attaching metadata to llvm::Argument

Hey everyone,

I'm trying to retrieve information about signed-/unsignedness of an
llvm::Argument so I can print out it's value to the user properly. llvm itself
doesn't distinguish signed and unsigned and so llvm::Type is of no help here.
Checking for nsw/usw is only an unreliable approximation and only available
for llvm::Instructions anyways.

I tried to use debugging information (llvm::DIType) for this, but
getMetadata() is not available for llvm::Argument, only for llvm::Instruction.

Is there any other way to get at this information?


I too would have an immediate application if metadata could be attached to arguments. I'm currently working around it by using named metadata in the module (matched by index to the arguments).


There is no support to have metadata attached with an argument because there was any need so far. If you have really good reason to have it then you'll at least need to

- propose llvm IR syntax and update llvm IR spec to attach metadata
- update llvm parser and asm writer
- update bitcode reader and writer

The reason that I need this is that I'm supporting runtime function specialization, where the arguments have known default values. When the function is specialized, I need to replace uses of the argument with the default value. I could not find any other way to store the metadata for the default values other than to use module-level data. Does anyone know a better way to accomplish this in the LLVM IR?