[PATCH] Handle mtsprg and mfsprg properly for BookE

Kumar Gala kumar.gala@freescale.com
Wed Mar 9 22:30:00 GMT 2005


On Mar 8, 2005, at 8:11 PM, Alan Modra wrote:

> On Tue, Mar 08, 2005 at 08:20:21PM -0500, Jeff Baker wrote:
>  > Would it be correct to change the generic PPC_OPCODE_BOOKE case to
> > always use user mode sprg2+ and then override it to be sprg3+ for
> > PPC_OPCODE_403 and PPC_OPCODE_440?  Should there be a version of 
> mtsprg3
> > for e500 and MPC8560 that encodes 259 instead of 275?
>
> That's what _you_ need to research.  If you can decide on the correct
>  mapping of sprg number to spr number for a given processor, and defend
>  your mapping against potential criticism, I'm more than happy to help
>  correct an implementation.
>
> Hmm, looking over your patch again, I suppose you could simply say that
>  your mapping of sprg number to spr number matches the existing gas
>  opcodes.  ie.  "mfsprg 0,4" generates the same as "mfsprg4 0" and so 
> on.
>  Enumerate all the possibilities in an addition to the testsuite, and
>  you've made that obvious.  If you fix the formatting, correct the 
> error
>  messages, and extend the testsuite this way I'll accept the patch.  
> I'll
>  also still be worried that gas isn't generating the right opcodes, but
>  I suppose that's another issue..

I'm confused what the correctness concern is.  The only subject that is 
up in the air is if SPRG3 (SPR #259) should allow read access on some 
book-e implementations.  It would seem allowing this is more broad and 
leaves the decision up to the user.

- kumar


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