001    /*
002     *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003     *
004     *  This file is licensed to You under the Eclipse Public License (EPL);
005     *  You may not use this file except in compliance with the License. You
006     *  may obtain a copy of the License at
007     *
008     *      http://www.opensource.org/licenses/eclipse-1.0.php
009     *
010     *  See the COPYRIGHT.txt file distributed with this work for information
011     *  regarding copyright ownership.
012     */
013    package org.jikesrvm.ia32;
014    
015    import org.jikesrvm.VM;
016    import org.jikesrvm.runtime.Magic;
017    import org.vmmagic.pragma.NoInline;
018    import org.vmmagic.pragma.Uninterruptible;
019    import org.vmmagic.unboxed.Address;
020    
021    /**
022     * Machine specific helper functions for dynamic linking.
023     */
024    @Uninterruptible
025    public abstract class DynamicLinkerHelper {
026    
027      /**
028       * Reach up two stack frames into a frame that is compiled
029       * with the DynamicBridge register protocol and grap
030       * the receiver object of the invoke (ie the first param).
031       * NOTE: assumes that caller has disabled GC.
032       */
033      @NoInline
034      public static Object getReceiverObject() {
035    
036        Address callingFrame = Magic.getCallerFramePointer(Magic.getFramePointer());
037        callingFrame = Magic.getCallerFramePointer(callingFrame);
038        Address location = Address.zero();
039        if (0 < RegisterConstants.NUM_PARAMETER_GPRS) {
040          location = callingFrame.plus(BaselineConstants.STACKFRAME_FIRST_PARAMETER_OFFSET).loadAddress();
041    
042        } else {
043          VM.sysFail("DynamicLinerHelper: assumes at least one param passed in registers");
044        }
045        return Magic.addressAsObject(location);
046      }
047    }