[cfe-dev] Big slowdown introduced in r92348

Douglas Gregor dgregor at apple.com
Mon Jan 11 11:24:40 CST 2010


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...


The parser ends up calling into this code to find template names...  
but it shouldn't ever do that for C. I'll look into it; thanks for  
tracking down this performance regression!

	- Doug


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