Re: GDB on SGI Irix 6.5

["Eli Zaretskii" <eliz@is.elta.co.il>]

> Date: Wed, 18 Apr 2001 19:31:42 +0300 (IDT)
> From: Eli Zaretskii <eliz@is.elta.co.il>
> 
> On Tue, 17 Apr 2001, Andrew Cagney wrote:
> 
> > Hmm, I've this sinking feeling that, prior to me adding the assert() it
> > was falling off the end of the regcache and just blatting memory :-/
> > 
> > 72, I've this feeling that it is the ``FP'':
> > 
> > ac131313@localhost$ grep 72 config/mips/tm-*
> > config/mips/tm-mips.h:#define FP_REGNUM 72              /* Pseudo
> > register that contains true address of executing stack frame */
> > 
> > As a quick hack, pump up NUM_PSEUDO_REGS to make space for this (and
> > possibly a few more).
> 
> Thanks for the hint.
> 
> However, this doesn't work: it again bumps into internal_error because 
> there's no gdbarch method for fetching pseudo registers.  How would such 
> a method look for a target that doesn't have a frame pointer?
> 
> Also, strangely enough, tm-irix3.h does define a place for FP in the 
> registers array (at index 30).  So why doesn't it define FP_REGNUM 
> accordingly?

I think I've got it: tm-irix3.h is simply wrong for either Irix 6.5 or
the N32 ABI and the MIPS CPUs that support it (or both).  Not only
should FP_REGNUM be set to 30, but the enumeration and the total
number of registers defined on tm-irix3.h is incorrect for the SGI
machine I have here.

tm-mips.h, which defines FP_REGNUM to 72, is also wrong for Irix, at
least for Irix 6.5 with N32 executables.  I have no idea how could
this possibly work for anyone in the past.

I have a provisional patch which seems to DTRT for me.  But to clean
it up (so that I can submit it without blushing ;-), I need help in
making several decisions, since I have no prior experience with, or
knowledge about, the different CPUs and ABIs supported by SGI Irix.

Questions:

  - Should I make the change in tm-irix5.h, or should I leave it alone
    and create irix6x.h?  The issue here is that perhaps Irix 5 did
    work like tm-irix5.h says, and I won't want to break that.

  - What should I do about the different ABIs?  At least 3 come to
    mind: O32, N32, and N64.  They have subtly different layouts of
    registers, so if I need to set things up for more than a single
    ABI, I'll need to know what's the current say-so about how this
    should be done (e.g., does gdbarch has some functionality for
    dynamically computing the registers array?).

Thanks in advance for any help.