[hardware2win]

Why would you want to remove those calculations?

You would change behavior of this program

[acimim_ha]

How? Except it would finish sooner. The is no behavior.

[hardware2win]

There is a side effect like cpu temperature increase

If I put my leg on my desktop tower then I may feel enjoyably warm or if I put some chocolate on my laptop then it may start melting

Also fans will be louder

[thfuran]

None of that is behavior according to the java (or any sane) language specification, so it can be optimized out of existence.

[hardware2win]

It is written in other, more general "specification" called physics

Computers arent purely abstract, they exist in real world and are affected by it, so lets do not try to pretend otherwise

[funcDropShadow]

So according to that "specification" no optimization is allowed. Since that would almost always change the "heating behavior" of code. Therefore, it is absurd.

[thfuran]

None at all, even out of order execution. For that matter, executing the same code on different hardware is right out. Every program must be implemented on single-purpose hardware, and you can't even manufacture two of them.

[lpapez]

Yet the compiler writers care only about the language spec, and you can bet that failing to optimize this as dead code would be considered a compiler bug.

This goes not only for Java compiler, but many other languages as well.

[hardware2win]

Sometimes compiler engineers try to be too smart and they end up creating a mess :)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537

>When optimizing code for "dead store removal" the optimizing compiler may remove code necessary for security.

[thfuran]

What exactly do you expect an optimizing compiler to do?

[hardware2win]

Leave code without obvious side effects alone (this is different from dead code)

[The_Colonel]

Not sure if being facetious, but FWIW you can't really rely on these. Next year you'll get a much faster CPU and memory and the timing will be all different. Or, tomorrow you run it while encoding video on the CPU which eats 99% of CPU, and it's hundred times slower.

[funcDropShadow]

Obviously, there is an xkcd for that: https://xkcd.com/1172/