oilgen: migrate to source parsing (#421)

Summary: oilgen: migrate to source parsing Using debug information generated from partial source (that is, not the final binary) has been insufficient to generally generate OIL code. A particular example is pointers to templates: ```cpp #include <oi/oi.h> template <typename T> struct Foo { T t; }; template <typename T> struct Bar { Foo<T>& f; }; void foo(const Bar<int>& b) { oi::introspect(b); } ``` The pointer/reference to `Foo<int>` appears in DWARF with `DW_AT_declaration(true)` because it could be specialised before its usage. However, with OIL, we are creating an implicit usage site in the `oi::introspect` call that the compiler is unable to see. This change reworks OILGen to work from a Clang command line rather than debug information. We setup and run a compiler on the source, giving us access to an AST and Semantic Analyser. We then: - Find the `oi::introspect` template. - Iterate through each of its callsites for their type. - Run `ClangTypeParser::parse` on each type. - Run codegen. - Compile into an object file. Having access to the semantic analyser allows us to forcefully complete a type, as it would be if it was used in the initial code. Test Plan: hope `buck2 run fbcode//mode/opt fbcode//object-introspection/oil/examples/compile-time:compile-time` Reviewed By: tyroguru Differential Revision: D51854477 Pulled By: JakeHillion
2024-09-16 17:59:05 +01:00 · 2023-12-19 11:57:44 -08:00 · 2023-12-19 11:57:44 -08:00 · 55989a9156
commit 55989a9156
parent 37b89d789d
20 changed files with 983 additions and 288 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -289,7 +289,7 @@ add_library(oicore
  oi/Serialize.cpp
 )
 add_dependencies(oicore libdrgn)
-target_include_directories(oicore SYSTEM PRIVATE ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
+target_include_directories(oicore SYSTEM PUBLIC ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
 target_compile_definitions(oicore PRIVATE ${LLVM_DEFINITIONS})
 target_include_directories(oicore PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)

@ -365,6 +365,7 @@ add_executable(oilgen
 target_link_libraries(oilgen
  drgn_utils
  oicore
+  clangTooling
 )

 ### Object Introspection cache Printer (OIP)
--- a/oi/CodeGen.cpp
+++ b/oi/CodeGen.cpp
@ -299,6 +299,11 @@ void genDefsThriftClass(const Class& c, std::string& code) {

 }  // namespace

+CodeGen::CodeGen(const OICodeGen::Config& config) : config_(config) {
+  DCHECK(!config.features[Feature::PolymorphicInheritance])
+      << "polymorphic inheritance requires symbol service!";
+}
+
 void CodeGen::genDefsThrift(const TypeGraph& typeGraph, std::string& code) {
  for (const Type& t : typeGraph.finalTypes) {
    if (const auto* c = dynamic_cast<const Class*>(&t)) {
@ -542,7 +547,7 @@ void CodeGen::getClassSizeFuncDef(const Class& c, std::string& code) {
    std::string childVtableName = "vtable for ";
    childVtableName += fqChildName;

-    auto optVtableSym = symbols_.locateSymbol(childVtableName, true);
+    auto optVtableSym = symbols_->locateSymbol(childVtableName, true);
    if (!optVtableSym) {
      //        LOG(ERROR) << "Failed to find vtable address for '" <<
      //        childVtableName; LOG(ERROR) << "Falling back to non dynamic
@ -1115,15 +1120,8 @@ bool CodeGen::codegenFromDrgn(struct drgn_type* drgnType, std::string& code) {
 bool CodeGen::codegenFromDrgn(struct drgn_type* drgnType,
                              std::string& code,
                              RootFunctionName name) {
-  try {
-    containerInfos_.reserve(config_.containerConfigPaths.size());
-    for (const auto& path : config_.containerConfigPaths) {
-      registerContainer(path);
-    }
-  } catch (const ContainerInfoError& err) {
-    LOG(ERROR) << "Error reading container TOML file " << err.what();
+  if (!registerContainers())
    return false;
-  }

  try {
    addDrgnRoot(drgnType, typeGraph_);
@ -1148,6 +1146,19 @@ void CodeGen::exportDrgnTypes(TypeHierarchy& th,
  }
 }

+bool CodeGen::registerContainers() {
+  try {
+    containerInfos_.reserve(config_.containerConfigPaths.size());
+    for (const auto& path : config_.containerConfigPaths) {
+      registerContainer(path);
+    }
+    return true;
+  } catch (const ContainerInfoError& err) {
+    LOG(ERROR) << "Error reading container TOML file " << err.what();
+    return false;
+  }
+}
+
 void CodeGen::registerContainer(std::unique_ptr<ContainerInfo> info) {
  VLOG(1) << "Registered container: " << info->typeName;
  containerInfos_.emplace_back(std::move(info));
@ -1189,7 +1200,7 @@ void CodeGen::transform(TypeGraph& typeGraph) {
        .chaseRawPointers = config_.features[Feature::ChaseRawPointers],
    };
    DrgnParser drgnParser{typeGraph, options};
-    pm.addPass(AddChildren::createPass(drgnParser, symbols_));
+    pm.addPass(AddChildren::createPass(drgnParser, *symbols_));

    // Re-run passes over newly added children
    pm.addPass(IdentifyContainers::createPass(containerInfos_));
--- a/oi/CodeGen.h
+++ b/oi/CodeGen.h
@ -41,8 +41,9 @@ namespace oi::detail {

 class CodeGen {
 public:
+  CodeGen(const OICodeGen::Config& config);
  CodeGen(const OICodeGen::Config& config, SymbolService& symbols)
-      : config_(config), symbols_(symbols) {
+      : config_(config), symbols_(&symbols) {
  }

  struct ExactName {
@ -65,6 +66,7 @@ class CodeGen {
                       std::list<drgn_type>& drgnTypes,
                       drgn_type** rootType) const;

+  bool registerContainers();
  void registerContainer(std::unique_ptr<ContainerInfo> containerInfo);
  void registerContainer(const std::filesystem::path& path);
  void addDrgnRoot(struct drgn_type* drgnType,
@ -77,7 +79,7 @@ class CodeGen {
 private:
  type_graph::TypeGraph typeGraph_;
  const OICodeGen::Config& config_;
-  SymbolService& symbols_;
+  SymbolService* symbols_ = nullptr;
  std::vector<std::unique_ptr<ContainerInfo>> containerInfos_;
  std::unordered_set<const ContainerInfo*> definedContainers_;
  std::unordered_map<const type_graph::Class*, const type_graph::Member*>
--- a/oi/OIGenerator.cpp
+++ b/oi/OIGenerator.cpp
@ -16,130 +16,149 @@

 #include "oi/OIGenerator.h"

+#include <clang/AST/Mangle.h>
+#include <clang/Frontend/CompilerInstance.h>
+#include <clang/Frontend/CompilerInvocation.h>
+#include <clang/Frontend/FrontendAction.h>
+#include <clang/Sema/Sema.h>
+#include <clang/Tooling/Tooling.h>
 #include <glog/logging.h>

-#include <boost/core/demangle.hpp>
 #include <fstream>
-#include <iostream>
-#include <string_view>
+#include <range/v3/core.hpp>
+#include <range/v3/view/drop.hpp>
+#include <range/v3/view/filter.hpp>
+#include <range/v3/view/for_each.hpp>
+#include <range/v3/view/take.hpp>
+#include <range/v3/view/transform.hpp>
+#include <stdexcept>
 #include <unordered_map>
 #include <variant>

 #include "oi/CodeGen.h"
 #include "oi/Config.h"
-#include "oi/DrgnUtils.h"
 #include "oi/Headers.h"
+#include "oi/type_graph/ClangTypeParser.h"
+#include "oi/type_graph/TypeGraph.h"
+#include "oi/type_graph/Types.h"

 namespace oi::detail {
+namespace {

-std::unordered_map<std::string, std::string>
-OIGenerator::oilStrongToWeakSymbolsMap(drgnplusplus::program& prog) {
-  static constexpr std::string_view strongSymbolPrefix =
-      "oi::IntrospectionResult oi::introspect<";
-  static constexpr std::string_view weakSymbolPrefix =
-      "oi::IntrospectionResult oi::introspectImpl<";
+class ConsumerContext;

-  std::unordered_map<std::string, std::pair<std::string, std::string>>
-      templateArgsToSymbolsMap;
-
-  auto symbols = prog.find_all_symbols();
-  for (drgn_symbol* sym : *symbols) {
-    auto symName = drgnplusplus::symbol::name(sym);
-    if (symName == nullptr || *symName == '\0')
-      continue;
-    auto demangled = boost::core::demangle(symName);
-
-    if (demangled.starts_with(strongSymbolPrefix)) {
-      auto& matchedSyms = templateArgsToSymbolsMap[demangled.substr(
-          strongSymbolPrefix.length())];
-      if (!matchedSyms.first.empty()) {
-        LOG(WARNING) << "non-unique symbols found: `" << matchedSyms.first
-                     << "` and `" << symName << '`';
-      }
-      matchedSyms.first = symName;
-    } else if (demangled.starts_with(weakSymbolPrefix)) {
-      auto& matchedSyms =
-          templateArgsToSymbolsMap[demangled.substr(weakSymbolPrefix.length())];
-      if (!matchedSyms.second.empty()) {
-        LOG(WARNING) << "non-unique symbols found: `" << matchedSyms.second
-                     << "` and `" << symName << "`";
-      }
-      matchedSyms.second = symName;
-    }
+class CreateTypeGraphConsumer;
+class CreateTypeGraphAction : public clang::ASTFrontendAction {
+ public:
+  CreateTypeGraphAction(ConsumerContext& ctx_) : ctx{ctx_} {
  }

-  std::unordered_map<std::string, std::string> strongToWeakSymbols;
-  for (auto& [_, val] : templateArgsToSymbolsMap) {
-    if (val.first.empty() || val.second.empty()) {
-      continue;
-    }
-    strongToWeakSymbols[std::move(val.first)] = std::move(val.second);
+  void ExecuteAction() override;
+  std::unique_ptr<clang::ASTConsumer> CreateASTConsumer(
+      clang::CompilerInstance& CI, clang::StringRef file) override;
+
+ private:
+  ConsumerContext& ctx;
+};
+
+class CreateTypeGraphActionFactory
+    : public clang::tooling::FrontendActionFactory {
+ public:
+  CreateTypeGraphActionFactory(ConsumerContext& ctx_) : ctx{ctx_} {
  }

-  return strongToWeakSymbols;
-}
+  std::unique_ptr<clang::FrontendAction> create() override {
+    return std::make_unique<CreateTypeGraphAction>(ctx);
+  }

-std::unordered_map<std::string, drgn_qualified_type>
-OIGenerator::findOilTypesAndNames(drgnplusplus::program& prog) {
-  auto strongToWeakSymbols = oilStrongToWeakSymbolsMap(prog);
+ private:
+  ConsumerContext& ctx;
+};

-  std::unordered_map<std::string, drgn_qualified_type> out;
+class ConsumerContext {
+ public:
+  ConsumerContext(const std::vector<std::unique_ptr<ContainerInfo>>& cis)
+      : containerInfos{cis} {
+  }

-  for (drgn_qualified_type& func : drgnplusplus::func_iterator(prog)) {
-    std::string strongLinkageName;
-    {
-      const char* linkageNameCstr;
-      if (auto err = drgnplusplus::error(
-              drgn_type_linkage_name(func.type, &linkageNameCstr))) {
-        // throw err;
+  type_graph::TypeGraph typeGraph;
+  std::unordered_map<std::string, type_graph::Type*> nameToTypeMap;
+  std::optional<bool> pic;
+  const std::vector<std::unique_ptr<ContainerInfo>>& containerInfos;
+
+ private:
+  clang::Sema* sema = nullptr;
+  friend CreateTypeGraphConsumer;
+  friend CreateTypeGraphAction;
+};
+
+}  // namespace
+
+int OIGenerator::generate(clang::tooling::CompilationDatabase& db,
+                          const std::vector<std::string>& sourcePaths) {
+  std::map<Feature, bool> featuresMap = {
+      {Feature::TypeGraph, true},
+      {Feature::TreeBuilderV2, true},
+      {Feature::Library, true},
+      {Feature::PackStructs, true},
+      {Feature::PruneTypeGraph, true},
+  };
+
+  OICodeGen::Config generatorConfig{};
+  OICompiler::Config compilerConfig{};
+
+  auto features = config::processConfigFiles(
+      configFilePaths, featuresMap, compilerConfig, generatorConfig);
+  if (!features) {
+    LOG(ERROR) << "failed to process config file";
+    return -1;
+  }
+  generatorConfig.features = *features;
+  compilerConfig.features = *features;
+
+  std::vector<std::unique_ptr<ContainerInfo>> containerInfos;
+  containerInfos.reserve(generatorConfig.containerConfigPaths.size());
+  try {
+    for (const auto& path : generatorConfig.containerConfigPaths) {
+      auto info = std::make_unique<ContainerInfo>(path);
+      if (info->requiredFeatures != (*features & info->requiredFeatures)) {
+        VLOG(1) << "Skipping container (feature conflict): " << info->typeName;
        continue;
      }
-      strongLinkageName = linkageNameCstr;
+      containerInfos.emplace_back(std::move(info));
    }
-
-    std::string weakLinkageName;
-    if (auto search = strongToWeakSymbols.find(strongLinkageName);
-        search != strongToWeakSymbols.end()) {
-      weakLinkageName = search->second;
-    } else {
-      continue;  // not an oil strong symbol
-    }
-
-    // IntrospectionResult (*)(const T&)
-    CHECK(drgn_type_has_parameters(func.type)) << "functions have parameters";
-    CHECK(drgn_type_num_parameters(func.type) == 1)
-        << "introspection func has one parameter";
-
-    auto* params = drgn_type_parameters(func.type);
-    drgn_qualified_type tType;
-    if (auto err =
-            drgnplusplus::error(drgn_parameter_type(&params[0], &tType))) {
-      throw err;
-    }
-
-    if (drgn_type_has_name(tType.type)) {
-      LOG(INFO) << "found OIL type: " << drgn_type_name(tType.type);
-    } else {
-      LOG(INFO) << "found OIL type: (no name)";
-    }
-    out.emplace(std::move(weakLinkageName), tType);
+  } catch (const ContainerInfoError& err) {
+    LOG(ERROR) << "Error reading container TOML file " << err.what();
+    return -1;
  }

-  return out;
-}
+  ConsumerContext ctx{containerInfos};
+  CreateTypeGraphActionFactory factory{ctx};

-fs::path OIGenerator::generateForType(const OICodeGen::Config& generatorConfig,
-                                      const OICompiler::Config& compilerConfig,
-                                      const drgn_qualified_type& type,
-                                      const std::string& linkageName,
-                                      SymbolService& symbols) {
-  CodeGen codegen{generatorConfig, symbols};
+  clang::tooling::ClangTool tool{db, sourcePaths};
+  if (auto ret = tool.run(&factory); ret != 0) {
+    return ret;
+  }
+
+  if (ctx.nameToTypeMap.size() > 1)
+    throw std::logic_error(
+        "found more than one site to generate for but we can't currently "
+        "handle this case");
+
+  if (ctx.nameToTypeMap.empty()) {
+    LOG(ERROR) << "Nothing to generate!";
+    return failIfNothingGenerated ? -1 : 0;
+  }
+  const auto& linkageName = ctx.nameToTypeMap.begin()->first;
+
+  compilerConfig.usePIC = ctx.pic.value();
+  CodeGen codegen{generatorConfig};
+  for (auto&& ptr : containerInfos)
+    codegen.registerContainer(std::move(ptr));
+  codegen.transform(ctx.typeGraph);

  std::string code;
-  if (!codegen.codegenFromDrgn(type.type, linkageName, code)) {
-    LOG(ERROR) << "codegen failed!";
-    return {};
-  }
+  codegen.generate(ctx.typeGraph, code, CodeGen::ExactName{linkageName});

  std::string sourcePath = sourceFileDumpPath;
  if (sourceFileDumpPath.empty()) {
@ -152,78 +171,110 @@ fs::path OIGenerator::generateForType(const OICodeGen::Config& generatorConfig,
  }

  OICompiler compiler{{}, compilerConfig};
-
-  // TODO: Revert to outputPath and remove printing when typegraph is done.
-  fs::path tmpObject = outputPath;
-  tmpObject.replace_extension(
-      "." + std::to_string(std::hash<std::string>{}(linkageName)) + ".o");
-
-  if (!compiler.compile(code, sourcePath, tmpObject)) {
-    return {};
-  }
-  return tmpObject;
+  return compiler.compile(code, sourcePath, outputPath) ? 0 : -1;
 }

-int OIGenerator::generate(fs::path& primaryObject, SymbolService& symbols) {
-  drgnplusplus::program prog;
+namespace {

-  {
-    std::array<const char*, 1> objectPaths = {{primaryObject.c_str()}};
-    if (auto err = drgnplusplus::error(
-            drgn_program_load_debug_info(prog.get(),
-                                         std::data(objectPaths),
-                                         std::size(objectPaths),
-                                         false,
-                                         false))) {
-      LOG(ERROR) << "error loading debug info program: " << err;
-      throw err;
+class CreateTypeGraphConsumer : public clang::ASTConsumer {
+ private:
+  ConsumerContext& ctx;
+
+ public:
+  CreateTypeGraphConsumer(ConsumerContext& ctx_) : ctx(ctx_) {
+  }
+
+  void HandleTranslationUnit(clang::ASTContext& Context) override {
+    auto* tu_decl = Context.getTranslationUnitDecl();
+    auto decls = tu_decl->decls();
+    auto oi_namespaces = decls | ranges::views::transform([](auto* p) {
+                           return llvm::dyn_cast<clang::NamespaceDecl>(p);
+                         }) |
+                         ranges::views::filter([](auto* ns) {
+                           return ns != nullptr && ns->getName() == "oi";
+                         });
+    if (oi_namespaces.empty()) {
+      LOG(WARNING) << "Failed to find `oi` namespace. Does this input "
+                      "include <oi/oi.h>?";
+      return;
    }
-  }

-  auto oilTypes = findOilTypesAndNames(prog);
-
-  std::map<Feature, bool> featuresMap = {
-      {Feature::TypeGraph, true},
-      {Feature::TreeBuilderV2, true},
-      {Feature::Library, true},
-      {Feature::PackStructs, true},
-      {Feature::PruneTypeGraph, true},
-  };
-
-  OICodeGen::Config generatorConfig{};
-  OICompiler::Config compilerConfig{};
-  compilerConfig.usePIC = pic;
-
-  auto features = config::processConfigFiles(
-      configFilePaths, featuresMap, compilerConfig, generatorConfig);
-  if (!features) {
-    LOG(ERROR) << "failed to process config file";
-    return -1;
-  }
-  generatorConfig.features = *features;
-  compilerConfig.features = *features;
-
-  size_t failures = 0;
-  for (const auto& [linkageName, type] : oilTypes) {
-    if (auto obj = generateForType(
-            generatorConfig, compilerConfig, type, linkageName, symbols);
-        !obj.empty()) {
-      std::cout << obj.string() << std::endl;
-    } else {
-      LOG(WARNING) << "failed to generate for symbol `" << linkageName
-                   << "`. this is non-fatal but the call will not work.";
-      failures++;
+    auto introspectImpl =
+        std::move(oi_namespaces) |
+        ranges::views::for_each([](auto* ns) { return ns->decls(); }) |
+        ranges::views::transform([](auto* p) {
+          return llvm::dyn_cast<clang::FunctionTemplateDecl>(p);
+        }) |
+        ranges::views::filter([](auto* td) {
+          return td != nullptr && td->getName() == "introspectImpl";
+        }) |
+        ranges::views::take(1) | ranges::to<std::vector>();
+    if (introspectImpl.empty()) {
+      LOG(WARNING)
+          << "Failed to find `oi::introspect` within the `oi` namespace. Did "
+             "you compile with `OIL_AOT_COMPILATION=1`?";
+      return;
    }
-  }

-  size_t successes = oilTypes.size() - failures;
-  LOG(INFO) << "object introspection generation complete. " << successes
-            << " successes and " << failures << " failures.";
+    auto nameToClangTypeMap =
+        introspectImpl | ranges::views::for_each([](auto* td) {
+          return td->specializations();
+        }) |
+        ranges::views::transform(
+            [](auto* p) { return llvm::dyn_cast<clang::FunctionDecl>(p); }) |
+        ranges::views::filter([](auto* p) { return p != nullptr; }) |
+        ranges::views::transform(
+            [](auto* fd) -> std::pair<std::string, const clang::Type*> {
+              clang::ASTContext& Ctx = fd->getASTContext();
+              clang::ASTNameGenerator ASTNameGen(Ctx);
+              std::string name = ASTNameGen.getName(fd);

-  if (failures > 0 || (failIfNothingGenerated && successes == 0)) {
-    return -1;
+              assert(fd->getNumParams() == 1);
+              const clang::Type* type =
+                  fd->parameters()[0]->getType().getTypePtr();
+              return {name, type};
+            }) |
+        ranges::to<std::unordered_map>();
+    if (nameToClangTypeMap.empty())
+      return;
+
+    type_graph::ClangTypeParserOptions opts;
+    type_graph::ClangTypeParser parser{ctx.typeGraph, ctx.containerInfos, opts};
+
+    auto& Sema = *ctx.sema;
+    auto els = nameToClangTypeMap |
+               ranges::views::transform(
+                   [&parser, &Context, &Sema](
+                       auto& p) -> std::pair<std::string, type_graph::Type*> {
+                     return {p.first, &parser.parse(Context, Sema, *p.second)};
+                   });
+    ctx.nameToTypeMap.insert(els.begin(), els.end());
+
+    for (const auto& [name, type] : ctx.nameToTypeMap)
+      ctx.typeGraph.addRoot(*type);
  }
-  return 0;
+};
+
+void CreateTypeGraphAction::ExecuteAction() {
+  clang::CompilerInstance& CI = getCompilerInstance();
+
+  // Compile the output as position independent if any input is position
+  // independent
+  bool pic = CI.getCodeGenOpts().RelocationModel == llvm::Reloc::PIC_;
+  ctx.pic = ctx.pic.value_or(false) || pic;
+
+  if (!CI.hasSema())
+    CI.createSema(clang::TU_Complete, nullptr);
+  ctx.sema = &CI.getSema();
+
+  clang::ASTFrontendAction::ExecuteAction();
 }

+std::unique_ptr<clang::ASTConsumer> CreateTypeGraphAction::CreateASTConsumer(
+    [[maybe_unused]] clang::CompilerInstance& CI,
+    [[maybe_unused]] clang::StringRef file) {
+  return std::make_unique<CreateTypeGraphConsumer>(ctx);
+}
+
+}  // namespace
 }  // namespace oi::detail
--- a/oi/OIGenerator.h
+++ b/oi/OIGenerator.h
@ -23,11 +23,19 @@
 #include "oi/OICodeGen.h"
 #include "oi/OICompiler.h"

+namespace clang::tooling {
+class CompilationDatabase;
+}
+
 namespace oi::detail {
+namespace type_graph {
+class Type;
+}

 class OIGenerator {
 public:
-  int generate(fs::path& primaryObject, SymbolService& symbols);
+  int generate(clang::tooling::CompilationDatabase&,
+               const std::vector<std::string>&);

  void setOutputPath(fs::path _outputPath) {
    outputPath = std::move(_outputPath);
@ -41,8 +49,8 @@ class OIGenerator {
  void setFailIfNothingGenerated(bool fail) {
    failIfNothingGenerated = fail;
  }
-  void setUsePIC(bool pic_) {
-    pic = pic_;
+  void setClangArgs(std::vector<std::string> args_) {
+    clangArgs = std::move(args_);
  }

 private:
@ -50,20 +58,7 @@ class OIGenerator {
  std::vector<std::filesystem::path> configFilePaths;
  std::filesystem::path sourceFileDumpPath;
  bool failIfNothingGenerated = false;
-  bool pic = false;
-
-  std::unordered_map<std::string, std::string> oilStrongToWeakSymbolsMap(
-      drgnplusplus::program& prog);
-
-  std::unordered_map<std::string, drgn_qualified_type> findOilTypesAndNames(
-      drgnplusplus::program& prog);
-
-  std::filesystem::path generateForType(
-      const OICodeGen::Config& generatorConfig,
-      const OICompiler::Config& compilerConfig,
-      const drgn_qualified_type& type,
-      const std::string& linkageName,
-      SymbolService& symbols);
+  std::vector<std::string> clangArgs;
 };

 }  // namespace oi::detail
--- a/oi/type_graph/CMakeLists.txt
+++ b/oi/type_graph/CMakeLists.txt
@ -2,6 +2,7 @@ add_library(type_graph
  AddChildren.cpp
  AddPadding.cpp
  AlignmentCalc.cpp
+  ClangTypeParser.cpp
  DrgnExporter.cpp
  DrgnParser.cpp
  EnforceCompatibility.cpp
@ -27,3 +28,4 @@ target_link_libraries(type_graph
  "-L${DRGN_PATH}/.libs"
  drgn
 )
+target_include_directories(type_graph SYSTEM PUBLIC ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
--- a/oi/type_graph/ClangTypeParser.cpp
+++ b/oi/type_graph/ClangTypeParser.cpp
@ -0,0 +1,418 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "ClangTypeParser.h"
+
+#include <clang/AST/ASTContext.h>
+#include <clang/AST/Decl.h>
+#include <clang/AST/DeclTemplate.h>
+#include <clang/AST/QualTypeNames.h>
+#include <clang/AST/Type.h>
+#include <clang/Basic/DiagnosticSema.h>
+#include <clang/Sema/Sema.h>
+#include <glog/logging.h>
+
+#include <regex>
+#include <stdexcept>
+
+#include "oi/type_graph/Types.h"
+
+namespace oi::detail::type_graph {
+namespace {
+bool requireCompleteType(clang::Sema& sema, const clang::Type& ty);
+}
+
+Type& ClangTypeParser::parse(clang::ASTContext& ast_,
+                             clang::Sema& sema_,
+                             const clang::Type& ty) {
+  ast = &ast_;
+  sema = &sema_;
+
+  depth_ = 0;
+  return enumerateType(ty);
+}
+
+Type& ClangTypeParser::enumerateType(const clang::Type& ty) {
+  // Avoid re-enumerating an already-processsed type
+  if (auto it = clang_types_.find(&ty); it != clang_types_.end())
+    return it->second;
+
+  struct DepthTracker {
+    DepthTracker(ClangTypeParser& self_) : self{self_} {
+      self.depth_++;
+    }
+    ~DepthTracker() {
+      self.depth_--;
+    }
+
+   private:
+    ClangTypeParser& self;
+  } d{*this};
+
+  if (VLOG_IS_ON(3)) {
+    std::string fqName = clang::TypeName::getFullyQualifiedName(
+        clang::QualType(&ty, 0), *ast, {ast->getLangOpts()});
+    VLOG(3) << std::string(depth_ * 2, ' ') << fqName;
+  }
+
+  // TODO: This check basically doesn't work. The action has failed before it
+  // returns false. Fix this.
+  if (!requireCompleteType(*sema, ty)) {
+    std::string fqName = clang::TypeName::getFullyQualifiedName(
+        clang::QualType(&ty, 0), *ast, {ast->getLangOpts()});
+    return makeType<Incomplete>(ty, std::move(fqName));
+  }
+
+  switch (ty.getTypeClass()) {
+    case clang::Type::Record:
+      return enumerateClass(llvm::cast<const clang::RecordType>(ty));
+    case clang::Type::LValueReference:
+      return enumerateReference(
+          llvm::cast<const clang::LValueReferenceType>(ty));
+    case clang::Type::Pointer:
+      return enumeratePointer(llvm::cast<const clang::PointerType>(ty));
+    case clang::Type::SubstTemplateTypeParm:
+      return enumerateSubstTemplateTypeParm(
+          llvm::cast<const clang::SubstTemplateTypeParmType>(ty));
+    case clang::Type::Builtin:
+      return enumeratePrimitive(llvm::cast<const clang::BuiltinType>(ty));
+    case clang::Type::Elaborated:
+      return enumerateElaboratedType(
+          llvm::cast<const clang::ElaboratedType>(ty));
+    case clang::Type::TemplateSpecialization:
+      return enumerateTemplateSpecialization(
+          llvm::cast<const clang::TemplateSpecializationType>(ty));
+    case clang::Type::UnaryTransform:
+      return enumerateUnaryTransformType(
+          llvm::cast<const clang::UnaryTransformType>(ty));
+    case clang::Type::Decltype:
+      return enumerateDecltypeType(llvm::cast<const clang::DecltypeType>(ty));
+    case clang::Type::Typedef:
+      return enumerateTypedef(llvm::cast<const clang::TypedefType>(ty));
+    case clang::Type::Using:
+      return enumerateUsing(llvm::cast<const clang::UsingType>(ty));
+    case clang::Type::ConstantArray:
+      return enumerateArray(llvm::cast<const clang::ConstantArrayType>(ty));
+    case clang::Type::Enum:
+      return enumerateEnum(llvm::cast<const clang::EnumType>(ty));
+
+    default:
+      throw std::logic_error(std::string("unsupported TypeClass `") +
+                             ty.getTypeClassName() + '`');
+  }
+}
+
+Type& ClangTypeParser::enumerateDecltypeType(const clang::DecltypeType& ty) {
+  return enumerateType(*ty.getUnderlyingType());
+}
+
+Type& ClangTypeParser::enumerateUnaryTransformType(
+    const clang::UnaryTransformType& ty) {
+  return enumerateType(*ty.getUnderlyingType());
+}
+
+Typedef& ClangTypeParser::enumerateUsing(const clang::UsingType& ty) {
+  auto& inner = enumerateType(*ty.desugar());
+  std::string name = ty.getFoundDecl()->getNameAsString();
+  return makeType<Typedef>(ty, std::move(name), inner);
+}
+
+Typedef& ClangTypeParser::enumerateTypedef(const clang::TypedefType& ty) {
+  auto& inner = enumerateType(*ty.desugar());
+
+  std::string name = ty.getDecl()->getNameAsString();
+  return makeType<Typedef>(ty, std::move(name), inner);
+}
+
+Enum& ClangTypeParser::enumerateEnum(const clang::EnumType& ty) {
+  std::string name = ty.getDecl()->getNameAsString();
+  auto size = ast->getTypeSize(clang::QualType(&ty, 0)) / 8;
+
+  std::map<int64_t, std::string> enumeratorMap;
+  if (options_.readEnumValues) {
+    for (const auto* enumerator : ty.getDecl()->enumerators()) {
+      enumeratorMap.emplace(enumerator->getInitVal().getExtValue(),
+                            enumerator->getNameAsString());
+    }
+  }
+
+  return makeType<Enum>(ty, std::move(name), size, std::move(enumeratorMap));
+}
+
+Array& ClangTypeParser::enumerateArray(const clang::ConstantArrayType& ty) {
+  uint64_t len = ty.getSize().getLimitedValue();
+  auto& t = enumerateType(*ty.getElementType());
+  return makeType<Array>(ty, t, len);
+}
+
+Type& ClangTypeParser::enumerateTemplateSpecialization(
+    const clang::TemplateSpecializationType& ty) {
+  if (ty.isSugared())
+    return enumerateType(*ty.desugar());
+
+  LOG(WARNING) << "failed on a TemplateSpecializationType";
+  ty.dump();
+  return makeType<Primitive>(ty, Primitive::Kind::Int32);
+}
+
+Type& ClangTypeParser::enumerateClass(const clang::RecordType& ty) {
+  std::string fqName = clang::TypeName::getFullyQualifiedName(
+      clang::QualType(&ty, 0), *ast, {ast->getLangOpts()});
+  auto size = ast->getTypeSize(clang::QualType(&ty, 0)) / 8;
+
+  if (auto* info = getContainerInfo(fqName)) {
+    auto& c = makeType<Container>(ty, *info, size, nullptr);
+    enumerateClassTemplateParams(ty, c.templateParams);
+    c.setAlign(ast->getTypeAlign(clang::QualType(&ty, 0)));
+    return c;
+  }
+
+  auto* decl = ty.getDecl();
+
+  std::string name = decl->getNameAsString();
+
+  auto kind = Class::Kind::Struct;  // TODO: kind
+
+  int virtuality = 0;
+
+  auto& c = makeType<Class>(
+      ty, kind, std::move(name), std::move(fqName), size, virtuality);
+
+  enumerateClassTemplateParams(ty, c.templateParams);
+  // enumerateClassParents(type, c.parents);
+  enumerateClassMembers(ty, c.members);
+  // enumerateClassFunctions(type, c.functions);
+
+  return c;
+}
+
+void ClangTypeParser::enumerateClassTemplateParams(
+    const clang::RecordType& ty, std::vector<TemplateParam>& params) {
+  assert(params.empty());
+
+  auto* decl = dyn_cast<clang::ClassTemplateSpecializationDecl>(ty.getDecl());
+  if (decl == nullptr)
+    return;
+
+  const auto& list = decl->getTemplateArgs();
+
+  params.reserve(list.size());
+  for (const auto& arg : list.asArray()) {
+    if (auto p = enumerateTemplateParam(arg))
+      params.emplace_back(std::move(p.value()));
+  }
+}
+
+std::optional<TemplateParam> ClangTypeParser::enumerateTemplateParam(
+    const clang::TemplateArgument& p) {
+  switch (p.getKind()) {
+    case clang::TemplateArgument::Type: {
+      auto qualType = p.getAsType();
+      QualifierSet qualifiers;
+      qualifiers[Qualifier::Const] = qualType.isConstQualified();
+      Type& ttype = enumerateType(*qualType);
+      return TemplateParam{ttype, qualifiers};
+    }
+    case clang::TemplateArgument::Integral: {
+      auto& ty = enumerateType(*p.getIntegralType());
+      llvm::SmallString<32> val;
+      p.getAsIntegral().toString(val);
+      return TemplateParam{ty, std::string(val)};
+    }
+    case clang::TemplateArgument::Template: {
+      return enumerateTemplateTemplateParam(p.getAsTemplate());
+    }
+
+#define X(name)                       \
+  case clang::TemplateArgument::name: \
+    throw std::logic_error("unsupported template argument kind: " #name);
+
+      X(Null)
+      X(Declaration)
+      X(NullPtr)
+      X(TemplateExpansion)
+      X(Expression)
+      X(Pack)
+#undef X
+  }
+}
+
+std::optional<TemplateParam> ClangTypeParser::enumerateTemplateTemplateParam(
+    const clang::TemplateName& tn) {
+  switch (tn.getKind()) {
+    case clang::TemplateName::Template:
+      return std::nullopt;
+
+#define X(name)                   \
+  case clang::TemplateName::name: \
+    throw std::logic_error("unsupported template name kind: " #name);
+
+      X(OverloadedTemplate)
+      X(AssumedTemplate)
+      X(QualifiedTemplate)
+      X(DependentTemplate)
+      X(SubstTemplateTemplateParm)
+      X(SubstTemplateTemplateParmPack)
+      X(UsingTemplate)
+#undef X
+  }
+}
+
+void ClangTypeParser::enumerateClassMembers(const clang::RecordType& ty,
+                                            std::vector<Member>& members) {
+  assert(members.empty());
+
+  auto* decl = ty.getDecl();
+
+  for (const auto* field : decl->fields()) {
+    clang::QualType qualType = field->getType();
+    std::string member_name = field->getNameAsString();
+
+    size_t size_in_bits = 0;
+    if (field->isBitField()) {
+      size_in_bits = field->getBitWidthValue(*ast);
+    }
+
+    size_t offset_in_bits = decl->getASTContext().getFieldOffset(field);
+
+    auto& mtype = enumerateType(*qualType);
+    Member m{mtype, std::move(member_name), offset_in_bits, size_in_bits};
+    members.push_back(m);
+  }
+
+  std::sort(members.begin(), members.end(), [](const auto& a, const auto& b) {
+    return a.bitOffset < b.bitOffset;
+  });
+}
+
+Type& ClangTypeParser::enumerateReference(
+    const clang::LValueReferenceType& ty) {
+  // TODO: function references
+  Type& t = enumerateType(*ty.getPointeeType());
+  if (dynamic_cast<Incomplete*>(&t))
+    return makeType<Pointer>(ty, t);
+
+  return makeType<Reference>(ty, t);
+}
+
+Type& ClangTypeParser::enumeratePointer(const clang::PointerType& ty) {
+  // TODO: function pointers
+  if (!chasePointer())
+    return makeType<Primitive>(ty, Primitive::Kind::StubbedPointer);
+
+  Type& t = enumerateType(*ty.getPointeeType());
+  return makeType<Reference>(ty, t);
+}
+
+Type& ClangTypeParser::enumerateSubstTemplateTypeParm(
+    const clang::SubstTemplateTypeParmType& ty) {
+  // Clang wraps any type that was substituted from e.g. `T` in this type. It
+  // should have no representation in the type graph.
+  return enumerateType(*ty.getReplacementType());
+}
+
+Type& ClangTypeParser::enumerateElaboratedType(
+    const clang::ElaboratedType& ty) {
+  // Clang wraps any type that is name qualified in this type. It should have no
+  // representation in the type graph.
+  return enumerateType(*ty.getNamedType());
+}
+
+Primitive& ClangTypeParser::enumeratePrimitive(const clang::BuiltinType& ty) {
+  switch (ty.getKind()) {
+    case clang::BuiltinType::Void:
+      return makeType<Primitive>(ty, Primitive::Kind::Void);
+
+    case clang::BuiltinType::Bool:
+      return makeType<Primitive>(ty, Primitive::Kind::Bool);
+
+    case clang::BuiltinType::Char_U:
+    case clang::BuiltinType::UChar:
+      return makeType<Primitive>(ty, Primitive::Kind::UInt8);
+    case clang::BuiltinType::WChar_U:
+      return makeType<Primitive>(ty, Primitive::Kind::UInt32);
+
+    case clang::BuiltinType::Char_S:
+    case clang::BuiltinType::SChar:
+      return makeType<Primitive>(ty, Primitive::Kind::Int8);
+    case clang::BuiltinType::WChar_S:
+      return makeType<Primitive>(ty, Primitive::Kind::Int32);
+    case clang::BuiltinType::Char16:
+      return makeType<Primitive>(ty, Primitive::Kind::Int16);
+    case clang::BuiltinType::Char32:
+      return makeType<Primitive>(ty, Primitive::Kind::Int32);
+
+    case clang::BuiltinType::UShort:
+      return makeType<Primitive>(ty, Primitive::Kind::UInt16);
+    case clang::BuiltinType::UInt:
+      return makeType<Primitive>(ty, Primitive::Kind::UInt32);
+    case clang::BuiltinType::ULong:
+      return makeType<Primitive>(ty, Primitive::Kind::UInt64);
+    case clang::BuiltinType::ULongLong:
+      return makeType<Primitive>(ty, Primitive::Kind::Int64);
+
+    case clang::BuiltinType::Short:
+      return makeType<Primitive>(ty, Primitive::Kind::Int16);
+    case clang::BuiltinType::Int:
+      return makeType<Primitive>(ty, Primitive::Kind::Int32);
+    case clang::BuiltinType::Long:
+    case clang::BuiltinType::LongLong:
+      return makeType<Primitive>(ty, Primitive::Kind::Int64);
+
+    case clang::BuiltinType::Float:
+      return makeType<Primitive>(ty, Primitive::Kind::Float32);
+    case clang::BuiltinType::Double:
+    case clang::BuiltinType::LongDouble:
+      return makeType<Primitive>(ty, Primitive::Kind::Float64);
+
+    case clang::BuiltinType::UInt128:
+    case clang::BuiltinType::Int128:
+    default:
+      throw std::logic_error(std::string("unsupported BuiltinType::Kind"));
+  }
+}
+
+bool ClangTypeParser::chasePointer() const {
+  // Always chase top-level pointers
+  if (depth_ == 1)
+    return true;
+  return options_.chaseRawPointers;
+}
+
+ContainerInfo* ClangTypeParser::getContainerInfo(
+    const std::string& fqName) const {
+  for (const auto& containerInfo : containers_) {
+    if (std::regex_search(fqName, containerInfo->matcher)) {
+      return containerInfo.get();
+    }
+  }
+  return nullptr;
+}
+
+namespace {
+
+bool requireCompleteType(clang::Sema& sema, const clang::Type& ty) {
+  if (ty.isSpecificBuiltinType(clang::BuiltinType::Void))
+    return true;  // treat as complete
+
+  // TODO: This is a terrible warning.
+  return !sema.RequireCompleteType(
+      sema.getASTContext().getTranslationUnitDecl()->getEndLoc(),
+      clang::QualType{&ty, 0},
+      clang::diag::warn_nsconsumed_attribute_mismatch);
+}
+
+}  // namespace
+}  // namespace oi::detail::type_graph
--- a/oi/type_graph/ClangTypeParser.h
+++ b/oi/type_graph/ClangTypeParser.h
@ -0,0 +1,131 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <cstdint>
+#include <functional>
+#include <unordered_map>
+
+#include "oi/type_graph/TypeGraph.h"
+
+namespace clang {
+class ASTContext;
+class BuiltinType;
+class ConstantArrayType;
+class DecltypeType;
+class ElaboratedType;
+class EnumType;
+class LValueReferenceType;
+class PointerType;
+class RecordType;
+class Sema;
+class SubstTemplateTypeParmType;
+class TemplateArgument;
+class TemplateName;
+class TemplateSpecializationType;
+class Type;
+class TypedefType;
+class UnaryTransformType;
+class UsingType;
+}  // namespace clang
+
+struct ContainerInfo;
+
+namespace oi::detail::type_graph {
+
+class Array;
+class Class;
+class Enum;
+class Member;
+class Primitive;
+class Reference;
+class Type;
+class TypeGraph;
+class Typedef;
+struct TemplateParam;
+
+struct ClangTypeParserOptions {
+  bool chaseRawPointers = false;
+  bool readEnumValues = false;
+};
+
+/*
+ * ClangTypeParser
+ *
+ * Reads source information from a source file to build a type graph.
+ * Returns a reference to the Type node corresponding to the given clang::Type.
+ */
+class ClangTypeParser {
+ public:
+  ClangTypeParser(TypeGraph& typeGraph,
+                  const std::vector<std::unique_ptr<ContainerInfo>>& containers,
+                  ClangTypeParserOptions options)
+      : typeGraph_{typeGraph}, containers_{containers}, options_{options} {
+  }
+
+  // Parse from a clang type.
+  Type& parse(clang::ASTContext&, clang::Sema&, const clang::Type&);
+
+ private:
+  TypeGraph& typeGraph_;
+  const std::vector<std::unique_ptr<ContainerInfo>>& containers_;
+  ClangTypeParserOptions options_;
+  clang::ASTContext* ast;
+  clang::Sema* sema;
+
+  uint_fast32_t depth_;
+  std::unordered_map<const clang::Type*, std::reference_wrapper<Type>>
+      clang_types_;
+
+  Type& enumerateType(const clang::Type&);
+  Type& enumerateClass(const clang::RecordType&);
+  Type& enumerateReference(const clang::LValueReferenceType&);
+  Type& enumeratePointer(const clang::PointerType&);
+  Type& enumerateSubstTemplateTypeParm(const clang::SubstTemplateTypeParmType&);
+  Primitive& enumeratePrimitive(const clang::BuiltinType&);
+  Type& enumerateElaboratedType(const clang::ElaboratedType&);
+  Type& enumerateTemplateSpecialization(
+      const clang::TemplateSpecializationType&);
+  Typedef& enumerateTypedef(const clang::TypedefType&);
+  Typedef& enumerateUsing(const clang::UsingType&);
+  Type& enumerateUnaryTransformType(const clang::UnaryTransformType&);
+  Type& enumerateDecltypeType(const clang::DecltypeType&);
+
+  Array& enumerateArray(const clang::ConstantArrayType&);
+  Enum& enumerateEnum(const clang::EnumType&);
+
+  void enumerateClassTemplateParams(const clang::RecordType&,
+                                    std::vector<TemplateParam>&);
+  std::optional<TemplateParam> enumerateTemplateParam(
+      const clang::TemplateArgument&);
+  std::optional<TemplateParam> enumerateTemplateTemplateParam(
+      const clang::TemplateName&);
+
+  void enumerateClassMembers(const clang::RecordType&, std::vector<Member>&);
+
+  ContainerInfo* getContainerInfo(const std::string& fqName) const;
+
+  template <typename T, typename... Args>
+  T& makeType(const clang::Type& clangType, Args&&... args) {
+    auto& newType = typeGraph_.makeType<T>(std::forward<Args>(args)...);
+    clang_types_.insert({&clangType, newType});
+    return newType;
+  }
+
+  bool chasePointer() const;
+};
+
+}  // namespace oi::detail::type_graph
--- a/oi/type_graph/DrgnExporter.cpp
+++ b/oi/type_graph/DrgnExporter.cpp
@ -200,6 +200,14 @@ drgn_type* DrgnExporter::visit(Pointer& p) {
  return drgnType;
 }

+drgn_type* DrgnExporter::visit(Reference& p) {
+  auto* drgnType =
+      makeDrgnType(DRGN_TYPE_POINTER, false, DRGN_NOT_PRIMITIVE_TYPE, p);
+  auto* pointeeType = accept(p.pointeeType());
+  th_.pointerToTypeMap[drgnType] = pointeeType;
+  return drgnType;
+}
+
 drgn_type* DrgnExporter::visit(Dummy& d) {
  return makeDrgnType(DRGN_TYPE_VOID, false, DRGN_C_TYPE_VOID, d);
 }
--- a/oi/type_graph/DrgnExporter.h
+++ b/oi/type_graph/DrgnExporter.h
@ -54,6 +54,7 @@ class DrgnExporter : public Visitor<drgn_type*> {
  drgn_type* visit(Array&) override;
  drgn_type* visit(Typedef&) override;
  drgn_type* visit(Pointer&) override;
+  drgn_type* visit(Reference&) override;
  drgn_type* visit(Dummy&) override;
  drgn_type* visit(DummyAllocator&) override;
  drgn_type* visit(CaptureKeys&) override;
--- a/oi/type_graph/NameGen.cpp
+++ b/oi/type_graph/NameGen.cpp
@ -200,6 +200,15 @@ void NameGen::visit(Pointer& p) {
  p.setInputName(inputName);
 }

+void NameGen::visit(Reference& r) {
+  RecursiveVisitor::visit(r);
+
+  r.regenerateName();
+  std::string inputName{r.pointeeType().inputName()};
+  inputName += '&';
+  r.setInputName(inputName);
+}
+
 void NameGen::visit(DummyAllocator& d) {
  RecursiveVisitor::visit(d);
  d.regenerateName();
--- a/oi/type_graph/NameGen.h
+++ b/oi/type_graph/NameGen.h
@ -46,6 +46,7 @@ class NameGen final : public RecursiveVisitor {
  void visit(Array& a) override;
  void visit(Typedef& td) override;
  void visit(Pointer& p) override;
+  void visit(Reference& r) override;
  void visit(DummyAllocator& d) override;
  void visit(CaptureKeys& d) override;

--- a/oi/type_graph/Printer.cpp
+++ b/oi/type_graph/Printer.cpp
@ -150,6 +150,17 @@ void Printer::visit(const Pointer& p) {
  print(p.pointeeType());
 }

+void Printer::visit(const Reference& r) {
+  if (prefix(r))
+    return;
+
+  out_ << "Reference";
+  if (auto inp = r.inputName(); !inp.empty())
+    out_ << " [" << inp << "]";
+  out_ << std::endl;
+  print(r.pointeeType());
+}
+
 void Printer::visit(const Dummy& d) {
  if (prefix(d))
    return;
--- a/oi/type_graph/Printer.h
+++ b/oi/type_graph/Printer.h
@ -40,6 +40,7 @@ class Printer : public ConstVisitor {
  void visit(const Array& a) override;
  void visit(const Typedef& td) override;
  void visit(const Pointer& p) override;
+  void visit(const Reference& r) override;
  void visit(const Dummy& d) override;
  void visit(const DummyAllocator& d) override;
  void visit(const CaptureKeys& d) override;
--- a/oi/type_graph/RemoveTopLevelPointer.cpp
+++ b/oi/type_graph/RemoveTopLevelPointer.cpp
@ -42,4 +42,8 @@ void RemoveTopLevelPointer::visit(Pointer& p) {
  topLevelType_ = &p.pointeeType();
 }

+void RemoveTopLevelPointer::visit(Reference& r) {
+  topLevelType_ = &r.pointeeType();
+}
+
 }  // namespace oi::detail::type_graph
--- a/oi/type_graph/RemoveTopLevelPointer.h
+++ b/oi/type_graph/RemoveTopLevelPointer.h
@ -36,6 +36,7 @@ class RemoveTopLevelPointer : public LazyVisitor {

  void removeTopLevelPointers(std::vector<std::reference_wrapper<Type>>& types);
  void visit(Pointer& p) override;
+  void visit(Reference& r) override;

 private:
  Type* topLevelType_ = nullptr;
--- a/oi/type_graph/Types.h
+++ b/oi/type_graph/Types.h
@ -49,6 +49,7 @@
  X(Array)           \
  X(Typedef)         \
  X(Pointer)         \
+  X(Reference)       \
  X(Dummy)           \
  X(DummyAllocator)  \
  X(CaptureKeys)
@ -734,6 +735,66 @@ class Pointer : public Type {
  std::string name_;
 };

+class Reference : public Type {
+ public:
+  explicit Reference(NodeId id, Type& pointeeType)
+      : pointeeType_(pointeeType), id_(id) {
+    regenerateName();
+  }
+
+  static inline constexpr bool has_node_id = true;
+
+  DECLARE_ACCEPT
+
+  virtual const std::string& name() const override {
+    return name_;
+  }
+
+  void regenerateName() {
+    // Following a reference wouldn't trigger cycle checking, as it would look
+    // like anything else we're sure is there. Generate as a pointer. It will be
+    // followed regardless of `ChaseRawPointers` because that affects whether a
+    // type becomes a `StubbedPointer` and not whether pointers are followed in
+    // the generated code.
+    name_ = pointeeType_.get().name() + "*";
+  }
+
+  virtual std::string_view inputName() const override {
+    return inputName_;
+  }
+
+  void setInputName(std::string name) {
+    inputName_ = std::move(name);
+  }
+
+  virtual size_t size() const override {
+    return sizeof(uintptr_t);
+  }
+
+  virtual uint64_t align() const override {
+    return size();
+  }
+
+  virtual NodeId id() const override {
+    return id_;
+  }
+
+  Type& pointeeType() const {
+    return pointeeType_;
+  }
+
+  void setPointeeType(Type& type) {
+    pointeeType_ = type;
+  }
+
+ private:
+  std::reference_wrapper<Type> pointeeType_;
+  std::string inputName_;
+  NodeId id_ = -1;
+
+  std::string name_;
+};
+
 /*
 * Dummy
 *
--- a/oi/type_graph/Visitor.h
+++ b/oi/type_graph/Visitor.h
@ -108,6 +108,9 @@ class RecursiveVisitor : public Visitor<void> {
  virtual void visit(Pointer& p) {
    accept(p.pointeeType());
  }
+  virtual void visit(Reference& r) {
+    accept(r.pointeeType());
+  }
  virtual void visit(Dummy&) {
  }
  virtual void visit(DummyAllocator& d) {
@ -175,6 +178,10 @@ class RecursiveMutator : public Visitor<Type&> {
    p.setPointeeType(mutate(p.pointeeType()));
    return p;
  }
+  virtual Type& visit(Reference& p) {
+    p.setPointeeType(mutate(p.pointeeType()));
+    return p;
+  }
  virtual Type& visit(Dummy& d) {
    return d;
  }
--- a/tools/OILGen.cpp
+++ b/tools/OILGen.cpp
@ -14,131 +14,80 @@
 * limitations under the License.
 */

+#include <clang/Tooling/CommonOptionsParser.h>
 #include <gflags/gflags.h>
 #include <glog/logging.h>

 #include <cstdlib>
 #include <filesystem>
 #include <iostream>
+#include <range/v3/range/conversion.hpp>
+#include <range/v3/view/transform.hpp>
 #include <vector>

 #include "oi/OICodeGen.h"
 #include "oi/OIGenerator.h"
-#include "oi/OIOpts.h"

 namespace fs = std::filesystem;
 using namespace oi::detail;

-constexpr static OIOpts opts{
-    OIOpt{'h', "help", no_argument, nullptr, "Print this message and exit."},
-    OIOpt{'o',
-          "output",
-          required_argument,
-          "<file>",
-          "Write output(s) to file(s) with this prefix."},
-    OIOpt{'c',
-          "config-file",
-          required_argument,
-          "<oid.toml>",
-          "Path to OI configuration file."},
-    OIOpt{'d',
-          "debug-level",
-          required_argument,
-          "<level>",
-          "Verbose level for logging"},
-    OIOpt{'j',
-          "dump-jit",
-          optional_argument,
-          "<jit.cpp>",
-          "Write generated code to a file (for debugging)."},
-    OIOpt{'e',
-          "exit-code",
-          no_argument,
-          nullptr,
-          "Return a bad exit code if nothing is generated."},
-    OIOpt{'p',
-          "pic",
-          no_argument,
-          nullptr,
-          "Generate position independent code."},
-};
+static llvm::cl::OptionCategory OilgenCategory("oilgen options");

-void usage() {
-  std::cerr << "usage: oilgen ARGS INPUT_OBJECT" << std::endl;
-  std::cerr << opts;
+static llvm::cl::list<std::string> ConfigFiles(
+    "config-file",
+    llvm::cl::desc(R"(</path/to/oid.toml>)"),
+    llvm::cl::cat(OilgenCategory));
+static llvm::cl::opt<std::string> OutputFile(
+    "output",
+    llvm::cl::desc(R"(Write output to this file.)"),
+    llvm::cl::init("a.o"),
+    llvm::cl::cat(OilgenCategory));
+static llvm::cl::opt<int> DebugLevel(
+    "debug-level",
+    llvm::cl::desc(R"(Verbose level for logging.)"),
+    llvm::cl::init(-1),
+    llvm::cl::cat(OilgenCategory));
+static llvm::cl::opt<std::string> DumpJit(
+    "dump-jit",
+    llvm::cl::desc(R"(Write the generated code to a file.)"),
+    llvm::cl::init("jit.cpp"),
+    llvm::cl::cat(OilgenCategory));

-  std::cerr << std::endl
-            << "You probably shouldn't be calling this application directly. "
-               "It's meant to be"
-            << std::endl
-            << "called by a clang plugin automatically with BUCK." << std::endl;
-}
-
-int main(int argc, char* argv[]) {
+int main(int argc, const char* argv[]) {
  google::InitGoogleLogging(argv[0]);
  FLAGS_minloglevel = 0;
  FLAGS_stderrthreshold = 0;

-  fs::path outputPath = "a.o";
-  std::vector<fs::path> configFilePaths;
-  fs::path sourceFileDumpPath = "";
-  bool exitCode = false;
-  bool pic = false;
-
-  int c;
-  while ((c = getopt_long(
-              argc, argv, opts.shortOpts(), opts.longOpts(), nullptr)) != -1) {
-    switch (c) {
-      case 'h':
-        usage();
-        return EXIT_SUCCESS;
-      case 'o':
-        outputPath = optarg;
-        break;
-      case 'c':
-        configFilePaths.emplace_back(optarg);
-        break;
-      case 'd':
-        google::LogToStderr();
-        google::SetStderrLogging(google::INFO);
-        google::SetVLOGLevel("*", atoi(optarg));
-        // Upstream glog defines `GLOG_INFO` as 0 https://fburl.com/ydjajhz0,
-        // but internally it's defined as 1 https://fburl.com/code/9fwams75
-        gflags::SetCommandLineOption("minloglevel", "0");
-        break;
-      case 'j':
-        sourceFileDumpPath = optarg != nullptr ? optarg : "jit.cpp";
-        break;
-      case 'e':
-        exitCode = true;
-        break;
-      case 'p':
-        pic = true;
-        break;
-    }
+  auto expectedParser =
+      clang::tooling::CommonOptionsParser::create(argc, argv, OilgenCategory);
+  if (!expectedParser) {
+    llvm::errs() << expectedParser.takeError();
+    return -1;
  }
+  clang::tooling::CommonOptionsParser& options = expectedParser.get();
+  auto& compilations = options.getCompilations();

-  if (optind >= argc) {
-    usage();
-    return EXIT_FAILURE;
-  }
-  fs::path primaryObject = argv[optind];
-
-  if ((setenv("DRGN_ENABLE_TYPE_ITERATOR", "1", 1)) < 0) {
-    LOG(ERROR) << "Failed to set environment variable\
-       DRGN_ENABLE_TYPE_ITERATOR\n";
-    exit(EXIT_FAILURE);
+  if (DebugLevel.getNumOccurrences()) {
+    google::LogToStderr();
+    google::SetStderrLogging(google::INFO);
+    google::SetVLOGLevel("*", DebugLevel);
+    // Upstream glog defines `GLOG_INFO` as 0 https://fburl.com/ydjajhz0,
+    // but internally it's defined as 1 https://fburl.com/code/9fwams75
+    gflags::SetCommandLineOption("minloglevel", "0");
  }

  OIGenerator oigen;

-  oigen.setOutputPath(std::move(outputPath));
-  oigen.setConfigFilePaths(std::move(configFilePaths));
-  oigen.setSourceFileDumpPath(sourceFileDumpPath);
-  oigen.setFailIfNothingGenerated(exitCode);
-  oigen.setUsePIC(pic);
+  oigen.setConfigFilePaths(ConfigFiles |
+                           ranges::views::transform([](const auto& p) {
+                             return std::filesystem::path(p);
+                           }) |
+                           ranges::to<std::vector>());
+  if (DumpJit.getNumOccurrences())
+    oigen.setSourceFileDumpPath(DumpJit.getValue());

-  SymbolService symbols(primaryObject);
+  oigen.setOutputPath(OutputFile.getValue());

-  return oigen.generate(primaryObject, symbols);
+  oigen.setFailIfNothingGenerated(true);
+  return oigen.generate(compilations, options.getSourcePathList());
 }
--- a/types/string_type.toml
+++ b/types/string_type.toml
@ -35,3 +35,34 @@ void getSizeType(const %1%<T, Traits, Allocator> &container, size_t& returnArg)
    );
 }
 """
+
+traversal_func = """
+    bool sso = ((uintptr_t)container.data() <
+                (uintptr_t)(&container + sizeof(std::__cxx11::basic_string<T0>))) &&
+               ((uintptr_t)container.data() >= (uintptr_t)&container);
+
+    return returnArg.write(container.capacity())
+        .write(sso)
+        .write(container.size());
+"""
+
+[[codegen.processor]]
+type = "types::st::VarInt<DB>"
+func = """
+uint64_t capacity = std::get<ParsedData::VarInt>(d.val).value;
+el.container_stats.emplace(result::Element::ContainerStats { .capacity = capacity });
+"""
+
+[[codegen.processor]]
+type = "types::st::VarInt<DB>"
+func = """
+bool sso = std::get<ParsedData::VarInt>(d.val).value;
+if (!sso)
+  el.exclusive_size += el.container_stats->capacity * sizeof(T0);
+"""
+
+[[codegen.processor]]
+type = "types::st::VarInt<DB>"
+func = """
+el.container_stats->length = std::get<ParsedData::VarInt>(d.val).value;
+"""