Reapply 201734 but with appropriate gcc compatibility
Because GCC incorrectly defines _mm_prefetch to take anything that casts 
to void*, people have started using that behavior.  The previous patch 
that made _mm_prefetch actually take a const char * broke compatibility 
with existing code.  This update to the patch leaves the macro that 
defines _mm_prefetch with the (void*) cast when _MSC_VER is not defined.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201901 91177308-0d34-0410-b5e6-96231b3b80d8
Add a VFSFromYAML class and a parser to create it

Provides a way to create a virtual file system using a YAML file that
supports mapping a file to a path on an 'external' file system. The
external file system will typically be the 'real' file system, but for
testing it can be changed.

A future patch will add a clang option to allow the user to specify such
a file and overlay it, but for now this code is only exercised by the
unit tests.

Differential Revision: http://llvm-reviews.chandlerc.com/D2835

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201905 91177308-0d34-0410-b5e6-96231b3b80d8
Complete Rewrite of CGRecordLayoutBuilder

CGRecordLayoutBuilder was aging, complex, multi-pass, and shows signs of 
existing before ASTRecordLayoutBuilder.  It redundantly performed many 
layout operations that are now performed by ASTRecordLayoutBuilder and 
asserted that the results were the same.  With the addition of support 
for the MS-ABI, such as placement of vbptrs, vtordisps, different 
bitfield layout and a variety of other features, CGRecordLayoutBuilder 
was growing unwieldy in its redundancy.

This patch re-architects CGRecordLayoutBuilder to not perform any 
redundant layout but rather, as directly as possible, lower an 
ASTRecordLayout to an llvm::type.  The new architecture is significantly 
smaller and simpler than the CGRecordLayoutBuilder and contains fewer 
ABI-specific code paths.  It's also one pass.

The architecture of the new system is described in the comments. For the 
most part, the new system simply takes all of the fields and bases from 
an ASTRecordLayout, sorts them, inserts padding and dumps a record. 
Bitfields, unions and primary virtual bases make this process a bit more 
complicated.  See the inline comments.

In addition, this patch updates a few lit tests due to the fact that the 
new system computes more accurate llvm types than CGRecordLayoutBuilder. 
Each change is commented individually in the review.

Differential Revision: http://llvm-reviews.chandlerc.com/D2795



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201907 91177308-0d34-0410-b5e6-96231b3b80d8