[llvm] r186634 - Debug Info: enable verifying by default and disable testing cases that fail.

[Duncan Sands]

Hi Manman,

On 19/07/13 07:07, Manman Ren wrote:
>
> Hi Duncan,
>
> How can I debug the failures?

this is coming from Fortran that likes to create anonymous global constants
like this:

   @0 = internal constant i32 77

I think it's so that it can pass a pointer to "77" around.  Anyway, the debug
code uses the name of the global as the "display name" but here there is none.
The verifier then barfs because it thinks everything should have a name.

I'm not sure why LLVM has this obsession that everything should have a name.
Is there a real reason for that?  If dwarf requires a name, then in this kind
of case someone will have to invent one.  The question then is whether it is
better to require front-ends to always supply a name (meaning the front-end has
to invent one), or to accept empty names and have the backend make something up
when outputting dwarf.  Any opinions?

Ciao, Duncan.


> Also getDICompositeType is not used on mainline but is used on dragonegg, how
> can I figure out the usage?
> Do  I have access to the source?
>
> Thanks,
> Manman
>
> On Jul 18, 2013, at 8:56 PM, Eric Christopher wrote:
>
>> Also this appears to have broken the dragonegg bots. :)
>>
>> -eric
>>
>> On Thu, Jul 18, 2013 at 6:08 PM, Eric Christopher <echristo at gmail.com
>> <mailto:echristo at gmail.com>> wrote:
>>>> Debug Info: enable verifying by default and disable testing cases that fail.
>>>>
>>>> 1> Use DebugInfoFinder to find debug info MDNodes.
>>>> 2> Add disable-debug-info-verifier to disable verifying debug info.
>>>> 3> Disable verifying for testing cases that fail (will update the testing cases
>>>>   later on).
>>>> 4> MDNodes generated by clang can have empty filename for TAG_inheritance and
>>>>   TAG_friend, so DIType::Verify is modified accordingly.
>>>>
>>>
>>> Cool, looks about like what I'd expected from when we discussed it.
>>> I'd have preferred you split out the change to verify :)
>>>
>>>> Note that DebugInfoFinder does not list all debug info MDNode.
>>>
>>> Seems like we should fix this? :)
>>>
>>>> For example, clang can generate:
>>>> metadata !{i32 786468}, which will fail to verify.
>>>
>>> This doesn't seem related to "not listing" all of the debug info, but
>>> a problem because of:
>>>
>>>> This MDNode is used by debug info but not included in DebugInfoFinder.
>>>> This MDNode is generated as a temporary node in DIBuilder::createFunction
>>>>  Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
>>>>  MDNode::getTemporary(VMContext, TElts)
>>>>
>>>
>>> This is the "we need a temporary placeholder" problem basically.
>>> You'll see it in GVs, subprograms etc when we construct the CU as
>>> well. Theoretically the verifier should catch these as "not
>>> important". What's actually going on here that's causing it to fail?
>>>
>>> -eric
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>