VirtRegMap keeps track of allocations so it knows what's not used. As a horrible hack, the stack coloring can color spill slots with *free* registers. That is, it replace reload and spills with copies from and to the free register. It unfold instructions that load and store the spill slot and replace them with register using variants.
Not yet enabled. This is part 1. More coming.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70787 91177308-0d34-0410-b5e6-96231b3b80d8
