[spacechild1]

> if a compiler can't prove that between accesses the variable hasn't been modified (which happens actually very frequently). I've seen x10 speedups of computations in tight loops when I explicitly cached a value used in the loop into a variable from under a pointer/reference.

This is indeed an important gotcha! Let's say you have a filter and want to process an array of floats. If the coefficient is a struct member and has the same type as the audio samples, you must cache it in a local variable, otherwise the compiler might reload it from memory on every loop iteration. ('restrict' can somewhat help with these kind of aliasing issues, but you need to be careful.)