[Bug rtl-optimization/89275] [9 Regression] Slowdown in mcperf on POWER

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89275

--- Comment #3 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
I just heard back from the performance lead.  He indicates that they can
reproduce the numbers from 9.0 trunk (compiled Feb 8, versus Feb 3 as reported
by Phoronix), but the numbers from 8.2 as tagged do not reproduce.  GCC 9
degrades a little on Add, but is in the noise range for Set/Append.

If we accept this (and I see no reason not to at the moment), we still have the
question of why GCC lags LLVM on this benchmark for *both* 8 and 9.  So we will
continue to work on root-cause analysis.