git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246646 91177308-0d34-0410-b5e6-96231b3b80d8

r246546, with a workaround for an MSVC 2013 miscompile and an MSVC 2015
rejects-valid.

Original commit message:

[modules] Rework serialized DeclContext lookup table management. Instead of
walking the loaded ModuleFiles looking for lookup tables for the context, store
them all in one place, and merge them together if we find we have too many
(currently, more than 4). If we do merge, include the merged form in our
serialized lookup table, so that downstream readers never need to look at our
imports' tables.

This gives a huge performance improvement to builds with very large numbers of
modules (in some cases, more than a 2x speedup was observed).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246582 91177308-0d34-0410-b5e6-96231b3b80d8

Reverting r246497 (which requires also reverting r246524 and r246521 to avoid merge conflicts). It broke the build on MSVC 2015. It also broke an MSVC 2013 bot with testing issues.

llvm\tools\clang\lib\serialization\MultiOnDiskHashTable.h(117):
error C2065: 'Files': undeclared identifier

http://bb.pgr.jp/builders/ninja-clang-i686-msc18-R/builds/2917

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246546 91177308-0d34-0410-b5e6-96231b3b80d8

predictable diagnostic experience. The hash-of-DeclID order we were using
before gave different results on Win32 due to a different predefined
declaration of __builtin_va_list.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246521 91177308-0d34-0410-b5e6-96231b3b80d8

walking the loaded ModuleFiles looking for lookup tables for the context, store
them all in one place, and merge them together if we find we have too many
(currently, more than 4). If we do merge, include the merged form in our
serialized lookup table, so that downstream readers never need to look at our
imports' tables.

This gives a huge performance improvement to builds with very large numbers of
modules (in some cases, more than a 2x speedup was observed).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246497 91177308-0d34-0410-b5e6-96231b3b80d8