[LLVMdev] removnig instructions with uses

[Patrick Meredith]

How do you remove an instruction with uses before replacing said uses?  Opt
exits immediately if you do this, it seems like it should wait until your
pass finishes running.  The only way I can get around it now is to work
recursively post order removing the use before the def, which is slower than
if I could just remove them in linear order!  Oh well.

~Patrick