Register allocator - add $I0, $I1, 1 ...
Register allocator - add $I0, $I1, 1 ...

* if $I0 isn't used before and $1 not after that instruction
  both $I0 and $I1 can share the same register, *if* this
  instruction isn't inside a loop
* turn on loop depth calculation again


git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@11403 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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