On Fri, Oct 05, 2012 at 10:00:25AM +0100, Russell King - ARM Linux wrote:

On Mon, Oct 01, 2012 at 01:53:26PM +0100, Dave Martin wrote:

quoted

A good starting point would be load/store emulation as this seems to be a
common theme, and we would need a credible deployment for any new
framework so that we know it's fit for purpose.

Probably not actually, that code is written to be fast, because things
like IP stack throughput depend on it - particularly when your network
card can only DMA packets to 32-bit aligned addresses (resulting in
virtually all network data being misaligned.)

A fair point, but surely it would still be worth a try?
 
We might decide that a few particular cases of instruction decode
should not use the generic framework for performance reaons, but in
most cases being critically dependent on fault-driven software
emulation for performance would be a serious mistake in the first place
(discussions about the network code notwithstanding).

This is not an argument for being slower just for the sake of it, but
it can make sense to factor code on paths where performance is not an
issue.

Cheers
---Dave