Opportunity: Improve compiler performance by avoiding property accesses

TypeScript Version: 3.9.5

Search Terms: compiler performance namespace run-time property access

Code

I have looked into TypeScript compiler performance in the past and I've always wondered why the TypeScript compiler code uses namespaces heavily, since run-time property accesses are slower than statically-bound identifiers in JavaScript.

I finally got around to writing a proof of concept:

let fs = require('fs')
let tscPath = __dirname + '/node_modules/typescript/lib/tsc.js'
let tsc = fs.readFileSync(tscPath, 'utf8')

let vars = new Set()
tsc = tsc.replace(/\bts\.(\w+)/gm, (_, id) => {
  id = `ts_${id}`
  vars.add(id)
  return id
})
tsc = `var ${[...vars].join(',\n  ')};\n${tsc}`

fs.writeFileSync(tscPath, tsc)

This post-processes tsc.js to convert run-time property accesses into statically-bound identifiers. I ran this on the Rome code as a benchmark of a reasonably-large TypeScript code base and got a noticeable speed boost:

	Before	After	Difference
Time to run `tsc.js`	29.5s	27.5s	2s faster

Each time is the best of 5 runs, and each run was time node node_modules/typescript/lib/tsc.js -noEmit -project rome.

The TypeScript compiler is leaving some performance on the table by using run-time property accesses where it could use statically-bound identifiers instead. I'm sure you are using namespaces for code organization for good reasons, but it does come at a cost. An alternative to namespaces that might have less performance overhead could be to use ES6 modules and bundler, for example.

I'm posting this issue because I think the results of this experiment are interesting. The issue tracker seemed like the most appropriate place to post this. Feel free to just close this issue if you'd like.

Gotta go fast!

Andrew Casey (@amcasey)

Andrew Casey (@amcasey) Anders Hejlsberg (@ahejlsberg) Wesley Wigham (@weswigham), it'd be nice to see if #38510 gives any observable performance boost.

#35561 is trying to use modules instead of namespaces

Mohsen Azimi (@mohsen1)

Whoops, that's the right link, thanks Mohsen Azimi (@mohsen1).

Mohsen Azimi (@mohsen1)

Cool! Mohsen Azimi (@mohsen1) I assume that if you run the tests in the other order (i.e. no-namespaces first), you get the same result? I've gotten into the habit of discarding the first run whenever I do perf testing to minimize the effects of disk caching.

I did my own run against ant-design and saw a ~5% reduction in total compilation time. Pretty impressive. I have yet to compare the compiler output (i.e. to confirm it hasn't changed).

This should go hand-in-hand with the modules work for 4.6. I would hope that a bundler with scope hoisting will allow us to avoid property accesses/function calls that serve no purpose.

For those following this issue, #51387 will fix this (though it was later than 4.6 😄).

Merge pull request #51387 from jakebailey/typeformer-2

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Opportunity: Improve compiler performance by avoiding property accesses #39247

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Opportunity: Improve compiler performance by avoiding property accesses #39247

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steakscience commented on Jun 25, 2020

DanielRosenwasser commented on Jun 25, 2020

mohsen1 commented on Jun 25, 2020

DanielRosenwasser commented on Jun 25, 2020

amcasey commented on Jun 25, 2020

amcasey commented on Jun 26, 2020

DanielRosenwasser commented on Nov 19, 2021

jakebailey commented on Nov 2, 2022

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