[llvm-commits] patch: use CallbackVH for metadata

[Chris Lattner]

On May 5, 2009, at 11:15 PM, Nick Lewycky wrote:

> This patch switches MDNode to using CallbackVH and adds a special  
> typeless "null" keyword that means "(Value*)0" within a metadata  
> node. Also change MDNode construction to accept Value* even though  
> we don't really permit non-Constant values yet.

Looks nice.  Please split MDNode (and the VH.h #include) out to a new  
MDNode.h file.

In ElementVH, what is the right behavior when RAUW and delete are  
called?  Shouldn't these go back through to be recursively uniqued,  
like what happens for Constants?

-Chris