[Flang][Driver] Add warning support for invalid R_Group options

[victorkingi]

Summary

With the R_Group options, invalid values e.g. '-Rpa' will not emit
a warning like clang. This patch enables warning reporting, as
well as suggestions on what option the user intended to select.

Depends on D158174 and D158436. The former, adds backend
support to R_Group options while the latter, implements
regex support with some tests refactoring that cause a merge
conflict.

[awarzynski]

Makes, just some minor suggestions.

flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp

137–144

flang/test/Driver/optimization-remark.f90

14–18 ↗

(On Diff #552654)

I would move all the tests that check for invalid usage into a dedicated test file, e.g. optimization-remark-invalid.f90.

[victorkingi]

Moved warning test cases from optimization-remark.f90 to
optimization-remark-invalid.f90
Added suggested comment to ExecuteCompilerInvocation.cpp

[awarzynski]

LGTM, thanks!

[victorkingi]

no changes, rebasing

[victorkingi]

no changes, rebasing

flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp

case PluginAction: {
     ci.getDiagnostics().Report(diagID) << ci.getFrontendOpts().actionName;
     return nullptr;
   }
   }
 
   llvm_unreachable("Invalid program action!");
 }
 
+static void emitUnknownDiagWarning(clang::DiagnosticsEngine &diags,
+                                   clang::diag::Flavor flavor,
+                                   llvm::StringRef prefix,
+                                   llvm::StringRef opt) {
+  llvm::StringRef suggestion =
+      clang::DiagnosticIDs::getNearestOption(flavor, opt);
+  diags.Report(clang::diag::warn_unknown_diag_option)
+      << (flavor == clang::diag::Flavor::WarningOrError ? 0 : 1)
+      << (prefix.str() += std::string(opt)) << !suggestion.empty()
+      << (prefix.str() += std::string(suggestion));
+}
+
 // Remarks are ignored by default in Diagnostic.td, hence, we have to
 // enable them here before execution. Clang follows same idea using
 // ProcessWarningOptions in Warnings.cpp
 // This function is also responsible for emitting early warnings for
 // invalid -R options.
 static void
 updateDiagEngineForOptRemarks(clang::DiagnosticsEngine &diagsEng,
                               const clang::DiagnosticOptions &opts) {
   llvm::SmallVector<clang::diag::kind, 10> diags;
   const llvm::IntrusiveRefCntPtr<clang::DiagnosticIDs> diagIDs =
       diagsEng.getDiagnosticIDs();
 
   for (unsigned i = 0; i < opts.Remarks.size(); i++) {
     llvm::StringRef remarkOpt = opts.Remarks[i];
     const auto flavor = clang::diag::Flavor::Remark;
 
     // Check to see if this opt starts with "no-", if so, this is a
     // negative form of the option.
     bool isPositive = !remarkOpt.startswith("no-");
     if (!isPositive)
       remarkOpt = remarkOpt.substr(3);
 
+    // Verify that this is a valid optimization remarks option
+    if (diagIDs->getDiagnosticsInGroup(flavor, remarkOpt, diags)) {
+      emitUnknownDiagWarning(diagsEng, flavor, isPositive ? "-R" : "-Rno-",
+                             remarkOpt);
+      return;
+    }
+
     diagsEng.setSeverityForGroup(flavor, remarkOpt,
                                  isPositive ? clang::diag::Severity::Remark
                                             : clang::diag::Severity::Ignored);
   }
 }
 
 bool executeCompilerInvocation(CompilerInstance *flang) {
   // Honor -help.

flang/test/Driver/optimization-remark-invalid.f90

 ! This file tests invalid usage of the -Rpass family of flags (-Rpass, -Rpass-missed
 ! and -Rpass-analysis)
 ! loop-delete isn't enabled at O0 so we use at least O1
 
 ! Check error on invalid regex -Rpass message is emitted
 ! RUN: not %flang %s -O1 -Rpass=[ -c 2>&1 | FileCheck %s --check-prefix=REGEX-INVALID
 
+! Check "unknown remark option" warning
+! RUN: %flang %s -O1 -R -c 2>&1 | FileCheck %s --check-prefix=WARN
+
+! Check "unknown remark option" warning with suggestion
+! RUN: %flang %s -O1 -Rpas -c 2>&1 | FileCheck %s --check-prefix=WARN-SUGGEST
 
 ! REGEX-INVALID: error: in pattern '-Rpass=[': brackets ([ ]) not balanced
+! WARN: warning: unknown remark option '-R'
+! WARN-SUGGEST: warning: unknown remark option '-Rpas'; did you mean '-Rpass'?
 
 program forttest
 end program forttest