[PATCH] D120952: [clang][AST matchers] adding submatchers under cudaKernelCallExpr to match kernel launch config

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D120952#3381224 <https://reviews.llvm.org/D120952#3381224>, @ajohnson-uoregon wrote:

> I still need to write tests but: I do have a use case for these over here: https://github.com/ajohnson-uoregon/llvm-project/blob/feature-ajohnson/clang-tools-extra/clang-rewrite/ConstructMatchers.cpp#L472 
> tl;dr, we'd like to match the kernel launch arguments (i.e., the arguments to `__cudaPushCallConfiguration()`) and these matchers made writing the code to generate those AST matchers much easier.

Thanks for the example use case, that helps! Do you expect to need it in more than one project though? We support defining local AST matchers so people can do one-off matching, but we typically only add AST matchers for things that we expect to be generally useful (multiple projects would benefit from it). For example, this project adds a number of local matchers: https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp#L435

> Without at least the `hasKernelConfig()` matcher, it's actually currently impossible to match the kernel launch args. (I wasn't able to find a way after quite a while poking at the AST, at least.) As for the others, it's not clear how to match the kernel launch args without exposing the fact that there's a second CallExpr inside the CUDAKernelCallExpr to the user and writing a pretty messy matcher, along the lines of `cudaKernelCallExpr(hasKernelConfig(callExpr(hasArgument(0, expr()))))` for the grid dim. `cudaKernelCallExpr(cudaGridDim())` is a lot cleaner and easier to understand.

Yup, I think you need these kind of matchers for what you want to do. What I'm less certain of is whether others will need them (we don't have any CUDA-specific clang-tidy modules, I don't think any of the existing coding standards we support checks for have anything to say about CUDA, etc).


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