[flang][debug] Don't generate debug for compiler-generated variables

flang/include/flang/Optimizer/Support/InternalNames.h

@@ -184,6 +184,10 @@ struct NameUniquer {
 
   static std::string replaceSpecialSymbols(const std::string &name);
 
+  /// Returns true if the passed name denotes a special symbol (e.g. global
+  /// symbol generated for derived type description).
+  static bool isSpecialSymbol(llvm::StringRef name);
+
 private:
   static std::string intAsString(std::int64_t i);
   static std::string doKind(std::int64_t kind);

flang/lib/Optimizer/Support/InternalNames.cpp

@@ -411,3 +411,7 @@ fir::NameUniquer::dropTypeConversionMarkers(llvm::StringRef mangledTypeName) {
 std::string fir::NameUniquer::replaceSpecialSymbols(const std::string &name) {
   return std::regex_replace(name, std::regex{"\\."}, "X");
 }
+
+bool fir::NameUniquer::isSpecialSymbol(llvm::StringRef name) {
+  return !name.empty() && (name[0] == '.' || name[0] == 'X');
+}

flang/lib/Optimizer/Transforms/AddDebugInfo.cpp

@@ -211,10 +211,7 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
   if (result.first != fir::NameUniquer::NameKind::VARIABLE)
     return;
 
-  // Discard entries that describe a derived type. Usually start with '.c.',
-  // '.dt.' or '.n.'. It would be better if result of the deconstruct had a flag
-  // for such values so that we dont have to look at string values.
-  if (!result.second.name.empty() && result.second.name[0] == '.')
+  if (fir::NameUniquer::isSpecialSymbol(result.second.name))
     return;
 
   unsigned line = getLineFromLoc(globalOp.getLoc());

flang/test/Integration/debug-extra-global-2.f90

@@ -0,0 +1,8 @@
+! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck  %s
+
+module m
+  integer XcX
+end
+
+! Test that global starting with 'X' don't get filtered.
+! CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})

flang/test/Integration/debug-extra-global.f90

@@ -0,0 +1,14 @@
+! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck  %s
+
+program test
+ type t1
+   integer :: XcX
+   integer :: xdtx
+ end type
+  type(t1) :: var
+  var%XcX = 2
+  var%xdtx = 3
+end
+
+! Test that there is no debug info for compiler generated globals.
+! CHECK-NOT: DIGlobalVariable

flang/test/Transforms/debug-extra-global.fir

@@ -0,0 +1,18 @@
+// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
+  fir.global linkonce_odr @_QFEXnXxcx constant target : !fir.char<1,3> {
+    %0 = fir.string_lit "xcx"(3) : !fir.char<1,3>
+    fir.has_value %0 : !fir.char<1,3>
+  } loc(#loc1)
+  fir.global linkonce_odr @_QFEXnXxdtx constant target : !fir.char<1,4> {
+    %0 = fir.string_lit "xdtx"(4) : !fir.char<1,4>
+    fir.has_value %0 : !fir.char<1,4>
+  } loc(#loc1)
+}
+#loc1 = loc("derived.f90":24:1)
+
+// Test that no di_global_variable gets created for these compile generated
+// globals.
+
+// CHECK-NOT: #di_global_variable