Source code of MARS Assembler
First commit of the 4.5 version (latest version available)
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/*
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Copyright (c) 2009, Ingo Kofler, ITEC, Klagenfurt University, Austria
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Developed by Ingo Kofler (ingo.kofler@itec.uni-klu.ac.at)
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject
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to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
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ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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(MIT license, http://www.opensource.org/licenses/mit-license.html)
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*/
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package mars.tools;//.bhtsim;
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import java.util.Vector;
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import javax.swing.table.AbstractTableModel;
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/**
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* Simulates the actual functionality of a Branch History Table (BHT).
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* <p>
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* The BHT consists of a number of BHT entries which are used to perform branch prediction.
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* The entries of the BHT are stored as a Vector of BHTEntry objects.
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* The number of entries is configurable but has to be a power of 2.
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* The history kept by each BHT entry is also configurable during run-time.
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* A change of the configuration however causes a complete reset of the BHT.
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* <p>
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* The typical interaction is as follows:
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* <ul>
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* <li>Construction of a BHT with a certain number of entries with a given history size.</li>
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* <li>When encountering a branch instruction the index of the relevant BHT entry is calculated via the {@link BHTableModel#getIdxForAddress(int)} method.</li>
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* <li>The current prediction of the BHT entry at the calculated index is obtained via the {@link BHTableModel#getPredictionAtIdx(int)} method.</li>
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* <li>After detecting if the branch was really taken or not, this feedback is provided to the BHT by the {@link BHTableModel#updatePredictionAtIdx(int, boolean)} method.</li>
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* </ul>
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* <p>
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* Additionally it serves as TableModel that can be directly used to render the state of the BHT in a JTable.
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* Feedback provided to the BHT causes a change of the internal state and a repaint of the table(s) associated to this model.
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*
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* @author ingo.kofler@itec.uni-klu.ac.at
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*/
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//@SuppressWarnings("serial")
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public class BHTableModel extends AbstractTableModel {
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/** vector holding the entries of the BHT */
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private Vector m_entries;
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/** number of entries in the BHT */
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private int m_entryCnt;
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/** number of past branch events to remember */
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private int m_historySize;
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/** name of the table columns */
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private String m_columnNames[] = { "Index", "History", "Prediction", "Correct", "Incorrect", "Precision"};
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/** type of the table columns */
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//@SuppressWarnings("unchecked")
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private Class m_columnClasses[] = { Integer.class, String.class, String.class, Integer.class, Integer.class, Double.class};
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/**
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* Constructs a new BHT with given number of entries and history size.
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*
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* @param numEntries number of entries in the BHT
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* @param historySize size of the history (in bits/number of past branches)
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*/
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public BHTableModel (int numEntries, int historySize, boolean initVal) {
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initBHT(numEntries, historySize, initVal);
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}
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/**
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* Returns the name of the i-th column of the table.
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* Required by the TableModel interface.
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*
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* @param i the index of the column
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* @return name of the i-th column
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*/
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public String getColumnName(int i) {
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if (i < 0 || i > m_columnNames.length)
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throw new IllegalArgumentException("Illegal column index " + i + " (must be in range 0.." + (m_columnNames.length-1) + ")");
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return m_columnNames[i];
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}
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/**
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* Returns the class/type of the i-th column of the table.
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* Required by the TableModel interface.
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*
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* @param i the index of the column
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* @return class representing the type of the i-th column
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*/
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public Class getColumnClass(int i) {
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if (i < 0 || i > m_columnClasses.length)
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throw new IllegalArgumentException("Illegal column index " + i + " (must be in range 0.." + (m_columnClasses.length-1) + ")");
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return m_columnClasses[i];
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}
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/**
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* Returns the number of columns.
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* Required by the TableModel interface.
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*
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* @return currently the constant 6
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*/
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public int getColumnCount() {
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return 6;
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}
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/**
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* Returns the number of entries of the BHT.
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* Required by the TableModel interface.
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*
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* @return number of rows / entries of the BHT
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*/
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public int getRowCount() {
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return m_entryCnt;
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}
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/**
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* Returns the value of the cell at the given row and column
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* Required by the TableModel interface.
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*
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* @param row the row index
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* @param col the column index
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* @return the value of the cell
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*/
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public Object getValueAt(int row, int col) {
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BHTEntry e = (BHTEntry) m_entries.elementAt(row);
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if (e==null) return "";
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if (col==0) return new Integer(row);
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if (col==1) return e.getHistoryAsStr();
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if (col==2) return e.getPredictionAsStr();
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if (col==3) return new Integer(e.getStatsPredCorrect());
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if (col==4) return new Integer(e.getStatsPredIncorrect());
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if (col==5) return new Double(e.getStatsPredPrecision());
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return "";
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}
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/**
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* Initializes the BHT with the given size and history.
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* All previous data like the BHT entries' history and statistics will get lost.
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* A refresh of the table that use this BHT as model will be triggered.
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*
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* @param numEntries number of entries in the BHT (has to be a power of 2)
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* @param historySize size of the history to consider
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* @param initVal initial value for each entry (true means take branch, false do not take branch)
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*/
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public void initBHT(int numEntries, int historySize, boolean initVal) {
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if (numEntries <= 0 || (numEntries & (numEntries-1)) != 0)
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throw new IllegalArgumentException("Number of entries must be a positive power of 2.");
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if (historySize < 1 || historySize > 2)
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throw new IllegalArgumentException("Only history sizes of 1 or 2 supported.");
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m_entryCnt = numEntries;
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m_historySize = historySize;
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m_entries = new Vector();
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for (int i=0; i < m_entryCnt; i++) {
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m_entries.add(new BHTEntry(m_historySize, initVal));
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}
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// refresh the table(s)
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fireTableStructureChanged();
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}
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/**
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* Returns the index into the BHT for a given branch instruction address.
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* A simple direct mapping is used.
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*
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* @param address the address of the branch instruction
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* @return the index into the BHT
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*/
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public int getIdxForAddress(int address) {
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if (address < 0)
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throw new IllegalArgumentException("No negative addresses supported");
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return (address >> 2) % m_entryCnt;
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}
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/**
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* Retrieve the prediction for the i-th BHT entry.
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*
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* @param index the index of the entry in the BHT
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* @return the prediction to take (true) or do not take (false) the branch
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*/
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public boolean getPredictionAtIdx(int index) {
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if (index < 0 || index > m_entryCnt)
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throw new IllegalArgumentException("Only indexes in the range 0 to " + (m_entryCnt-1) + " allowed");
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return ((BHTEntry) m_entries.elementAt(index)).getPrediction();
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}
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/**
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* Updates the BHT entry with the outcome of the branch instruction.
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* This causes a change in the model and signals to update the connected table(s).
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*
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* @param index the index of the entry in the BHT
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* @param branchTaken
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*/
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public void updatePredictionAtIdx(int index, boolean branchTaken) {
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if (index < 0 || index > m_entryCnt)
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throw new IllegalArgumentException("Only indexes in the range 0 to " + (m_entryCnt-1) + " allowed");
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((BHTEntry) m_entries.elementAt(index)).updatePrediction(branchTaken);
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fireTableRowsUpdated(index, index);
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}
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}
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