unwinding fallback for mips-irix6 n32

[Olivier Hainque]

Hi Rainer,

Rainer Orth wrote:
> I've finally gotten around to this.  Apart from some comment and code
> cleanups along the lines of the sol2-unwind.h files, I had to minimally
> adapt the N32 multithreaded code sequence for IRIX 6.5.30 that I'm
> running here.  While I was at it, I added N64 support which proved to be
> almost trivial.  You'll probably have to adapt this for the version of
> IRIX 6.5 you're running, or we could simply skip the single varying
> insn.
 
 Either way is fine with me. There's a micro stronger confidence
 in exact matches, but this could lead to spurious propagation failures
 on other variants of the OS where a third version of that insn
 could show up while still part of a valid context.

> With this patch, a couple of gnat.dg tests are fixed:

 Nice :)

> 64-bit stack_check2.adb remains broken, though.  It SEGVs in memcpy, but
> the stack is corrupted, so I cannot say yet what's going on.
> 
> I'll run a full bootstrap over the weekend.  It seems that the remaining
> libjava failures are unrelated.

 OK ...
 
> I may backport this to the 4.6 branch after some time (trivial apart
> from the gcc -> libgcc move).  I will only try 4.5 if I manage to add
> O32 support.  This might be a non-trivial excercise since the libc
> implementation is quite different.

 Understood;

> Thanks for providing the patch.  

 My pleasure. Thanks a lot for your work over it and feedback, much
 appreciated.

 Cheers,

 Olivier