Implement serialization and lazy deserialization of the preprocessing

record (which includes all macro instantiations and definitions). As
with all lay deserialization, this introduces a new external source
(here, an external preprocessing record source) that loads all of the
preprocessed entities prior to iterating over the entities.

The preprocessing record is an optional part of the precompiled header
that is disabled by default (enabled with
-detailed-preprocessing-record). When the preprocessor given to the
PCH writer has a preprocessing record, that record is written into the
PCH file. When the PCH reader is given a PCH file that contains a
preprocessing record, it will be lazily loaded (which, effectively,
implicitly adds -detailed-preprocessing-record). This is the first
case where we have sections of the precompiled header that are
added/removed based on a compilation flag, which is
unfortunate. However, this data consumes ~550k in the PCH file for
Cocoa.h (out of ~9.9MB), and there is a non-trivial cost to gathering
this detailed preprocessing information, so it's too expensive to turn
on by default. In the future, we should investigate a better encoding
of this information.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99002 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 2 deletions

diff --git a/include/clang/Frontend/PCHBitCodes.h b/include/clang/Frontend/PCHBitCodes.h
index e2c27e6ddf..de7888e797 100644
--- a/include/clang/Frontend/PCHBitCodes.h
+++ b/include/clang/Frontend/PCHBitCodes.h
@@ -224,8 +224,11 @@ namespace clang {
       VERSION_CONTROL_BRANCH_REVISION = 21,
       
       /// \brief Record code for the array of unused static functions.
-      UNUSED_STATIC_FUNCS = 22
+      UNUSED_STATIC_FUNCS = 22,
       
+      /// \brief Record code for the table of offsets to macro definition
+      /// entries in the preprocessing record.
+      MACRO_DEFINITION_OFFSETS = 23
     };
 
     /// \brief Record types used within a source manager block.
@@ -264,7 +267,14 @@ namespace clang {
 
       /// \brief Describes one token.
       /// [PP_TOKEN, SLoc, Length, IdentInfoID, Kind, Flags]
-      PP_TOKEN = 3
+      PP_TOKEN = 3,
+
+      /// \brief Describes a macro instantiation within the preprocessing 
+      /// record.
+      PP_MACRO_INSTANTIATION = 4,
+      
+      /// \brief Describes a macro definition within the preprocessing record.
+      PP_MACRO_DEFINITION = 5
     };
 
     /// \defgroup PCHAST Precompiled header AST constants