Adding Function Parameter + Return Attributes

[jpmedinagl]

Adding the functions LLVMRustAddFncParamAttr and LLVMRustAddRetFncAttr to RustWrapper.cpp.

This will be used so that later we can link type trees to specific parameters/return value for Enzyme.

For the c->rust wrapper, do I add an implementation for the LLVMRustAddFncParamAttr, LLVMRustAddRetAttr functions?

Also do I need lines 6-7?

[ZuseZ4]

Thanks!

[ZuseZ4]

Oh actually pub fn LLVMRustAddRetAttr(V: &Value, attr: AttributeKind); here you should have used Attr, like you did in the other function that you added, but I'll fix it in the PR2. The reason is that AttributeKind is one of the enum variant hardcoded by rustc, but we create our own Attributes, containing tt.

Also, you named the Rust version LLVMRustAddRetAttr, and the C version LLVMRustAddRetFncAttr. These two files exist s.t. the linker can link the Rust version against the C version (which wrapps the real, c++ version), so they have to have identical names to allow the linker to link the c implementation against the rust declaration (linkers ignore argument numbers and types, they only go after names).