[llvm] r203983 - Debug info: Unique types before emitting them to DWARF, where applicable.

[Adrian Prantl]

On Mar 14, 2014, at 17:59, David Blaikie <dblaikie at gmail.com> wrote:

> On Fri, Mar 14, 2014 at 4:08 PM, Adrian Prantl <aprantl at apple.com> wrote:
>> Author: adrian
>> Date: Fri Mar 14 18:08:29 2014
>> New Revision: 203983
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=203983&view=rev
>> Log:
>> Debug info: Unique types before emitting them to DWARF, where applicable.
>> 
>> Modified:
>>    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>>    llvm/trunk/test/Linker/type-unique-odr-a.ll
>> 
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=203983&r1=203982&r2=203983&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Fri Mar 14 18:08:29 2014
>> @@ -958,6 +958,9 @@ DIE *DwarfUnit::getOrCreateTypeDIE(const
>>   DIE *ContextDIE = getOrCreateContextDIE(Context);
>>   assert(ContextDIE);
>> 
>> +  // Unique the type. This is a noop if the type has no unique identifier.
>> +  Ty = DIType(resolve(Ty.getRef()));
> 
> While this might be a good catch-all - I'm confused/concerned about
> what this implies. How did we get here? We must have some code
> referencing this type by node rather than name, yes? We should
> probably find what that is and fix it because that would mean the type
> won't be metadata node uniqued properly...
> 
> Might be worth just turning this into an assert instead so we can find
> bugs like this more quickly if they arise.

[+Manman]

Interesting. It appears that the only callers of DIScope::getRef() are in DIBuilder, which explains why before this change, no ODR/name-based uniquing happened during LTO. (Only fully identical MDNodes would be uniqued).
What would be a more natural place to put this? AsmParser?

-- adrian