unsafe fn opaque_cmp_type(&self) -> LLVMTypeRef {
        let mut arg_tys = [self.void_pointer_type(), self.void_pointer_type()];
        let fn_type = LLVMFunctionType(
            self.i32_type(),
            arg_tys.as_mut_ptr(),
            arg_tys.len() as u32,
            0,
        );
        LLVMPointerType(fn_type, 0)
    }
Returns the type of the key comparator over opaque pointers.
weld/src/codegen/llvm2/mod.rs