Do C++11 compilers turn local variables into rvalues when they can during code optimization?

Question

Sometimes it\'s wise to split complicated or long expressions into multiple steps, for example (the 2nd version isn\'t more clear, but it\'s just an example):

Answer 1

As juanchopanza said, the compiler cannot (at C++ level) violate the "as-if" rule; that is all transformations should produce a semantically equivalent code.

However, beyond the C++ level, when the code is optimized, further opportunities may arise.

As such, it really depends on the objects themselves: if the move-constructors/destructors have side effects, and (de)allocating memory is a side effect, then the optimization cannot occur. If you use only PODs, with default move-constructors/destructors, then it will probably be automatically optimized.