1058651 - Add MOZ_UNLIKELY to codegen argc and exception checks

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

The codegen for DOM bindings (<https://mxr.mozilla.org/mozilla-central/source/dom/bindings/Codegen.py>) generates code that includes checks on the number of arguments and checks if the native function threw an exception.

We expect that these checks are only quite rarely true, so it seems worthwhile to wrap those checks in the MOZ_UNLIKELY() macro, to potentially improve the compiled code.

For number of arguments: <https://mxr.mozilla.org/mozilla-central/source/dom/bindings/Codegen.py?rev=1a3d7ec1a840&mark=6710-6712#6707>
For exceptions: <https://mxr.mozilla.org/mozilla-central/source/dom/bindings/Codegen.py?rev=1a3d7ec1a840&mark=6156-6158#6153>

Comment 1

[Mohit Tirkey]

I want to patch this,but need some help.

Comment 2

[Mike Hoye [:mhoye]]

Thanks, Mohit. The first thing to do is get your development environment set up; a good place to read how to do that is here: 

https://developer.mozilla.org/en-US/docs/Introduction

BZ, can you point to an example of where we're already using MOZ_UNLIKELY() so Mohit can get a sense of what a successful patch looks like here?

Comment 3

[Mohit Tirkey]

I've gone through the docs and also completed the code for firefox exercise which was a part of it and as I'm working on linux I've setup an enviroment by the help of instructions given in the docs.

Comment 4

[Akshendra Pratap Singh]

What is the status of this bug?

Comment 5

[Akshendra Pratap Singh]

Attachment: 1058651.patch

Comment 6

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8507854 [details] [diff] [review]
1058651.patch

I missed the part of comment 2 directed at me.  :(

r=me

Comment 7

[Boris Zbarsky [:bzbarsky]]

Akshendra, are you able to push this to try yourself, or do you need me to do it?

Comment 8

[Akshendra Pratap Singh]

I don't seem to have a level 1 hg account, so I cannot I suppose.

Comment 9

[Boris Zbarsky [:bzbarsky]]

https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=465ef6e52b93

Comment 10

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/04a6548edd2b

Comment 11

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/04a6548edd2b