876916 - optimize sqrt on asm.js

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[Dan Gohman [:sunfish]]

Math.sqrt under asm.js is currently lowered to a library call. IonMonkey already has an optimized implementation of Math.sqrt which is capable of emitting a single instruction on platforms which support it, so asm.js just needs to use it.

Comment 1

[Dan Gohman [:sunfish]]

Attachment: a proposed fix

Comment 2

[Luke Wagner [:luke]]

Thanks!

Comment 3

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/17143afc4fab

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/17143afc4fab

Do we have tests for this? If not, should we?

Comment 5

[Dan Gohman [:sunfish]]

There are existing tests that Math.sqrt returns the right answer for a variety of interesting inputs and existing tests that call Math.sqrt from asm.js. Unfortunately however, there's no framework for testing that the JIT performed a particular optimization or emitted a particular code sequence.

Comment 6

[Ryan VanderMeulen [:RyanVM]]

Correctness is my concern, so it sounds like we're good. Thanks.