Explain the mechanism of JIT compilation and its role in program execution.

JIT compilation (Just-In-Time) is a mechanism where the program's bytecode is compiled into machine code directly during runtime, rather than beforehand. In the context of Flutter, which uses Dart, JIT compilation allows for quick app launching and debugging, as the code is compiled "on the fly."

The main role of JIT is to improve performance compared to interpreted code, while maintaining flexibility and the ability for dynamic changes. During execution, the program is analyzed, and frequently used code sections are compiled into native code, speeding up their execution.

Example: When launching a Flutter app in debug mode, JIT is used, allowing for quick changes without a full recompile.

void main() {
  print('Example of JIT compilation in Dart');
}

Here, the code is first compiled into bytecode, and then the JIT compiler transforms it into machine code during runtime.