This is a bit tricky to articulate.
(using Core.h), I need to create a LLVMValueRef, then later replace all uses
of it with another, using LLVMReplaceAllUsesWith. But I need several different
such temporary LLVMValueRefs that don't get all thrown together, so "All"
means all uses of a specific one of these. but not the others.
So, for example, if I execute a call LLVMConstNull(sometype) twice, will I
get two independently replaceable values? Or are all independently
created null constants of the same type a single value?