[PATCH] D49729: [AST][1/4] Move the bit-fields from TagDecl, EnumDecl and RecordDecl into DeclContext

[Bruno Ricci via Phabricator via cfe-commits]

bricci created this revision.
bricci added a project: clang.
Herald added a subscriber: cfe-commits.

DeclContext has a little less than 8 bytes free due to the alignment
requirements on 64 bits archs. This set of patches moves the
bit-fields from classes deriving from DeclContext into DeclContext.

On 32 bits archs this increases the size of DeclContext by 4 bytes
but this is balanced by an equal or larger reduction in the size
of the classes deriving from it.

On 64 bits archs the size of DeclContext stays the same but
all the classes deriving from it shrink by 8/16 bytes.
(-print-stats diff here https://reviews.llvm.org/D49728)
When doing an -fsyntax-only on all of Boost this result
in a 3.6% reduction in the size of all Decls and
a 1% reduction in the run time due to the lower cache
miss rate.

This first patch introduces the anonymous union in DeclContext
and all the *DeclBitfields classes holding the bit-fields, and moves
the bits from TagDecl, EnumDecl and RecordDecl into DeclContext.


Repository:
  rC Clang

https://reviews.llvm.org/D49729

Files:
  include/clang/AST/Decl.h
  include/clang/AST/DeclBase.h
  lib/AST/Decl.cpp
  lib/AST/DeclBase.cpp
  lib/AST/DeclCXX.cpp
  lib/AST/DeclTemplate.cpp
  lib/Serialization/ASTReaderDecl.cpp
  lib/Serialization/ASTWriter.cpp
  lib/Serialization/ASTWriterDecl.cpp

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