* Use LI(S) to copy constants into registers intead of ADDI(S) as the latter is

  a funky way to "use" R0 for a 0-valued operand
* Add IMPLICIT_DEFs for incoming function arguments via registers to help the
  register allocator not clobber those registers
* Implement comparisons with longs
* Teach emitSelectOperation() to fold the SetCC operation

Patch contributed by Nate Begeman

llvm-svn: 14901