Messages in this thread | | | Subject | Re: [PATCH 5 of 7] x86/paravirt: add register-saving thunks to reduce caller register pressure | From | Andi Kleen <> | Date | Fri, 06 Feb 2009 08:28:26 +0100 |
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Jeremy Fitzhardinge <jeremy@goop.org> writes:
> One of the problems with inserting a pile of C calls where previously > there were none is that the register pressure is greatly increased. > The C calling convention says that the caller must expect a certain > set of registers may be trashed by the callee, and that the callee can > use those registers without restriction. This includes the function > argument registers, and several others. > > This patch seeks to alleviate this pressure by introducing wrapper > thunks that will do the register saving/restoring, so that the > callsite doesn't need to worry about it, but the callee function can > be conventional compiler-generated code.
I had something like this (but not as generic) for the old pre unification semaphores on x86-64 too. I think it's a generally useful facility for lots of things (in fact I've been asking gcc developers for providing this in a general way for some time).
So I would suggest to move the necessary macros to do that outside paravirt.h into a separate include so that it can be used independently and not call it PV_*.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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