[cfe-dev] Big slowdown introduced in r92348

[Douglas Gregor]

http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20100111/026231.html

On Jan 11, 2010, at 9:16 AM, Abramo Bagnara wrote:

>
> Using as usual the big gcc.c source from
>
> http://people.csail.mit.edu/smcc/projects/single-file-programs/
>
> $ time ~/llvm_opt/Release/bin/clang -w -fsyntax-only gcc.c
>
> real	0m3.792s
> user	0m3.472s
> sys	0m0.319s
> $ time ~/llvm_opt/Release/bin/clang -w -fsyntax-only gcc.c
>
> real	0m13.384s
> user	0m13.046s
> sys	0m0.335s
>
> Using bisection I've found the culprit in commit r92348.
>
> Why a modify to Sema::LookupTemplateName could impact a non C++  
> program
> is beyond my comprehension, but perhaps the name of function is
> misleading I don't know...

This should be fixed in r93207, here:

	http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20100111/026231.html

I can't check your particular example on my system (since I don't have  
all of the headers that gcc.c relies on), but the change improved  
performance on Cocoa.h. Actually, since this change eliminates a bunch  
of extra name lookup, r93207 may even be faster than r92347 was.

	- Doug