1 /*

     2  * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 

    25 package org.graalvm.compiler.hotspot;

    26 

    27 import org.graalvm.compiler.debug.GraalError;

    28 

    29 import jdk.vm.ci.meta.JavaConstant;

    30 

    31 /**

    32  * A context for scoping the lifetime of foreign objects.

    33  *

    34  * The need for this mechanism is best explained with an example. When folding a GETFIELD bytecode

    35  * denoting a {@code final static} non-primitive field, libgraal can create a {@link JavaConstant}

    36  * wrapping a handle to the field's value in the HotSpot heap. This handle must be released before

    37  * HotSpot can reclaim the object it references. Performing a compilation in the scope of a

    38  * {@linkplain HotSpotGraalServices#openLocalCompilationContext local} context ensures the handle is

    39  * released once the compilation completes, allowing the HotSpot GC to subsequently reclaim the

    40  * HotSpot object. When libgraal creates data structures that outlive a single compilation and may

    41  * contain foreign object references (e.g. snippet graphs), it must enter the

    42  * {@linkplain HotSpotGraalServices#enterGlobalCompilationContext global} context. Foreign object

    43  * handles created in the global context are only released once their {@link JavaConstant} wrappers

    44  * are reclaimed by the libgraal GC.

    45  *

    46  * {@link CompilationContext}s have no impact on {@link JavaConstant}s that do not encapsulate a

    47  * foreign object reference.

    48  *

    49  * The object returned by {@link HotSpotGraalServices#enterGlobalCompilationContext} or

    50  * {@link HotSpotGraalServices#openLocalCompilationContext} should be used in a try-with-resources

    51  * statement. Failure to close a context will almost certainly result in foreign objects being

    52  * leaked.

    53  */

    54 public class CompilationContext implements AutoCloseable {

    55     private final AutoCloseable impl;

    56 

    57     CompilationContext(AutoCloseable impl) {

    58         this.impl = impl;

    59     }

    60 

    61     @Override

    62     public void close() {

    63         try {

    64             impl.close();

    65         } catch (Exception e) {

    66             GraalError.shouldNotReachHere(e);

    67         }

    68     }

    69 }