https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85216
--- Comment #10 from Timothy Pearson <tpearson at raptorengineering dot com> --- (In reply to Bill Schmidt from comment #9) > You mentioned you're on a POWER9 machine. It could be that you have > firmware with Spectre mitigations applied, which will affect all indirect > branches. It may be that you do not have Spectre mitigations applied on > your x86 machine, in which case the comparison would be expected to be quite > different. Depending on firmware levels, the mitigations may be able to be > switched off, so you should check into that first. PHP is known to be > sensitive to indirect branch performance. > > The Power landing page for these mitigations is > https://www.ibm.com/blogs/psirt/potential-impact-processors-power-family/. > From here you should be able to get to further information for your specific > hardware and OS version. It's even slow compared to P8 with mitigations applied. Do you have a link to the hostboot commit that may have enabled the P9 mitigation, or to the register name (SCOM) that was modified to enable the mitigation?
