Re: [WIP/RFC] MIPS registers overhaul

Kevin Buettner
2003-05-21T19:45:12Z

On May 21, 3:15pm, Andrew Cagney wrote:

> > On May 21, 12:58pm, Daniel Jacobowitz wrote:
> >
> >> > From GDB's view point, the ISA is 64 bit.
> >> >
> >> > The fact that a specific remote debug agent choses to use 32 bit
> >> > registers is a limitation of that debug agent / kernel. An embedded
> >> > target, and I'm pretty sure IRIX 6.5, for instance, don't do that.
> >
> >>
> >> No, from GDB's view point in this situation, the target ISA is _NOT_ 64
> >> bit. Nothing 64-bit is available, either to the inferior or to the
> >> debugger. Period.
> >>
> >> I would be a little surprised if IRIX didn't work that way too, but I
> >> don't have access to IRIX to poke around.
> >
> >
> > I too would be surprised. I should think that SGI would want to
> > ensure that legacy programs (i.e, those using the o32 ABI) behave the
> > same when run on 64-bit hardware as they do when run on 32-bit
> > hardware. One of the implications of this is that illegal
> > instructions in the 32-bit ISA should continue to be illegal when run
> > on the 64-bit hardware.
>
> Er, it's the same deal as for SPARC. If GDB is built against the 64 bit
> debug interface, it can debug both 32 and 64 bit applications. This is
> the debuggers view, not the program being run's view.

Well, sure. But for such applications, you don't lose anything by
permitting GDB to view it as a 32-bit application only. I.e, there's
nothing that the application is going to do for which there will be a
benefit to have a 64-bit view of it from the outside.

Kevin