Exposing conversions from clang::QualType to llvm::Type

Hello,

First of all, some context. I'm currently working on an LLVM-based compiler for a language that needs advanced interoperability with C. One key point of this is to be able to parse function declarations from C headers to then call into C seamlessly. I'd like to use the Clang API to build the correct declarations in LLVM IR but as far as I can tell based on my (limited) knowledge of the Clang code base, this isn't currently possible out of the box.

Clang currently exposes the CGFunctionInfo data structure, which provides exhaustive information on function ABIs. However, the construction of an llvm::Type from a CGFunctionInfo is implemented in the CodeGenTypes::ConvertType functions, which are part of the internal API. These functions are rather complex so I don't think that reimplementing them in my compiler would be a good idea.

It seems to me that exposing the ConvertType functions in the public API would be the correct way to solve the problem. I wanted to get feedback on whether this would be a good idea, or if another direction should be taken. I'd be happy to submit a patch once we've agreed on a way forward.

Benoit Vey