Add Cross Translation Unit support library

This patch introduces a class that can help to build tools that require cross
translation unit facilities. This class allows function definitions to be loaded
from external AST files based on an index. In order to use this functionality an
index is required. The index format is a flat text file but it might be
replaced with a different solution in the near future. USRs are used as names to
look up the functions definitions. This class also does caching to avoid
redundant loading of AST files.

Right now only function defnitions can be loaded using this API because this is
what the in progress cross translation unit feature of the Static Analyzer
requires. In to future this might be extended to classes, types etc.

Differential Revision: https://reviews.llvm.org/D34512


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313975 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 284 insertions, 0 deletions

diff --git a/lib/CrossTU/CMakeLists.txt b/lib/CrossTU/CMakeLists.txt
new file mode 100644
index 0000000000..632b5072ad
--- /dev/null
+++ b/lib/CrossTU/CMakeLists.txt
@@ -0,0 +1,13 @@
+set(LLVM_LINK_COMPONENTS
+  Support
+  )
+
+add_clang_library(clangCrossTU
+  CrossTranslationUnit.cpp
+
+  LINK_LIBS
+  clangAST
+  clangBasic
+  clangFrontend
+  clangIndex
+  )
diff --git a/lib/CrossTU/CrossTranslationUnit.cpp b/lib/CrossTU/CrossTranslationUnit.cpp
new file mode 100644
index 0000000000..833fb57860
--- /dev/null
+++ b/lib/CrossTU/CrossTranslationUnit.cpp
@@ -0,0 +1,271 @@
+//===--- CrossTranslationUnit.cpp - -----------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the CrossTranslationUnit interface.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/CrossTU/CrossTranslationUnit.h"
+#include "clang/AST/ASTImporter.h"
+#include "clang/AST/Decl.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/CrossTU/CrossTUDiagnostic.h"
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "clang/Index/USRGeneration.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include <fstream>
+#include <sstream>
+
+namespace clang {
+namespace cross_tu {
+
+namespace {
+// FIXME: This class is will be removed after the transition to llvm::Error.
+class IndexErrorCategory : public std::error_category {
+public:
+  const char *name() const noexcept override { return "clang.index"; }
+
+  std::string message(int Condition) const override {
+    switch (static_cast<index_error_code>(Condition)) {
+    case index_error_code::unspecified:
+      return "An unknown error has occurred.";
+    case index_error_code::missing_index_file:
+      return "The index file is missing.";
+    case index_error_code::invalid_index_format:
+      return "Invalid index file format.";
+    case index_error_code::multiple_definitions:
+      return "Multiple definitions in the index file.";
+    case index_error_code::missing_definition:
+      return "Missing definition from the index file.";
+    case index_error_code::failed_import:
+      return "Failed to import the definition.";
+    case index_error_code::failed_to_get_external_ast:
+      return "Failed to load external AST source.";
+    case index_error_code::failed_to_generate_usr:
+      return "Failed to generate USR.";
+    }
+    llvm_unreachable("Unrecognized index_error_code.");
+  }
+};
+
+static llvm::ManagedStatic<IndexErrorCategory> Category;
+} // end anonymous namespace
+
+char IndexError::ID;
+
+void IndexError::log(raw_ostream &OS) const {
+  OS << Category->message(static_cast<int>(Code)) << '\n';
+}
+
+std::error_code IndexError::convertToErrorCode() const {
+  return std::error_code(static_cast<int>(Code), *Category);
+}
+
+llvm::Expected<llvm::StringMap<std::string>>
+parseCrossTUIndex(StringRef IndexPath, StringRef CrossTUDir) {
+  std::ifstream ExternalFnMapFile(IndexPath);
+  if (!ExternalFnMapFile)
+    return llvm::make_error<IndexError>(index_error_code::missing_index_file,
+                                        IndexPath.str());
+
+  llvm::StringMap<std::string> Result;
+  std::string Line;
+  unsigned LineNo = 1;
+  while (std::getline(ExternalFnMapFile, Line)) {
+    const size_t Pos = Line.find(" ");
+    if (Pos > 0 && Pos != std::string::npos) {
+      StringRef LineRef{Line};
+      StringRef FunctionLookupName = LineRef.substr(0, Pos);
+      if (Result.count(FunctionLookupName))
+        return llvm::make_error<IndexError>(
+            index_error_code::multiple_definitions, IndexPath.str(), LineNo);
+      StringRef FileName = LineRef.substr(Pos + 1);
+      SmallString<256> FilePath = CrossTUDir;
+      if (llvm::sys::path::is_absolute(FileName))
+        FilePath = FileName;
+      else
+        llvm::sys::path::append(FilePath, FileName);
+      Result[FunctionLookupName] = FilePath.str().str();
+    } else
+      return llvm::make_error<IndexError>(
+          index_error_code::invalid_index_format, IndexPath.str(), LineNo);
+    LineNo++;
+  }
+  return Result;
+}
+
+std::string
+createCrossTUIndexString(const llvm::StringMap<std::string> &Index) {
+  std::ostringstream Result;
+  for (const auto &E : Index)
+    Result << E.getKey().str() << " " << E.getValue() << '\n';
+  return Result.str();
+}
+
+CrossTranslationUnitContext::CrossTranslationUnitContext(CompilerInstance &CI)
+    : CI(CI), Context(CI.getASTContext()) {}
+
+CrossTranslationUnitContext::~CrossTranslationUnitContext() {}
+
+std::string CrossTranslationUnitContext::getLookupName(const NamedDecl *ND) {
+  SmallString<128> DeclUSR;
+  bool Ret = index::generateUSRForDecl(ND, DeclUSR);
+  assert(!Ret && "Unable to generate USR");
+  return DeclUSR.str();
+}
+
+/// Recursively visits the function decls of a DeclContext, and looks up a
+/// function based on USRs.
+const FunctionDecl *
+CrossTranslationUnitContext::findFunctionInDeclContext(const DeclContext *DC,
+                                                       StringRef LookupFnName) {
+  assert(DC && "Declaration Context must not be null");
+  for (const Decl *D : DC->decls()) {
+    const auto *SubDC = dyn_cast<DeclContext>(D);
+    if (SubDC)
+      if (const auto *FD = findFunctionInDeclContext(SubDC, LookupFnName))
+        return FD;
+
+    const auto *ND = dyn_cast<FunctionDecl>(D);
+    const FunctionDecl *ResultDecl;
+    if (!ND || !ND->hasBody(ResultDecl))
+      continue;
+    if (getLookupName(ResultDecl) != LookupFnName)
+      continue;
+    return ResultDecl;
+  }
+  return nullptr;
+}
+
+llvm::Expected<const FunctionDecl *>
+CrossTranslationUnitContext::getCrossTUDefinition(const FunctionDecl *FD,
+                                                  StringRef CrossTUDir,
+                                                  StringRef IndexName) {
+  assert(!FD->hasBody() && "FD has a definition in current translation unit!");
+  const std::string LookupFnName = getLookupName(FD);
+  if (LookupFnName.empty())
+    return llvm::make_error<IndexError>(
+        index_error_code::failed_to_generate_usr);
+  llvm::Expected<ASTUnit *> ASTUnitOrError =
+      loadExternalAST(LookupFnName, CrossTUDir, IndexName);
+  if (!ASTUnitOrError)
+    return ASTUnitOrError.takeError();
+  ASTUnit *Unit = *ASTUnitOrError;
+  if (!Unit)
+    return llvm::make_error<IndexError>(
+        index_error_code::failed_to_get_external_ast);
+  assert(&Unit->getFileManager() ==
+         &Unit->getASTContext().getSourceManager().getFileManager());
+
+  TranslationUnitDecl *TU = Unit->getASTContext().getTranslationUnitDecl();
+  if (const FunctionDecl *ResultDecl =
+          findFunctionInDeclContext(TU, LookupFnName))
+    return importDefinition(ResultDecl);
+  return llvm::make_error<IndexError>(index_error_code::failed_import);
+}
+
+void CrossTranslationUnitContext::emitCrossTUDiagnostics(const IndexError &IE) {
+  switch (IE.getCode()) {
+  case index_error_code::missing_index_file:
+    Context.getDiagnostics().Report(diag::err_fe_error_opening)
+        << IE.getFileName() << "required by the CrossTU functionality";
+    break;
+  case index_error_code::invalid_index_format:
+    Context.getDiagnostics().Report(diag::err_fnmap_parsing)
+        << IE.getFileName() << IE.getLineNum();
+  case index_error_code::multiple_definitions:
+    Context.getDiagnostics().Report(diag::err_multiple_def_index)
+        << IE.getLineNum();
+    break;
+  default:
+    break;
+  }
+}
+
+llvm::Expected<ASTUnit *> CrossTranslationUnitContext::loadExternalAST(
+    StringRef LookupName, StringRef CrossTUDir, StringRef IndexName) {
+  // FIXME: The current implementation only supports loading functions with
+  //        a lookup name from a single translation unit. If multiple
+  //        translation units contains functions with the same lookup name an
+  //        error will be returned.
+  ASTUnit *Unit = nullptr;
+  auto FnUnitCacheEntry = FunctionASTUnitMap.find(LookupName);
+  if (FnUnitCacheEntry == FunctionASTUnitMap.end()) {
+    if (FunctionFileMap.empty()) {
+      SmallString<256> IndexFile = CrossTUDir;
+      if (llvm::sys::path::is_absolute(IndexName))
+        IndexFile = IndexName;
+      else
+        llvm::sys::path::append(IndexFile, IndexName);
+      llvm::Expected<llvm::StringMap<std::string>> IndexOrErr =
+          parseCrossTUIndex(IndexFile, CrossTUDir);
+      if (IndexOrErr)
+        FunctionFileMap = *IndexOrErr;
+      else
+        return IndexOrErr.takeError();
+    }
+
+    auto It = FunctionFileMap.find(LookupName);
+    if (It == FunctionFileMap.end())
+      return llvm::make_error<IndexError>(index_error_code::missing_definition);
+    StringRef ASTFileName = It->second;
+    auto ASTCacheEntry = FileASTUnitMap.find(ASTFileName);
+    if (ASTCacheEntry == FileASTUnitMap.end()) {
+      IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
+      TextDiagnosticPrinter *DiagClient =
+          new TextDiagnosticPrinter(llvm::errs(), &*DiagOpts);
+      IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
+      IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
+          new DiagnosticsEngine(DiagID, &*DiagOpts, DiagClient));
+
+      std::unique_ptr<ASTUnit> LoadedUnit(ASTUnit::LoadFromASTFile(
+          ASTFileName, CI.getPCHContainerOperations()->getRawReader(),
+          ASTUnit::LoadEverything, Diags, CI.getFileSystemOpts()));
+      Unit = LoadedUnit.get();
+      FileASTUnitMap[ASTFileName] = std::move(LoadedUnit);
+    } else {
+      Unit = ASTCacheEntry->second.get();
+    }
+    FunctionASTUnitMap[LookupName] = Unit;
+  } else {
+    Unit = FnUnitCacheEntry->second;
+  }
+  return Unit;
+}
+
+llvm::Expected<const FunctionDecl *>
+CrossTranslationUnitContext::importDefinition(const FunctionDecl *FD) {
+  ASTImporter &Importer = getOrCreateASTImporter(FD->getASTContext());
+  auto *ToDecl =
+      cast<FunctionDecl>(Importer.Import(const_cast<FunctionDecl *>(FD)));
+  assert(ToDecl->hasBody());
+  assert(FD->hasBody() && "Functions already imported should have body.");
+  return ToDecl;
+}
+
+ASTImporter &
+CrossTranslationUnitContext::getOrCreateASTImporter(ASTContext &From) {
+  auto I = ASTUnitImporterMap.find(From.getTranslationUnitDecl());
+  if (I != ASTUnitImporterMap.end())
+    return *I->second;
+  ASTImporter *NewImporter =
+      new ASTImporter(Context, Context.getSourceManager().getFileManager(),
+                      From, From.getSourceManager().getFileManager(), false);
+  ASTUnitImporterMap[From.getTranslationUnitDecl()].reset(NewImporter);
+  return *NewImporter;
+}
+
+} // namespace cross_tu
+} // namespace clang