[llvm-dev] How to know the sub-class of a Value class?

[Jeremy Lakeman via llvm-dev]

I'm certainly no expert, but how you use that Value* would depend on what
you want to do with it.

>From the documentation, it looks like Value->getValueID() is how the RTTI
implementation determines the subclass.
So you could switch over the values returned (defined in llvm/IR/Value.def).

Or dyn_cast to each of the types you need to deal with. Or use some other
helper functions that strip noops like bitcasts for you.

On Mon, Jun 12, 2017 at 3:42 PM, Dipanjan Das via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
>
> On 11 June 2017 at 23:06, Jeremy Lakeman <Jeremy.Lakeman at gmail.com> wrote:
>
>> http://llvm.org/docs/ProgrammersManual.html#the-isa-cast-
>> and-dyn-cast-templates
>>
>
> I understand isa and dyn-cast let you test the type of an object at
> run-time by leveraging LLVM's custom implementation of RTTI. However, it
> doesn't make much sense to test out for all possible sub-classes to get to
> know what it actually is. If I just want to know sub-class a Value* is,
> what's the way out (other than testing with isa<>())?
>
>
>
>>
>>
>> On Mon, Jun 12, 2017 at 3:24 PM, Dipanjan Das via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>>
>>> As a concrete question, I understand 'Value' class is the parent of many
>>> concrete sub-classes. Let's say I retrieve a Value* value =
>>> store_inst->getValueOperand(). Unless I know what the sub-type is, how can
>>> I further use this object? I tried something like this:
>>>
>>> =================================================
>>>
>>>          Value* value = store_inst->getValueOperand()
>>>          errs() << value->getValueID; // Which ID corresponds to which
>>> sub-class?
>>>          errs() << value->getValueName(); // Prints numeric memory
>>> addresses
>>>          errs() << *value->getValueName(); // Doesn't compile
>>>
>>> =================================================
>>>
>>> I have mentioned the issues in each of the cases above. I am not sure if
>>> the approach is correct or not. Please help me out.
>>>
>>> --
>>>
>>> Thanks & Regards,
>>> Dipanjan
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>
>
> --
>
> Thanks & Regards,
> Dipanjan
>
> _______________________________________________
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> llvm-dev at lists.llvm.org
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>
>
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