Some functions run only once with this pattern: function foo() { if (foo$ran) return; foo$ran = 1; ... } If that global is not ever set to 0, then the function's payload (after the initial if and return) will never execute more than once. That means we can optimize away dominated calls: foo(); foo(); // we can remove this To do this, we find which globals are "once", which means they can fit in that pattern, as they are never set to 0. If a function looks like the above pattern, and it's global is "once", then the function is "once" as well, and we can perform this optimization. This removes over 8% of static calls in j2cl.