JIT taken on the face value is really old concept and when viewed from the right angle it was the original way how programming languages worked (in the sense th

JIT taken on the face value is really old concept and when viewed from the right angle it was the original way how programming languages worked (in the sense that you brough stack of punch cards with your program to datacenter, it got compiled, resulting code was ran and the object file was simply thrown away). There is then some marketing hype around JIT from late 90's that is mostly only relevant for Java, which implies that "true JIT" does things like hot spot detection, deoptimalization traps and trace-based program flow reconstruction. This is mostly only done in production only by JVM implementations and fallback interpreters in hypervisors and is based on 80's research projects. Somewhat notably in early 90's there was HP Dynamo, which was userspace PA-RISC emulator that ran on PA-RISC host by means of trace based JIT which was able to agressively optimize the code to the extent that it was actually faster than running natively in not insignificant number of (real world!) cases.