[CIR] Cleanup support for C functions

[andykaylor]

The initial function support is working for C++ functions, but C functions trigger the following error:

error: ClangIR code gen Not Yet Implemented: non-prototype function type

Some additional handling needs to be added so that this diagnostic isn't generated and C test cases can be created.

[andykaylor]

This isn't as bad as I initally thought. I think the problem is limited to functions with no arguments that don't have an explicit void for the arguments in the function definition, and that's probably trivial to handle.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Andy Kaylor (andykaylor)

The initial function support is working for C++ functions, but C functions trigger the following error:

error: ClangIR code gen Not Yet Implemented: non-prototype function type

Some additional handling needs to be added so that this diagnostic isn't generated and C test cases can be created.

[Ajay-26]

Hi! I would like to take a shot at this issue, I see that it isn't assigned to anyone. It's my first time contributing to the project - could someone point me in the right direction to get started off ? Outside of reading the contribution guidelines, which part of the code should I be looking at ?

[AmrDeveloper]

Hello @Ajay-26,

If you have a simple C file like this (A function without parameters)

main.c

void foo() {}

and you try to run clang on it with the emit cir flag

./llvm/bin/clang -emit-cir main.c -o main.cir

You will get the same error as the one in the issue description

error: ClangIR code gen Not Yet Implemented: non-prototype function type

But if you run the same command from Clang built from llvm/clangir repo you will be able to compile the code without any errors,
so what you should do is to upstream the part that makes it work to llvm repository.

What I recommend for you to do:

• Search on the codebase with the error message to find the part that reports it.
• Open the same location in llvm/clangir and understand the logic.
• Upstream the missing part from llvm/clangir to llvm/llvm-project repo following the code style standards.
• Add new test cases that check the cir and ir outputs.

[Ajay-26]

Makes sense! Thanks a lot for the guidance! Feel free to assign this one to me and I can try it out!

[andykaylor]

This might extremely simple, but there is a slight wrinkle to it. When David Olsen upstreamed the initial function support, he diverged from the incubator implementation a bit. I think we're likely to move back to something closer to what's in the incubator, but we didn't need the full incubator logic to get the most basic support working.

Feel free to take this on, @Ajay-26. I just wanted to mention this so you'd know what you're getting into. Rather than simply transferring code from the incubator, you'll want to understand what is happening in both places and start with only the change that is needed to avoid the current error.

[Ajay-26]

Makes sense! Thank you!

[el-ev]

@Ajay-26 Are you still working on this?

[Ajay-26]

Hi, sorry I haven't had the time to complete this task. I can try to work on this but please feel free to reassign it to someone else