[clang] 11d612a - [clang][Preprocessor] Replace the slow translateFile call by a new, faster isMainFile check

[Alex Lorenz via cfe-commits]

Author: Alex Lorenz
Date: 2020-05-14T14:13:34-07:00
New Revision: 11d612ac99a621c762c2cc8f7bacbb8ae32d7fe9

URL: https://github.com/llvm/llvm-project/commit/11d612ac99a621c762c2cc8f7bacbb8ae32d7fe9
DIFF: https://github.com/llvm/llvm-project/commit/11d612ac99a621c762c2cc8f7bacbb8ae32d7fe9.diff

LOG: [clang][Preprocessor] Replace the slow translateFile call by a new, faster isMainFile check

The commit 3c28a2dc6bdc331e5a0d8097a5fa59d06682b9d0 introduced the check that checks if we're
trying to re-enter a main file when building a preamble. Unfortunately this slowed down the preamble
compilation by 80-90% in some test cases, as translateFile is really slow. This change checks
to see if the FileEntry is the main file without calling translateFile, but by using the new
isMainFile check instead. This speeds up preamble building by 1.5-2x for certain test cases that we have.

rdar://59361291

Differential Revision: https://reviews.llvm.org/D79834

Added: 
    

Modified: 
    clang/include/clang/Basic/SourceManager.h
    clang/lib/Basic/SourceManager.cpp
    clang/lib/Lex/PPDirectives.cpp
    clang/unittests/Basic/SourceManagerTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
index d0910ea31827..693ae4f938e1 100644
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -813,6 +813,11 @@ class SourceManager : public RefCountedBase<SourceManager> {
     MainFileID = FID;
   }
 
+  /// Returns true when the given FileEntry corresponds to the main file.
+  ///
+  /// The main file should be set prior to calling this function.
+  bool isMainFile(FileEntryRef SourceFile);
+
   /// Set the file ID for the precompiled preamble.
   void setPreambleFileID(FileID Preamble) {
     assert(PreambleFileID.isInvalid() && "PreambleFileID already set!");

diff  --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index e42c3f4ca73f..6e4c8e8052bd 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -389,6 +389,14 @@ void SourceManager::clearIDTables() {
   createExpansionLoc(SourceLocation(), SourceLocation(), SourceLocation(), 1);
 }
 
+bool SourceManager::isMainFile(FileEntryRef SourceFile) {
+  assert(MainFileID.isValid() && "expected initialized SourceManager");
+  auto FE = getFileEntryRefForID(MainFileID);
+  if (!FE)
+    return false;
+  return FE->getUID() == SourceFile.getUID();
+}
+
 void SourceManager::initializeForReplay(const SourceManager &Old) {
   assert(MainFileID.isInvalid() && "expected uninitialized SourceManager");
 

diff  --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index db249126d393..396ba529fc9a 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -2054,8 +2054,7 @@ Preprocessor::ImportAction Preprocessor::HandleHeaderIncludeOrImport(
   // some directives (e.g. #endif of a header guard) will never be seen.
   // Since this will lead to confusing errors, avoid the inclusion.
   if (Action == Enter && File && PreambleConditionalStack.isRecording() &&
-      SourceMgr.translateFile(&File->getFileEntry()) ==
-          SourceMgr.getMainFileID()) {
+      SourceMgr.isMainFile(*File)) {
     Diag(FilenameTok.getLocation(),
          diag::err_pp_including_mainfile_in_preamble);
     return {ImportAction::None};

diff  --git a/clang/unittests/Basic/SourceManagerTest.cpp b/clang/unittests/Basic/SourceManagerTest.cpp
index 850a08b74ace..5fd7607f76d7 100644
--- a/clang/unittests/Basic/SourceManagerTest.cpp
+++ b/clang/unittests/Basic/SourceManagerTest.cpp
@@ -491,6 +491,30 @@ TEST_F(SourceManagerTest, isBeforeInTranslationUnitWithMacroInInclude) {
   EXPECT_TRUE(SourceMgr.isBeforeInTranslationUnit(Macros[10].Loc, Macros[11].Loc));
 }
 
+TEST_F(SourceManagerTest, isMainFile) {
+  const char *Source = "int x;";
+
+  std::unique_ptr<llvm::MemoryBuffer> Buf =
+      llvm::MemoryBuffer::getMemBuffer(Source);
+  const FileEntry *SourceFile =
+      FileMgr.getVirtualFile("mainFile.cpp", Buf->getBufferSize(), 0);
+  SourceMgr.overrideFileContents(SourceFile, std::move(Buf));
+
+  std::unique_ptr<llvm::MemoryBuffer> Buf2 =
+      llvm::MemoryBuffer::getMemBuffer(Source);
+  const FileEntry *SecondFile =
+      FileMgr.getVirtualFile("file2.cpp", Buf2->getBufferSize(), 0);
+  SourceMgr.overrideFileContents(SecondFile, std::move(Buf2));
+
+  FileID MainFileID = SourceMgr.getOrCreateFileID(SourceFile, SrcMgr::C_User);
+  SourceMgr.setMainFileID(MainFileID);
+
+  EXPECT_TRUE(SourceMgr.isMainFile(FileEntryRef("mainFile.cpp", *SourceFile)));
+  EXPECT_TRUE(
+      SourceMgr.isMainFile(FileEntryRef("anotherName.cpp", *SourceFile)));
+  EXPECT_FALSE(SourceMgr.isMainFile(FileEntryRef("mainFile.cpp", *SecondFile)));
+}
+
 #endif
 
 } // anonymous namespace