[llvm] r194300 - Rewrite the PBQP graph data structure.

[Rafael Espíndola]

looks like this is causing a -Werror build failure:

include/llvm/CodeGen/PBQP/Graph.h:362:14: error: implicit conversion
from 'type' (aka 'unsigned long') to 'EdgeId' (aka 'unsigned int')
changes value from 18446744073709551615 to 4294967295
[-Werror,-Wconstant-conversion]
      return std::numeric_limits<EdgeVector::size_type>::max();

Cheers,
Rafael