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  function define() {...}
  function require() {...}
  define("one", function() { return 1; });
  define("two", function() { return require("one") + require("one"); });
  define("three", function() { return require("two") + require("one"); });
  three = require("three");
--->

  three = 3;
There is a certain irony that now it's possible to do optimisations like that in javascript - a dynamically typed language with almost no compile time guarantees.

Meanwhile java used to have easy static analysis as a design goal (and I think a lot of boilerplate is due to that goal) but the community relies so much on reflection, unsafe access, dynamic bytecode generation, bytecode parsing etc that such an optimisation would be almost impossible to get right.




it's possible to do such optimizations for a (safe) subset of javascript, such as these pure functions.

Arguably java has a larger subset even today.


I think the remarkable point in the above optimisation was that the non-pure functions define() and require() were also subject of optimisation even though the optimizer had no special knowledge about them. Using symbolic execution, the optimizer nevertheless was able to reason about them.




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