https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85740
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Target| |x86_64-*-*, i?86-*-*
Status|UNCONFIRMED |NEW
Last reconfirmed| |2018-05-11
CC| |hubicka at gcc dot gnu.org,
| |marxin at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed with a Haswell CPU as well. Without the __builtin_expect we
rightfully predict the branch to be 50%/50% which means BB re-ordering will do
either nothing to pre-existing order or apply some other magic. CFG
construction makes the
flow exactly as visible in the source.
So not sure what you are asking here, but annotating the libgfortran routines
or inline expansion from the FE with __builtin_expect is probably a good idea.
At least I can't really see how to easily derive a new predictor that would
match
this case...
