[webkit-dev] Proposal on retiring JIT on Windows

Fujii Hironori fujii.hironori at gmail.com
Sat Mar 25 15:02:24 PDT 2023

It sounds reasonable. I don't object to removing Windows JIT support.

How about LLInt? LLInt has some Windows specific code.
Can I revert the change if the JSC team breaks Windows port even though we
have no EWS nor maintainers?

On Sun, Mar 26, 2023 at 6:52 AM Yusuke Suzuki via webkit-dev <
webkit-dev at lists.webkit.org> wrote:

> Hello,
> I would like to propose retiring JIT on Windows JavaScriptCore.
> Recently, Apple Windows EWS bots get removed. As a result, there is no
> test-running EWS bots on Windows.
> This can work for the other part of WebKit since other ports EWS bots are
> running tests. However this does not work well for JSC.
> Compile-tests is not sufficient for JIT since JIT is dynamically
> generated. And JIT is very architecture and platform specific.
> Windows has different ABI, different calling convention, and register
> usage. JIT on Windows has very specific things.
> Now, because there is no running EWS bots on Windows, it is not possible
> to catch Windows specific JIT related issues before landing.
> Recently, JSC DFG patch has been reverted because Windows gets broken[1].
> But this puts high burden to JSC maintenance since
> there is no way to test it before landing, and it makes DFG changes very
> hard due to Windows.
> So, given that there is no active maintainers of Windows JSC JIT and no
> EWS bots running tests, I propose retiring JIT on Windows.
> [1]:
> https://github.com/WebKit/WebKit/commit/58f0d9e4a395e0173e4d3f59888bf0e761cf6ce3
> -Yusuke
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