[RFC VTV] Fix VTV for targets that have section anchors.

[Jeff Law]

On 10/09/2015 03:17 AM, Ramana Radhakrishnan wrote:
> This started as a Friday afternoon project ...
>
> It turned out enabling VTV for AArch64 and ARM was a matter of fixing
> PR67868 which essentially comes from building libvtv with section
> anchors turned on. The problem was that the flow of control from
> output_object_block through to switch_section did not have the same
> special casing for the vtable section that exists in
> assemble_variable.
That's some ugly code.  You might consider factoring that code into a 
function and just calling it from both places.  Your version doesn't 
seem to handle PECOFF, so I'd probably refactor from assemble_variable.

>
> However both these failures also occur on x86_64 - so I'm content to
> declare victory on AArch64 as far as basic enablement goes.
Cool.

>
> 1. Are the generic changes to varasm.c ok ? 2. Can we take the
> AArch64 support in now, given this amount of testing ? Marcus /
> Caroline ? 3. Any suggestions / helpful debug hints for VTV debugging
> (other than turning VTV_DEBUG on and inspecting trace) ?
I think that with refactoring they'd be good to go.  No opinions on the 
AArch64 specific question -- call for the AArch64 maintainers.

Good to see someone hacking on vtv.  It's in my queue to look at as well.

jeff