[llvm] r187285 - Debug Info Verifier: verify SPs in llvm.dbg.sp.

[Manman Ren]

In r187609.

I realized that my commit messages were a little terse, hopefully the 
commit message for r187609 is verbose enough.

Thanks,
Manman

On 7/31/13, 3:39 PM, David Blaikie wrote:
> On Wed, Jul 31, 2013 at 3:32 PM, Manman Ren <manman.ren at gmail.com> wrote:
>> On 7/26/13, 11:05 PM, David Blaikie wrote:
>>> On Fri, Jul 26, 2013 at 10:45 PM, Manman <manman.ren at gmail.com> wrote:
>>>>
>>>>> On Jul 26, 2013, at 8:31 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>>>>
>>>>>> On Fri, Jul 26, 2013 at 6:26 PM, Manman Ren <manman.ren at gmail.com>
>>>>>> wrote:
>>>>>> Author: mren
>>>>>> Date: Fri Jul 26 20:26:08 2013
>>>>>> New Revision: 187285
>>>>>>
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=187285&view=rev
>>>>>> Log:
>>>>>> Debug Info Verifier: verify SPs in llvm.dbg.sp.
>>>>> Wait do we still even do anything with that named metadata anymore? I
>>>>> don't think we do - we killed off that kind of debug info a while ago,
>>>>> I thought. (the only named metadata should be llvm.dbg.cu, right?)
>>>> That sounds true. But it is still used in the testing cases. After we
>>>> replace those with dbg.cu, we can probably remove checking for dbg.sp.
>>> It may still be /present/ in the testing cases, but not actually used,
>>> since the debug info code never walks from that root node...
>> "llvm.dbg.sp" is only used in IPO/StripSymbols.cpp.
>>
>> The verifier currently does not check the debug location attached to an
>> instruction. I had a patch ready, but it requires updating 30+ testing cases
>> and I didn't get a chance to update the testing cases yet.
>>
>> For testing cases that do not have dbg.cu,
> Any test case that doesn't have dbg.cu shouldn't be considered to be a
> debug info testcase, just bogus/malformed debug info.
>
>> the only way to reach some of the
>> SPs is through the debug locations or through dbg.sp.
> But if the rest of LLVM doesn't access them through dbg.sp, why are we
> verifying them? They're not actually used.
>
> I'd like to ensure that the verifier, ideally, only accesses debug
> info metadata through the same mechanisms as the actual LLVM
> production code (& that it accesses them through all such mechanisms).
> That way the verifier ensures that the debug info that matters is in
> the right form, and that any other pseudo debug info (such as entries
> that look like line entries but aren't, because they aren't referenced
> from the debugloc attribute in an Instruction) is ignored.
>
>> For now, we can check the SPs listed in dbg.sp to provide more coverage for the verifier.
> It's false/irrelevant coverage though, isn't it?
>
>> Once the verifier verifies DbgLoc, we can remove dbg.sp from the testing
>> cases and also remove checking them from the verifier.
> OK. I'd probably be happy enough not to check them until we check them
> correctly, rather than check incorrect stuff.
>
> But so long as you've got a plan, I can live with that.
>
> - David