Fix the updating of LiveIntervals after splitting a critical edge. PHI operand
live ranges should always be extended, and the only successor that should be
considered for extension of other ranges is the target of the split edge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174935 91177308-0d34-0410-b5e6-96231b3b80d8
Add blocks to the LiveIntervalAnalysis RegMaskBlocks array when splitting
a critical edge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174936 91177308-0d34-0410-b5e6-96231b3b80d8
Renumber SlotIndexes locally when a new block is inserted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174937 91177308-0d34-0410-b5e6-96231b3b80d8
Add a hidden option to PHIElimination to split all critical edges. This is
particularly useful for catching issues with architectures that have exotic
terminators like MIPS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174938 91177308-0d34-0410-b5e6-96231b3b80d8