[LLVMdev] RFC: Proposal to Remove Poison

[John Regehr]

> I have serious doubts about this approach.  This is essentially how 
> undef was originally implemented in LLVM, back in the mists of time. 
> It led to a lot of bugs that Dan (and others) fixed in the 2008-2010 
> timeframe, culminating in the modern definition of undef, and poison as 
> a complementary concept.  Unfortunately, I don?t have pointers to those 
> bugs, but I imagine some codebase archeology could turn them up.

We need a library of allowed / disallowed / disputed transformations, 
including the rationale for each.  I'm happy to start working on this 
though my available bandwidth isn't too high right now.  Does a github 
repo sound like the right thing here?

John