Re: [PATCH 2/2] powerpc: Switch to generic WARN_ON()/BUG_ON()

Olof Johansson
2007-10-12T02:36:25Z

On Thu, Oct 11, 2007 at 10:04:19PM -0400, Kyle McMartin wrote:
> On Fri, Oct 12, 2007 at 11:23:39AM +1000, Paul Mackerras wrote:
> > Olof Johansson writes:
> >
> > > Not using the ppc-specific WARN_ON/BUG_ON constructs actually saves about
> > > 4K text on a ppc64_defconfig. The main reason seems to be that prepping
> > > the arguments to the conditional trap instructions is more work than
> > > just doing a compare and branch.
> >
> > It might be more instructions but it takes fewer cycles, I would
> > expect. Do you have the actual instruction sequences to compare?
> >
>
> I really hope WARN_ON/BUG_ON aren't hotpaths on powerpc. ;-)

Not the taken branch of them, no. :) But making it past them as fast
as possible when they're not tripping is always good.

-Olof