CODEWITHSUNDEEP
c++parsingclangopencl
pkreutzer
pkreutzer

Reputation: 63

Use clang as a library to parse OpenCL code extended with some C++ elements

I am currently working on a Source-to-source compiler that transforms code wirtten in an OpenCL superset to "ordinary" OpenCL. I would really like to use clang as a library to parse and analyze the source code. Especially, I really need all the available type information and I would like to have an AST to make use of clang's Rewrite capabilities.

Fortunately, the OpenCL superset that needs to be parsed is really a "mixture" between OpenCL and C++, i.e. the code is basically OpenCL extended with some C++ stuff. In detail, there are possibly template annotations before a function definition and there may be structs containing methods (including operator definitions).

I was hoping that I can use clang to parse this language, since the clang parser is capable of parsing all these constructs. However, I am not sure how (if possible) to tell clang to parse OpenCL and C++ constructs at once. If possible, I really want to avoid touching the clang code base, but I would prefer using clang as a library instead. Maybe it is possible to setup an appropriate instance of clang's LangOptions class that tells clang to parse all these constructs?

Any ideas on how to make clang parse this mixture between OpenCL and C++? Any help is appreciated, and thanks in advance!

Upvotes: 2

Views: 655

Answers (1)

Ira Baxter
Ira Baxter

Reputation: 95400

You're trying to mix two different front ends, involving both parsing and name resolution.

I think you are in for a rough trip. The key problem is you are trying to glue together things that had no effort expended, to make them gluable. This usually leads to integration hell. You don't see people doing this with Fortran and C++ for the same reasons.

To start with, you'll discover you will have to define the semantics of how the C++ extensions interact with those of OpenCL. If you check out the C++ standard, you'll discover 600 pages of results from committee arguments on how C++ interacts with itself. So unless you can define a radically simple interaction, you'll have a tough time knowing what your mixed OpenCL/C++ program means.

Your second problem will be interleaving the Clang parsing machinery for C++ (AFAIK hand written code) with the Clang parsing machinery for OpenCL (don't know anything about it, but assumed it follows the C++ style). There's no obviously good reason to believe you can just pick and choose these to interleave easily. It may work out fine; just not a bet I'd care to make.

The next place you are likely to have trouble is in building an AST for the joint language. Maybe it is the case that Clang has defined AST nodes for both C++ and OpenCL in a way that easily composes to a joint Clang/OpenCL tree. Since the node types are chosen by hand, and there was no specific reason to design them to work together, it is also not obvious they will compose nicely.

Your last task, given a "valid" OpenCL/C++ tree, to transform it to OpenCL. How in fact will you expand a C++ template (or any general C++ code) to OpenCL code?

[Check my bio for another system, DMS, that might be a bit better for this task; it provides uniform infrastructure for multiple languages that would make some of this easier. Somewhat similar to what you are trying to do, we have used DMS to mix C++ with F90 and APL concepts for easy expression of vector operations in a prototype Vector C++, but we did not try to preserve F90 and APL syntax and semantics exactly for all the above reasons].

It isn't my purpose to rain on your parade; progress is made by the unreasonable man. Just be sure you understand how big a task you are taking on.

Upvotes: 2

Related Questions