llvm dev - Jul 2011 - [LLVMdev] Identifying classes and its member functions

Hi,

I am new to LLVM and am trying to identify all the member functions of a
class.

Currently, I am converting the source code into the IR using a llvm
frontend. I have written a module-pass which will take in the IR thus
generated and iterate over the various types (classes/structs) defined in
the source. For every such type, I will iterate over the sub-types (types of
its members). I was expecting to see a member of type *FunctionTyID* to
indicate a member function but this is not the case. Hence, I am not able to
iterate over the member functions.

On looking into the IR (dumped out in human readable format), I see that the
class defined in the source code has been stripped out of its member
functions and only a structure containing the member variables is created.
The member functions are written out separately with their mangled names.
Hence, I suspect if it is possible to iterate over only the member functions
of a particular class.

Kindly let me know if my approach is correct when it comes to identifying
only the member functions of a class. If not, please suggest the best method
of doing so. Please let me know if you need any further
information/clarification.

Regards,
Sandeep
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>
> On looking into the IR (dumped out in human readable format), I see that
> the class defined in the source code has been stripped out of its member
> functions and only a structure containing the member variables is created.
> The member functions are written out separately with their mangled names.
> Hence, I suspect if it is possible to iterate over only the member
functions
> of a particular class.
>
Indeed, as you've seen (& so far as I know), LLVM IR is too low level
for
your task - there are no member functions at this level, they've all been
transformed into free functions and structs.

What kind of optimization were you hoping to implement based on this
information?

If you aren't trying to implement an optimization, but instead try to
process source code in some way (indexing, source to source transformations,
etc) then you might want to use clang instead.
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We have built a tool which will take in a CDFG (in a particular format) and
do some design automation based on it. The effort is to extend this tool to
take an input from in the form of a systemC (extension of C++) code. The IR
was used to generate the CDFG of the source code.

But the requirement is to generate the CDFG of only a specific function and
hence I am looking to iterate over the member functions only. Currently, I
was achieving this by filtering out the function by their name. But
evidently this is inefficient.

Will I be able to achieve this (iterating over member functions alone and
generate a CDFG of it) using clang?

Regards,
Sandeep


On Thu, Jul 7, 2011 at 9:47 AM, David Blaikie <dblaikie at gmail.com>
wrote:
> On looking into the IR (dumped out in human readable format), I see that
>> the class defined in the source code has been stripped out of its
member
>> functions and only a structure containing the member variables is
created.
>> The member functions are written out separately with their mangled
names.
>> Hence, I suspect if it is possible to iterate over only the member
functions
>> of a particular class.
>>
>
> Indeed, as you've seen (& so far as I know), LLVM IR is too low
level for
> your task - there are no member functions at this level, they've all
been
> transformed into free functions and structs.
>
> What kind of optimization were you hoping to implement based on this
> information?
>
> If you aren't trying to implement an optimization, but instead try to
> process source code in some way (indexing, source to source
transformations,
> etc) then you might want to use clang instead.
>
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