Re:Brendan Eich on Ecma TC39, JavaScript.next, and Google Dash
by BrendanEich on Saturday September 17, 2011 @03:28PM
(#3008741)
JS has notorious optimization hazards such as holes in arrays (Array.prototype[1] = "ha ha"; a = [0,,2]; ... a[i] for i=1 must find the prototype element), prototype delegation in general, delete and default-mutability, plus the eval of old and 'with' (respectively reformed in modern impls and specs, and banned in strict mode).
These all add some cost in either runtime guards, static analysis burdens, or a mix.
A new language could leave out most of these, but it would still want inheritance. Then the question would be: how useful is mutability along the inheritance chain, i.e. shadowing -- even if you remove 'delete'.
Beyond this, a new language or a JS extension (this is what the Dash memo rules out as un-possible, without evidence) could allow pinning down the shape of objects, even to include machine types such as int32, etc. That would allow for big speedups on certain benchmarks.
These all add some cost in either runtime guards, static analysis burdens, or a mix.
A new language could leave out most of these, but it would still want inheritance. Then the question would be: how useful is mutability along the inheritance chain, i.e. shadowing -- even if you remove 'delete'.
Beyond this, a new language or a JS extension (this is what the Dash memo rules out as un-possible, without evidence) could allow pinning down the shape of objects, even to include machine types such as int32, etc. That would allow for big speedups on certain benchmarks.