   return diagOpts;
 }
 
-static int ExecuteFC1Tool(llvm::SmallVectorImpl<const char *> &argV) {
+static int executeFC1Tool(llvm::SmallVectorImpl<const char *> &argV) {
   llvm::StringRef tool = argV[1];
   if (tool == "-fc1")
     return fc1_main(makeArrayRef(argV).slice(2), argV[0]);
@@ -73,7 +73,7 @@
   llvm::SmallVector<const char *, 256> args(argv, argv + argc);
 
   clang::driver::ParsedClangName targetandMode("flang", "--driver-mode=flang");
-  std::string driverPath = GetExecutablePath(args[0]);
+  std::string driverPath = getExecutablePath(args[0]);
 
   // Check if flang-new is in the frontend mode
   auto firstArg = std::find_if(
@@ -86,7 +86,7 @@
     }
     // Call flang-new frontend
     if (llvm::StringRef(args[1]).startswith("-fc1")) {
-      return ExecuteFC1Tool(args);
+      return executeFC1Tool(args);
     }
   }
 
@@ -94,14 +94,14 @@
 
   // Create DiagnosticsEngine for the compiler driver
   llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagOpts =
-      CreateAndPopulateDiagOpts(args);
+      createAndPopulateDiagOpts(args);
   llvm::IntrusiveRefCntPtr<clang::DiagnosticIDs> diagID(
       new clang::DiagnosticIDs());
   Fortran::frontend::TextDiagnosticPrinter *diagClient =
       new Fortran::frontend::TextDiagnosticPrinter(llvm::errs(), &*diagOpts);
 
-  diagClient->set_prefix(
-      std::string(llvm::sys::path::stem(GetExecutablePath(args[0]))));
+  diagClient->setPrefix(
+      std::string(llvm::sys::path::stem(getExecutablePath(args[0]))));
 
   clang::DiagnosticsEngine diags(diagID, &*diagOpts, diagClient);
 
@@ -120,18 +120,18 @@
   res = theDriver.ExecuteCompilation(*c, failingCommands);
 
   for (const auto &p : failingCommands) {
-    int CommandRes = p.first;
+    int commandRes = p.first;
     const clang::driver::Command *failingCommand = p.second;
     if (!res)
-      res = CommandRes;
+      res = commandRes;
 
     // If result status is < 0 (e.g. when sys::ExecuteAndWait returns -1),
     // then the driver command signalled an error. On Windows, abort will
     // return an exit code of 3. In these cases, generate additional diagnostic
     // information if possible.
-    isCrash = CommandRes < 0;
+    isCrash = commandRes < 0;
 #ifdef _WIN32
-    isCrash |= CommandRes == 3;
+    isCrash |= commandRes == 3;
 #endif
     if (isCrash) {
       theDriver.generateCompilationDiagnostics(*c, *failingCommand);
diff --git a/flang/tools/flang-driver/fc1_main.cpp b/flang/tools/flang-driver/fc1_main.cpp
--- a/flang/tools/flang-driver/fc1_main.cpp
+++ b/flang/tools/flang-driver/fc1_main.cpp
@@ -31,8 +31,8 @@
   std::unique_ptr<CompilerInstance> flang(new CompilerInstance());
 
   // Create DiagnosticsEngine for the frontend driver
-  flang->CreateDiagnostics();
-  if (!flang->HasDiagnostics())
+  flang->createDiagnostics();
+  if (!flang->hasDiagnostics())
     return 1;
 
   // We will buffer diagnostics from argument parsing so that we can output
@@ -47,23 +47,23 @@
       new clang::DiagnosticOptions();
   clang::DiagnosticsEngine diags(diagID, &*diagOpts, diagsBuffer);
   bool success =
-      CompilerInvocation::CreateFromArgs(flang->invocation(), argv, diags);
+      CompilerInvocation::createFromArgs(flang->getInvocation(), argv, diags);
 
   // Initialize targets first, so that --version shows registered targets.
   llvm::InitializeAllTargets();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllAsmPrinters();
 
-  diagsBuffer->FlushDiagnostics(flang->diagnostics());
+  diagsBuffer->flushDiagnostics(flang->getDiagnostics());
 
   if (!success)
     return 1;
 
   // Execute the frontend actions.
-  success = ExecuteCompilerInvocation(flang.get());
+  success = executeCompilerInvocation(flang.get());
 
   // Delete output files to free Compiler Instance
-  flang->ClearOutputFiles(/*EraseFiles=*/false);
+  flang->clearOutputFiles(/*EraseFiles=*/false);
 
   return !success;
 }
diff --git a/flang/unittests/Frontend/.clang-tidy b/flang/unittests/Frontend/.clang-tidy
new file mode 100644
--- /dev/null
+++ b/flang/unittests/Frontend/.clang-tidy
@@ -0,0 +1,9 @@
+Checks: '-readability-braces-around-statements,readability-identifier-naming,llvm-include-order,clang-diagnostic-*'
+InheritParentConfig: true
+CheckOptions:
+  - key:             readability-identifier-naming.MemberCase
+    value:           camelBack
+  - key:             readability-identifier-naming.ParameterCase
+    value:           camelBack
+  - key:             readability-identifier-naming.VariableCase
+    value:           camelBack
diff --git a/flang/unittests/Frontend/CompilerInstanceTest.cpp b/flang/unittests/Frontend/CompilerInstanceTest.cpp
--- a/flang/unittests/Frontend/CompilerInstanceTest.cpp
+++ b/flang/unittests/Frontend/CompilerInstanceTest.cpp
@@ -44,10 +44,10 @@
 
   // 2. Set up CompilerInstance (i.e. specify the input file)
   std::string buf;
-  llvm::raw_string_ostream error_stream{buf};
+  llvm::raw_string_ostream errorStream{buf};
   CompilerInstance compInst;
   const Fortran::parser::SourceFile *sf =
-      compInst.allSources().Open(testFilePath, error_stream);
+      compInst.getAllSources().Open(testFilePath, errorStream);
 
   // 3. Verify the content of the input file
   // This is just a sanity check to make sure that CompilerInstance is capable
@@ -82,7 +82,7 @@
 
   // 4. Create a DiagnosticEngine with an unowned consumer
   IntrusiveRefCntPtr<clang::DiagnosticsEngine> diags =
-      compInst.CreateDiagnostics(diagOpts, diagPrinter.get(),
+      compInst.createDiagnostics(diagOpts, diagPrinter.get(),
           /*ShouldOwnClient=*/false);
 
   // 5. Report a diagnostic
diff --git a/flang/unittests/Frontend/FrontendActionTest.cpp b/flang/unittests/Frontend/FrontendActionTest.cpp
--- a/flang/unittests/Frontend/FrontendActionTest.cpp
+++ b/flang/unittests/Frontend/FrontendActionTest.cpp
@@ -27,51 +27,51 @@
   // AllSources (which is used to manage files inside every compiler
   // instance), works with paths. So we need a filename and a path for the
   // input file.
-  // TODO: We could use `-` for inputFilePath_, but then we'd need a way to
+  // TODO: We could use `-` for inputFilePath, but then we'd need a way to
   // write to stdin that's then read by AllSources. Ideally, AllSources should
   // be capable of reading from any stream.
-  std::string inputFileName_;
-  std::string inputFilePath_;
+  std::string inputFileName;
+  std::string inputFilePath;
   // The output stream for the input file. Use this to populate the input.
-  std::unique_ptr<llvm::raw_fd_ostream> inputFileOs_;
+  std::unique_ptr<llvm::raw_fd_ostream> inputFileOs;
 
-  std::error_code ec_;
+  std::error_code ec;
 
-  CompilerInstance compInst_;
-  std::shared_ptr<CompilerInvocation> invocation_;
+  CompilerInstance compInst;
+  std::shared_ptr<CompilerInvocation> invoc;
 
   void SetUp() override {
     // Generate a unique test file name.
-    const testing::TestInfo *const test_info =
+    const testing::TestInfo *const testInfo =
         testing::UnitTest::GetInstance()->current_test_info();
-    inputFileName_ = std::string(test_info->name()) + "_test-file.f90";
+    inputFileName = std::string(testInfo->name()) + "_test-file.f90";
 
     // Create the input file stream. Note that this stream is populated
     // separately in every test (i.e. the input is test specific).
-    inputFileOs_ = std::make_unique<llvm::raw_fd_ostream>(
-        inputFileName_, ec_, llvm::sys::fs::OF_None);
-    if (ec_)
+    inputFileOs = std::make_unique<llvm::raw_fd_ostream>(
+        inputFileName, ec, llvm::sys::fs::OF_None);
+    if (ec)
       FAIL() << "Failed to create the input file";
 
     // Get the path of the input file.
     llvm::SmallString<256> cwd;
-    if (std::error_code ec_ = llvm::sys::fs::current_path(cwd))
+    if (std::error_code ec = llvm::sys::fs::current_path(cwd))
       FAIL() << "Failed to obtain the current working directory";
-    inputFilePath_ = cwd.c_str();
-    inputFilePath_ += "/" + inputFileName_;
+    inputFilePath = cwd.c_str();
+    inputFilePath += "/" + inputFileName;
 
     // Prepare the compiler (CompilerInvocation + CompilerInstance)
-    compInst_.CreateDiagnostics();
-    invocation_ = std::make_shared<CompilerInvocation>();
+    compInst.createDiagnostics();
+    invoc = std::make_shared<CompilerInvocation>();
 
-    compInst_.set_invocation(std::move(invocation_));
-    compInst_.frontendOpts().inputs.push_back(
-        FrontendInputFile(inputFilePath_, Language::Fortran));
+    compInst.setInvocation(std::move(invoc));
+    compInst.getFrontendOpts().inputs.push_back(
+        FrontendInputFile(inputFilePath, Language::Fortran));
   }
 
   void TearDown() override {
     // Clear the input file.
-    llvm::sys::fs::remove(inputFileName_);
+    llvm::sys::fs::remove(inputFileName);
 
     // Clear the output files.
     // Note that these tests use an output buffer (as opposed to an output
@@ -79,27 +79,27 @@
     // `EraseFiles` is set to `false`. Also, some actions (e.g.
     // `ParseSyntaxOnly`) don't generated output. In such cases there's no
     // output to clear and `ClearOutputFile` returns immediately.
-    compInst_.ClearOutputFiles(/*EraseFiles=*/false);
+    compInst.clearOutputFiles(/*EraseFiles=*/false);
   }
 };
 
 TEST_F(FrontendActionTest, TestInputOutput) {
   // Populate the input file with the pre-defined input and flush it.
-  *(inputFileOs_) << "End Program arithmetic";
-  inputFileOs_.reset();
+  *(inputFileOs) << "End Program arithmetic";
+  inputFileOs.reset();
 
   // Set-up the action kind.
-  compInst_.invocation().frontendOpts().programAction = InputOutputTest;
+  compInst.getInvocation().getFrontendOpts().programAction = InputOutputTest;
 
   // Set-up the output stream. Using output buffer wrapped as an output
   // stream, as opposed to an actual file (or a file descriptor).
   llvm::SmallVector<char, 256> outputFileBuffer;
   std::unique_ptr<llvm::raw_pwrite_stream> outputFileStream(
       new llvm::raw_svector_ostream(outputFileBuffer));
-  compInst_.set_outputStream(std::move(outputFileStream));
+  compInst.setOutputStream(std::move(outputFileStream));
 
   // Execute the action.
-  bool success = ExecuteCompilerInvocation(&compInst_);
+  bool success = executeCompilerInvocation(&compInst);
 
   // Validate the expected output.
   EXPECT_TRUE(success);
@@ -110,26 +110,27 @@
 
 TEST_F(FrontendActionTest, PrintPreprocessedInput) {
   // Populate the input file with the pre-defined input and flush it.
-  *(inputFileOs_) << "#ifdef NEW\n"
-                  << "  Program A \n"
-                  << "#else\n"
-                  << "  Program B\n"
-                  << "#endif";
-  inputFileOs_.reset();
+  *(inputFileOs) << "#ifdef NEW\n"
+                 << "  Program A \n"
+                 << "#else\n"
+                 << "  Program B\n"
+                 << "#endif";
+  inputFileOs.reset();
 
   // Set-up the action kind.
-  compInst_.invocation().frontendOpts().programAction = PrintPreprocessedInput;
-  compInst_.invocation().preprocessorOpts().noReformat = true;
+  compInst.getInvocation().getFrontendOpts().programAction =
+      PrintPreprocessedInput;
+  compInst.getInvocation().getPreprocessorOpts().noReformat = true;
 
   // Set-up the output stream. We are using output buffer wrapped as an output
   // stream, as opposed to an actual file (or a file descriptor).
   llvm::SmallVector<char, 256> outputFileBuffer;
   std::unique_ptr<llvm::raw_pwrite_stream> outputFileStream(
       new llvm::raw_svector_ostream(outputFileBuffer));
-  compInst_.set_outputStream(std::move(outputFileStream));
+  compInst.setOutputStream(std::move(outputFileStream));
 
   // Execute the action.
-  bool success = ExecuteCompilerInvocation(&compInst_);
+  bool success = executeCompilerInvocation(&compInst);
 
   // Validate the expected output.
   EXPECT_TRUE(success);
@@ -140,21 +141,21 @@
 
 TEST_F(FrontendActionTest, ParseSyntaxOnly) {
   // Populate the input file with the pre-defined input and flush it.
-  *(inputFileOs_) << "IF (A > 0.0) IF (B < 0.0) A = LOG (A)\n"
-                  << "END";
-  inputFileOs_.reset();
+  *(inputFileOs) << "IF (A > 0.0) IF (B < 0.0) A = LOG (A)\n"
+                 << "END";
+  inputFileOs.reset();
 
   // Set-up the action kind.
-  compInst_.invocation().frontendOpts().programAction = ParseSyntaxOnly;
+  compInst.getInvocation().getFrontendOpts().programAction = ParseSyntaxOnly;
 
   // Set-up the output stream for the semantic diagnostics.
   llvm::SmallVector<char, 256> outputDiagBuffer;
   std::unique_ptr<llvm::raw_pwrite_stream> outputStream(
       new llvm::raw_svector_ostream(outputDiagBuffer));
-  compInst_.set_semaOutputStream(std::move(outputStream));
+  compInst.setSemaOutputStream(std::move(outputStream));
 
   // Execute the action.
-  bool success = ExecuteCompilerInvocation(&compInst_);
+  bool success = executeCompilerInvocation(&compInst);
 
   // Validate the expected output.
   EXPECT_FALSE(success);
@@ -167,14 +168,14 @@
 
 TEST_F(FrontendActionTest, EmitLLVM) {
   // Populate the input file with the pre-defined input and flush it.
-  *(inputFileOs_) << "end program";
-  inputFileOs_.reset();
+  *(inputFileOs) << "end program";
+  inputFileOs.reset();
 
   // Set-up the action kind.
-  compInst_.invocation().frontendOpts().programAction = EmitLLVM;
+  compInst.getInvocation().getFrontendOpts().programAction = EmitLLVM;
 
   // Set-up default target triple.
-  compInst_.invocation().targetOpts().triple =
+  compInst.getInvocation().getTargetOpts().triple =
       llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple());
 
   // Set-up the output stream. We are using output buffer wrapped as an output
@@ -182,10 +183,10 @@
   llvm::SmallVector<char> outputFileBuffer;
   std::unique_ptr<llvm::raw_pwrite_stream> outputFileStream(
       new llvm::raw_svector_ostream(outputFileBuffer));
-  compInst_.set_outputStream(std::move(outputFileStream));
+  compInst.setOutputStream(std::move(outputFileStream));
 
   // Execute the action.
-  bool success = ExecuteCompilerInvocation(&compInst_);
+  bool success = executeCompilerInvocation(&compInst);
 
   // Validate the expected output.
   EXPECT_TRUE(success);
@@ -197,14 +198,14 @@
 
 TEST_F(FrontendActionTest, EmitAsm) {
   // Populate the input file with the pre-defined input and flush it.
-  *(inputFileOs_) << "end program";
-  inputFileOs_.reset();
+  *(inputFileOs) << "end program";
+  inputFileOs.reset();
 
   // Set-up the action kind.
-  compInst_.invocation().frontendOpts().programAction = EmitAssembly;
+  compInst.getInvocation().getFrontendOpts().programAction = EmitAssembly;
 
   // Set-up default target triple.
-  compInst_.invocation().targetOpts().triple =
+  compInst.getInvocation().getTargetOpts().triple =
       llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple());
 
   // Initialise LLVM backend
@@ -217,10 +218,10 @@
   llvm::SmallVector<char, 256> outputFileBuffer;
   std::unique_ptr<llvm::raw_pwrite_stream> outputFileStream(
       new llvm::raw_svector_ostream(outputFileBuffer));
-  compInst_.set_outputStream(std::move(outputFileStream));
+  compInst.setOutputStream(std::move(outputFileStream));
 
   // Execute the action.
-  bool success = ExecuteCompilerInvocation(&compInst_);
+  bool success = executeCompilerInvocation(&compInst);
 
   // Validate the expected output.
   EXPECT_TRUE(success);