linux-kernel - Re: [PATCH 2/2] powerpc: Switch to generic WARN_ON()/BUG

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Message-ID: <20071012020419.GB19268@fattire.cabal.ca>
Date:	Thu, 11 Oct 2007 22:04:19 -0400
From:	Kyle McMartin <kyle@...artin.ca>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Olof Johansson <olof@...om.net>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, lethal@...ux-sh.org,
	kyle@...isc-linux.org, grundler@...isc-linux.org,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH 2/2] powerpc: Switch to generic WARN_ON()/BUG_ON()

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. ;-)

Cheers,
	Kyle
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