Write the identifier offsets array into the PCH file as a blob, so

that the PCH reader does not have to decode the VBR encoding at PCH
load time.

Also, reduce the size of the identifier offsets from 64 bits down to
32 bits. The identifier table itself isn't going to grow to more than
4GB :)

Overall, this results in a 13% speedup in the Cocoa-prefixed "Hello,
World" benchmark.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70063 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 47 insertions, 42 deletions

diff --git a/lib/Frontend/PCHReader.cpp b/lib/Frontend/PCHReader.cpp
index 897a0e7713..005436dccf 100644
--- a/lib/Frontend/PCHReader.cpp
+++ b/lib/Frontend/PCHReader.cpp
@@ -1837,28 +1837,23 @@ PCHReader::ReadPCHBlock(uint64_t &PreprocessorBlockOffset) {
 
     case pch::IDENTIFIER_TABLE:
       IdentifierTableData = BlobStart;
-      IdentifierLookupTable 
-        = PCHIdentifierLookupTable::Create(
+      if (Record[0]) {
+        IdentifierLookupTable 
+          = PCHIdentifierLookupTable::Create(
                         (const unsigned char *)IdentifierTableData + Record[0],
                         (const unsigned char *)IdentifierTableData, 
                         PCHIdentifierLookupTrait(*this));
-      PP.getIdentifierTable().setExternalIdentifierLookup(this);
+        PP.getIdentifierTable().setExternalIdentifierLookup(this);
+      }
       break;
 
     case pch::IDENTIFIER_OFFSET:
-      if (!IdentifierData.empty()) {
+      if (!IdentifiersLoaded.empty()) {
         Error("Duplicate IDENTIFIER_OFFSET record in PCH file");
         return Failure;
       }
-      IdentifierData.swap(Record);
-#ifndef NDEBUG
-      for (unsigned I = 0, N = IdentifierData.size(); I != N; ++I) {
-        if ((IdentifierData[I] & 0x01) == 0) {
-          Error("Malformed identifier table in the precompiled header");
-          return Failure;
-        }
-      }
-#endif
+      IdentifierOffsets = (const uint32_t *)BlobStart;
+      IdentifiersLoaded.resize(Record[0]);
       break;
 
     case pch::EXTERNAL_DEFINITIONS:
@@ -2710,22 +2705,20 @@ void PCHReader::StartTranslationUnit(ASTConsumer *Consumer) {
 void PCHReader::PrintStats() {
   std::fprintf(stderr, "*** PCH Statistics:\n");
 
-  unsigned NumTypesLoaded = 
-    TypesLoaded.size() - std::count(TypesLoaded.begin(), TypesLoaded.end(),
-                                    (Type *)0);
-  unsigned NumDeclsLoaded = 
-    DeclsLoaded.size() - std::count(DeclsLoaded.begin(), DeclsLoaded.end(),
-                                    (Decl *)0);
-  unsigned NumIdentifiersLoaded = 0;
-  for (unsigned I = 0; I < IdentifierData.size(); ++I) {
-    if ((IdentifierData[I] & 0x01) == 0)
-      ++NumIdentifiersLoaded;
-  }
-  unsigned NumSelectorsLoaded = 0;
-  for (unsigned I = 0; I < SelectorsLoaded.size(); ++I) {
-    if (SelectorsLoaded[I].getAsOpaquePtr())
-      ++NumSelectorsLoaded;
-  }
+  unsigned NumTypesLoaded 
+    = TypesLoaded.size() - std::count(TypesLoaded.begin(), TypesLoaded.end(),
+                                      (Type *)0);
+  unsigned NumDeclsLoaded
+    = DeclsLoaded.size() - std::count(DeclsLoaded.begin(), DeclsLoaded.end(),
+                                      (Decl *)0);
+  unsigned NumIdentifiersLoaded
+    = IdentifiersLoaded.size() - std::count(IdentifiersLoaded.begin(),
+                                            IdentifiersLoaded.end(),
+                                            (IdentifierInfo *)0);
+  unsigned NumSelectorsLoaded 
+    = SelectorsLoaded.size() - std::count(SelectorsLoaded.begin(),
+                                          SelectorsLoaded.end(),
+                                          Selector());
 
   if (!TypesLoaded.empty())
     std::fprintf(stderr, "  %u/%u types read (%f%%)\n",
@@ -2735,10 +2728,10 @@ void PCHReader::PrintStats() {
     std::fprintf(stderr, "  %u/%u declarations read (%f%%)\n",
                  NumDeclsLoaded, (unsigned)DeclsLoaded.size(),
                  ((float)NumDeclsLoaded/DeclsLoaded.size() * 100));
-  if (!IdentifierData.empty())
+  if (!IdentifiersLoaded.empty())
     std::fprintf(stderr, "  %u/%u identifiers read (%f%%)\n",
-                 NumIdentifiersLoaded, (unsigned)IdentifierData.size(),
-                 ((float)NumIdentifiersLoaded/IdentifierData.size() * 100));
+                 NumIdentifiersLoaded, (unsigned)IdentifiersLoaded.size(),
+                 ((float)NumIdentifiersLoaded/IdentifiersLoaded.size() * 100));
   if (TotalNumSelectors)
     std::fprintf(stderr, "  %u/%u selectors read (%f%%)\n",
                  NumSelectorsLoaded, TotalNumSelectors,
@@ -2832,27 +2825,28 @@ PCHReader::ReadMethodPool(Selector Sel) {
   return *Pos;
 }
 
-void PCHReader::SetIdentifierInfo(unsigned ID, const IdentifierInfo *II) {
+void PCHReader::SetIdentifierInfo(unsigned ID, IdentifierInfo *II) {
   assert(ID && "Non-zero identifier ID required");
-  IdentifierData[ID - 1] = reinterpret_cast<uint64_t>(II);
+  assert(ID <= IdentifiersLoaded.size() && "Identifier ID out of range");
+  IdentifiersLoaded[ID - 1] = II;
 }
 
 IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
   if (ID == 0)
     return 0;
   
-  if (!IdentifierTableData || IdentifierData.empty()) {
+  if (!IdentifierTableData || IdentifiersLoaded.empty()) {
     Error("No identifier table in PCH file");
     return 0;
   }
   
-  if (IdentifierData[ID - 1] & 0x01) {
-    uint64_t Offset = IdentifierData[ID - 1] >> 1;
-    IdentifierData[ID - 1] = reinterpret_cast<uint64_t>(
-                               &Context.Idents.get(IdentifierTableData + Offset));
+  if (!IdentifiersLoaded[ID - 1]) {
+    uint32_t Offset = IdentifierOffsets[ID - 1];
+    IdentifiersLoaded[ID - 1] 
+      = &Context.Idents.get(IdentifierTableData + Offset);
   }
   
-  return reinterpret_cast<IdentifierInfo *>(IdentifierData[ID - 1]);
+  return IdentifiersLoaded[ID - 1];
 }
 
 Selector PCHReader::DecodeSelector(unsigned ID) {
diff --git a/lib/Frontend/PCHWriter.cpp b/lib/Frontend/PCHWriter.cpp
index 91ddbf4182..4ac836419e 100644
--- a/lib/Frontend/PCHWriter.cpp
+++ b/lib/Frontend/PCHWriter.cpp
@@ -2119,7 +2119,18 @@ void PCHWriter::WriteIdentifierTable(Preprocessor &PP) {
   }
 
   // Write the offsets table for identifier IDs.
-  Stream.EmitRecord(pch::IDENTIFIER_OFFSET, IdentifierOffsets);
+  BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
+  Abbrev->Add(BitCodeAbbrevOp(pch::IDENTIFIER_OFFSET));
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32)); // # of identifiers
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
+  unsigned IdentifierOffsetAbbrev = Stream.EmitAbbrev(Abbrev);
+
+  RecordData Record;
+  Record.push_back(pch::IDENTIFIER_OFFSET);
+  Record.push_back(IdentifierOffsets.size());
+  Stream.EmitRecordWithBlob(IdentifierOffsetAbbrev, Record,
+                            (const char *)&IdentifierOffsets.front(),
+                            IdentifierOffsets.size() * sizeof(uint32_t));
 }
 
 /// \brief Write a record containing the given attributes.
@@ -2253,7 +2264,7 @@ void PCHWriter::AddString(const std::string &Str, RecordData &Record) {
 /// \brief Note that the identifier II occurs at the given offset
 /// within the identifier table.
 void PCHWriter::SetIdentifierOffset(const IdentifierInfo *II, uint32_t Offset) {
-  IdentifierOffsets[IdentifierIDs[II] - 1] = (Offset << 1) | 0x01;
+  IdentifierOffsets[IdentifierIDs[II] - 1] = Offset;
 }
 
 /// \brief Note that the selector Sel occurs at the given offset