My guess here is that either the Partial Redundancy Elimination or Loop Invariant Code Motion (or some interaction between the two) in MSVC2010 needed a helping

My guess here is that either the Partial Redundancy Elimination or Loop Invariant Code Motion (or some interaction between the two) in MSVC2010 needed a helping hand, but I agree with mmastrac, it's hard to know exactly what's going on without seeing the assembler.