Re: [PATCH] Enable DWARF-2 frames on S/390

[Ulrich Weigand <weigand@i1.informatik.uni-erlangen.de>]

Hello Andrew,

> > now that all pieces of the DWARF-2 CFI rework have gone in, and
> > the big s390 backend reorganization was also committed, this patch
> > is the only thing that's missing to enable DWARF-2 frame support
> > on s390.
> > 
> > Do you think a copyright assignment is required for this?  While
> > it's longer than 10 lines, it doesn't really contain anything
> > that should be significant w.r.t. intellectual property -- the
> > s390_dwarf2_frame_init_reg routine only implements the publicly
> > documented s390 ABI calling convention ...
> 
> Can you describe the change with one paragraph of english?

The change consists of installing a dwarf2_frame_set_init_reg
callback that overrides the default register state initializtion
to instead perform the following: set all call-saved registers to 
DWARF2_FRAME_REG_SAME_VALUE, all call-clobbered registers to
DWARF2_FRAME_REG_UNDEFINED, and the virtual PC register to
DWARF2_FRAME_REG_RA.  Which registers count as call-saved vs.
call-clobbered is defined by the Linux for S/390 and Linux for
zSeries ABI documents.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  weigand@informatik.uni-erlangen.de