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

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:

quoted

Olof Johansson writes:

quoted

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