optimization - Does Java optimize division by powers of two to bitshifting?

Question

Does the Java compiler or the JIT compiler optimize divisions or multiplications by a constant power of two down to bitshifting?

For example, are the following two statements optimized to be the same?

int median = start + (end - start) >>> 1;
int median = start + (end - start) / 2;

_{(basically this question but for Java)}

Answer 1

While the accepted answer is right in the sense that the division can't be simply replaced by a right shift, the benchmark is terribly wrong. Any Java benchmark running for less than one second is probably measuring the interpreter's performance - not something you usually care about.

I couldn't resist and wrote an own benchmark which mainly shows that it's all more complicated. I'm not trying to fully explain the results, but I can say that

• a general division is a damn slow operation
• it gets avoided is much as possible
• division by a constant gets AFAIK always somehow optimized
• division by a power of two gets replaced by a right shift and an adjustment for negative numbers
• a manually optimized expression might be better