Teach PHIElimination to split critical edges when -split-phi-edges is enabled.

Critical edges leading to a PHI node are split when the PHI source variable is
live out from the predecessor block. This help the coalescer eliminate more
PHI joins.

llvm-svn: 86725
4 files changed
tree: 1b490bd88acbda1f07e4398f30d56ca32933052f
  1. clang/
  2. compiler-rt/
  3. llvm/