[PATCH] Expose custom MC-JIT memory allocation through the C API

[Filip Pizlo]

On May 16, 2013, at 10:42 AM, Sean Silva <silvas at purdue.edu> wrote:

> Is basing the JSC fourth tier on LLVM something that you guys have committed to, or mainly exploratory? You seem to describe it as a "study" on <https://bugs.webkit.org/show_bug.cgi?id=112840>.

If we can get LLVM to provide a speed-up over our own optimizing JIT, then it will be turned on in WebKit trunk.  As you can see from that bug, we've put a lot of work into this so far, and still have a lot of work ahead of us.  The results so far are promising and I like where it's going, but given the amount of work remaining I cannot commit to anything.

> 
> The reason I ask is because we generally add things to the C API on a strictly as-needed basis.

We need it for the WebKit-LLVM integration project to be successful.  It's not possible to run any meaningful programs without getting the memory management story right.

> So unless you guys have committed to using LLVM for the fourth tier, it probably doesn't make sense to add this functionality to the C API yet. Regardless, this patch probably won't make it into a release until 3.4 (which is going to be months from now, as we are currently in the process of releasing 3.3), so for the purposes of using this for current development, you will need to use a custom-built LLVM anyway, and you can easily add this patch on top in the meantime.

We are fine with building from trunk.

On the other hand, requiring WebKit contributors to apply large meaty patches onto llvm trunk in order to build WebKit is a non-starter.

> 
> TBH I'm surprised we don't already support this functionality (i.e., that somebody hasn't needed it; it seems like a common need), but unless you are committed to shipping a real product with it I think it would be best to avoid the scenario where this is added to the C API, and then if it turns out that LLVM doesn't suit your needs, to end up with an unused feature in the C API.

I'm also surprised that this functionality isn't already available, which is why I added it.

-Filip

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