RFR(S) 8016157: During CTW: C2: assert(!def_outside->member(r)) failed: Use of external LRG overlaps the same LRG defined in this block

[Roland Westrelin]

>> Also why is it better to filter out NegDNodes in the adlc rather than in MachNode::rematerialize()?
> 
> It was my suggestion. Why mark a node as rematerializable if we never rematerialize it?

Ok. Thanks, Vladimir.

Roland.