[PATCH-WIP 01/13] xen/arm: use r12 to pass the hypercall number to the hypervisor
nicolas.pitre at linaro.org
Fri Mar 9 16:20:20 UTC 2012
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.
> 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
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