[LLVMdev] DebugInfo: DW_AT_GNU_ranges_base in non-fission

[Eric Christopher]

On Mon, Dec 9, 2013 at 12:01 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Mon, Dec 9, 2013 at 11:48 AM, Eric Christopher <echristo at gmail.com> wrote:
>> On Mon, Dec 9, 2013 at 9:47 AM, David Blaikie <dblaikie at gmail.com> wrote:
>>> It looks like we only attach the GNU_ranges_base to skeleton CUs, and
>>> never use the attribute under non-fission. Is that right? It's not
>>> obvious to me why we'd want to only include this under fission, but I
>>> admittedly don't fully understand it anyway.
>>>
>>
>> So we're not particularly using it correctly at the moment (given that
>> it was relatively undocumented and I had word of mouth when
>> implementing it), but the basic idea is that relocations to the range
>> sections will be based off of a single relocation rather than have a
>> bunch of them.
>
> Right - use one reloc and then offsets for the rest I suppose. Seems
> like a reasonable feature but one we're basically not using at all
> (just not "not using correctly"). As usual, I'd be inclined to rip it
> out until it's used (until we actually emit the non-reloc,
> offset-based AT_range values), but not too fussed.
>

Yep. And sure, that seems reasonable.

>> It's not necessarily fission only, but it hasn't been standardized yet
>> and is a bit of an experiment and still undergoing revision. I can
>> disable it/command line if you think that's appropriate as well.
>
> Doesn't seem terribly necessary - was more just curious about the
> inconsistency & whether there was some logic to that I was missing or
> an oversight we should fix.

Yep. Pretty much got left behind in the ever evolving standardization thing.

-eric