On 09/03/12 16:20, Nicolas Pitre wrote: > On Fri, 9 Mar 2012, Dave Martin wrote: > >> Register variables feel like a red herring though. We're only using >> those because we can't do the needful thing and actually desscribe >> these constraints in the asm constraints (which would seem to be the >> right place). We specifically don't care where those values are >> except at the boundaries of the asm block itself. > > Absolutely. > >> Is there a reason why ARM gcc doesn't provide the ability to specify >> such exact-register constraints, or is this more for historical >> reasons? It is possible? > > I don't know how much things have changed since I last looked at the gcc > code, but implementing this seemed to be pretty trivial at the time. > The problem would be to determine a good letter scheme to map to actual > registers. > > > Nicolas > While it is technically possible, it is likely to end up hurting overall compiler performance as we'll then have to define the machine as having small register classes. -- Richard Earnshaw Email: Richard.Earnshaw@xxxxxxx Engineering Manager Phone: +44 1223 400569 (Direct + VoiceMail) OpenSource Tools Switchboard: +44 1223 400400 ARM Ltd Fax: +44 1223 400410 110 Fulbourn Rd Web: http://www.arm.com/ Cambridge, UK. CB1 9NJ -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
