I think the l.movhi should be added back as "(e.g., l.movhi r0, 0)". Otherwise someone might try to use a some other, not safe way of setting r0 to 0.
---Matthew Hicks On Sat, Apr 21, 2012 at 10:13 AM, Julius Baxter <[email protected]> wrote: > On Sat, Apr 21, 2012 at 4:05 PM, R. Diez <[email protected]> wrote: >> >> >>> I've posted my proposed change to the architecture spec on the wiki: >>> http://opencores.org/or1k/Architecture_Specification#GPR0_usage.2C_implementation >> >> The change you've proposed in the Wiki makes the specification incompatible >> with any implementation that actually hard-wires R0 to 0, which is allowed >> according to the original spec, because the software is free to use the >> OpenRISC CPU but not the C ABI. I don't think the spec should force the >> l.movhi instruction either, the software should be free to use whatever >> means it wants to clear R0. >> >> I would mention in the new spec that an implementation may have hard-wired >> R0 to 0, and that writing 0 to R0 should not raise an exception on those >> implementations. > > Fair enough. Proposal has been updated. > > Thanks > > Julius > _______________________________________________ > OpenRISC mailing list > [email protected] > http://lists.openrisc.net/listinfo/openrisc _______________________________________________ OpenRISC mailing list [email protected] http://lists.openrisc.net/listinfo/openrisc
