[PATCH] D20401: [Lexer] Don't merge macro args from different macro files

[Argyrios Kyrtzidis via cfe-commits]

Could you also check performance of creating a PCH file out of Cocoa.h ?

> On May 19, 2016, at 1:47 PM, Vedant Kumar <vsk at apple.com> wrote:
> 
> vsk added a comment.
> 
> I discussed this bug with Argyrios off-list, who lgtm'd on the condition that it doesn't introduce a performance regression. He suggested preprocessing Cocoa.h to stress the patch. After running a stabilization script, I used this command to stress RelNoAsserts builds of clang both with and without this patch.
> 
>  for I in $(seq 1 100); do time $CC -F /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/System/Library/Frameworks -E Cocoa.h -o /dev/null; done
> 
> The results are basically in the noise (link to raw data: https://ghostbin.com/paste/r6cyh):
> 
> | Compiler           | **Unpatched** TOT | **Patched** TOT |
> | Avg. wall time (s) | 0.21709           | 0.21608         |
> | Std. deviation     | 0.02101           | 0.02219         |
> 
> I also made sure that the preprocessed sources emitted by the two compilers are the same.
> 
> 
> http://reviews.llvm.org/D20401
> 
> 
>