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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DOMJIT] Add DOMJITSignature"
href="https://bugs.webkit.org/show_bug.cgi?id=162980">162980</a>
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<th>Summary</th>
<td>[DOMJIT] Add DOMJITSignature
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<th>Classification</th>
<td>Unclassified
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>WebKit Nightly Build
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<th>Hardware</th>
<td>Unspecified
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<th>OS</th>
<td>Unspecified
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>utatane.tea@gmail.com
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<p>
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<pre>We should have two type of DOMJIT functionality.
1. DOMJIT::GetterSetter based inlining system
We can define all the DOMJIT operations in DOMJIT::Patchpoint. It is great since we have a chance to inline it completely!
While it's quite good for performance, ASM is typically written by hand.
I explored the way to generate ASM automatically from IDL compiler, but the accessors we can do so is still limited.
For example, even in Node::firstChild, it has special check path for ContainerNode, while nextSibling, parentNode, and previousSibling do not have such a path.
And this fact is not exposed in IDL.
We manually write ASM in this case. It has scalability & complexity (But CSS Selector JIT already does the similar things for parentNode, siblings) problem.
So we will write this for super hot accessors. Like parentNode, firstChild etc.
2. DOMJIT::Signature based type checking elimination
On the other hand, this can be applied to many bindings automatically.
We support DOMJIT::Signature. That is the way to express DOM function's signature to DFG/FTL.
DFG / FTL recognizes and emit Checks instead of binding code. And in the middle of code, we will invoke the thin binding code that does not have any checks.</pre>
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