[Cbe-oss-dev] [PATCH] force -mno-string option on cell
benh at kernel.crashing.org
Sat Mar 24 06:38:23 EST 2007
On Fri, 2007-03-23 at 13:56 +0100, Segher Boessenkool wrote:
> > GCC may generate inline copy loop to handle memcpy() function
> > instead of kernel defined memcpy() with -mstring or -Os.
> > But this inlined version of memcpy() caused an alignment interrupt
> > when copying from SPU local store on PS3.
> > (http://ozlabs.org/pipermail/cbe-oss-dev/2007-March/001348.html)
> > This patch deletes -mstring option on all powerpc and force -mno-string
> > option on Cell.
> Please split into two patches, the first half (deleting
> -mstring) we can all agree on and "the other half".
> What your patch does is setting -mno-string for all files
> if your kernel is configured to support Cell. It would be
> better to set this option (and all other options needed,
> -mno-multiple and -mno-algebraic come to mind, and that last
> compiler option doesn't even exist yet) unconditionally on
> the few Cell-specific files that are affected, not on the
> whole kernel:
> CFLAGS_whatever.o := -msome-flags
> It would be even better to not lie to the compiler by
> telling it it can use the LS area as normal memory, since
> evidently it cannot :-)
It's fair enough to use -mno-string overall. If the kernel is going to
run on cell, performance will suck with string instructions. In fact,
I'm not sure they are worth having on anything anyway.
More information about the cbe-oss-dev