[CIR] Upstream enum support

[andykaylor]

Overview

Upstream support for enum types. This is mostly handled by the AST builder. We just need to handle the decl type.

Suggested minimal test case

enum A {
  A_one,
  A_two
};
A a;

Existing incubator tests

One test case in basic.cpp

[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)

### Overview Upstream support for enum types. This is mostly handled by the AST builder. We just need to handle the decl type.

Suggested minimal test case

enum A {
  A_one,
  A_two
};
A a;

Existing incubator tests

One test case in basic.cpp

[amansharma612]

I would like to work on this issue

[andykaylor]

Hi @amansharma612, are you familiar with the ClangIR upstreaming work? This task requires moving a piece of code from the ClangIR incubator repostitory (https://github.com/llvm/clangir) to the main LLVM repository and creating or moving associated tests. Some changes may be needed to match LLVM coding standards.

Let me know if you need any additional guidance. Thanks!

[Ankur-0429]

Hey @andykaylor, I would like to take a look at this issue. Is there a commit similar to what I would be doing here?

[andykaylor]

@Ankur-0429 As I said in my previous comment, this involves moving code from the ClangIR incubator to the main LLVM repository. I would recommend starting by adding a test in your local sandbox to verify that it fails. If a new test with an enum declaration doesn't fail for you, it would mean you don't have your build configured correctly to enable ClangIR.

Here is a similar commit: #136335

[andykaylor]

Before any changes, you should see an error like this:

error: ClangIR code gen Not Yet Implemented: declaration of kind: Enum