RFA: ia64 patch required after recent osabi changes

[J. Johnston]

The latest changes by Mark K. have caused regressions in the ia64 signal handler 
back-tracing.  What happens is that the ia64_gdbarch_init function is called 
without a bfd to calculate the os_ident field.  The os_ident field is later used 
to set up the gdbarch_tdep structure which contains the sigcontext register 
address function address.  We end up with an os_ident of -1 and don't set up the 
sigcontext register address function pointing to the ia64-linux-tdep.c function. 
  This kills backtracing across signal handlers because we can't figure out the 
previous ip value without fishing it out of the sigcontext area.

After discussing this with Andrew, it appears the ia64 code is a bit old.  The 
info.osabi field is set properly so we don't have to calculate the os_ident. 
This patch removes the gdbarch_tdep os_ident field and uses instead the 
info.osabi field in ia64_gdbarch_init.  It also copies code from i386 which 
looks for a gdbarch candidate.  This code is much more efficient than the old code.

With this patch, the ia64 signal backtracing works again and there are no 
regressions in the testsuite.

Ok to commit?

-- Jeff J.

2003-11-04  Jeff Johnston  <jjohnstn@redhat.com>

	* ia64-tdep.c (struct gdbarch_tdep): Remove os_ident field.
	(ia64_gdbarch_init): Don't bother calculating the os.  Instead use the 
gdbarch_info struct and look at the osabi field.  Also use           		 
gdbarch_list_lookup_by_info() to look for a candidate gdbarch.
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