llvm dev - Oct 2010 - [LLVMdev] Associating types directly with debug metadata?

>>> I thought about that more, and I think the "right" way
would be to have a syntax like
>>> 
>>> !21 = metadata !{ typeval %struct.T, metadata !11 }
>>> 
>>> to avoid the problem with the keyword 'type'.
>>> 
> 
> Anyway, I already implemented an early patch for making Types representable
as Values.  For that I created a new class, TypeValue, which represents a type
as a value.  An early patch for that enclosed.  Works when reading or writing
textual representations; no BC representation yet.  And no test case yet.
Here is another version of the patch.  This one includes also a small patch to
llvm-gcc so that it generates the type metadata for structures and classes. 
This one also generates and parses correctly the metadata for .ll files.  No .bc
support yet.  The biggest problem with this version is that it breaks when the
compiler/linker performs type reductions, and I don't understand why.

--Pekka

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Pekka Nikander wrote:
>>>> I thought about that more, and I think the "right"
way would be to have a syntax like
>>>>
>>>> !21 = metadata !{ typeval %struct.T, metadata !11 }
>>>>
>>>> to avoid the problem with the keyword 'type'.
>>>>
>>
>> Anyway, I already implemented an early patch for making Types
representable as Values.  For that I created a new class, TypeValue, which
represents a type as a value.  An early patch for that enclosed.  Works when
reading or writing textual representations; no BC representation yet.  And no
test case yet.
>
> Here is another version of the patch.  This one includes also a small patch
to llvm-gcc so that it generates the type metadata for structures and classes. 
This one also generates and parses correctly the metadata for .ll files.  No .bc
support yet.  The biggest problem with this version is that it breaks when the
compiler/linker performs type reductions, and I don't understand why.
Please don't do this. My objection to the type value is on the grounds 
that it is not a value. It does not match the conceptual meaning of a 
value, that is, something you could put in a machine register on some 
machine.

If you need to name an LLVM type in your MDNode, just create an undef 
value of that type.

Nick

On Oct 5, 2010, at 11:23 PM, Nick Lewycky wrote:
>> 
>> Here is another version of the patch.  This one includes also a small
patch to llvm-gcc so that it generates the type metadata for structures and
classes.  This one also generates and parses correctly the metadata for .ll
files.  No .bc support yet.  The biggest problem with this version is that it
breaks when the compiler/linker performs type reductions, and I don't
understand why.
> 
> Please don't do this. My objection to the type value is on the grounds 
> that it is not a value. It does not match the conceptual meaning of a 
> value, that is, something you could put in a machine register on some 
> machine.
> 
> If you need to name an LLVM type in your MDNode, just create an undef 
> value of that type.
I agree completely.

-Chris