LiveIntervals was recently refactored to eliminate its dependency on LiveVariables, so it's now theoretically possible to run it in a late pass (with care). The patch attached here does this, so that it can also move RegStackify and RegColoring late also. That means that all code expanded by PEI, tail duplication, and other things is all automatically exposed to stackification and coloring.
This is an alternative to http://reviews.llvm.org/D19345 . Instead of moving PEI earlier, this pass moves stackification and coloring later.