[Reproducers] Refactor reproducer info

In the original reproducer design, I expected providers to be more
dynamic than they turned out. For example, we don't have any instances
where one provider has multiple files. Additionally, I expected there to
be less locality between capture and replay, with the provider being
defined in one place and the replay code to live in another. Both
contributed to the design of the provider info.

This patch refactors the reproducer info to be something static. This
means less magic strings and better type checking. The new design still
allows for the capture and replay code to live in different places as
long as they both have access to the new statically defined info class.

I didn't completely get rid of the index, because it is useful for (1)
sanity checking and (2) knowing what files are used by the reproducer.

Differential revision: https://reviews.llvm.org/D56814

llvm-svn: 351501

lldb/include/lldb/Utility/Reproducer.h

@@ -31,24 +31,14 @@ enum class ReproducerMode {
   Off,
 };
 
-/// Abstraction for information associated with a provider. This information
-/// is serialized into an index which is used by the loader.
-struct ProviderInfo {
-  std::string name;
-  std::vector<std::string> files;
-};
-
 /// The provider defines an interface for generating files needed for
-/// reproducing. The provider must populate its ProviderInfo to communicate
-/// its name and files to the index, before registering with the generator,
-/// i.e. in the constructor.
+/// reproducing.
 ///
 /// Different components will implement different providers.
 class ProviderBase {
 public:
   virtual ~ProviderBase() = default;
 
-  const ProviderInfo &GetInfo() const { return m_info; }
   const FileSpec &GetRoot() const { return m_root; }
 
   /// The Keep method is called when it is decided that we need to keep the
@@ -65,11 +55,12 @@ public:
   // Returns the class ID for the dynamic type of this Provider instance.
   virtual const void *DynamicClassID() const = 0;
 
+  virtual llvm::StringRef GetName() const = 0;
+  virtual llvm::StringRef GetFile() const = 0;
+
 protected:
   ProviderBase(const FileSpec &root) : m_root(root) {}
 
-  /// Every provider keeps track of its own files.
-  ProviderInfo m_info;
 private:
   /// Every provider knows where to dump its potential files.
   FileSpec m_root;
@@ -84,6 +75,9 @@ public:
 
   const void *DynamicClassID() const override { return &ThisProviderT::ID; }
 
+  llvm::StringRef GetName() const override { return ThisProviderT::info::name; }
+  llvm::StringRef GetFile() const override { return ThisProviderT::info::file; }
+
 protected:
   using ProviderBase::ProviderBase; // Inherit constructor.
 };
@@ -152,14 +146,22 @@ class Loader final {
 public:
   Loader(const FileSpec &root);
 
-  llvm::Optional<ProviderInfo> GetProviderInfo(llvm::StringRef name);
+  template <typename T> FileSpec GetFile() {
+    if (!HasFile(T::file))
+      return {};
+
+    return GetRoot().CopyByAppendingPathComponent(T::file);
+  }
+
   llvm::Error LoadIndex();
 
   const FileSpec &GetRoot() const { return m_root; }
 
 private:
-  llvm::StringMap<ProviderInfo> m_provider_info;
+  bool HasFile(llvm::StringRef file);
+
   FileSpec m_root;
+  std::vector<std::string> m_files;
   bool m_loaded;
 };
 
@@ -198,18 +200,4 @@ private:
 } // namespace repro
 } // namespace lldb_private
 
-LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(lldb_private::repro::ProviderInfo)
-
-namespace llvm {
-namespace yaml {
-
-template <> struct MappingTraits<lldb_private::repro::ProviderInfo> {
-  static void mapping(IO &io, lldb_private::repro::ProviderInfo &info) {
-    io.mapRequired("name", info.name);
-    io.mapOptional("files", info.files);
-  }
-};
-} // namespace yaml
-} // namespace llvm
-
 #endif // LLDB_UTILITY_REPRODUCER_H

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

@@ -157,17 +157,24 @@ static const ProcessKDPPropertiesSP &GetGlobalPluginProperties() {
   return g_settings_sp;
 }
 
+struct ProcessGDBRemoteInfo {
+  static const char *name;
+  static const char *file;
+};
+
+const char *ProcessGDBRemoteInfo::name = "gdb-remote";
+const char *ProcessGDBRemoteInfo::file = "gdb-remote.yaml";
+
 class ProcessGDBRemoteProvider
     : public repro::Provider<ProcessGDBRemoteProvider> {
 public:
+  typedef ProcessGDBRemoteInfo info;
+
   ProcessGDBRemoteProvider(const FileSpec &directory) : Provider(directory) {
-    m_info.name = "gdb-remote";
-    m_info.files.push_back("gdb-remote.yaml");
   }
 
   raw_ostream *GetHistoryStream() {
-    FileSpec history_file =
-        GetRoot().CopyByAppendingPathComponent("gdb-remote.yaml");
+    FileSpec history_file = GetRoot().CopyByAppendingPathComponent(info::file);
 
     std::error_code EC;
     m_stream_up = llvm::make_unique<raw_fd_ostream>(history_file.GetPath(), EC,
@@ -3432,16 +3439,10 @@ Status ProcessGDBRemote::ConnectToReplayServer(repro::Loader *loader) {
   if (!loader)
     return Status("No loader provided.");
 
-  auto provider_info = loader->GetProviderInfo("gdb-remote");
-  if (!provider_info)
-    return Status("No provider for gdb-remote.");
-
-  if (provider_info->files.empty())
-    return Status("Provider for  gdb-remote contains no files.");
-
   // Construct replay history path.
-  FileSpec history_file = loader->GetRoot().CopyByAppendingPathComponent(
-      provider_info->files.front());
+  FileSpec history_file = loader->GetFile<ProcessGDBRemoteInfo>();
+  if (!history_file)
+    return Status("No provider for gdb-remote.");
 
   // Enable replay mode.
   m_replay_mode = true;

lldb/source/Utility/Reproducer.cpp

@@ -178,10 +178,13 @@ void Generator::AddProvidersToIndex() {
                                                 sys::fs::OpenFlags::F_None);
   yaml::Output yout(*strm);
 
+  std::vector<std::string> files;
+  files.reserve(m_providers.size());
   for (auto &provider : m_providers) {
-    auto &provider_info = provider.second->GetInfo();
-    yout << const_cast<ProviderInfo &>(provider_info);
+    files.emplace_back(provider.second->GetFile());
   }
+
+  yout << files;
 }
 
 Loader::Loader(const FileSpec &root) : m_root(root), m_loaded(false) {}
@@ -196,29 +199,24 @@ llvm::Error Loader::LoadIndex() {
   if (auto err = error_or_file.getError())
     return make_error<StringError>("unable to load reproducer index", err);
 
-  std::vector<ProviderInfo> provider_info;
   yaml::Input yin((*error_or_file)->getBuffer());
-  yin >> provider_info;
-
+  yin >> m_files;
   if (auto err = yin.error())
     return make_error<StringError>("unable to read reproducer index", err);
 
-  for (auto &info : provider_info)
-    m_provider_info[info.name] = info;
+  // Sort files to speed up search.
+  llvm::sort(m_files);
 
+  // Remember that we've loaded the index.
   m_loaded = true;
 
   return llvm::Error::success();
 }
 
-llvm::Optional<ProviderInfo> Loader::GetProviderInfo(StringRef name) {
+bool Loader::HasFile(StringRef file) {
   assert(m_loaded);
-
-  auto it = m_provider_info.find(name);
-  if (it == m_provider_info.end())
-    return llvm::None;
-
-  return it->second;
+  auto it = std::lower_bound(m_files.begin(), m_files.end(), file.str());
+  return (it != m_files.end()) && (*it == file);
 }
 
 void ProviderBase::anchor() {}