tree ca3c65a123fff4e56a3b6d2090f716334c63aade
parent 8d52cbdce856d6498a5c454b8e113498e645cc4d
author Douglas Gregor <dgregor@apple.com> 1269035514 +0000
committer Douglas Gregor <dgregor@apple.com> 1269035514 +0000

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