LLVM internals, part 4: attributes and attribute groups

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ENOSUCHBLOGProgramming, philosophy, pedaling.PrewordThis is the last post I plan to do on parsing LLVM’s bitcode, at least for a while. I’ll keep working on the various libraries that I’ve started under the mollusc umbrella, but they won’t be accompanied by regular posts anymore — I’d like to refocus on writing smaller, less dense (read: lower-pressure) posts for a while.Also, as a sort of update: all four of the patchsets that I mentioned in the previous post have been fully merged into LLVM, including a couple of documentation and bitcode parsing bugfixes. Many thanks to the LLVM maintainers for reviewing and approving my changes!LLVM has no less than three different ways to represent some of the metadata that gets stored in its intermediate representation of a program: metadata, attributes, and intrinsics. All three are represented differently in the bitcode format and this post will focus only on attributes, but it’s important to understand the semantic difference between t…