[spectre]

A programmer is always capable of writing better parallel code then such a compiler but writing safe and correct parallel code is beyond the skills of many programmers. A good analogy is that a good programmer can hand write assembly that out performs compiled code but that is too hard for most programmers to achieve.

There is some interesting research into languages that explicitly control mutability and object reachability (A set of objects don't need to be immutable if we can guarantee that only one thread has access to them).

http://ecs.victoria.ac.nz/foswiki/pub/Main/TechnicalReportSe...