[LLVMdev] Function attribute for non-memory side effects?

[Philip Reames]

I've got a library function which writes to external state, but which 
does not update any location addressable from the code being compiled.  
I'd like to mark this function as read only to enable store forwarding, 
but I still need to model the side effect. (Otherwise, LLVM will happily 
remove any calls to the function since it returns void.)

Does LLVM have a mechanism to describe something like this?  I can't 
find anything along these lines.

Philip