[webkit-dev] Bring back ARMv6 support to JSC

[Filip Pizlo]

To be clear, I’m concerned that the 32-bit JIT backends have such bad tuning for these embedded platforms that it’s just pure badness. Until you can prove that you can change this, I think that porting should focus on making the cloop great. Then, we can rip out support for weird CPUs rather than bringing it back. 

-Filip

> On Jul 5, 2017, at 6:14 PM, Caio Lima <ticaiolima at gmail.com> wrote:
> 
> 2017-07-05 18:25 GMT-03:00 Filip Pizlo <fpizlo at apple.com>:
>> You need to establish that the JIT is a performance progression over the LLInt on ARMv6. I am opposed to more ARMv6 patches landing until there is some evidence provided that you’re actually getting speed-ups.
> 
> It makes sense. I can get these numbers related to JIT.
> 
> BTW, there is a Patch that isn't JIT related
> (https://bugs.webkit.org/show_bug.cgi?id=172766).
> 
> Regards,
> Caio.
> 
>> -Filip
>> 
>>> On Jun 13, 2017, at 6:48 PM, Caio Lima <ticaiolima at gmail.com> wrote:
>>> 
>>> Hi All.
>>> 
>>> Some of you guys might know me through the work I have been doing in
>>> JSC. The experience working with WebKit has been great so far, thank
>>> you for the reviews!
>>> 
>>> Since 1st May, we at Igalia have been working on bring back the ARMv6
>>> support into JSC. We already have commits into our downstream branch
>>> port[2] that fixes some compile/runtime errors when building JSC to
>>> ARMv6 and also fixes some bugs. However, this branch is not synced
>>> with WebKit upstream tree and I would like to pursue the upstreaming
>>> of this ARMv6/JSC support to WebKit.
>>> 
>>> As a long shot, we are planning to maintain the ARMv6 support and make
>>> tests run as green as possible. Also, it's our goal make ARMv6 support
>>> not interfere with other ARM versions support code negatively and we
>>> will be in charge of implement platform-specific fixes/features for
>>> JSC/ARM6, this way no imposing burden to the rest of the community.
>>> 
>>> To keep track of work to be done, I've create a meta-bug in
>>> bugzilla[3] and it's going to be used firstly to organize the commits
>>> from our downstream branch, but pretty soon I'm going to create issues
>>> related with javascriptcore-test failures and send patches to fix
>>> them. We have already submitted 3 patches (they are marked as
>>> dependence of [3]) that fixes ARMv6 into LLInt and JIT layers and got
>>> a round of review into them.
>>> 
>>> Best Regards,
>>> Caio.
>>> 
>>> [1] - https://www.igalia.com/about-us/coding-experience
>>> [2] - https://github.com/WebPlatformForEmbedded/WPEWebKit
>>> [3] - https://bugs.webkit.org/show_bug.cgi?id=172765
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