Start factoring the on-disk records for an AST file into a control

block, which stores information about how the AST file to generated,
from the AST block, which stores the actual serialized AST. The
information in the control block should be enough to determine whether
the AST file is up-to-date and compatible with the current translation
unit, and reading it should not cause any side effects that aren't
easy to undo. That way, we can back out from an attempt to read an
incompatible or out-of-date AST file.

Note that there is still more factoring to do. In particular,
information about the source files used to generate the AST file
(along with their time stamps, sizes, etc.) still resides in the
source manager block. 


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166166 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 87 insertions, 79 deletions

diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index 68b8bf00cc..b5171f529b 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -216,7 +216,46 @@ namespace clang {
       SUBMODULE_BLOCK_ID,
 
       /// \brief The block containing comments.
-      COMMENTS_BLOCK_ID
+      COMMENTS_BLOCK_ID,
+
+      /// \brief The control block, which contains all of the
+      /// information that needs to be validated prior to committing
+      /// to loading the AST file.
+      CONTROL_BLOCK_ID
+    };
+
+    /// \brief Record types that occur within the control block.
+    enum ControlRecordTypes {
+      /// \brief AST file metadata, including the AST file version number
+      /// and the target triple used to build the AST file.
+      METADATA = 1,
+
+      /// \brief Record code for the list of other AST files imported by
+      /// this AST file.
+      IMPORTS = 2,
+
+      /// \brief Record code for the language options table.
+      ///
+      /// The record with this code contains the contents of the
+      /// LangOptions structure. We serialize the entire contents of
+      /// the structure, and let the reader decide which options are
+      /// actually important to check.
+      LANGUAGE_OPTIONS = 3,
+
+      /// \brief Record code for the original file that was used to
+      /// generate the AST file.
+      ORIGINAL_FILE_NAME = 4,
+
+      /// \brief Record code for the file ID of the original file used to 
+      /// generate the AST file.
+      ORIGINAL_FILE_ID = 5,
+      
+      /// \brief The directory that the PCH was originally created in.
+      ORIGINAL_PCH_DIR = 6,
+
+      /// \brief Record code for the version control branch and revision
+      /// information of the compiler used to build this AST file.
+      VERSION_CONTROL_BRANCH_REVISION = 7
     };
 
     /// \brief Record types that occur within the AST block itself.
@@ -247,25 +286,13 @@ namespace clang {
       /// reserved for the translation unit declaration.
       DECL_OFFSET = 2,
 
-      /// \brief Record code for the language options table.
-      ///
-      /// The record with this code contains the contents of the
-      /// LangOptions structure. We serialize the entire contents of
-      /// the structure, and let the reader decide which options are
-      /// actually important to check.
-      LANGUAGE_OPTIONS = 3,
-
-      /// \brief AST file metadata, including the AST file version number
-      /// and the target triple used to build the AST file.
-      METADATA = 4,
-
       /// \brief Record code for the table of offsets of each
       /// identifier ID.
       ///
       /// The offset table contains offsets into the blob stored in
       /// the IDENTIFIER_TABLE record. Each offset points to the
       /// NULL-terminated string that corresponds to that identifier.
-      IDENTIFIER_OFFSET = 5,
+      IDENTIFIER_OFFSET = 3,
 
       /// \brief Record code for the identifier table.
       ///
@@ -279,7 +306,7 @@ namespace clang {
       /// between offsets (for unresolved identifier IDs) and
       /// IdentifierInfo pointers (for already-resolved identifier
       /// IDs).
-      IDENTIFIER_TABLE = 6,
+      IDENTIFIER_TABLE = 4,
 
       /// \brief Record code for the array of external definitions.
       ///
@@ -289,7 +316,7 @@ namespace clang {
       /// reported to the AST consumer after the AST file has been
       /// read, since their presence can affect the semantics of the
       /// program (e.g., for code generation).
-      EXTERNAL_DEFINITIONS = 7,
+      EXTERNAL_DEFINITIONS = 5,
 
       /// \brief Record code for the set of non-builtin, special
       /// types.
@@ -298,33 +325,33 @@ namespace clang {
       /// that are constructed during semantic analysis (e.g.,
       /// __builtin_va_list). The SPECIAL_TYPE_* constants provide
       /// offsets into this record.
-      SPECIAL_TYPES = 8,
+      SPECIAL_TYPES = 6,
 
       /// \brief Record code for the extra statistics we gather while
       /// generating an AST file.
-      STATISTICS = 9,
+      STATISTICS = 7,
 
       /// \brief Record code for the array of tentative definitions.
-      TENTATIVE_DEFINITIONS = 10,
+      TENTATIVE_DEFINITIONS = 8,
 
       /// \brief Record code for the array of locally-scoped external
       /// declarations.
-      LOCALLY_SCOPED_EXTERNAL_DECLS = 11,
+      LOCALLY_SCOPED_EXTERNAL_DECLS = 9,
 
       /// \brief Record code for the table of offsets into the
       /// Objective-C method pool.
-      SELECTOR_OFFSETS = 12,
+      SELECTOR_OFFSETS = 10,
 
       /// \brief Record code for the Objective-C method pool,
-      METHOD_POOL = 13,
+      METHOD_POOL = 11,
 
       /// \brief The value of the next __COUNTER__ to dispense.
       /// [PP_COUNTER_VALUE, Val]
-      PP_COUNTER_VALUE = 14,
+      PP_COUNTER_VALUE = 12,
 
       /// \brief Record code for the table of offsets into the block
       /// of source-location information.
-      SOURCE_LOCATION_OFFSETS = 15,
+      SOURCE_LOCATION_OFFSETS = 13,
 
       /// \brief Record code for the set of source location entries
       /// that need to be preloaded by the AST reader.
@@ -332,164 +359,145 @@ namespace clang {
       /// This set contains the source location entry for the
       /// predefines buffer and for any file entries that need to be
       /// preloaded.
-      SOURCE_LOCATION_PRELOADS = 16,
+      SOURCE_LOCATION_PRELOADS = 14,
 
       /// \brief Record code for the stat() cache.
-      STAT_CACHE = 17,
+      STAT_CACHE = 15,
 
       /// \brief Record code for the set of ext_vector type names.
-      EXT_VECTOR_DECLS = 18,
-
-      /// \brief Record code for the original file that was used to
-      /// generate the AST file.
-      ORIGINAL_FILE_NAME = 19,
-
-      /// \brief Record code for the file ID of the original file used to 
-      /// generate the AST file.
-      ORIGINAL_FILE_ID = 20,
-      
-      /// \brief Record code for the version control branch and revision
-      /// information of the compiler used to build this AST file.
-      VERSION_CONTROL_BRANCH_REVISION = 21,
+      EXT_VECTOR_DECLS = 16,
       
       /// \brief Record code for the array of unused file scoped decls.
-      UNUSED_FILESCOPED_DECLS = 22,
+      UNUSED_FILESCOPED_DECLS = 17,
       
       /// \brief Record code for the table of offsets to entries in the
       /// preprocessing record.
-      PPD_ENTITIES_OFFSETS = 23,
+      PPD_ENTITIES_OFFSETS = 18,
 
       /// \brief Record code for the array of VTable uses.
-      VTABLE_USES = 24,
+      VTABLE_USES = 19,
 
       /// \brief Record code for the array of dynamic classes.
-      DYNAMIC_CLASSES = 25,
-
-      /// \brief Record code for the list of other AST files imported by
-      /// this AST file.
-      IMPORTS = 26,
+      DYNAMIC_CLASSES = 20,
 
       /// \brief Record code for referenced selector pool.
-      REFERENCED_SELECTOR_POOL = 27,
+      REFERENCED_SELECTOR_POOL = 21,
 
       /// \brief Record code for an update to the TU's lexically contained
       /// declarations.
-      TU_UPDATE_LEXICAL = 28,
+      TU_UPDATE_LEXICAL = 22,
       
       /// \brief Record code for the array describing the locations (in the
       /// LOCAL_REDECLARATIONS record) of the redeclaration chains, indexed by
       /// the first known ID.
-      LOCAL_REDECLARATIONS_MAP = 29,
+      LOCAL_REDECLARATIONS_MAP = 23,
 
       /// \brief Record code for declarations that Sema keeps references of.
-      SEMA_DECL_REFS = 30,
+      SEMA_DECL_REFS = 24,
 
       /// \brief Record code for weak undeclared identifiers.
-      WEAK_UNDECLARED_IDENTIFIERS = 31,
+      WEAK_UNDECLARED_IDENTIFIERS = 25,
 
       /// \brief Record code for pending implicit instantiations.
-      PENDING_IMPLICIT_INSTANTIATIONS = 32,
+      PENDING_IMPLICIT_INSTANTIATIONS = 26,
 
       /// \brief Record code for a decl replacement block.
       ///
       /// If a declaration is modified after having been deserialized, and then
       /// written to a dependent AST file, its ID and offset must be added to
       /// the replacement block.
-      DECL_REPLACEMENTS = 33,
+      DECL_REPLACEMENTS = 27,
 
       /// \brief Record code for an update to a decl context's lookup table.
       ///
       /// In practice, this should only be used for the TU and namespaces.
-      UPDATE_VISIBLE = 34,
+      UPDATE_VISIBLE = 28,
 
       /// \brief Record for offsets of DECL_UPDATES records for declarations
       /// that were modified after being deserialized and need updates.
-      DECL_UPDATE_OFFSETS = 35,
+      DECL_UPDATE_OFFSETS = 29,
 
       /// \brief Record of updates for a declaration that was modified after
       /// being deserialized.
-      DECL_UPDATES = 36,
+      DECL_UPDATES = 30,
       
       /// \brief Record code for the table of offsets to CXXBaseSpecifier
       /// sets.
-      CXX_BASE_SPECIFIER_OFFSETS = 37,
+      CXX_BASE_SPECIFIER_OFFSETS = 31,
 
       /// \brief Record code for \#pragma diagnostic mappings.
-      DIAG_PRAGMA_MAPPINGS = 38,
+      DIAG_PRAGMA_MAPPINGS = 32,
 
       /// \brief Record code for special CUDA declarations.
-      CUDA_SPECIAL_DECL_REFS = 39,
+      CUDA_SPECIAL_DECL_REFS = 33,
       
       /// \brief Record code for header search information.
-      HEADER_SEARCH_TABLE = 40,
-
-      /// \brief The directory that the PCH was originally created in.
-      ORIGINAL_PCH_DIR = 41,
+      HEADER_SEARCH_TABLE = 34,
 
       /// \brief Record code for floating point \#pragma options.
-      FP_PRAGMA_OPTIONS = 42,
+      FP_PRAGMA_OPTIONS = 35,
 
       /// \brief Record code for enabled OpenCL extensions.
-      OPENCL_EXTENSIONS = 43,
+      OPENCL_EXTENSIONS = 36,
 
       /// \brief The list of delegating constructor declarations.
-      DELEGATING_CTORS = 44,
+      DELEGATING_CTORS = 37,
 
       /// \brief Record code for the table of offsets into the block
       /// of file source-location information.
-      FILE_SOURCE_LOCATION_OFFSETS = 45,
+      FILE_SOURCE_LOCATION_OFFSETS = 38,
       
       /// \brief Record code for the set of known namespaces, which are used
       /// for typo correction.
-      KNOWN_NAMESPACES = 46,
+      KNOWN_NAMESPACES = 39,
 
       /// \brief Record code for the remapping information used to relate
       /// loaded modules to the various offsets and IDs(e.g., source location 
       /// offests, declaration and type IDs) that are used in that module to
       /// refer to other modules.
-      MODULE_OFFSET_MAP = 47,
+      MODULE_OFFSET_MAP = 40,
 
       /// \brief Record code for the source manager line table information,
       /// which stores information about \#line directives.
-      SOURCE_MANAGER_LINE_TABLE = 48,
+      SOURCE_MANAGER_LINE_TABLE = 41,
 
       /// \brief Record code for map of Objective-C class definition IDs to the 
       /// ObjC categories in a module that are attached to that class.
-      OBJC_CATEGORIES_MAP = 49,
+      OBJC_CATEGORIES_MAP = 42,
 
       /// \brief Record code for a file sorted array of DeclIDs in a module.
-      FILE_SORTED_DECLS = 50,
+      FILE_SORTED_DECLS = 43,
       
       /// \brief Record code for an array of all of the (sub)modules that were
       /// imported by the AST file.
-      IMPORTED_MODULES = 51,
+      IMPORTED_MODULES = 44,
       
       /// \brief Record code for the set of merged declarations in an AST file.
-      MERGED_DECLARATIONS = 52,
+      MERGED_DECLARATIONS = 45,
       
       /// \brief Record code for the array of redeclaration chains.
       ///
       /// This array can only be interpreted properly using the local 
       /// redeclarations map.
-      LOCAL_REDECLARATIONS = 53,
+      LOCAL_REDECLARATIONS = 46,
       
       /// \brief Record code for the array of Objective-C categories (including
       /// extensions).
       ///
       /// This array can only be interpreted properly using the Objective-C
       /// categories map.
-      OBJC_CATEGORIES = 54,
+      OBJC_CATEGORIES = 47,
 
       /// \brief Record code for the table of offsets of each macro ID.
       ///
       /// The offset table contains offsets into the blob stored in
       /// the preprocessor block. Each offset points to the corresponding
       /// macro definition.
-      MACRO_OFFSET = 55,
+      MACRO_OFFSET = 48,
 
       /// \brief Record of updates for a macro that was modified after
       /// being deserialized.
-      MACRO_UPDATES = 56
+      MACRO_UPDATES = 49
     };
 
     /// \brief Record types used within a source manager block.