[llvm] r192118 - Formally added an explicit enum for DWARF TLS support. No functionality change.

[dblaikie at gmail.com]

On Tue Jan 07 2014 at 3:25:31 PM, Adrian Prantl <aprantl at apple.com> wrote:

>
> On Jan 7, 2014, at 15:23, Eric Christopher <echristo at gmail.com> wrote:
>
> > On Tue, Jan 7, 2014 at 3:09 PM, Adrian Prantl <aprantl at apple.com> wrote:
> >> Hi Richard,
> >>
> >> [Apologies for replying to age-old commits]
> >
> > Heh. I've got 1 from June or something I still need to look at :)
> >
> >> I’m wondering why we are using the custom DW_OP_GNU_push_tls_address
> when there is a DW_OP_form_tls_address since DWARF 3. Are there historical
> or technical reasons why we do this? Could we change it to use the DWARF
> version?
> >>
> >
> > We can. My guess is that there are pre-dwarf3 readers that understand
> > the OP_GNU one and not the other, but I'm not very sympathetic. Could
> > just pick it as < dwarf3 use the OP_GNU one, otherwise use the
> > standard one.
>
> So the two are functionally equivalent?
>
> I’m inclined to implement a patch that switches to the DWARF version for
> >=3 then. Would that break gdb on your end?


Given that I implemented this functionality, I can probably speak with some
authority... - I just implemented this based on what GCC does, and the fact
that that passes the GDB 7.5 test suite. I didn't consult the DWARF
standard, nor specifically justify implementing it this way for backwards
compatibility.

So, yeah, I'm happy for myself or anyone else to try doing this the
standard-supported way, see if it passes the GDB 7.5 test suite/bot, and if
it does, move on. If anyone else has any particular need for backcompat,
they can speak up when things break. But given that no one noticed except
me when running the GDB 7.5 suite... I'm not sure anyone does.

- David
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