Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
On Mon, Feb 29, 2016 at 9:31 PM, Scott Hulbert wrote:
> Jakob, here is a reproducible example (
> https://github.com/hulbert/bookshelf-sample-v8). I’m running this with
> node 5.6.0 on OS X (10.10.4).
>
That example explains a lot. Here, you're using "for (let virtualName in
virtuals) {", whereas the original example used "var". "const" and "let"
are similar in that they're both block-scoped, which isn't properly
supported by Crankshaft. The error message wasn't updated to reflect this.
Since Crankshaft is deprecated and scoping is nasty, I'm hesitant to spend
time on adding better support for let/const. Instead, what we should do is
use Turbofan in cases like this -->
https://codereview.chromium.org/1751873002/ (which as a drive-by fix
updates the bailout message).
git clone g...@github.com:hulbert/bookshelf-sample-v8.git
> npm install
> node --trace-opt index.js | grep ‘getVirtuals'
>
> outputs:
>
> [marking 0x185d96391a91 0x185d96347581)> for recompilation, reason: small function, ICs with
> typeinfo: 2/4 (50%), generic ICs: 0/4 (0%)]
> [compiling method 0x185d96391a91 (SharedFunctionInfo 0x185d96347581)> using Crankshaft]
> [aborted optimizing 0x185d96391a91 (SharedFunctionInfo 0x185d96347581)> because: Unsupported phi use of const
> variable]
> [disabled optimization for 0x185d96347581 getVirtuals>, reason: Unsupported phi use of const variable]
>
> > Also, is this actually a performance problem for you? Crankshaft aborts
> compilation in some cases by design, often there's no need to worry about
> it.
>
> This code is part of serialization in a web app and we’re trying to eek
> some extra performance out of it when serializing really large numbers of
> objects populated by an ORM. There are a couple other cases like this (for
> example I believe `_toJSON` in my example isn’t optimized because of the
> same issue), but `getVirtuals` is the most isolated case IMO.
>
> I am also hoping to get a better understanding of the "Unsupported phi use
> of const variable” reason as there is very little information about it
> available on the web. I’d like to contribute details to the list of V8
> bailout reasons (https://github.com/vhf/v8-bailout-reasons).
>
> Thanks,
>
> Scott Hulbert
>
>
> On Mon, Feb 29, 2016 at 4:23 AM, Jakob Kummerow
> wrote:
>
>> This is indeed surprising.
>> Crankshaft predates ES6, so this has nothing to do with ES6 const. That
>> said, I don't see why this function would bail out; and in a quick repro
>> attempt it doesn't. Do you have an example I can run that reproduces this
>> behavior?
>>
>> Also, is this actually a performance problem for you? Crankshaft aborts
>> compilation in some cases by design, often there's no need to worry about
>> it.
>>
>> On Mon, Feb 29, 2016 at 9:30 AM, Scott Hulbert
>> wrote:
>>
>>> I am seeing lines such as:
>>>
>>> [compiling method 0x39790c6f2379 >> (SharedFunctionInfo 0x2e54cd11ffa9)> using Crankshaft]
>>> [aborted optimizing 0x39790c6f2379 >> (SharedFunctionInfo 0x2e54cd11ffa9)> because: Unsupported phi use of const
>>> variable]
>>>
>>> In spite of this code not using `const` declarations (nor the method
>>> that invokes it). I even tried replacing `const` with `var` in all
>>> `node_modules` files on a smaller project and saw the same issue.
>>>
>>> This leads me to believe the explanation is inaccurate and the aborted
>>> optimization is not directly related to use of ES6 const?
>>>
>>> Here's the above function that won't optimize, though it's technically
>>> already copied into our codebase and I've tried rewriting it a few
>>> different ways:
>>> https://github.com/tgriesser/bookshelf/blob/ca08ec0850f758ec5610e3c543db5a276026624e/plugins/virtuals.js#L92-L100
>>>
>>> Thanks,
>>>
>>> Scott Hulbert
>>>
>>> --
>>>
>>
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Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
I found the bailout reason message to be confusing too. What it really is
trying to check is if there is a 'unsupport Phi use of a constant HOLE
value' (Here's the bailout check: [1]).
Changing the `let virtualName` to `var virtualName` in the for-in loop in
your code would fix the problem with the bailout:
function getVirtuals(model) {
var virtuals
var attrs = {}
if (virtuals = model.virtuals) {
for (*var* virtualName in virtuals) {
attrs[virtualName] = getVirtual(model, virtualName)
}
}
return attrs
}
As for the explanation, someone who understands Hydrogen IR better
would have to explain that. I don't understand why the culprit phi
value (v88) is there to begin with. It doesn't seem to have real uses.
For convenience, here's a link to the Hydrogen IR for the
`getVirtuals` function: [2].
[1]
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/crankshaft/hydrogen.cc&sq=package:chromium&type=cs&rcl=1456748799&l=4005
[2] https://gist.github.com/ofrobots/6d8d391a047ee8f0766a
On Mon, Feb 29, 2016 at 2:12 PM, Scott Hulbert wrote:
> In interest of providing extra information, my installation of Node 5.6.0
> is using V8 version 4.6.85.31.
>
> I’ve also committed the `node_modules` directory for my sample project and
> replaced all the instances of `const` I could find via search with `var`:
> https://github.com/hulbert/bookshelf-sample-v8/commits/modules-directory
>
> Results are the same.
>
> Best,
> Scott Hulbert
>
> On Mon, Feb 29, 2016 at 12:40 PM, Ben Noordhuis
> wrote:
>
>> On Mon, Feb 29, 2016 at 1:23 PM, Jakob Kummerow
>> wrote:
>> > This is indeed surprising.
>> > Crankshaft predates ES6, so this has nothing to do with ES6 const. That
>> > said, I don't see why this function would bail out; and in a quick repro
>> > attempt it doesn't. Do you have an example I can run that reproduces
>> this
>> > behavior?
>> >
>> > Also, is this actually a performance problem for you? Crankshaft aborts
>> > compilation in some cases by design, often there's no need to worry
>> about
>> > it.
>>
>> If it helps, see [0] - we had to revert some changes to the url module
>> because of this issue. That's with V8 4.8.271.17.
>>
>> The benchmarks are in [1]. They normally run in a child process but
>> you can run an individual benchmark directly with `./node
>> benchmark/url/url-parse.js type=one n=25e4`.
>>
>> [0] https://github.com/nodejs/node/pull/5300
>> [1] https://github.com/nodejs/node/blob/v5.7.0/benchmark/url/url-parse.js
>>
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>
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Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
In interest of providing extra information, my installation of Node 5.6.0 is using V8 version 4.6.85.31. I’ve also committed the `node_modules` directory for my sample project and replaced all the instances of `const` I could find via search with `var`: https://github.com/hulbert/bookshelf-sample-v8/commits/modules-directory Results are the same. Best, Scott Hulbert On Mon, Feb 29, 2016 at 12:40 PM, Ben Noordhuis wrote: > On Mon, Feb 29, 2016 at 1:23 PM, Jakob Kummerow > wrote: > > This is indeed surprising. > > Crankshaft predates ES6, so this has nothing to do with ES6 const. That > > said, I don't see why this function would bail out; and in a quick repro > > attempt it doesn't. Do you have an example I can run that reproduces this > > behavior? > > > > Also, is this actually a performance problem for you? Crankshaft aborts > > compilation in some cases by design, often there's no need to worry about > > it. > > If it helps, see [0] - we had to revert some changes to the url module > because of this issue. That's with V8 4.8.271.17. > > The benchmarks are in [1]. They normally run in a child process but > you can run an individual benchmark directly with `./node > benchmark/url/url-parse.js type=one n=25e4`. > > [0] https://github.com/nodejs/node/pull/5300 > [1] https://github.com/nodejs/node/blob/v5.7.0/benchmark/url/url-parse.js > > -- > -- > v8-users mailing list > v8-users@googlegroups.com > http://groups.google.com/group/v8-users > --- > You received this message because you are subscribed to a topic in the > Google Groups "v8-users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/v8-users/hsUrt4I2D98/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > v8-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
On Mon, Feb 29, 2016 at 1:23 PM, Jakob Kummerow wrote: > This is indeed surprising. > Crankshaft predates ES6, so this has nothing to do with ES6 const. That > said, I don't see why this function would bail out; and in a quick repro > attempt it doesn't. Do you have an example I can run that reproduces this > behavior? > > Also, is this actually a performance problem for you? Crankshaft aborts > compilation in some cases by design, often there's no need to worry about > it. If it helps, see [0] - we had to revert some changes to the url module because of this issue. That's with V8 4.8.271.17. The benchmarks are in [1]. They normally run in a child process but you can run an individual benchmark directly with `./node benchmark/url/url-parse.js type=one n=25e4`. [0] https://github.com/nodejs/node/pull/5300 [1] https://github.com/nodejs/node/blob/v5.7.0/benchmark/url/url-parse.js -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
Jakob, here is a reproducible example ( https://github.com/hulbert/bookshelf-sample-v8). I’m running this with node 5.6.0 on OS X (10.10.4). git clone g...@github.com:hulbert/bookshelf-sample-v8.git npm install node --trace-opt index.js | grep ‘getVirtuals' outputs: [marking 0x185d96391a91 for recompilation, reason: small function, ICs with typeinfo: 2/4 (50%), generic ICs: 0/4 (0%)] [compiling method 0x185d96391a91 using Crankshaft] [aborted optimizing 0x185d96391a91 because: Unsupported phi use of const variable] [disabled optimization for 0x185d96347581 , reason: Unsupported phi use of const variable] > Also, is this actually a performance problem for you? Crankshaft aborts compilation in some cases by design, often there's no need to worry about it. This code is part of serialization in a web app and we’re trying to eek some extra performance out of it when serializing really large numbers of objects populated by an ORM. There are a couple other cases like this (for example I believe `_toJSON` in my example isn’t optimized because of the same issue), but `getVirtuals` is the most isolated case IMO. I am also hoping to get a better understanding of the "Unsupported phi use of const variable” reason as there is very little information about it available on the web. I’d like to contribute details to the list of V8 bailout reasons (https://github.com/vhf/v8-bailout-reasons). Thanks, Scott Hulbert On Mon, Feb 29, 2016 at 4:23 AM, Jakob Kummerow wrote: > This is indeed surprising. > Crankshaft predates ES6, so this has nothing to do with ES6 const. That > said, I don't see why this function would bail out; and in a quick repro > attempt it doesn't. Do you have an example I can run that reproduces this > behavior? > > Also, is this actually a performance problem for you? Crankshaft aborts > compilation in some cases by design, often there's no need to worry about > it. > > On Mon, Feb 29, 2016 at 9:30 AM, Scott Hulbert > wrote: > >> I am seeing lines such as: >> >> [compiling method 0x39790c6f2379 > (SharedFunctionInfo 0x2e54cd11ffa9)> using Crankshaft] >> [aborted optimizing 0x39790c6f2379 > (SharedFunctionInfo 0x2e54cd11ffa9)> because: Unsupported phi use of const >> variable] >> >> In spite of this code not using `const` declarations (nor the method that >> invokes it). I even tried replacing `const` with `var` in all >> `node_modules` files on a smaller project and saw the same issue. >> >> This leads me to believe the explanation is inaccurate and the aborted >> optimization is not directly related to use of ES6 const? >> >> Here's the above function that won't optimize, though it's technically >> already copied into our codebase and I've tried rewriting it a few >> different ways: >> https://github.com/tgriesser/bookshelf/blob/ca08ec0850f758ec5610e3c543db5a276026624e/plugins/virtuals.js#L92-L100 >> >> Thanks, >> >> Scott Hulbert >> >> -- >> -- >> v8-users mailing list >> v8-users@googlegroups.com >> http://groups.google.com/group/v8-users >> --- >> You received this message because you are subscribed to the Google Groups >> "v8-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to v8-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. >> > > -- > -- > v8-users mailing list > v8-users@googlegroups.com > http://groups.google.com/group/v8-users > --- > You received this message because you are subscribed to a topic in the > Google Groups "v8-users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/v8-users/hsUrt4I2D98/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > v8-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
This is indeed surprising. Crankshaft predates ES6, so this has nothing to do with ES6 const. That said, I don't see why this function would bail out; and in a quick repro attempt it doesn't. Do you have an example I can run that reproduces this behavior? Also, is this actually a performance problem for you? Crankshaft aborts compilation in some cases by design, often there's no need to worry about it. On Mon, Feb 29, 2016 at 9:30 AM, Scott Hulbert wrote: > I am seeing lines such as: > > [compiling method 0x39790c6f2379 (SharedFunctionInfo 0x2e54cd11ffa9)> using Crankshaft] > [aborted optimizing 0x39790c6f2379 (SharedFunctionInfo 0x2e54cd11ffa9)> because: Unsupported phi use of const > variable] > > In spite of this code not using `const` declarations (nor the method that > invokes it). I even tried replacing `const` with `var` in all > `node_modules` files on a smaller project and saw the same issue. > > This leads me to believe the explanation is inaccurate and the aborted > optimization is not directly related to use of ES6 const? > > Here's the above function that won't optimize, though it's technically > already copied into our codebase and I've tried rewriting it a few > different ways: > https://github.com/tgriesser/bookshelf/blob/ca08ec0850f758ec5610e3c543db5a276026624e/plugins/virtuals.js#L92-L100 > > Thanks, > > Scott Hulbert > > -- > -- > v8-users mailing list > v8-users@googlegroups.com > http://groups.google.com/group/v8-users > --- > You received this message because you are subscribed to the Google Groups > "v8-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to v8-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[v8-users] Perplexed by aborted optimizations for reason "Unsupported phi use of const variable"
I am seeing lines such as: [compiling method 0x39790c6f2379 using Crankshaft] [aborted optimizing 0x39790c6f2379 because: Unsupported phi use of const variable] In spite of this code not using `const` declarations (nor the method that invokes it). I even tried replacing `const` with `var` in all `node_modules` files on a smaller project and saw the same issue. This leads me to believe the explanation is inaccurate and the aborted optimization is not directly related to use of ES6 const? Here's the above function that won't optimize, though it's technically already copied into our codebase and I've tried rewriting it a few different ways: https://github.com/tgriesser/bookshelf/blob/ca08ec0850f758ec5610e3c543db5a276026624e/plugins/virtuals.js#L92-L100 Thanks, Scott Hulbert -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
