On Fri, Feb 10, 2017 at 09:49:17AM +0530, Nikunj A Dadhania wrote: > David Gibson <da...@gibson.dropbear.id.au> writes: > > > [ Unknown signature status ] > > On Thu, Feb 09, 2017 at 04:04:04PM +0530, Nikunj A Dadhania wrote: > >> POWER ISA 3.0 adds CA32 and OV32 status in 64-bit mode. Add the flags > >> and corresponding defines. Moreover, CA32 is set when CA is set and > >> OV32 is set when OV is set, there is no need to have a new > >> fields in the CPUPPCState structure. > >> > >> Signed-off-by: Nikunj A Dadhania <nik...@linux.vnet.ibm.com> > > > > Um.. I don't quite understand this. If CA always has the same value > > as CA32, what's the point? > > I am not clear either. I think that as CA was set for both 32/64-bit > mode, that couldn't be changed for backward compatibility. CA32 should > have affected only the instructions working one word variants. > > Re-scanning the ISA 3.0, found this in 3.3.9 Fixed-Point Arithmetic > Instructions: > > ================================================================= > addic, addic., subfic, addc, subfc, adde, subfe, > addme, subfme, addze, and subfze always set CA, to > reflect the carry out of bit 0 in 64-bit mode and out of bit > 32 in 32-bit mode. These instructions also always set > CA32 to reflect the carry out of bit 32. > ================================================================= > > Which is conflicting to what is said in 3.2.2 Fixed-Point Exception > Register: > ================================================================= > Carry32 (CA32) > CA32 is set whenever CA is set, and is set to > the same value that CA is defined to be set to > in 32-bit mode. > =================================================================
Well, that's certainly confusing.
Can you try and find out what's going on here within IBM, and repost
these patches once there's a straight story about how this bit works.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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