| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| #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) |