MI Sched fix: assert "Disconnected LRG within the scheduling region."

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187435 91177308-0d34-0410-b5e6-96231b3b80d8
MI Sched: Track live-thru registers.

When registers must be live throughout the scheduling region, increase
the limit for the register class. Once we exceed the original limit,
they will be spilled, and there's no point further reducing pressure.

This isn't a perfect heuristics but avoids a situation where the
scheduler could become trapped by trying to achieve the impossible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187436 91177308-0d34-0410-b5e6-96231b3b80d8
whitespace

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187437 91177308-0d34-0410-b5e6-96231b3b80d8
Down-scale slot index distance to save bits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187438 91177308-0d34-0410-b5e6-96231b3b80d8
Remove dead code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187439 91177308-0d34-0410-b5e6-96231b3b80d8