Hi,Why I use `d8 --trace_opt` output nothing?  My v8 version is 5.8.

On Wednesday, February 8, 2017 at 7:09:53 PM UTC+8, Ben Noordhuis wrote:
>
> On Wed, Feb 8, 2017 at 10:29 AM, Alex Goldsmith 
> <[email protected] <javascript:>> wrote: 
> > Howdy. 
> > 
> > I was just reading through the Optimization Killers article on the 
> Bluebird 
> > wiki, trying to work out whether the following would be optimized: 
> > 
> > function get(/* ...k, j, i */) { 
> >    const a = arguments, l = a.length, n = l - 1 
> >    switch (l) { 
> >       case 0: return this 
> >       case 1: return this[a[n]] 
> >       default: return get.apply(this[a[a.length = n]], a) // a.length = 
> n = 
> > a.length - 1 
> >    } 
> > } 
> > 
> > console.log(get.call({x:{y:{z:'!!!'}}}, 'z','y','x')) // => "!!!" 
> > 
> > 
> > Shedding an argument in this way isn't really discussed (anywhere that I 
> can 
> > find), but it seems like it should be okay (at least it doesn't appear 
> to be 
> > leaking). 
> > 
> > Any insight would be highly appreciated. Thanks in advance! 
>
> Start node or d8 with --trace_opt and it will tell you.  My bet is 
> that you'll see a "Bad value context for arguments value" warning; V8 
> really doesn't like it when you modify arguments objects. 
>

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