------- Comment #4 from law at redhat dot com 2010-03-22 19:49 -------
FWIW, I seem to get considerably worse code from mainline than you -- for -O3
-ffast-math -mcpu=power7 -mvsx -maltivec I get 140 stfs and 192 lfs insns
(compared to 117 & 139 respectively that you reported).
Just for fun, I ran the same code through the a ppc compiler with the LRS code
from reload-v2 and get 133:178 stfs/lsf insns, so that code clearly is helping,
but it's not enough to offset the badness shown by IRA.
I couldn't reconcile how -fno-ira-share-spill-slots would be changing the
number of load/store insns, so I poked at that a bit.
-fno-ira-share-spill-slots twiddles whether or not a pseudo which gets assigned
a hard reg is put into live_throughout or dead_or_set_p in the reload chain
structures, which in turn changes what pseudos get reassigned hard regs during
reload. This is a somewhat odd effect and should be investigated further.
--
law at redhat dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Powerpc generates worse code|Powerpc generates worse code
|for -mvsx on gromacs even |for -mvsx on gromacs even
|though there are no VSX |though there are no VSX
|instructions used |instructions used
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43413
