Optimization by Java Compiler

java optimization javac
Mahesh Gupta picture Mahesh Gupta · May 12, 2011 · Viewed 20.9k times · Source

Recently, I was reading this article.

According to that article, Java Compiler i.e. javac does not perform any optimization while generating bytecode. Is it really true? If so, then can it be implemented as an intermediate code generator to remove redundancy and generate optimal code?

Answer

Jon Skeet picture Jon Skeet · May 12, 2011

javac will only do a very little optimization, if any.

The point is that the JIT compiler does most of the optimization - and it works best if it has a lot of information, some of which may be lost if javac performed optimization too. If javac performed some sort of loop unrolling, it would be harder for the JIT to do that itself in a general way - and it has more information about which optimizations will actually work, as it knows the target platform.

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