Recommit "[RegAlloc] Make sure live-ranges reflect the state of the IR when

         removing them"

This was temporarily reverted, but now that the fix has been commited (r313197)
it should be put back in place.

https://bugs.llvm.org/show_bug.cgi?id=34502

This reverts commit 9ef93d9dc4c51568e858cf8203cd2c5ce8dca796.

llvm-svn: 313349