[Bug rtl-optimization/68920] [6 Regression] Undesirable if-conversion for a rarely taken branch

[ysrumyan at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68920

--- Comment #4 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
You are quite right - the cost model is very poor. We did simple experiment and
set up the branch cost to 1 but noticed performance regressions on other
benchmarks. when we set it to 2 we did not see any difference  since likely
branch deletion is preferred for equal costs. Is there any tuned option in
if-converter to revert this decision? Secondly, we must enhance cost model by
adding cost of conditional move for all targets but this is for GCC 7.