IncrementalParser.cpp

//===--------- IncrementalParser.cpp - Incremental Compilation  -----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the class which performs incremental code compilation.
//
//===----------------------------------------------------------------------===//

#include "IncrementalParser.h"

#include "clang/AST/DeclContextInternals.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Interpreter/PartialTranslationUnit.h"
#include "clang/Parse/Parser.h"
#include "clang/Sema/Sema.h"
#include "llvm/Support/CrashRecoveryContext.h"
#include "llvm/Support/Error.h"

#include <sstream>

namespace clang {

// IncrementalParser::IncrementalParser() {}

IncrementalParser::IncrementalParser(CompilerInstance &Instance,
                                     llvm::Error &Err)
    : S(Instance.getSema()) {
  llvm::ErrorAsOutParameter EAO(&Err);
  Consumer = &S.getASTConsumer();
  P.reset(new Parser(S.getPreprocessor(), S, /*SkipBodies=*/false));
  P->Initialize();
}

IncrementalParser::~IncrementalParser() { P.reset(); }

llvm::Expected<TranslationUnitDecl *>
IncrementalParser::ParseOrWrapTopLevelDecl() {
  // Recover resources if we crash before exiting this method.
  llvm::CrashRecoveryContextCleanupRegistrar<Sema> CleanupSema(&S);
  Sema::GlobalEagerInstantiationScope GlobalInstantiations(S, /*Enabled=*/true);
  Sema::LocalEagerInstantiationScope LocalInstantiations(S);

  // Add a new PTU.
  ASTContext &C = S.getASTContext();
  C.addTranslationUnitDecl();

  // Skip previous eof due to last incremental input.
  if (P->getCurToken().is(tok::annot_repl_input_end)) {
    P->ConsumeAnyToken();
    // FIXME: Clang does not call ExitScope on finalizing the regular TU, we
    // might want to do that around HandleEndOfTranslationUnit.
    P->ExitScope();
    S.CurContext = nullptr;
    // Start a new PTU.
    P->EnterScope(Scope::DeclScope);
    S.ActOnTranslationUnitScope(P->getCurScope());
  }

  Parser::DeclGroupPtrTy ADecl;
  Sema::ModuleImportState ImportState;
  for (bool AtEOF = P->ParseFirstTopLevelDecl(ADecl, ImportState); !AtEOF;
       AtEOF = P->ParseTopLevelDecl(ADecl, ImportState)) {
    if (ADecl && !Consumer->HandleTopLevelDecl(ADecl.get()))
      return llvm::make_error<llvm::StringError>("Parsing failed. "
                                                 "The consumer rejected a decl",
                                                 std::error_code());
  }

  DiagnosticsEngine &Diags = S.getDiagnostics();
  if (Diags.hasErrorOccurred()) {
    CleanUpPTU(C.getTranslationUnitDecl());

    Diags.Reset(/*soft=*/true);
    Diags.getClient()->clear();
    return llvm::make_error<llvm::StringError>("Parsing failed.",
                                               std::error_code());
  }

  // Process any TopLevelDecls generated by #pragma weak.
  for (Decl *D : S.WeakTopLevelDecls()) {
    DeclGroupRef DGR(D);
    Consumer->HandleTopLevelDecl(DGR);
  }

  LocalInstantiations.perform();
  GlobalInstantiations.perform();

  Consumer->HandleTranslationUnit(C);

  return C.getTranslationUnitDecl();
}

llvm::Expected<TranslationUnitDecl *>
IncrementalParser::Parse(llvm::StringRef input) {
  Preprocessor &PP = S.getPreprocessor();
  assert(PP.isIncrementalProcessingEnabled() && "Not in incremental mode!?");

  std::ostringstream SourceName;
  SourceName << "input_line_" << InputCount++;

  // Create an uninitialized memory buffer, copy code in and append "\n"
  size_t InputSize = input.size(); // don't include trailing 0
  // MemBuffer size should *not* include terminating zero
  std::unique_ptr<llvm::MemoryBuffer> MB(
      llvm::WritableMemoryBuffer::getNewUninitMemBuffer(InputSize + 1,
                                                        SourceName.str()));
  char *MBStart = const_cast<char *>(MB->getBufferStart());
  memcpy(MBStart, input.data(), InputSize);
  MBStart[InputSize] = '\n';

  SourceManager &SM = S.getSourceManager();

  // FIXME: Create SourceLocation, which will allow clang to order the overload
  // candidates for example
  SourceLocation NewLoc = SM.getLocForStartOfFile(SM.getMainFileID());

  // Create FileID for the current buffer.
  FileID FID = SM.createFileID(std::move(MB), SrcMgr::C_User, /*LoadedID=*/0,
                               /*LoadedOffset=*/0, NewLoc);

  // NewLoc only used for diags.
  if (PP.EnterSourceFile(FID, /*DirLookup=*/nullptr, NewLoc))
    return llvm::make_error<llvm::StringError>("Parsing failed. "
                                               "Cannot enter source file.",
                                               std::error_code());

  auto PTU = ParseOrWrapTopLevelDecl();
  if (!PTU)
    return PTU.takeError();

  if (PP.getLangOpts().DelayedTemplateParsing) {
    // Microsoft-specific:
    // Late parsed templates can leave unswallowed "macro"-like tokens.
    // They will seriously confuse the Parser when entering the next
    // source file. So lex until we are EOF.
    Token Tok;
    do {
      PP.Lex(Tok);
    } while (Tok.isNot(tok::annot_repl_input_end));
  } else {
    Token AssertTok;
    PP.Lex(AssertTok);
    assert(AssertTok.is(tok::annot_repl_input_end) &&
           "Lexer must be EOF when starting incremental parse!");
  }

  return PTU;
}

void IncrementalParser::CleanUpPTU(TranslationUnitDecl *MostRecentTU) {
  if (StoredDeclsMap *Map = MostRecentTU->getPrimaryContext()->getLookupPtr()) {
    for (auto &&[Key, List] : *Map) {
      DeclContextLookupResult R = List.getLookupResult();
      std::vector<NamedDecl *> NamedDeclsToRemove;
      bool RemoveAll = true;
      for (NamedDecl *D : R) {
        if (D->getTranslationUnitDecl() == MostRecentTU)
          NamedDeclsToRemove.push_back(D);
        else
          RemoveAll = false;
      }
      if (LLVM_LIKELY(RemoveAll)) {
        Map->erase(Key);
      } else {
        for (NamedDecl *D : NamedDeclsToRemove)
          List.remove(D);
      }
    }
  }

  // FIXME: We should de-allocate MostRecentTU
  for (Decl *D : MostRecentTU->decls()) {
    auto *ND = dyn_cast<NamedDecl>(D);
    if (!ND)
      continue;
    // Check if we need to clean up the IdResolver chain.
    if (ND->getDeclName().getFETokenInfo() && !D->getLangOpts().ObjC &&
        !D->getLangOpts().CPlusPlus)
      S.IdResolver.RemoveDecl(ND);
  }
}

} // end namespace clang