[Webkit-unassigned] [Bug 212962] 4x slow execution slowdown when comparing the same codebase targeting ES2015 vs. ES5

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=212962

--- Comment #2 from Mihai Parparita <mihaip at chromium.org> ---
As a further experiment, I generated a variant of the ES2015 output that did not wrap the output in an IIFE, and that had comparable performance to the ES5 output that did:

http://persistent.info/webkit/test-cases/es2015-slowness/?es2015-no-iife - takes around 91ms

However, that pollutes the global namespace (and exposes symbols that we would prefer not to be accessible). If we take the script and load it with <script type="module">, then we're back to where we started from:

http://persistent.info/webkit/test-cases/es2015-slowness/?es2015-no-iife-module - takes around 330ms

So taking off the IIFE and using module scripts is not a feasible workaround for us.

These are the sources for the variants used:

http://persistent.info/webkit/test-cases/es2015-slowness/es5.js
http://persistent.info/webkit/test-cases/es2015-slowness/es2015.js
http://persistent.info/webkit/test-cases/es2015-slowness/es2015-var.js
http://persistent.info/webkit/test-cases/es2015-slowness/es2015-no-iife.js

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