PreRA scheduler heuristic fixes: VRegCycle, TokenFactor latency.

UnitsSharePred was a source of randomness in the scheduler: node
priority depended on the queue data structure. I rewrote the recent
VRegCycle heuristics to completely replace the old heuristic without
any randomness. To make these heuristic adjustments to node latency work,
I also needed to do something a little more reasonable with TokenFactor. I
gave it zero latency to its consumers and always schedule it as low as
possible.

llvm-svn: 129383
4 files changed
tree: a2ed15ecd7de38846a9451ab06b9e92b56f55a1b
  1. clang/
  2. compiler-rt/
  3. debuginfo-tests/
  4. libcxx/
  5. lldb/
  6. llvm/