Re: [PATCH, rs6000, libitm] Enable Hardware Transactional Memory (HTM) support on Power

[Peter Bergner <bergner at vnet dot ibm dot com>]

On Mon, 2013-07-15 at 21:13 +0200, Jakub Jelinek wrote:
> > Looking at the patch, you've changed FIRST_PSEUDO_REGISTER (internal gcc
> > thing, so fine), but that also changed DWARF_FRAME_REGISTER which was
> > computed based on FIRST_PSEUDO_REGISTER.  Isn't that an ABI break in the
> > unwinder (think about having parts of unwinder linked from different
> > versions of libgcc)?
> > Can't we just tweak DWARF_FRAME_REGISTER not to include those registers?

Thanks for noticing this.


> I'd say something like (but, untested and can't test it right now (and no
> access to power8 anyway)):

Do we also need to update DWARF_REG_TO_UNWIND_COLUMN similarly, which
also uses FIRST_PSEUDO_REGISTER when the dwarf reg is an SPE synthetic
register?  Or should we just break the dependence on FIRST_PSEUDO_REGISTER
altogether so this type of thing doesn't happen again?  Otherwise, we
should place a comment at the definition of FIRST_PSEUDO_REGISTER
warning of it's use in DWARF_FRAME_REGISTER.

Peter