Re: [WIP/RFC] MIPS registers overhaul

[Andrew Cagney <ac131313@redhat.com>]

> 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.

Andrew