[flang] Add options -W[no-]unused-dummy-argument and -W[no-]unused-variable

Addition of two new warning options and a diagnostic system for Flang
based on the Clang's diagnostics.

Author: JDPailleux

clang/include/clang/Basic/Diagnostic.td

@@ -55,11 +55,14 @@ class DiagCategory<string Name> {
 }
 
 // Diagnostic Groups.
-class DiagGroup<string Name, list<DiagGroup> subgroups = [], code docs = [{}]> {
+class DiagGroup<string Name, list<DiagGroup> subgroups = [], code docs = [{}],
+                bit clangDiag = 1, bit flangDiag = 0> {
   string GroupName = Name;
   list<DiagGroup> SubGroups = subgroups;
   string CategoryName = "";
   code Documentation = docs;
+  bit IsClangDiag = clangDiag;
+  bit IsFlangDiag = flangDiag;
 }
 class InGroup<DiagGroup G> { DiagGroup Group = G; }
 //class IsGroup<string Name> { DiagGroup Group = DiagGroup<Name>; }

clang/include/clang/Basic/DiagnosticCategories.h

@@ -21,7 +21,8 @@ namespace clang {
     };
 
     enum class Group {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)    \
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs,    \
+                       IsClang, IsFlang)                                       \
       GroupName,
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef CATEGORY

clang/include/clang/Basic/DiagnosticGroups.td

@@ -885,12 +885,13 @@ def UnevaluatedExpression : DiagGroup<"unevaluated-expression",
 def UnusedValue : DiagGroup<"unused-value", [UnusedComparison, UnusedResult,
                                              UnevaluatedExpression]>;
 def UnusedConstVariable : DiagGroup<"unused-const-variable">;
-def UnusedVariable : DiagGroup<"unused-variable",
-                               [UnusedConstVariable]>;
+def UnusedVariable
+    : DiagGroup<"unused-variable", [UnusedConstVariable], [{}], 1, 1>;
 def UnusedButSetVariable : DiagGroup<"unused-but-set-variable">;
 def UnusedLocalTypedef : DiagGroup<"unused-local-typedef">;
 def UnusedPropertyIvar :  DiagGroup<"unused-property-ivar">;
 def UnusedGetterReturnValue : DiagGroup<"unused-getter-return-value">;
+def UnusedDummyArgument : DiagGroup<"unused-dummy-argument", [], [{}], 0, 1>;
 def UsedButMarkedUnused : DiagGroup<"used-but-marked-unused">;
 def UsedSearchPath : DiagGroup<"search-path-usage">;
 def UserDefinedLiterals : DiagGroup<"user-defined-literals">;

clang/include/clang/Basic/DiagnosticIDs.h

@@ -365,6 +365,11 @@ class DiagnosticIDs : public RefCountedBase<DiagnosticIDs> {
   /// Given a diagnostic group ID, return its documentation.
   static StringRef getWarningOptionDocumentation(diag::Group GroupID);
 
+  /// Given a diagnostic group ID, return true if its a Flang warning.
+  static bool isFlangWarningOption(diag::Group Group);
+  /// Given a diagnostic group ID, return true if its a Clang warning.
+  static bool isClangWarningOption(diag::Group Group);
+
   void setGroupSeverity(StringRef Group, diag::Severity);
   void setGroupNoWarningsAsError(StringRef Group, bool);
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -12966,4 +12966,10 @@ def note_acc_atomic_mismatch_compound_operand
 // AMDGCN builtins diagnostics
 def err_amdgcn_global_load_lds_size_invalid_value : Error<"invalid size value">;
 def note_amdgcn_global_load_lds_size_valid_value : Note<"size must be %select{1, 2, or 4|1, 2, 4, 12 or 16}0">;
+
+// Flang diagnostics
+def warn_unused_dummy_argument : Warning<"unused dummy argument %0">,
+                                 InGroup<UnusedDummyArgument>,
+                                 DefaultIgnore;
+
 } // end of sema component.

clang/lib/Basic/DiagnosticIDs.cpp

@@ -585,15 +585,18 @@ namespace {
     uint16_t Members;
     uint16_t SubGroups;
     StringRef Documentation;
+    bool IsClangDiag;
+    bool IsFlangDiag;
 
     StringRef getName() const { return DiagGroupNames[NameOffset]; }
   };
 }
 
 // Second the table of options, sorted by name for fast binary lookup.
 static const WarningOption OptionTable[] = {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
-  {FlagNameOffset, Members, SubGroups, Docs},
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs,        \
+                   IsClang, IsFlang)                                           \
+  {FlagNameOffset, Members, SubGroups, Docs, IsClang, IsFlang},
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef DIAG_ENTRY
 };
@@ -607,6 +610,13 @@ StringRef DiagnosticIDs::getWarningOptionForGroup(diag::Group Group) {
   return OptionTable[static_cast<int>(Group)].getName();
 }
 
+bool DiagnosticIDs::isFlangWarningOption(diag::Group Group) {
+  return OptionTable[static_cast<int>(Group)].IsFlangDiag;
+}
+
+bool DiagnosticIDs::isClangWarningOption(diag::Group Group) {
+  return OptionTable[static_cast<int>(Group)].IsClangDiag;
+}
 std::optional<diag::Group>
 DiagnosticIDs::getGroupForWarningOption(StringRef Name) {
   const auto *Found = llvm::partition_point(

clang/lib/Basic/Warnings.cpp

@@ -106,6 +106,15 @@ void clang::ProcessWarningOptions(DiagnosticsEngine &Diags,
       diag::Severity Mapping =
           isPositive ? diag::Severity::Warning : diag::Severity::Ignored;
 
+      // Check if the warning option is valid for Clang
+      std::optional<diag::Group> Group = DiagIDs->getGroupForWarningOption(Opt);
+      if (Group.has_value() && !DiagIDs->isClangWarningOption(Group.value())) {
+        const unsigned DiagID = Diags.getCustomDiagID(
+            DiagnosticsEngine::Error,
+            "Warning option \"%0\" is valid for Fortran but not for C++.");
+        Diags.Report(DiagID) << Opt;
+      }
+
       // -Wsystem-headers is a special case, not driven by the option table.  It
       // cannot be controlled with -Werror.
       if (Opt == "system-headers") {

clang/test/TableGen/DiagnosticBase.inc

@@ -55,11 +55,13 @@ class DiagCategory<string Name> {
 }
 
 // Diagnostic Groups.
-class DiagGroup<string Name, list<DiagGroup> subgroups = []> {
+class DiagGroup<string Name, list<DiagGroup> subgroups = [], bit clangDiag = 1, bit flangDiag = 0> {
   string GroupName = Name;
   list<DiagGroup> SubGroups = subgroups;
   string CategoryName = "";
   code Documentation = [{}];
+  bit IsClangDiag = clangDiag;
+  bit IsFlangDiag = flangDiag;
 }
 class InGroup<DiagGroup G> { DiagGroup Group = G; }
 //class IsGroup<string Name> { DiagGroup Group = DiagGroup<Name>; }

clang/tools/diagtool/DiagnosticNames.cpp

@@ -62,7 +62,8 @@ const DiagnosticRecord &diagtool::getDiagnosticForID(short DiagID) {
 
 // Second the table of options, sorted by name for fast binary lookup.
 static const GroupRecord OptionTable[] = {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs,        \
+                   IsClang, IsFlang)                                           \
   {FlagNameOffset, Members, SubGroups},
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef DIAG_ENTRY

clang/utils/TableGen/ClangDiagnosticsEmitter.cpp

@@ -1890,6 +1890,10 @@ static void emitDiagTable(DiagsInGroupTy &DiagsInGroup,
 
     OS << "R\"(" << StringRef(Documentation).trim() << ")\"";
 
+    OS << ", /*IsClangDiag*/ "
+       << bool(GroupInfo.Defs.back()->getValueAsBit("IsClangDiag"));
+    OS << ", /*IsFlangDiag*/ "
+       << bool(GroupInfo.Defs.back()->getValueAsBit("IsFlangDiag"));
     OS << ")\n";
   }
   OS << "#endif // DIAG_ENTRY\n\n";