[Bug c++/23608] constant propagation (CCP) would improve -Wsign-compare

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23608

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> ---
(Nit: the location is off by 2 chars, I think I can easily fix this separately:
build_new_op_1 isn't propagating loc to cp_build_binary_op)