[lldb] Check if interop is enabled only on compile unit

When deciding whether to format a C++ type as a Swiftified type or not,
checking if Swift/C++ interop is enabled on the entire target can be
very expensive for big projects, and may not swiftify types that should
be.

rdar://117708944

Author: augusto2112

lldb/source/Plugins/Language/Swift/SwiftLanguage.cpp

@@ -1159,9 +1159,6 @@ SwiftLanguage::GetHardcodedSynthetics() {
 
       Log *log(GetLog(LLDBLog::DataFormatters));
 
-      if (!valobj.GetTargetSP()->IsSwiftCxxInteropEnabled())
-        return nullptr;
-
       CompilerType type(valobj.GetCompilerType());
       auto swift_type_system =
           type.GetTypeSystem().dyn_cast_or_null<TypeSystemSwift>();
@@ -1191,6 +1188,29 @@ SwiftLanguage::GetHardcodedSynthetics() {
         return nullptr;
       }
 
+      // Find the compile unit and module using the frame, because the value
+      // object may not have a module in the case of an expression that
+      // evaluates to a type.
+      if (!valobj.GetFrameSP())
+        return nullptr;
+
+      auto sc = valobj.GetFrameSP()->GetSymbolContext(
+          lldb::SymbolContextItem::eSymbolContextCompUnit |
+          lldb::SymbolContextItem::eSymbolContextModule);
+
+      // If there is a compile unit, use that to check if C++ interop should be
+      // enabled. If there is no compiler unit, use the module. If neither
+      // exist, assume that C++ interop is disabled.
+      if (auto *cu = sc.comp_unit) {
+        if (!SwiftASTContext::ShouldEnableCXXInterop(cu))
+          return nullptr;
+      } else if (sc.module_sp) {
+        if (!sc.module_sp->IsSwiftCxxInteropEnabled())
+          return nullptr;
+      } else {
+        return nullptr;
+      }
+
       casted->SetName(ConstString("Clang_Type"));
 
       SyntheticChildrenSP synth_sp =

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -2264,7 +2264,7 @@ SwiftASTContext::CreateInstance(lldb::LanguageType language, Module &module,
 }
 
 /// Determine whether this CU was compiled with C++ interop enabled.
-static bool ShouldEnableCXXInterop(CompileUnit *cu) {
+bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
   AutoBool interop_enabled =
     ModuleList::GetGlobalModuleListProperties().GetSwiftEnableCxxInterop();
   switch (interop_enabled) {

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h

@@ -208,6 +208,9 @@ class SwiftASTContext : public TypeSystemSwift {
   CreateInstance(const SymbolContext &sc,
                  TypeSystemSwiftTypeRefForExpressions &typeref_typesystem);
 
+  /// Returns true if Swift C++ interop is enabled for the given compiler unit.
+  static bool ShouldEnableCXXInterop(CompileUnit *cu);
+
   static void EnumerateSupportedLanguages(
       std::set<lldb::LanguageType> &languages_for_types,
       std::set<lldb::LanguageType> &languages_for_expressions);