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ComplexGetStatus.h
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109 lines (96 loc) · 4.32 KB
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/*
* Copyright (C) 2014, 2015 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <JavaScriptCore/ObjectPropertyConditionSet.h>
#include <JavaScriptCore/PropertyOffset.h>
namespace JSC {
class CodeBlock;
class StructureChain;
// This class is useful for figuring out how to inline a cached get-like access. We
// say "get-like" because this is appropriate for loading the GetterSetter object in
// a put_by_id that hits a setter. Notably, this doesn't figure out how to call
// accessors, or even whether they should be called. What it gives us, is a way of
// determining how to load the value from the requested property (identified by a
// StringImpl* uid) from an object of the given structure in the given CodeBlock,
// assuming that such an access had already been cached by Repatch (and so Repatch had
// already done a bunch of safety checks). This doesn't reexecute any checks that
// Repatch would have executed, and for prototype chain accesses, it doesn't ask the
// objects in the prototype chain whether their getOwnPropertySlot would attempt to
// intercept the access - so this really is only appropriate if you already know that
// one of the JITOperations had OK'd this for caching and that Repatch concurred.
//
// The typical use pattern is something like:
//
// ComplexGetStatus status = ComplexGetStatus::computeFor(...);
// switch (status.kind()) {
// case ComplexGetStatus::ShouldSkip:
// // Handle the case where this kind of access is possibly safe but wouldn't
// // pass the required safety checks. For example, if an IC gives us a list of
// // accesses and one of them is ShouldSkip, then we should pretend as if it
// // wasn't even there.
// break;
// case ComplexGetStatus::TakesSlowPath:
// // This kind of access is not safe to inline. Bail out of any attempst to
// // inline.
// break;
// case ComplexGetStatus::Inlineable:
// // The good stuff goes here. If it's Inlineable then the other properties of
// // the 'status' object will tell you everything you need to know about how
// // to execute the get-like operation.
// break;
// }
class ComplexGetStatus final {
public:
enum Kind {
ShouldSkip,
TakesSlowPath,
Inlineable
};
ComplexGetStatus()
: m_kind(ShouldSkip)
, m_offset(invalidOffset)
{
}
static ComplexGetStatus skip()
{
return ComplexGetStatus();
}
static ComplexGetStatus takesSlowPath()
{
ComplexGetStatus result;
result.m_kind = TakesSlowPath;
return result;
}
static ComplexGetStatus computeFor(
Structure* headStructure, const ObjectPropertyConditionSet&, UniquedStringImpl* uid);
Kind kind() const { return m_kind; }
PropertyOffset offset() const { return m_offset; }
const ObjectPropertyConditionSet& conditionSet() const LIFETIME_BOUND { return m_conditionSet; }
private:
Kind m_kind;
PropertyOffset m_offset;
ObjectPropertyConditionSet m_conditionSet;
};
} // namespace JSC