[Bug middle-end/90283] 519.lbm_r is 7%-10% slower with -Ofast -march=native and both LTO and PGO than with GCC 8

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90283

--- Comment #5 from Martin Jambor <jamborm at gcc dot gnu.org> ---
The numbers from this year are:

- on Intel Cascade Lake server CPU the regression disappeared, if
  there ever was one, I don't have Skylake numbers this year.

- On AMD Zen1 CPU, the measured regression is 20% compared to GCC 8
  (15% compared to GCC 9) but that most likely means we hit the known
  code-placement problem again.

- On AMD Zen2 CPU, there is actually 6.8% regression compared to GCC
  8 (and only negligible one compared to GCC 9).  It may or may not be
  the same problem we were looking at last year.  In any event,
  probably not very pressing, given the behavior of the benchmark :-/