Load most of the source manager's information lazily from the PCH

file. In particular, only eagerly load source location entries for
files and for the predefines buffer. Other buffers and
macro-instantiation source location entries are loaded lazily.

With the Cocoa-prefixed "Hello, World", we only load 815/26555 source
location entities. This halves the amount of user time we spend in
this "Hello, World" program with -fsyntax-only (down to .007s).

This optimization is part 1 of 2 for the source manager. This
eliminates most of the user time in loading a PCH file. We still spend
too much time initialize File structures (especially in the calls to
stat), so we need to either make the loading of source location
entries for files lazy or import the stat cache from the PTH
implementation.

llvm-svn: 70196

1 files changed, 136 insertions, 56 deletions

diff --git a/clang/lib/Frontend/PCHReader.cpp b/clang/lib/Frontend/PCHReader.cpp
index 86848758ad6..ff8795ca640 100644
--- a/clang/lib/Frontend/PCHReader.cpp
+++ b/clang/lib/Frontend/PCHReader.cpp
@@ -43,8 +43,8 @@ PCHReader::PCHReader(Preprocessor &PP, ASTContext &Context)
     IdentifierOffsets(0),
     MethodPoolLookupTable(0), MethodPoolLookupTableData(0),
     TotalSelectorsInMethodPool(0), SelectorOffsets(0),
-    TotalNumSelectors(0), NumStatementsRead(0), NumMacrosRead(0),
-    NumMethodPoolSelectorsRead(0), NumMethodPoolMisses(0),
+    TotalNumSelectors(0), NumSLocEntriesRead(0), NumStatementsRead(0), 
+    NumMacrosRead(0), NumMethodPoolSelectorsRead(0), NumMethodPoolMisses(0),
     NumLexicalDeclContextsRead(0), NumVisibleDeclContextsRead(0) { }
 
 PCHReader::~PCHReader() {}
@@ -423,7 +423,21 @@ static bool ParseLineTable(SourceManager &SourceMgr,
 /// \brief Read the source manager block
 PCHReader::PCHReadResult PCHReader::ReadSourceManagerBlock() {
   using namespace SrcMgr;
-  if (Stream.EnterSubBlock(pch::SOURCE_MANAGER_BLOCK_ID)) {
+
+  // Set the source-location entry cursor to the current position in
+  // the stream. This cursor will be used to read the contents of the
+  // source manager block initially, and then lazily read
+  // source-location entries as needed.
+  SLocEntryCursor = Stream;
+
+  // The stream itself is going to skip over the source manager block.
+  if (Stream.SkipBlock()) {
+    Error("Malformed block record");
+    return Failure;
+  }
+
+  // Enter the source manager block.
+  if (SLocEntryCursor.EnterSubBlock(pch::SOURCE_MANAGER_BLOCK_ID)) {
     Error("Malformed source manager block record");
     return Failure;
   }
@@ -432,20 +446,19 @@ PCHReader::PCHReadResult PCHReader::ReadSourceManagerBlock() {
   RecordData Record;
   unsigned NumHeaderInfos = 0;
   while (true) {
-    unsigned Code = Stream.ReadCode();
+    unsigned Code = SLocEntryCursor.ReadCode();
     if (Code == llvm::bitc::END_BLOCK) {
-      if (Stream.ReadBlockEnd()) {
+      if (SLocEntryCursor.ReadBlockEnd()) {
         Error("Error at end of Source Manager block");
         return Failure;
       }
-
       return Success;
     }
     
     if (Code == llvm::bitc::ENTER_SUBBLOCK) {
       // No known subblocks, always skip them.
-      Stream.ReadSubBlockID();
-      if (Stream.SkipBlock()) {
+      SLocEntryCursor.ReadSubBlockID();
+      if (SLocEntryCursor.SkipBlock()) {
         Error("Malformed block record");
         return Failure;
       }
@@ -453,7 +466,7 @@ PCHReader::PCHReadResult PCHReader::ReadSourceManagerBlock() {
     }
     
     if (Code == llvm::bitc::DEFINE_ABBREV) {
-      Stream.ReadAbbrevRecord();
+      SLocEntryCursor.ReadAbbrevRecord();
       continue;
     }
     
@@ -461,56 +474,10 @@ PCHReader::PCHReadResult PCHReader::ReadSourceManagerBlock() {
     const char *BlobStart;
     unsigned BlobLen;
     Record.clear();
-    switch (Stream.ReadRecord(Code, Record, &BlobStart, &BlobLen)) {
+    switch (SLocEntryCursor.ReadRecord(Code, Record, &BlobStart, &BlobLen)) {
     default:  // Default behavior: ignore.
       break;
 
-    case pch::SM_SLOC_FILE_ENTRY: {
-      // FIXME: We would really like to delay the creation of this
-      // FileEntry until it is actually required, e.g., when producing
-      // a diagnostic with a source location in this file.
-      const FileEntry *File 
-        = PP.getFileManager().getFile(BlobStart, BlobStart + BlobLen);
-      // FIXME: Error recovery if file cannot be found.
-      FileID ID = SourceMgr.createFileID(File,
-                                SourceLocation::getFromRawEncoding(Record[1]),
-                                         (CharacteristicKind)Record[2]);
-      if (Record[3])
-        const_cast<SrcMgr::FileInfo&>(SourceMgr.getSLocEntry(ID).getFile())
-          .setHasLineDirectives();
-      break;
-    }
-
-    case pch::SM_SLOC_BUFFER_ENTRY: {
-      const char *Name = BlobStart;
-      unsigned Code = Stream.ReadCode();
-      Record.clear();
-      unsigned RecCode = Stream.ReadRecord(Code, Record, &BlobStart, &BlobLen);
-      assert(RecCode == pch::SM_SLOC_BUFFER_BLOB && "Ill-formed PCH file");
-      (void)RecCode;
-      llvm::MemoryBuffer *Buffer
-        = llvm::MemoryBuffer::getMemBuffer(BlobStart, 
-                                           BlobStart + BlobLen - 1,
-                                           Name);
-      FileID BufferID = SourceMgr.createFileIDForMemBuffer(Buffer);
-
-      if (strcmp(Name, "<built-in>") == 0
-          && CheckPredefinesBuffer(BlobStart, BlobLen - 1, BufferID))
-        return IgnorePCH;
-      break;
-    }
-
-    case pch::SM_SLOC_INSTANTIATION_ENTRY: {
-      SourceLocation SpellingLoc 
-        = SourceLocation::getFromRawEncoding(Record[1]);
-      SourceMgr.createInstantiationLoc(
-                              SpellingLoc,
-                              SourceLocation::getFromRawEncoding(Record[2]),
-                              SourceLocation::getFromRawEncoding(Record[3]),
-                              Record[4]);
-      break;
-    }
-
     case pch::SM_LINE_TABLE:
       if (ParseLineTable(SourceMgr, Record))
         return Failure;
@@ -525,10 +492,98 @@ PCHReader::PCHReadResult PCHReader::ReadSourceManagerBlock() {
       PP.getHeaderSearchInfo().setHeaderFileInfoForUID(HFI, NumHeaderInfos++);
       break;
     }
+
+    case pch::SM_SLOC_FILE_ENTRY:
+    case pch::SM_SLOC_BUFFER_ENTRY:
+    case pch::SM_SLOC_INSTANTIATION_ENTRY:
+      // Once we hit one of the source location entries, we're done.
+      return Success;
     }
   }
 }
 
+/// \brief Read in the source location entry with the given ID.
+PCHReader::PCHReadResult PCHReader::ReadSLocEntryRecord(unsigned ID) {
+  if (ID == 0)
+    return Success;
+
+  if (ID > TotalNumSLocEntries) {
+    Error("source location entry ID out-of-range for PCH file");
+    return Failure;
+  }
+
+  ++NumSLocEntriesRead;
+  SLocEntryCursor.JumpToBit(SLocOffsets[ID - 1]);
+  unsigned Code = SLocEntryCursor.ReadCode();
+  if (Code == llvm::bitc::END_BLOCK ||
+      Code == llvm::bitc::ENTER_SUBBLOCK ||
+      Code == llvm::bitc::DEFINE_ABBREV) {
+    Error("incorrectly-formatted source location entry in PCH file");
+    return Failure;
+  }
+
+  SourceManager &SourceMgr = Context.getSourceManager();
+  RecordData Record;
+  const char *BlobStart;
+  unsigned BlobLen;
+  switch (SLocEntryCursor.ReadRecord(Code, Record, &BlobStart, &BlobLen)) {
+  default:
+    Error("incorrectly-formatted source location entry in PCH file");
+    return Failure;
+
+  case pch::SM_SLOC_FILE_ENTRY: {
+    const FileEntry *File 
+      = PP.getFileManager().getFile(BlobStart, BlobStart + BlobLen);
+    // FIXME: Error recovery if file cannot be found.
+    FileID FID = SourceMgr.createFileID(File,
+                                SourceLocation::getFromRawEncoding(Record[1]),
+                                       (SrcMgr::CharacteristicKind)Record[2],
+                                        ID, Record[0]);
+    if (Record[3])
+      const_cast<SrcMgr::FileInfo&>(SourceMgr.getSLocEntry(FID).getFile())
+        .setHasLineDirectives();
+
+    break;
+  }
+
+  case pch::SM_SLOC_BUFFER_ENTRY: {
+    const char *Name = BlobStart;
+    unsigned Offset = Record[0];
+    unsigned Code = SLocEntryCursor.ReadCode();
+    Record.clear();
+    unsigned RecCode 
+      = SLocEntryCursor.ReadRecord(Code, Record, &BlobStart, &BlobLen);
+    assert(RecCode == pch::SM_SLOC_BUFFER_BLOB && "Ill-formed PCH file");
+    (void)RecCode;
+    llvm::MemoryBuffer *Buffer
+      = llvm::MemoryBuffer::getMemBuffer(BlobStart, 
+                                         BlobStart + BlobLen - 1,
+                                         Name);
+    FileID BufferID = SourceMgr.createFileIDForMemBuffer(Buffer, ID, Offset);
+      
+    if (strcmp(Name, "<built-in>") == 0
+        && CheckPredefinesBuffer(BlobStart, BlobLen - 1, BufferID))
+      return IgnorePCH;
+
+    break;
+  }
+
+  case pch::SM_SLOC_INSTANTIATION_ENTRY: {
+    SourceLocation SpellingLoc 
+      = SourceLocation::getFromRawEncoding(Record[1]);
+    SourceMgr.createInstantiationLoc(SpellingLoc,
+                              SourceLocation::getFromRawEncoding(Record[2]),
+                              SourceLocation::getFromRawEncoding(Record[3]),
+                                     Record[4],
+                                     ID,
+                                     Record[0]);
+    break;
+  }  
+  }
+
+  return Success;
+}
+
 /// ReadBlockAbbrevs - Enter a subblock of the specified BlockID with the
 /// specified cursor.  Read the abbreviations that are at the top of the block
 /// and then leave the cursor pointing into the block.
@@ -807,6 +862,7 @@ PCHReader::ReadPCHBlock() {
       TotalLexicalDeclContexts = Record[2];
       TotalVisibleDeclContexts = Record[3];
       break;
+
     case pch::TENTATIVE_DEFINITIONS:
       if (!TentativeDefinitions.empty()) {
         Error("Duplicate TENTATIVE_DEFINITIONS record in PCH file");
@@ -844,6 +900,22 @@ PCHReader::ReadPCHBlock() {
       if (!Record.empty())
         PP.setCounterValue(Record[0]);
       break;
+
+    case pch::SOURCE_LOCATION_OFFSETS:
+      SLocOffsets = (const uint64_t *)BlobStart;
+      TotalNumSLocEntries = Record[0];
+      PP.getSourceManager().PreallocateSLocEntries(this, 
+                                                   TotalNumSLocEntries, 
+                                                   Record[1]);
+      break;
+
+    case pch::SOURCE_LOCATION_PRELOADS:
+      for (unsigned I = 0, N = Record.size(); I != N; ++I) {
+        PCHReadResult Result = ReadSLocEntryRecord(Record[I]);
+        if (Result != Success)
+          return Result;
+      }
+      break;
     }
   }
   Error("Premature end of bitstream");
@@ -1434,6 +1506,10 @@ void PCHReader::PrintStats() {
                                           SelectorsLoaded.end(),
                                           Selector());
 
+  if (TotalNumSLocEntries)
+    std::fprintf(stderr, "  %u/%u source location entries read (%f%%)\n",
+                 NumSLocEntriesRead, TotalNumSLocEntries,
+                 ((float)NumSLocEntriesRead/TotalNumSLocEntries * 100));
   if (!TypesLoaded.empty())
     std::fprintf(stderr, "  %u/%u types read (%f%%)\n",
                  NumTypesLoaded, (unsigned)TypesLoaded.size(),
@@ -1604,6 +1680,10 @@ IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
   return IdentifiersLoaded[ID - 1];
 }
 
+void PCHReader::ReadSLocEntry(unsigned ID) {
+  ReadSLocEntryRecord(ID);
+}
+
 Selector PCHReader::DecodeSelector(unsigned ID) {
   if (ID == 0)
     return Selector();