[lldb] Implement LLDBMemoryReader::resolvePointer

lldb/include/lldb/Core/Section.h

@@ -201,6 +201,8 @@ class Section : public std::enable_shared_from_this<Section>,
   ObjectFile *GetObjectFile() { return m_obj_file; }
   const ObjectFile *GetObjectFile() const { return m_obj_file; }
 
+  bool CanContainSwiftReflectionData() const;
+
   /// Read the section data from the object file that the section
   /// resides in.
   ///

lldb/include/lldb/Symbol/ObjectFile.h

@@ -689,6 +689,12 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
   virtual llvm::StringRef
   GetReflectionSectionIdentifier(swift::ReflectionSectionKind section);
 
+#ifdef LLDB_ENABLE_SWIFT
+  virtual bool CanContainSwiftReflectionData(const Section &section) {
+    return false;
+  }
+#endif // LLDB_ENABLE_SWIFT
+
   /// Load binaries listed in a corefile
   ///
   /// A corefile may have metadata listing binaries that can be loaded,

lldb/include/lldb/Target/Target.h

@@ -173,6 +173,8 @@ class TargetProperties : public Properties {
 
   bool GetSwiftReadMetadataFromFileCache() const;
 
+  bool GetSwiftUseReflectionSymbols() const;
+
   bool GetEnableAutoImportClangModules() const;
 
   bool GetUseAllCompilerFlags() const;

lldb/source/Core/Section.cpp

@@ -390,6 +390,14 @@ void Section::SetPermissions(uint32_t permissions) {
   m_executable = (permissions & ePermissionsExecutable) != 0;
 }
 
+bool Section::CanContainSwiftReflectionData() const {
+#ifdef LLDB_ENABLE_SWIFT
+  return m_obj_file->CanContainSwiftReflectionData(*this);
+#else
+  return false;
+#endif // LLDB_ENABLE_SWIFT
+}
+
 lldb::offset_t Section::GetSectionData(void *dst, lldb::offset_t dst_len,
                                        lldb::offset_t offset) {
   if (m_obj_file)

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.cpp

@@ -1,7 +1,9 @@
 #include "LLDBMemoryReader.h"
+#include "lldb/Core/Address.h"
 #include "lldb/Core/Section.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/Logging.h"
+#include "swift/Demangling/Demangle.h"
 
 #include "llvm/Support/MathExtras.h"
 
@@ -117,6 +119,50 @@ LLDBMemoryReader::getSymbolAddress(const std::string &name) {
   return swift::remote::RemoteAddress(load_addr);
 }
 
+swift::remote::RemoteAbsolutePointer
+LLDBMemoryReader::resolvePointer(swift::remote::RemoteAddress address,
+                                 uint64_t readValue) {
+  // If an address has a symbol, that symbol provides additional useful data to
+  // MetadataReader. Without the symbol, MetadataReader can derive the symbol
+  // by loading other parts of reflection metadata, but that work has a cost.
+  // For lldb, that data loading can be a significant performance hit. Providing
+  // a symbol greatly reduces memory read traffic to the process.
+  auto pointer = swift::remote::RemoteAbsolutePointer("", readValue);
+
+  auto &target = m_process.GetTarget();
+  if (!target.GetSwiftUseReflectionSymbols())
+    return pointer;
+
+  llvm::Optional<Address> maybeAddr =
+      resolveRemoteAddress(address.getAddressData());
+  // This is not an assert, but should never happen.
+  if (!maybeAddr)
+    return pointer;
+
+  Address addr;
+  if (maybeAddr->IsSectionOffset()) {
+    // `address` was tagged, and then successfully mapped (resolved).
+    addr = *maybeAddr;
+  } else {
+    // `address` is a real load address.
+    if (!target.ResolveLoadAddress(address.getAddressData(), addr))
+      return pointer;
+  }
+
+  if (!addr.GetSection()->CanContainSwiftReflectionData())
+    return pointer;
+
+  if (auto *symbol = addr.CalculateSymbolContextSymbol()) {
+    auto mangledName = symbol->GetMangled().GetMangledName().GetStringRef();
+    // MemoryReader requires this to be a Swift symbol. LLDB can also be
+    // aware of local symbols, so avoid returning those.
+    if (swift::Demangle::isSwiftSymbol(mangledName))
+      return {mangledName, 0};
+  }
+
+  return pointer;
+}
+
 bool LLDBMemoryReader::readBytes(swift::remote::RemoteAddress address,
                                  uint8_t *dest, uint64_t size) {
   if (m_local_buffer) {

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.h

@@ -23,6 +23,10 @@ class LLDBMemoryReader : public swift::remote::MemoryReader {
   swift::remote::RemoteAddress
   getSymbolAddress(const std::string &name) override;
 
+  swift::remote::RemoteAbsolutePointer
+  resolvePointer(swift::remote::RemoteAddress address,
+                 uint64_t readValue) override;
+
   bool readBytes(swift::remote::RemoteAddress address, uint8_t *dest,
                  uint64_t size) override;
 

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

@@ -3429,3 +3429,11 @@ llvm::StringRef ObjectFileELF::GetReflectionSectionIdentifier(
   llvm_unreachable("Swift support disabled");
 #endif //LLDB_ENABLE_SWIFT
 }
+
+#ifdef LLDB_ENABLE_SWIFT
+bool ObjectFileELF::CanContainSwiftReflectionData(const Section &section) {
+  swift::SwiftObjectFileFormatELF file_format;
+  return file_format.sectionContainsReflectionData(
+      section.GetName().GetStringRef());
+}
+#endif // LLDB_ENABLE_SWIFT

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h

@@ -395,6 +395,11 @@ class ObjectFileELF : public lldb_private::ObjectFile {
 
   llvm::StringRef
   GetReflectionSectionIdentifier(swift::ReflectionSectionKind section) override;
+
+#ifdef LLDB_ENABLE_SWIFT
+  bool
+  CanContainSwiftReflectionData(const lldb_private::Section &section) override;
+#endif // LLDB_ENABLE_SWIFT
 };
 
 #endif // LLDB_SOURCE_PLUGINS_OBJECTFILE_ELF_OBJECTFILEELF_H

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

@@ -7019,6 +7019,23 @@ llvm::StringRef ObjectFileMachO::GetReflectionSectionIdentifier(
 #endif //LLDB_ENABLE_SWIFT
 }
 
+#ifdef LLDB_ENABLE_SWIFT
+bool ObjectFileMachO::CanContainSwiftReflectionData(const Section &section) {
+  swift::SwiftObjectFileFormatMachO file_format;
+  if (file_format.sectionContainsReflectionData(
+          section.GetName().GetStringRef()))
+    return true;
+  // Some section names are not unique, such as `__const`, which could be in
+  // `__TEXT` or `__DATA`. For these, also check the segment,section name.
+  if (auto segment = section.GetParent()) {
+    std::string segmentSectionName =
+        llvm::formatv("{0},{1}", segment->GetName(), section.GetName()).str();
+    return file_format.sectionContainsReflectionData(segmentSectionName);
+  }
+  return false;
+}
+#endif // LLDB_ENABLE_SWIFT
+
 ObjectFileMachO::MachOCorefileAllImageInfos
 ObjectFileMachO::GetCorefileAllImageInfos() {
   MachOCorefileAllImageInfos image_infos;

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h

@@ -220,6 +220,11 @@ class ObjectFileMachO : public lldb_private::ObjectFile {
   llvm::StringRef
   GetReflectionSectionIdentifier(swift::ReflectionSectionKind section) override;
 
+#ifdef LLDB_ENABLE_SWIFT
+  bool
+  CanContainSwiftReflectionData(const lldb_private::Section &section) override;
+#endif // LLDB_ENABLE_SWIFT
+
   /// A corefile may include metadata about all of the binaries that were
   /// present in the process when the corefile was taken.  This is only
   /// implemented for Mach-O files for now; we'll generalize it when we

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

@@ -1217,3 +1217,10 @@ llvm::StringRef ObjectFilePECOFF::GetReflectionSectionIdentifier(
 #endif //LLDB_ENABLE_SWIFT
 }
 
+#ifdef LLDB_ENABLE_SWIFT
+bool ObjectFilePECOFF::CanContainSwiftReflectionData(const Section &section) {
+  swift::SwiftObjectFileFormatCOFF file_format;
+  return file_format.sectionContainsReflectionData(
+      section.GetName().GetStringRef());
+}
+#endif // LLDB_ENABLE_SWIFT

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.h

@@ -288,6 +288,11 @@ class ObjectFilePECOFF : public lldb_private::ObjectFile {
   llvm::StringRef
   GetReflectionSectionIdentifier(swift::ReflectionSectionKind section) override;
 
+#ifdef LLDB_ENABLE_SWIFT
+  bool
+  CanContainSwiftReflectionData(const lldb_private::Section &section) override;
+#endif // LLDB_ENABLE_SWIFT
+
   typedef std::vector<section_header_t> SectionHeaderColl;
   typedef SectionHeaderColl::iterator SectionHeaderCollIter;
   typedef SectionHeaderColl::const_iterator SectionHeaderCollConstIter;

lldb/source/Target/Target.cpp

@@ -4168,6 +4168,18 @@ bool TargetProperties::GetSwiftReadMetadataFromFileCache() const {
   return true;
 }
 
+bool TargetProperties::GetSwiftUseReflectionSymbols() 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, ePropertySwiftUseReflectionSymbols, true);
+  else
+    return true;
+}
+
 ArchSpec TargetProperties::GetDefaultArchitecture() const {
   OptionValueArch *value = m_collection_sp->GetPropertyAtIndexAsOptionValueArch(
       nullptr, ePropertyDefaultArch);

lldb/source/Target/TargetProperties.td

@@ -10,6 +10,9 @@ let Definition = "target_experimental" in {
   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">;
+  def SwiftUseReflectionSymbols : Property<"swift-use-reflection-symbols", "Boolean">,
+    Global, DefaultTrue,
+    Desc<"if true, optimize the loading of Swift reflection metadata by making use of available symbols.">;
 }
 
 let Definition = "target" in {