Date: Wed, 8 Jul 2009 09:34:42 -0400 From: Justin Hibbits <jrh29@alumni.cwru.edu> To: Peter Grehan <grehan@freebsd.org> Cc: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: FreeBSD/ppc ABI Message-ID: <fd9cd3450907080634g4101ead1ic2bf5694d44e7772@mail.gmail.com> In-Reply-To: <4A538B64.2080506@freebsd.org> References: <fd9cd3450907070641l45223e72p5f7147b97fc5755f@mail.gmail.com> <A07805D6-CAD5-4721-86AC-DE1751831D3C@semihalf.com> <fd9cd3450907071007l5501ea85y81bcb1ee8f4b8bdc@mail.gmail.com> <4A538B64.2080506@freebsd.org>
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On Tue, Jul 7, 2009 at 1:52 PM, Peter Grehan<grehan@freebsd.org> wrote: > Hi Justin, > >> The trick is only needed in user space, as a shim between two >> functions, so I just need any volatile registers that I can use but >> aren't function arguments. =A0The target is G4/G5. =A0I only need 3 or 4 >> volatile registers, but the more the better. > > =A0You'll probably have to use the stack to spill the param register. Hav= e =A0a > look at the MCOUNT macro in ppc's <machine/profile.h> for an example of c= ode > that is an intercept between two routines and has to assume that all para= m > registers are used > > (http://svn.freebsd.org/viewvc/base/head/sys/powerpc/include/profile.h?vi= ew=3Dmarkup&pathrev=3D153813 > is the version that has the code fragment commented). > > later, > > Peter. > Thanks Peter, and Rafal, I think this is just what I need. I can use the 3 volatile registers, and save the parameter registers when I need to call library functions. I'm doing this largely in assembly for performance reasons, but knowing how mcount does it will help for the uncommon case branches. - Justin
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