Write the declaration and type offset arrays into the bitstream as

blobs, so that we don't need to do any work to get these arrays into
memory at PCH load time.

This gives another 19% performance improvement to the Cocoa-prefixed
"Hello, World!".

llvm-svn: 70059

1 files changed, 29 insertions, 3 deletions

diff --git a/clang/lib/Frontend/PCHWriter.cpp b/clang/lib/Frontend/PCHWriter.cpp
index 56c8296c949..91ddbf41826 100644
--- a/clang/lib/Frontend/PCHWriter.cpp
+++ b/clang/lib/Frontend/PCHWriter.cpp
@@ -2270,6 +2270,8 @@ PCHWriter::PCHWriter(llvm::BitstreamWriter &Stream)
     NumVisibleDeclContexts(0) { }
 
 void PCHWriter::WritePCH(Sema &SemaRef) {
+  using namespace llvm;
+
   ASTContext &Context = SemaRef.Context;
   Preprocessor &PP = SemaRef.PP;
 
@@ -2315,7 +2317,7 @@ void PCHWriter::WritePCH(Sema &SemaRef) {
 
   // Write the remaining PCH contents.
   RecordData Record;
-  Stream.EnterSubblock(pch::PCH_BLOCK_ID, 3);
+  Stream.EnterSubblock(pch::PCH_BLOCK_ID, 4);
   WriteTargetTriple(Context.Target);
   WriteLanguageOptions(Context.getLangOptions());
   WriteSourceManagerBlock(Context.getSourceManager());
@@ -2324,8 +2326,32 @@ void PCHWriter::WritePCH(Sema &SemaRef) {
   WriteDeclsBlock(Context);
   WriteMethodPool(SemaRef);
   WriteIdentifierTable(PP);
-  Stream.EmitRecord(pch::TYPE_OFFSET, TypeOffsets);
-  Stream.EmitRecord(pch::DECL_OFFSET, DeclOffsets);
+
+  // Write the type offsets array
+  BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
+  Abbrev->Add(BitCodeAbbrevOp(pch::TYPE_OFFSET));
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32)); // # of types
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // types block
+  unsigned TypeOffsetAbbrev = Stream.EmitAbbrev(Abbrev);
+  Record.clear();
+  Record.push_back(pch::TYPE_OFFSET);
+  Record.push_back(TypeOffsets.size());
+  Stream.EmitRecordWithBlob(TypeOffsetAbbrev, Record,
+                            (const char *)&TypeOffsets.front(), 
+                            TypeOffsets.size() * sizeof(uint64_t));
+  
+  // Write the declaration offsets array
+  Abbrev = new BitCodeAbbrev();
+  Abbrev->Add(BitCodeAbbrevOp(pch::DECL_OFFSET));
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32)); // # of declarations
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // declarations block
+  unsigned DeclOffsetAbbrev = Stream.EmitAbbrev(Abbrev);
+  Record.clear();
+  Record.push_back(pch::DECL_OFFSET);
+  Record.push_back(DeclOffsets.size());
+  Stream.EmitRecordWithBlob(DeclOffsetAbbrev, Record,
+                            (const char *)&DeclOffsets.front(), 
+                            DeclOffsets.size() * sizeof(uint64_t));
 
   // Write the record of special types.
   Record.clear();