[Bug target/85216] Performance issue with PHP on ppc64 systems

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85216

--- Comment #15 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
PHP's reliance on frequent indirect branches makes it essentially the worst
case for this sort of thing.  When Spectre v2 CVE mitigations are in place for
user code, you will see performance issues on all architectures that rely on
speculation for indirect branch performance.  When user code is running in an
"unsafe" configuration, you will not see those issues.  (We have seen similar
issues on x86 when retpoline is used for user code.)