mirror of
https://github.com/darlinghq/darling-JavaScriptCore.git
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93 lines
3.9 KiB
C++
93 lines
3.9 KiB
C++
/*
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* Copyright (C) 2014-2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#if ENABLE(DFG_JIT)
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namespace JSC { namespace DFG {
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class AtTailAbstractState;
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class Graph;
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struct Node;
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// A *very* conservative approximation of whether or not a node could possibly exit. Usually
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// returns true except in cases where we obviously don't expect an exit.
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enum ExitMode {
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// The node does not exit at all. This means that it's legal to eliminate the first store in a
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// program like:
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//
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// global = 1 // first store
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// DoesNotExit(); // let's assume that this also doesn't read "global"
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// global = 2 // second store
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//
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// It's legal to eliminate the first one since nobody will see it; the second store is always
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// executed right after.
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DoesNotExit,
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// The node will exit, but only by properly throwing exceptions. A proper exception throw will
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// divert execution to the matching op_catch and will not reexecute the exit origin. This means
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// that the store elimination optimization above would be illegal, but the following would be OK:
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//
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// SideEffect(..., exit: bc#42)
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// ExitsForExceptions(..., exit: #bc42, ExitInvalid)
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//
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// In particular, it's OK for a node that reports ExitsForExceptions to be executed in a context
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// where !Node::origin.exitOK. That's because this node will not exit in a manner that could lead
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// to the reexecution of SideEffect().
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ExitsForExceptions,
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// The node will exit to the exit origin. This means that we cannot do store elimination like for
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// DoesNotExit and also we cannot place this node in an ExitInvalid context, since this will exit
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// in a manner that will cause the reexecution of all previous operations within this exit origin.
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Exits
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};
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// FIXME: This currently consumes the Check: flag produced by AI, and will claim that something doesn't
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// exit if the Check: flag was cleared. This makes it hard to use mayExit() for things like hoisting
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// (for example in LICM), since that wants to know if the node would exit if it was moved somewhere
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// else.
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// https://bugs.webkit.org/show_bug.cgi?id=148545
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ExitMode mayExit(Graph&, Node*);
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// Like mayExit(), but instead of using the Check: flag to determine if something exits, it
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// evaluates whether it will exit based on the tail state. This is useful for LICM. This *may* also
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// use the AtTailAbstractState to return more precise answers for other nodes.
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ExitMode mayExit(Graph&, Node*, AtTailAbstractState&);
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} } // namespace JSC::DFG
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namespace WTF {
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class PrintStream;
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void printInternal(PrintStream&, JSC::DFG::ExitMode);
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} // namespace WTF
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#endif // ENABLE(DFG_JIT)
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