[webkit-dev] x32 support of JavaScriptCore

[Xian, Yuqiang]

Hi,

As you may already know there's a new x32 ABI - a 32-bit psABI for x86-64 with 32-bit pointer size. It tries to leverage the advantage of more registers and IP relative addressing from x64 and the advantage of smaller memory footprint from IA32. You can find more details of the x32 ABI here: https://sites.google.com/site/x32abi/.

The Linux kernel supports x32 since 3.4, and the commonly used development tools and libraries are getting in the x32 support. Also more details about current status is available in the above link.

Now back to WebKit. In theory most part of the WebKit code should be fine (or require less efforts) to support x32, if they're pure C++ code and can be compiled with the x32 toolchain. The major challenge is the JIT compiler in the JavaScript engine (and the low level interpreter) and some hand-written assembly code. So I'm currently working on enabling the x32 support of JavaScriptCore, the WebKit JavaScript engine, to try to remove the major obstacle. My current status is that I have enabled the baseline JIT, the DFG JIT and the Yarr JIT on x32 - it passes all the JavaScriptCore tests and the 3 major benchmarks.

I'm posting this message in order to seek for some advices on how we should have our work shared to more people. I understand that it's not very appropriate to try to get it into current WebKit trunk considering current x32 support status in major systems and the lack of maintenance in upstream, but we want to keep it synchronized with the newest changes of the WebKit code. So is it possible for us to maintain the code in a separate branch hosted at the WebKit server?

Any suggestions are appreciated.

Thanks, -Yuqiang
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