[lldb] Check if Embedded Swift is enabled only on the compile unit

Reading debug info of an entire module to check whether embedded Swift
is enabled or not can be very slow. This patch replaces that check with
only checking the compile unit instead.

rdar://147009063

Author: augusto2112

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

@@ -2628,8 +2628,7 @@ SwiftASTContext::CreateInstance(lldb::LanguageType language, Module &module,
   return swift_ast_sp;
 }
 
-/// Determine whether this CU was compiled with C++ interop enabled.
-bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
+bool SwiftASTContext::CheckFlagInCU(CompileUnit *cu, const char *flag) {
   AutoBool interop_enabled =
     ModuleList::GetGlobalModuleListProperties().GetSwiftEnableCxxInterop();
   switch (interop_enabled) {
@@ -2643,8 +2642,6 @@ bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
     lldb::ModuleSP module = cu->CalculateSymbolContextModule();
     if (!module)
       return false;
-    // Look for the "-enable-experimental-cxx-interop" compile flag in the
-    // args of the compile units this module is composed of.
     auto *sym_file = module->GetSymbolFile();
     if (!sym_file)
       return false;
@@ -2653,7 +2650,7 @@ bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
       if (unit.get() == cu) {
         if (cu->GetLanguage() == eLanguageTypeSwift)
           for (const char *arg : args.GetArgumentArrayRef())
-            if (strcmp(arg, "-enable-experimental-cxx-interop") == 0)
+            if (strcmp(arg, flag) == 0)
               return true;
         return false;
       }
@@ -2663,6 +2660,15 @@ bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
   return false;
 }
 
+/// Determine whether this CU was compiled with C++ interop enabled.
+bool SwiftASTContext::ShouldEnableCXXInterop(CompileUnit *cu) {
+  return CheckFlagInCU(cu, "-enable-experimental-cxx-interop");
+}
+
+bool SwiftASTContext::ShouldEnableEmbeddedSwift(CompileUnit *cu) {
+  return CheckFlagInCU(cu, "-enable-embedded-swift");
+}
+
 static bool IsUnitTestExecutable(lldb_private::Module &module) {
   static ConstString s_xctest("xctest");
   static ConstString s_XCTRunner("XCTRunner");
@@ -2776,7 +2782,7 @@ SwiftASTContext::CreateInstance(const SymbolContext &sc,
     swift_ast_sp->m_is_scratch_context = true;
     auto &lang_opts = swift_ast_sp->GetLanguageOptions();
     lang_opts.EnableCXXInterop = ShouldEnableCXXInterop(cu);
-    if (target_sp->IsEmbeddedSwift())
+    if (ShouldEnableEmbeddedSwift(cu))
       lang_opts.enableFeature(swift::Feature::Embedded);
   } else {
     // Typesystem fallback context.
@@ -2793,7 +2799,7 @@ SwiftASTContext::CreateInstance(const SymbolContext &sc,
     auto &lang_opts = swift_ast_sp->GetLanguageOptions();
     lang_opts.EnableAccessControl = false;
     lang_opts.EnableCXXInterop = ShouldEnableCXXInterop(cu);
-    if (module_sp->IsEmbeddedSwift())
+    if (ShouldEnableEmbeddedSwift(cu))
       lang_opts.enableFeature(swift::Feature::Embedded);
   }
   auto defer_log = llvm::make_scope_exit(

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

@@ -210,9 +210,13 @@ class SwiftASTContext : public TypeSystemSwift {
                  TypeSystemSwiftTypeRef &typeref_typesystem,
                  const char *extra_options = nullptr);
 
-  /// Returns true if Swift C++ interop is enabled for the given compiler unit.
+  /// Returns true if the given flag is present in the given compile unit.
+  static bool CheckFlagInCU(CompileUnit *cu, const char *flag);
+
   static bool ShouldEnableCXXInterop(CompileUnit *cu);
 
+  static bool ShouldEnableEmbeddedSwift(CompileUnit *cu);
+
   static void EnumerateSupportedLanguages(
       std::set<lldb::LanguageType> &languages_for_types,
       std::set<lldb::LanguageType> &languages_for_expressions);