Bug 38747 – mingw-w64 and JIT support

• Component: Platform
• Status: CLOSED FIXED

Since the recently landed patches for bug https://bugs.webkit.org/show_bug.cgi?id=35607 (which have been introduced in QtWebkit as well), I have stumbled upon a serious issue with mingw-w64 and enabled JIT.

The above patches (see bug report) enable JIT for a X86_64 Windows when using mingw-w64. This was a mistake, as even MSVC x64 builds don't enable it and the JIT crashes any webkit program using the build. Without it, everything is perfectly fine.

I'm sorry I didn't upload a patch, but there are only two lines to be removed (line 943-944 (trunk) of JavaScriptCore/wtf/Platform.h, those enabling JIT on the x64 Windows builds with mingw-w64).

It would of course be better to fix JIT on Win64, but I am in no position (knowledge or otherwise) to do so, and I'm leaving that to more experienced people.

[Benjamin Poulain]

Thanks for adding me in CC. This is blocking for QtWebKit.

Any chance this could still be pushed to 4.7 before release?

The true fixing for Win64 JIT can come later...

[Kenneth Rohde Christiansen]

(In reply to comment #2)
> Any chance this could still be pushed to 4.7 before release?
> 
> The true fixing for Win64 JIT can come later...

It is already blocking on the release bug, so we will have to look at this before the release, yes.

[Laszlo Gombos]

Created attachment 55509 [details]
proposed patch

[Laszlo Gombos]

Gabor, any idea what is involved actually fixing JIT for MINGW64 ?

[Darin Adler]

Comment on attachment 55509 [details]
proposed patch

Seems OK, rs=me

[Gabor Loki]

At first I do not see why it is not working. JSValue64 is enabled, JIT stubs routines are there for GCC. There's nothing missing here. I am going to ask Ossy or someone else to reproduce the error.

[WebKit Commit Bot]

Comment on attachment 55509 [details]
proposed patch

Clearing flags on attachment: 55509

Committed r59074: <http://trac.webkit.org/changeset/59074>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Gabor Loki]

Unfortunately, we were not able to build QtWebKit with mingw-w64. It would be nice if someone writes a "works-for-me" section for mingw-w64 at http://trac.webkit.org/wiki/BuildingQtOnWindows wiki. Apart from that, no other magic should be needed to fire JIT up with mingw-w64.
In additional, the x86_64 based QtWebKit runs fine on linux, see at http://www.sed.hu/webkit/qtbuildbot/builders/x86-64%20Linux%20Qt%20Release. It is red, but the JIT runs (only 3 layout tests fail).
The JIT only has the following OS dependent sections: memory allocation, make a mem. range executable, flush a mem. region on some targets, and the function call abi (nothing else). So if this problem is not related to mingw-w64 compiler, the bug should be in ExecutableAllocator or JITStubs (or maybe in privateCompileCTIMachineTrampolines), but they look nice.
Well, a good back-trace is essential for efficient debugging. ;) Could someone make a detailed bug report for mingw-w64 JIT?

[WebKit Review Bot]

http://trac.webkit.org/changeset/59074 might have broken Qt Linux ARMv5 Release

By popular demand:

https://trac.webkit.org/wiki/BuildingQtOnWindows#AWorksForMeStep-by-StepGuidetobuildingQtWebKitonWindowsusingmingw-w64w32

If it doesn't work, please say so, then I may have missed a step...

[Simon Hausmann]

Revision r59074 cherry-picked into qtwebkit-2.0 with commit dc5821c3df2ef60456d85263160852f5335cf946