TypeSystemSwiftTypeRef: Make SwiftASTContext fallback switchable

adrian-prantl · adrian-prantl · commit a120b8e5d147 · 2025-02-14T11:26:18.000-08:00
via a new setting symbols.swift-typesystem-fallback

The new setting is currently on by default, prints a warning if the
fallback was engaged and successful, and is meant to eventually be
turned off when running the LLDB testsuite.

rdar://142512839
diff --git a/lldb/include/lldb/Core/ModuleList.h b/lldb/include/lldb/Core/ModuleList.h
@@ -82,6 +82,7 @@ class ModuleListProperties : public Properties {
   bool GetUseSwiftDWARFImporter() const;
   bool SetUseSwiftDWARFImporter(bool new_value);
   bool GetSwiftValidateTypeSystem() const;
+  bool GetSwiftTypeSystemFallback() const;
   bool GetSwiftLoadConformances() const;
   SwiftModuleLoadingMode GetSwiftModuleLoadingMode() const;
   bool SetSwiftModuleLoadingMode(SwiftModuleLoadingMode);
diff --git a/lldb/packages/Python/lldbsuite/test/lldbtest.py b/lldb/packages/Python/lldbsuite/test/lldbtest.py
@@ -778,6 +778,7 @@ def setUpCommands(cls):
             ),
             # Enable expensive validations in TypeSystemSwiftTypeRef.
             "settings set symbols.swift-validate-typesystem true",
+            "settings set symbols.swift-typesystem-compiler-fallback true",
             "settings set use-color false",
         ]
 
diff --git a/lldb/source/Core/CoreProperties.td b/lldb/source/Core/CoreProperties.td
@@ -28,6 +28,11 @@ let Definition = "modulelist" in {
   def SwiftValidateTypeSystem: Property<"swift-validate-typesystem", "Boolean">,
     DefaultFalse,
     Desc<"Validate all Swift typesystem queries. Used for testing an asserts-enabled LLDB only.">;
+  def SwiftTypeSystemFallback
+      : Property<"swift-typesystem-compiler-fallback", "Boolean">,
+        DefaultTrue,
+        Desc<"If a query against reflection metadata / debug info fails, retry "
+             "using Swift modules.">;
   def SwiftLoadConformances: Property<"swift-load-conformances", "Boolean">,
     DefaultFalse,
     Desc<"Resolve type alias via the conformance section. Disabled for performance reasons">;
diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp
@@ -200,6 +200,12 @@ bool ModuleListProperties::GetSwiftValidateTypeSystem() const {
       idx, g_modulelist_properties[idx].default_uint_value != 0);
 }
 
+bool ModuleListProperties::GetSwiftTypeSystemFallback() const {
+  const uint32_t idx = ePropertySwiftTypeSystemFallback;
+  return GetPropertyAtIndexAs<bool>(
+      idx, g_modulelist_properties[idx].default_uint_value != 0);
+}
+
 bool ModuleListProperties::GetSwiftLoadConformances() const {
   const uint32_t idx = ePropertySwiftLoadConformances;
   return GetPropertyAtIndexAs<bool>(
diff --git a/lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.cpp b/lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.cpp
@@ -2735,12 +2735,42 @@ constexpr ExecutionContextScope *g_no_exe_ctx = nullptr;
 #define FORWARD_TO_EXPRAST_ONLY(FUNC, ARGS, DEFAULT_RETVAL)                    \
   do {                                                                         \
     if (auto target_sp = GetTargetWP().lock())                                 \
-      if (auto swift_ast_ctx = GetSwiftASTContext(                            \
+      if (auto swift_ast_ctx = GetSwiftASTContext(                             \
               SymbolContext(target_sp, target_sp->GetExecutableModule())))     \
         return swift_ast_ctx->FUNC ARGS;                                       \
     return DEFAULT_RETVAL;                                                     \
   } while (0)
 
+bool TypeSystemSwiftTypeRef::UseSwiftASTContextFallback(
+    const char *func_name, lldb::opaque_compiler_type_t type) {
+  if (!ModuleList::GetGlobalModuleListProperties().GetSwiftTypeSystemFallback())
+    return false;
+
+  LLDB_LOGF(GetLog(LLDBLog::Types),
+            "TypeSystemSwiftTypeRef::%s(): Engaging SwiftASTContext fallback "
+            "for type %s",
+            func_name, AsMangledName(type));
+  return true;
+}
+
+bool TypeSystemSwiftTypeRef::DiagnoseSwiftASTContextFallback(
+    const char *func_name, lldb::opaque_compiler_type_t type) {
+  const char *type_name = AsMangledName(type);
+
+  std::optional<lldb::user_id_t> debugger_id;
+  if (auto target_sp = GetTargetWP().lock())
+    debugger_id = target_sp->GetDebugger().GetID();
+
+  std::string msg;
+  llvm::raw_string_ostream(msg)
+      << "TypeSystemSwiftTypeRef::" << func_name
+      << ": had to engage SwiftASTContext fallback for type " << type_name;
+  Debugger::ReportWarning(msg, debugger_id, &m_fallback_warning);
+
+  LLDB_LOGF(GetLog(LLDBLog::Types), "%s", msg.c_str());
+  return true;
+}
+
 CompilerType
 TypeSystemSwiftTypeRef::RemangleAsType(swift::Demangle::Demangler &dem,
                                        swift::Demangle::NodePointer node,
@@ -3453,14 +3483,16 @@ TypeSystemSwiftTypeRef::GetBitSize(opaque_compiler_type_t type,
       if (auto result = runtime->GetBitSize({weak_from_this(), type}, exe_scope))
         return result;
       // Runtime failed, fallback to SwiftASTContext.
-      LLDB_LOGF(GetLog(LLDBLog::Types),
-                "Couldn't compute size of type %s using SwiftLanguageRuntime.",
-                AsMangledName(type));
-
-      if (auto swift_ast_context =
-              GetSwiftASTContext(GetSymbolContext(exe_scope)))
-        return swift_ast_context->GetBitSize(ReconstructType(type, exe_scope),
-                                             exe_scope);
+      if (UseSwiftASTContextFallback(__FUNCTION__, type)) {
+        if (auto swift_ast_context =
+                GetSwiftASTContext(GetSymbolContext(exe_scope))) {
+          auto result = swift_ast_context->GetBitSize(
+              ReconstructType(type, exe_scope), exe_scope);
+          if (result)
+            DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+          return result;
+        }
+      }
     }
 
     // FIXME: Move this to the top. Currently this causes VALIDATE
@@ -3501,12 +3533,16 @@ TypeSystemSwiftTypeRef::GetByteStride(opaque_compiler_type_t type,
         return stride;
     }
     // Runtime failed, fallback to SwiftASTContext.
-    LLDB_LOGF(GetLog(LLDBLog::Types),
-              "Couldn't compute stride of type %s using SwiftLanguageRuntime.",
-              AsMangledName(type));
-    if (auto swift_ast_context =
-            GetSwiftASTContext(GetSymbolContext(exe_scope)))
-      return swift_ast_context->GetByteStride(ReconstructType(type), exe_scope);
+    if (UseSwiftASTContextFallback(__FUNCTION__, type)) {
+      if (auto swift_ast_context =
+              GetSwiftASTContext(GetSymbolContext(exe_scope))) {
+        auto result =
+            swift_ast_context->GetByteStride(ReconstructType(type), exe_scope);
+        if (result)
+          DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+        return result;
+      }
+    }
     return {};
   };
   VALIDATE_AND_RETURN(impl, GetByteStride, type, exe_scope,
@@ -3624,19 +3660,19 @@ TypeSystemSwiftTypeRef::GetNumChildren(opaque_compiler_type_t type,
         impl, GetNumChildren, type, exe_ctx_obj,
         (ReconstructType(type, exe_ctx), omit_empty_base_classes, exe_ctx));
   }
-  LLDB_LOGF(GetLog(LLDBLog::Types),
-            "Using SwiftASTContext::GetNumChildren fallback for type %s",
-            AsMangledName(type));
-
-  // Try SwiftASTContext.
-  if (auto swift_ast_context = GetSwiftASTContext(GetSymbolContext(exe_ctx)))
-    if (auto n = llvm::expectedToStdOptional(swift_ast_context->GetNumChildren(
-            ReconstructType(type, exe_ctx), omit_empty_base_classes,
-            exe_ctx))) {
-      LLDB_LOG_ERRORV(GetLog(LLDBLog::Types), num_children.takeError(),
-                      "SwiftLanguageRuntime::GetNumChildren() failed: {0}");
-      return *n;
-    }
+  // Runtime failed, fallback to SwiftASTContext.
+  if (UseSwiftASTContextFallback(__FUNCTION__, type)) {
+    if (auto swift_ast_context = GetSwiftASTContext(GetSymbolContext(exe_ctx)))
+      if (auto n =
+              llvm::expectedToStdOptional(swift_ast_context->GetNumChildren(
+                  ReconstructType(type, exe_ctx), omit_empty_base_classes,
+                  exe_ctx))) {
+        LLDB_LOG_ERRORV(GetLog(LLDBLog::Types), num_children.takeError(),
+                        "SwiftLanguageRuntime::GetNumChildren() failed: {0}");
+        DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+        return *n;
+      }
+  }
 
   // Otherwise return the error from the runtime.
   return num_children.takeError();
@@ -3686,12 +3722,16 @@ uint32_t TypeSystemSwiftTypeRef::GetNumFields(opaque_compiler_type_t type,
                         .value_or(0);
   }
 
-  LLDB_LOGF(GetLog(LLDBLog::Types),
-            "Using SwiftASTContext::GetNumFields fallback for type %s",
-            AsMangledName(type));
-
-  if (auto swift_ast_context = GetSwiftASTContext(GetSymbolContext(exe_ctx)))
-    return swift_ast_context->GetNumFields(ReconstructType(type, exe_ctx), exe_ctx);
+  // Runtime failed, fallback to SwiftASTContext.
+  if (UseSwiftASTContextFallback(__FUNCTION__, type))
+    if (auto swift_ast_context =
+            GetSwiftASTContext(GetSymbolContext(exe_ctx))) {
+      auto result = swift_ast_context->GetNumFields(
+          ReconstructType(type, exe_ctx), exe_ctx);
+      if (result)
+        DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+      return result;
+    }
   return {};
 }
 
@@ -3787,6 +3827,7 @@ TypeSystemSwiftTypeRef::GetChildCompilerTypeAtIndex(
     return ast_num_children.value_or(0);
   };
   auto impl = [&]() -> llvm::Expected<CompilerType> {
+    std::string error = "unknown error";
     ExecutionContextScope *exe_scope = nullptr;
     if (exe_ctx)
       exe_scope = exe_ctx->GetBestExecutionContextScope();
@@ -3809,7 +3850,7 @@ TypeSystemSwiftTypeRef::GetChildCompilerTypeAtIndex(
           return result;
         }
         if (!result)
-          llvm::consumeError(result.takeError());
+          error = llvm::toString(result.takeError());
       }
       // Clang types can be resolved even without a process.
       bool is_signed;
@@ -3923,10 +3964,17 @@ TypeSystemSwiftTypeRef::GetChildCompilerTypeAtIndex(
                 "Couldn't compute size of type %s without a process.",
                 AsMangledName(type));
 
-    // FIXME: SwiftASTContext can sometimes find more Clang types because it
-    // imports Clang modules from source. We should be able to replicate this
-    // and remove this fallback.
-    return fallback();
+    // Runtime failed, fallback to SwiftASTContext.
+    if (UseSwiftASTContextFallback(__FUNCTION__, type)) {
+      // FIXME: SwiftASTContext can sometimes find more Clang types because it
+      // imports Clang modules from source. We should be able to replicate this
+      // and remove this fallback.
+      auto result = fallback();
+      if (result)
+        DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+      return result;
+    }
+    return llvm::createStringError(llvm::inconvertibleErrorCode(), error);
   };
   // Skip validation when there is no process, because then we also
   // don't have a runtime.
@@ -4080,10 +4128,17 @@ size_t TypeSystemSwiftTypeRef::GetIndexOfChildMemberWithName(
             "type %s",
             AsMangledName(type));
 
-  if (auto swift_ast_context = GetSwiftASTContext(GetSymbolContext(exe_ctx)))
-    return swift_ast_context->GetIndexOfChildMemberWithName(
-        ReconstructType(type, exe_ctx), name, exe_ctx, omit_empty_base_classes,
-        child_indexes);
+  // Runtime failed, fallback to SwiftASTContext.
+  if (UseSwiftASTContextFallback(__FUNCTION__, type))
+    if (auto swift_ast_context =
+            GetSwiftASTContext(GetSymbolContext(exe_ctx))) {
+      auto result = swift_ast_context->GetIndexOfChildMemberWithName(
+          ReconstructType(type, exe_ctx), name, exe_ctx,
+          omit_empty_base_classes, child_indexes);
+      if (result)
+        DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+      return result;
+    }
   return {};
 }
 
@@ -4388,10 +4443,16 @@ TypeSystemSwiftTypeRef::GetInstanceType(opaque_compiler_type_t type,
       // type alias isn't possible, or the user might have defined the
       // type alias in the REPL. In these cases, fallback to asking the AST
       // for the canonical type.
-      if (auto swift_ast_context =
-              GetSwiftASTContext(GetSymbolContext(exe_scope)))
-        return swift_ast_context->GetInstanceType(
-            ReconstructType(type, exe_scope), exe_scope);
+      // Runtime failed, fallback to SwiftASTContext.
+      if (UseSwiftASTContextFallback(__FUNCTION__, type))
+        if (auto swift_ast_context =
+                GetSwiftASTContext(GetSymbolContext(exe_scope))) {
+          auto result = swift_ast_context->GetInstanceType(
+              ReconstructType(type, exe_scope), exe_scope);
+          if (result)
+            DiagnoseSwiftASTContextFallback(__FUNCTION__, type);
+          return result;
+        }
       return {};
     }
 
diff --git a/lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.h b/lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.h
@@ -441,6 +441,13 @@ class TypeSystemSwiftTypeRef : public TypeSystemSwift {
   GetManglingFlavor(ExecutionContext *exe_ctx = nullptr);
 
 protected:
+  /// Determine whether the fallback is enabled via setting.
+  bool UseSwiftASTContextFallback(const char *func_name,
+                                  lldb::opaque_compiler_type_t type);
+  /// Print a warning that a fallback was necessary.
+  bool DiagnoseSwiftASTContextFallback(const char *func_name,
+                                       lldb::opaque_compiler_type_t type);
+
   /// Helper that creates an AST type from \p type.
   ///
   /// FIXME: This API is dangerous, it would be better to return a
@@ -555,6 +562,7 @@ class TypeSystemSwiftTypeRef : public TypeSystemSwift {
     unsigned char retry_count = 0;
   };
 
+  std::once_flag m_fallback_warning;
   mutable std::mutex m_swift_ast_context_lock;
   /// The "precise" SwiftASTContexts managed by this scratch context. There
   /// exists one per Swift module. The keys in this map are module names.
diff --git a/lldb/test/Shell/lit-lldb-init.in b/lldb/test/Shell/lit-lldb-init.in
@@ -9,3 +9,4 @@ settings set target.auto-apply-fixits false
 settings set target.inherit-tcc true
 settings set target.detach-on-error false
 settings set symbols.swift-validate-typesystem true
+settings set symbols.swift-typesystem-compiler-fallback true

Original file line number	Diff line number	Diff line change
`@@ -778,6 +778,7 @@ def setUpCommands(cls):`
`778`	`778`	`),`
`779`	`779`	`# Enable expensive validations in TypeSystemSwiftTypeRef.`
`780`	`780`	`"settings set symbols.swift-validate-typesystem true",`
	`781`	`+ "settings set symbols.swift-typesystem-compiler-fallback true",`
`781`	`782`	`"settings set use-color false",`
`782`	`783`	`]`
`783`	`784`