Do not mark obviously unreachable blocks live when processing PHI nodes,
and handle incomplete control dependences correctly.  This fixes:

Regression/Transforms/ADCE/dead-phi-edge.ll
  -> a missed optimization

Regression/Transforms/ADCE/dead-phi-edge.ll
  -> a compiler crash distilled from QT4


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20227 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed