[cfe-dev] Huge slowdown introduced in r91449

[Abramo Bagnara]

Tracking a slowdown observed after a clang update, I've bisected the
problem to commit r91449.

r91448:
$ ~/llvm_opt/Release/bin/clang -w -fsyntax-only gcc.c

real	0m3.683s
user	0m3.354s
sys	0m0.325s

r91449:
$ time ~/llvm_opt/Release/bin/clang -w -fsyntax-only gcc.c

real	0m38.764s
user	0m38.378s
sys	0m0.374s

The very large source file gcc.c (22 MB) is from:

http://people.csail.mit.edu/smcc/projects/single-file-programs/