Bug 159081 – make rest parameters faster

• Status: NEW
• Component: JavaScriptCore

[Saam Barati]

....

[Filip Pizlo]

Thought about this more.  I like that CopyRest is a node.  If only we could make it so that the use of the rest array for forwarding arguments was also a node so that:

function foo(a, b, c, ...args) { return bar(b, c, d, ...args); }

looked like this:

w: CopyRest(...)
x: NewArray(b, c, d)
y: ConcatArray(@x, @w)
z: TailCallVarargs(bar, @y)

I'm not sure how we'll compile "...args" in the call to bar(), but I'm pretty sure it'll be more obfuscated than this.

If we could get to a point where the DFG saw this, then we could have arguments forwarding turn this into code that never allocated anything.