[PCH] When serializing Stmts, keep track of when sub statements are referenced again and

in such a case just write out a reference of a previously serialized Stmt, instead
of serializing it all over again.

This saves memory + space + [de]serializing time, and avoids blowing up memory
with pathological cases. rdar://10293911

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142696 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 6 insertions, 1 deletions

diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index e7f126514b..49f1ddfa26 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -875,6 +875,8 @@ namespace clang {
       STMT_STOP = 100,
       /// \brief A NULL expression.
       STMT_NULL_PTR,
+      /// \brief A reference to a previously [de]serialized Stmt record.
+      STMT_REF_PTR,
       /// \brief A NullStmt record.
       STMT_NULL,
       /// \brief A CompoundStmt record.
diff --git a/include/clang/Serialization/ASTWriter.h b/include/clang/Serialization/ASTWriter.h
index 7a49e485f2..7d89ce7db0 100644
--- a/include/clang/Serialization/ASTWriter.h
+++ b/include/clang/Serialization/ASTWriter.h
@@ -24,6 +24,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include <map>
 #include <queue>
@@ -331,7 +332,9 @@ private:
   SmallVector<QueuedCXXBaseSpecifiers, 2> CXXBaseSpecifiersToWrite;
                     
   /// \brief Write the given subexpression to the bitstream.
-  void WriteSubStmt(Stmt *S);
+  void WriteSubStmt(Stmt *S,
+                    llvm::DenseMap<Stmt *, uint64_t> &SubStmtEntries,
+                    llvm::DenseSet<Stmt *> &ParentStmts);
 
   void WriteBlockInfoBlock();
   void WriteMetadata(ASTContext &Context, StringRef isysroot,