[Bug lto/82229] GCC7's LTO underperforms compared to GCC6

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82229

--- Comment #14 from Martin Liška <marxin at gcc dot gnu.org> ---
So for GCC 7 the drop is caused by r237791:

SVN revision: 237791
Author: hubicka

        * gcc.dg/predict-12.c: New testcase.

        * predict.c: Include gimple-pretty-print.h
        (predicted_by_loop_heuristics_p): Check also
        PRED_LOOP_EXIT_WITH_RECURSION
        (predict_loops): Find self recursive calls and use special purpose
        predictors for them; dump log about decisions.
        (pass_profile::execute): Dump info about #of iterations.
        * predict.def (PRED_LOOP_EXIT_WITH_RECURSION,
        (PRED_LOOP_GUARD_WITH_RECURSION): New predictors.

and the performance for current trunk is similar to GCC 6.x, starting from
r248334:

Author: hubicka
        * ipa-inline.c (edge_badness): Use inlined_time instead of
        inline_summaries->get.

That said it's sensitive to inlining.