[LLVMdev] RFC: Proposal to Remove Poison

[John Regehr]

David, this sounds promising.  One thing we should do is dig up some of 
Dan Gohman's old emails on this topic and make sure that your idea passes 
his litmus tests.

A few random things that want to be discussed in the detailed RFC:

- what constitutes separate reads of an undef? for example is "%1 = xor 
undef, undef" different from "%0 = undef ; %1 = xor %0, %0"?

- how do select and phi and br work in the value dependent and 
not-value-dependent cases?

- what is the list of "true UBs" that do not fall into your proposed 
model?  for example, I assume divide by zero and OOB store

John