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/*
* Copyright (C) 2014-2016 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
#if ENABLE(DFG_JIT)
namespace JSC { namespace DFG {
class AtTailAbstractState;
class Graph;
struct Node;
// A *very* conservative approximation of whether or not a node could possibly exit. Usually
// returns true except in cases where we obviously don't expect an exit.
enum ExitMode {
// The node does not exit at all. This means that it's legal to eliminate the first store in a
// program like:
//
// global = 1 // first store
// DoesNotExit(); // let's assume that this also doesn't read "global"
// global = 2 // second store
//
// It's legal to eliminate the first one since nobody will see it; the second store is always
// executed right after.
DoesNotExit,
// The node will exit, but only by properly throwing exceptions. A proper exception throw will
// divert execution to the matching op_catch and will not reexecute the exit origin. This means
// that the store elimination optimization above would be illegal, but the following would be OK:
//
// SideEffect(..., exit: bc#42)
// ExitsForExceptions(..., exit: #bc42, ExitInvalid)
//
// In particular, it's OK for a node that reports ExitsForExceptions to be executed in a context
// where !Node::origin.exitOK. That's because this node will not exit in a manner that could lead
// to the reexecution of SideEffect().
ExitsForExceptions,
// The node will exit to the exit origin. This means that we cannot do store elimination like for
// DoesNotExit and also we cannot place this node in an ExitInvalid context, since this will exit
// in a manner that will cause the reexecution of all previous operations within this exit origin.
Exits
};
// FIXME: This currently consumes the Check: flag produced by AI, and will claim that something doesn't
// exit if the Check: flag was cleared. This makes it hard to use mayExit() for things like hoisting
// (for example in LICM), since that wants to know if the node would exit if it was moved somewhere
// else.
// https://bugs.webkit.org/show_bug.cgi?id=148545
ExitMode mayExit(Graph&, Node*);
// Like mayExit(), but instead of using the Check: flag to determine if something exits, it
// evaluates whether it will exit based on the tail state. This is useful for LICM. This *may* also
// use the AtTailAbstractState to return more precise answers for other nodes.
ExitMode mayExit(Graph&, Node*, AtTailAbstractState&);
} } // namespace JSC::DFG
namespace WTF {
class PrintStream;
void printInternal(PrintStream&, JSC::DFG::ExitMode);
} // namespace WTF
#endif // ENABLE(DFG_JIT)
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