Operand numbers are now ints. Save the register allocation of the value

Operand numbers are now ints. Save the register allocation of the value
each instruction produces as "operand" -1, and the other operands as 0
.. n, as before. PhyRegAlloc::saveState() is refactored into
PhyRegAlloc::saveStateForValue().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9842 91177308-0d34-0410-b5e6-96231b3b80d8