/* * Copyright (C) 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 #if ENABLE(DFG_JIT) namespace JSC { namespace DFG { class Graph; struct Node; // A conservative approximation of whether the node will perform the kind of effect that would prevent // subsequent nodes from exiting to this node's exit origin. Exiting after an effect to that effect's // exit origin would cause the effect to execute a second time. Two kinds of such effects can exist: // // Observable heap or stack effect: If we perform such an effect and then exit to the same origin, that // effect will be executed a second time, which is incorrect. // // OSR exit state update: This doesn't do any observable side-effect, but it tells OSR exit that it // should recover some value as if an effect had happened. For example, a MovHint will tell OSR exit // that some bytecode variable now has a new value. If we exit to the exit origin of a MovHint after we // "execute" the MovHint, then the bytecode state will look as if we had already executed that bytecode // instruction. This could cause issues for example for bytecode like: // // op_add r1, r1, r2 // // which will get lowered to something like: // // a: ArithAdd(...) // b: MovHint(@a, r1) // // If we exit to the op_add after executing the MovHint, then r1 will already contain the result of the // add. Then after exit we'll do the add again, and r1 will have the wrong value. Because of object // allocation elimination and PutStack sinking, we can also have other OSR exit updates, like // KillStack, PutHint, among others. They don't do anything so long as we stay in optimized code, but // they tell OSR exit how to reconstitute state. bool clobbersExitState(Graph&, Node*); } } // namespace JSC::DFG #endif // ENABLE(DFG_JIT)