Get SwiftASTContextForExpression's SDK path straight from debug info.

This mostly-NFC patch cuts out the middle-person and directly parses
the SDK info from the debug info in SwiftASTContextForExpression, rhus
avoiding the costly need to iterate over all SwiftASTContext and the
last call to warmup_contexts().

Author: adrian-prantl

lldb/include/lldb/Target/Target.h

@@ -169,8 +169,6 @@ class TargetProperties : public Properties {
 
   llvm::StringRef GetSwiftExtraClangFlags() const;
 
-  bool GetSwiftCreateModuleContextsInParallel() const;
-
   bool GetSwiftReadMetadataFromFileCache() const;
 
   bool GetSwiftUseReflectionSymbols() const;

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

@@ -2136,42 +2136,19 @@ lldb::TypeSystemSP SwiftASTContext::CreateInstance(lldb::LanguageType language,
     handled_sdk_path = true;
   }
 
-  auto warmup_astcontexts = [&]() {
-    if (target.GetSwiftCreateModuleContextsInParallel()) {
-      // The first call to GetTypeSystemForLanguage() on a module will
-      // trigger the import (and thus most likely the rebuild) of all
-      // the Clang modules that were imported in this module. This can
-      // be a lot of work (potentially ten seconds per module), but it
-      // can be performed in parallel.
-      llvm::ThreadPool pool(llvm::hardware_concurrency());
-      for (size_t mi = 0; mi != num_images; ++mi) {
-        auto module_sp = target.GetImages().GetModuleAtIndex(mi);
-        pool.async([=] {
-          GetModuleSwiftASTContext(*module_sp);
-        });
-      }
-      pool.wait();
-    }
-  };
-
   if (!handled_sdk_path) {
-    warmup_astcontexts();
     for (size_t mi = 0; mi != num_images; ++mi) {
       ModuleSP module_sp = target.GetImages().GetModuleAtIndex(mi);
       if (!HasSwiftModules(*module_sp))
         continue;
 
-      SwiftASTContext *module_swift_ast = GetModuleSwiftASTContext(*module_sp);
-      if (!module_swift_ast || module_swift_ast->HasFatalErrors() ||
-          !module_swift_ast->GetClangImporter())
-        continue;
+      std::string sdk_path = GetSDKPathFromDebugInfo(m_description, *module_sp);
 
-      StringRef platform_sdk_path = module_swift_ast->GetPlatformSDKPath();
-      if (platform_sdk_path.empty())
+      if (sdk_path.empty())
         continue;
 
       handled_sdk_path = true;
-      swift_ast_sp->SetPlatformSDKPath(platform_sdk_path);
+      swift_ast_sp->SetPlatformSDKPath(sdk_path);
       break;
     }
   }

lldb/source/Target/Target.cpp

@@ -4146,18 +4146,6 @@ void TargetProperties::SetInjectLocalVariables(ExecutionContext *exe_ctx,
                                             true);
 }
 
-bool TargetProperties::GetSwiftCreateModuleContextsInParallel() const {
-  const Property *exp_property = m_collection_sp->GetPropertyAtIndex(
-      nullptr, false, ePropertyExperimental);
-  OptionValueProperties *exp_values =
-      exp_property->GetValue()->GetAsProperties();
-  if (exp_values)
-    return exp_values->GetPropertyAtIndexAsBoolean(
-        nullptr, ePropertySwiftCreateModuleContextsInParallel, true);
-  else
-    return true;
-}
-
 bool TargetProperties::GetSwiftReadMetadataFromFileCache() const {
   const Property *exp_property = m_collection_sp->GetPropertyAtIndex(
       nullptr, false, ePropertyExperimental);

lldb/source/Target/TargetProperties.td

@@ -4,9 +4,6 @@ let Definition = "target_experimental" in {
   def InjectLocalVars : Property<"inject-local-vars", "Boolean">,
     Global, DefaultTrue,
     Desc<"If true, inject local variables explicitly into the expression text. This will fix symbol resolution when there are name collisions between ivars and local variables. But it can make expressions run much more slowly.">;
-  def SwiftCreateModuleContextsInParallel : Property<"swift-create-module-contexts-in-parallel", "Boolean">,
-    DefaultTrue,
-    Desc<"Create the per-module Swift AST contexts in parallel.">;
   def SwiftReadMetadataFromFileCache: Property<"swift-read-metadata-from-file-cache", "Boolean">,
     DefaultTrue,
     Desc<"Read Swift reflection metadata from the file cache instead of the process when possible">;