Ahead-of-Time Compilation
This is great news, though it initially only supports Linux x86-64 and is decades late for Java desktop apps (and not having non-blocking I&#x2F;O until Java 1.4 was shameful for a language explicitly targeted and a pervasively networked ecosystem.)<p>In their &quot;tiered mode&quot;, they put sampling instrumentation into the native code, and if they detect a hotspot, regenerate fully instrumented native code from bytecode using the C1 (fast) JIT, which then allows the C2 JIT to do its full optimizations on the code as if AoT were not involved.<p>Since the invention of tracing JITs, I&#x27;ve often wondered why languages don&#x27;t package together a compact serialized SSA form such as LLVM bitcode or SafeTSA along with storing functions as lists of pointers to space-optimized compilations of extended basic blocks (strait-line code), similar to how some Forth compilers generate threaded code.  A threaded code dispatcher over these strait-line segments of native code would have minimal overhead, and when a simple SIGPROF lightweight sampler detected a hotspot, a tracing version of the dispatcher could collect a trace, and then generate native code from the visited traces using the stored SSA for the basic blocks.<p>In this way, they&#x27;d have a light-weight tracing JIT for re-optimizing native code.