Re: support for different sized FPU registers

Re: support for different sized FPU registers

[Peter Barada]

I'm trying to add GDB remote support for the ColdFire v4e, and I'm
running into problems with the FPU register definitions.

On the ColdFire v4e, the FPU registers are 64 bit, but the gdb is
expecting 96 bit register values from a 68881.  As a result I'm
getting some 'Remote reply is too short' messages from gdb when the
stub responds to a 'g' packet and on the host the register contents
are all wrong(from 'info reg').

What's the best way of telling gdb(for the coldfire portion of a
m68k-elf configured build) that the FPU registers are only 64 bits
instead of 96)?  I still want this configuration to support 040s and
060s which have the 96 bit FPU registers as well as a ColdFire's 64
bit FPU registers...

Any suggestions are appreciated.

-- 
Peter Barada                                   Peter.Barada@motorola.com
Wizard                                         781-852-2768 (direct)
WaveMark Solutions(wholly owned by Motorola)   781-270-0193 (fax)

Re: support for different sized FPU registers

[Andrew Cagney]

> I'm trying to add GDB remote support for the ColdFire v4e, and I'm
> running into problems with the FPU register definitions.
> 
> On the ColdFire v4e, the FPU registers are 64 bit, but the gdb is
> expecting 96 bit register values from a 68881.  As a result I'm
> getting some 'Remote reply is too short' messages from gdb when the
> stub responds to a 'g' packet and on the host the register contents
> are all wrong(from 'info reg').
> 
> What's the best way of telling gdb(for the coldfire portion of a
> m68k-elf configured build) that the FPU registers are only 64 bits
> instead of 96)?  I still want this configuration to support 040s and
> 060s which have the 96 bit FPU registers as well as a ColdFire's 64
> bit FPU registers...

The most immediate thing that is needed is for the m68k family to be 
up-dated to the new multi-arch framework.  Once that is done, handling 
both a coldfire and an m68k is fairly mechanical.  Check other targets 
such as PPC, xstormy16, mn10300 et.al. for examples.

Do you have an FSF assignment in place?

Andrew

Re: support for different sized FPU registers

[Peter Barada]

>The most immediate thing that is needed is for the m68k family to be 
>up-dated to the new multi-arch framework.  Once that is done, handling 
>both a coldfire and an m68k is fairly mechanical.  Check other targets 
>such as PPC, xstormy16, mn10300 et.al. for examples.

I've hacked together a 'set m68kfpu' command to switch the fpu length,
and that seems to work for me.

Is there a document anywhere that has a 'recipe' for converting a old
back-end into a new and improved multi-arched framework?

>Do you have an FSF assignment in place?

I'm working on convincing the lawyers that the FSF assignment is a
good thing(tm).... 

-- 
Peter Barada                                   Peter.Barada@motorola.com
Wizard                                         781-852-2768 (direct)
WaveMark Solutions(wholly owned by Motorola)   781-270-0193 (fax)