All new virtual registers created for spilling or splitting point back to their original.

llvm-svn: 125980

llvm-svn: 118661

give them individual stack slots once the are actually spilled.

llvm-svn: 117945

llvm-svn: 116962

llvm-svn: 116951

All registers created during splitting or spilling are assigned to the same
stack slot as the parent register.

When splitting or rematting, we may not spill at all. In that case the stack
slot is still assigned, but it will be dead.

llvm-svn: 116546

splitting or spillling, and to help with rematerialization.

Use LiveRangeEdit in InlineSpiller and SplitKit. This will eventually make it
possible to share remat code between InlineSpiller and SplitKit.

llvm-svn: 116543