[Bug target/87565] suboptimal memory-indirect tailcalls on arm

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87565

Andrew Pinski  changed:

   What|Removed |Added

   Severity|normal  |enhancement

[Bug target/87565] suboptimal memory-indirect tailcalls on arm

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87565

--- Comment #1 from Richard Earnshaw  ---
Not a good idea.  Modern CPUs often don't predict such operations correctly

[Bug target/87565] suboptimal memory-indirect tailcalls on arm

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87565

--- Comment #2 from Alexander Monakov  ---
PLT trampolines all end with 'ldr pc, [ip, xxx]!', so do all calls via PLT
suffer from poor branch prediction of such indirect jumps?

[Bug target/87565] suboptimal memory-indirect tailcalls on arm

[ramana at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87565

Ramana Radhakrishnan  changed:

   What|Removed |Added

 CC||ramana at gcc dot gnu.org

--- Comment #3 from Ramana Radhakrishnan  ---
(In reply to Alexander Monakov from comment #2)
> PLT trampolines all end with 'ldr pc, [ip, xxx]!', so do all calls via PLT
> suffer from poor branch prediction of such indirect jumps?

IIRC you still need to use that in the PLT trampoline for folks to use Linux
like userland on strongarm which has a small user constituency still.