Bug 820583 increased the script length limit during compilation to 20000 when running off thread. This is still not large enough to compile some critical scripts in asm.js benchmarks, greatly hurting performance on those. The attached patch bumps the absolute limit to 100000, about twice the size of the biggest important script in box2d, removes the local/arg limit when compiling off thread and scales the use count for large scripts according to their size --- a script of length 100000 needs a use count of about 50000 before being compiled, rather than 1000 with small scripts. Per the formula in bug 807464 comment 3 a script of length 100000 should take a bit less than a second to compile, which isn't bad and of course can be canceled by the main thread when necessary. The only major benchmark I know which is affected by this threshold is octane-mandreel, which improves a few hundred points with this patch on my machine.