[Bug tree-optimization/85964] [8/9 Regression] Compile time hog w/ -O3 -ftracer -fno-guess-branch-probability

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85964

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
For the FSM part since we walk the whole function for _each_ control stmt name
this analysis part, find_jump_threads_backwards (basic_block bb, bool speed_p),
is quadratic in the number of BBs.

There's limiting via PARAM_FSM_MAXIMUM_PHI_ARGUMENTS but I guess it should
instead limit itself on the maximum length of a jump threading path and
do that already during analysis rather than only later throwing away
non-profitable ones.