Needs a correct review because I'm not too confident with how this works.
All tests related to the C ABI are now passing.
References:
- dbe68fecd0/lib/CodeGen/TargetInfo.cpp (L479-L489)
- dbe68fecd0/lib/CodeGen/TargetInfo.cpp (L466-L477)
The `classifyArgumentType` function has two different paths depending on `RAA == CGCXXABI::RAA_DirectInMemory`, but I don't really know what's the corresponding option in Rust.
cc @brson @eddyb
9a7913786c