Comment by sieve
2 days ago
> if javac involves IR, SSA based analysis and transformation (which I assume it does)
https://github.com/openjdk/jdk/blob/master/src/jdk.compiler/...
I am fairly certain that it does not. The JVM is a stack-machine.
I wrote a compiler for a simple programming language that compiled down to JVM bytecode for a project in the early 2010s. Its output for test programs was as fast as the comparative Java ones because they were fairly similar at the bytecode level.
The HotSpot JVM is where all the optimization effort is applied.
I believe there’s some trivial optimization done by the frontend (constant folding, simplifying string concatenation, converting switch statements to lookup tables) but I think they’d agree with you that javac doesn’t really fit their definition of a compiler and that the HotSpot JIT is the true compiler based on how they talked about the Python interpreter pre-JIT.