InstructionFinder xref

View Javadoc

    1   /*
    2    * Copyright  2000-2004 The Apache Software Foundation
    3    *
    4    *  Licensed under the Apache License, Version 2.0 (the "License");
    5    *  you may not use this file except in compliance with the License.
    6    *  You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   *  Unless required by applicable law or agreed to in writing, software
    11   *  distributed under the License is distributed on an "AS IS" BASIS,
    12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   *  See the License for the specific language governing permissions and
    14   *  limitations under the License.
    15   *
    16   */
    17  package org.apache.bcel.util;
    18
    19  import java.util.ArrayList;
    20  import java.util.HashMap;
    21  import java.util.Iterator;
    22  import java.util.List;
    23  import java.util.Locale;
    24  import java.util.Map;
    25  import java.util.regex.Matcher;
    26  import java.util.regex.Pattern;
    27  import org.apache.bcel.Constants;
    28  import org.apache.bcel.generic.ClassGenException;
    29  import org.apache.bcel.generic.Instruction;
    30  import org.apache.bcel.generic.InstructionHandle;
    31  import org.apache.bcel.generic.InstructionList;
    32
    33  /***
    34   * InstructionFinder is a tool to search for given instructions patterns, i.e.,
    35   * match sequences of instructions in an instruction list via regular
    36   * expressions. This can be used, e.g., in order to implement a peep hole
    37   * optimizer that looks for code patterns and replaces them with faster
    38   * equivalents.
    39   *
    40   * <p>
    41   * This class internally uses the <a href="http://jakarta.apache.org/regexp/">
    42   * Regexp</a> package to search for regular expressions.
    43   *
    44   * A typical application would look like this:
    45   *
    46   * <pre>
    47   *
    48   *
    49   *   InstructionFinder f   = new InstructionFinder(il);
    50   *   String            pat = &quot;IfInstruction ICONST_0 GOTO ICONST_1 NOP (IFEQ|IFNE)&quot;;
    51   *
    52   *   for(Iterator i = f.search(pat, constraint); i.hasNext(); ) {
    53   *   InstructionHandle[] match = (InstructionHandle[])i.next();
    54   *   ...
    55   *   il.delete(match[1], match[5]);
    56   *   ...
    57   *   }
    58   *
    59   *
    60   * </pre>
    61   *
    62   * @version $Id: InstructionFinder.java 386056 2006-03-15 11:31:56Z tcurdt $
    63   * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
    64   * @see Instruction
    65   * @see InstructionList
    66   */
    67  public class InstructionFinder {
    68
    69      private static final int OFFSET = 32767; // char + OFFSET is
    70      // outside of
    71      // LATIN-1
    72      private static final int NO_OPCODES = 256; // Potential number,
    73      // some are not used
    74      private static final Map map = new HashMap(); // Map<String,Pattern>
    75      private InstructionList il;
    76      private String il_string; // instruction list
    77      // as string
    78      private InstructionHandle[] handles; // map instruction
    79
    80
    81      // list to array
    82      /***
    83       * @param il
    84       *          instruction list to search for given patterns
    85       */
    86      public InstructionFinder(InstructionList il) {
    87          this.il = il;
    88          reread();
    89      }
    90
    91
    92      /***
    93       * Reread the instruction list, e.g., after you've altered the list upon a
    94       * match.
    95       */
    96      public final void reread() {
    97          int size = il.getLength();
    98          char[] buf = new char[size]; // Create a string with length equal to il
    99          // length
    100         handles = il.getInstructionHandles();
    101         // Map opcodes to characters
    102         for (int i = 0; i < size; i++) {
    103             buf[i] = makeChar(handles[i].getInstruction().getOpcode());
    104         }
    105         il_string = new String(buf);
    106     }
    107
    108
    109     /***
    110      * Map symbolic instruction names like "getfield" to a single character.
    111      *
    112      * @param pattern
    113      *          instruction pattern in lower case
    114      * @return encoded string for a pattern such as "BranchInstruction".
    115      */
    116     private static final String mapName( String pattern ) {
    117         String result = (String) map.get(pattern);
    118         if (result != null) {
    119             return result;
    120         }
    121         for (short i = 0; i < NO_OPCODES; i++) {
    122             if (pattern.equals(Constants.OPCODE_NAMES[i])) {
    123                 return "" + makeChar(i);
    124             }
    125         }
    126         throw new RuntimeException("Instruction unknown: " + pattern);
    127     }
    128
    129
    130     /***
    131      * Replace symbolic names of instructions with the appropiate character and
    132      * remove all white space from string. Meta characters such as +, * are
    133      * ignored.
    134      *
    135      * @param pattern
    136      *          The pattern to compile
    137      * @return translated regular expression string
    138      */
    139     private static final String compilePattern( String pattern ) {
    140         //Bug: 38787 - Instructions are assumed to be english, to avoid odd Locale issues
    141         String lower = pattern.toLowerCase(Locale.ENGLISH);
    142         StringBuffer buf = new StringBuffer();
    143         int size = pattern.length();
    144         for (int i = 0; i < size; i++) {
    145             char ch = lower.charAt(i);
    146             if (Character.isLetterOrDigit(ch)) {
    147                 StringBuffer name = new StringBuffer();
    148                 while ((Character.isLetterOrDigit(ch) || ch == '_') && i < size) {
    149                     name.append(ch);
    150                     if (++i < size) {
    151                         ch = lower.charAt(i);
    152                     } else {
    153                         break;
    154                     }
    155                 }
    156                 i--;
    157                 buf.append(mapName(name.toString()));
    158             } else if (!Character.isWhitespace(ch)) {
    159                 buf.append(ch);
    160             }
    161         }
    162         return buf.toString();
    163     }
    164
    165
    166     /***
    167      * @return the matched piece of code as an array of instruction (handles)
    168      */
    169     private InstructionHandle[] getMatch( int matched_from, int match_length ) {
    170         InstructionHandle[] match = new InstructionHandle[match_length];
    171         System.arraycopy(handles, matched_from, match, 0, match_length);
    172         return match;
    173     }
    174
    175
    176     /***
    177      * Search for the given pattern in the instruction list. You can search for
    178      * any valid opcode via its symbolic name, e.g. "istore". You can also use a
    179      * super class or an interface name to match a whole set of instructions, e.g.
    180      * "BranchInstruction" or "LoadInstruction". "istore" is also an alias for all
    181      * "istore_x" instructions. Additional aliases are "if" for "ifxx", "if_icmp"
    182      * for "if_icmpxx", "if_acmp" for "if_acmpxx".
    183      *
    184      * Consecutive instruction names must be separated by white space which will
    185      * be removed during the compilation of the pattern.
    186      *
    187      * For the rest the usual pattern matching rules for regular expressions
    188      * apply.
    189      * <P>
    190      * Example pattern:
    191      *
    192      * <pre>
    193      * search(&quot;BranchInstruction NOP ((IfInstruction|GOTO)+ ISTORE Instruction)*&quot;);
    194      * </pre>
    195      *
    196      * <p>
    197      * If you alter the instruction list upon a match such that other matching
    198      * areas are affected, you should call reread() to update the finder and call
    199      * search() again, because the matches are cached.
    200      *
    201      * @param pattern
    202      *          the instruction pattern to search for, where case is ignored
    203      * @param from
    204      *          where to start the search in the instruction list
    205      * @param constraint
    206      *          optional CodeConstraint to check the found code pattern for
    207      *          user-defined constraints
    208      * @return iterator of matches where e.nextElement() returns an array of
    209      *         instruction handles describing the matched area
    210      */
    211     public final Iterator search( String pattern, InstructionHandle from, CodeConstraint constraint ) {
    212         String search = compilePattern(pattern);
    213         int start = -1;
    214         for (int i = 0; i < handles.length; i++) {
    215             if (handles[i] == from) {
    216                 start = i; // Where to start search from (index)
    217                 break;
    218             }
    219         }
    220         if (start == -1) {
    221             throw new ClassGenException("Instruction handle " + from
    222                     + " not found in instruction list.");
    223         }
    224         Pattern regex = Pattern.compile(search);
    225         List matches = new ArrayList();
    226         Matcher matcher = regex.matcher(il_string);
    227         while (start < il_string.length() && matcher.find(start)) {
    228             int startExpr = matcher.start();
    229             int endExpr = matcher.end();
    230             int lenExpr = (endExpr - startExpr) + 1;
    231             InstructionHandle[] match = getMatch(startExpr, lenExpr);
    232             if ((constraint == null) || constraint.checkCode(match)) {
    233                 matches.add(match);
    234             }
    235             start = endExpr;
    236         }
    237         return matches.iterator();
    238     }
    239
    240
    241     /***
    242      * Start search beginning from the start of the given instruction list.
    243      *
    244      * @param pattern
    245      *          the instruction pattern to search for, where case is ignored
    246      * @return iterator of matches where e.nextElement() returns an array of
    247      *         instruction handles describing the matched area
    248      */
    249     public final Iterator search( String pattern ) {
    250         return search(pattern, il.getStart(), null);
    251     }
    252
    253
    254     /***
    255      * Start search beginning from `from'.
    256      *
    257      * @param pattern
    258      *          the instruction pattern to search for, where case is ignored
    259      * @param from
    260      *          where to start the search in the instruction list
    261      * @return iterator of matches where e.nextElement() returns an array of
    262      *         instruction handles describing the matched area
    263      */
    264     public final Iterator search( String pattern, InstructionHandle from ) {
    265         return search(pattern, from, null);
    266     }
    267
    268
    269     /***
    270      * Start search beginning from the start of the given instruction list. Check
    271      * found matches with the constraint object.
    272      *
    273      * @param pattern
    274      *          the instruction pattern to search for, case is ignored
    275      * @param constraint
    276      *          constraints to be checked on matching code
    277      * @return instruction handle or `null' if the match failed
    278      */
    279     public final Iterator search( String pattern, CodeConstraint constraint ) {
    280         return search(pattern, il.getStart(), constraint);
    281     }
    282
    283
    284     /***
    285      * Convert opcode number to char.
    286      */
    287     private static final char makeChar( short opcode ) {
    288         return (char) (opcode + OFFSET);
    289     }
    290
    291
    292     /***
    293      * @return the inquired instruction list
    294      */
    295     public final InstructionList getInstructionList() {
    296         return il;
    297     }
    298
    299     /***
    300      * Code patterns found may be checked using an additional user-defined
    301      * constraint object whether they really match the needed criterion. I.e.,
    302      * check constraints that can not expressed with regular expressions.
    303      *
    304      */
    305     public static interface CodeConstraint {
    306
    307         /***
    308          * @param match
    309          *          array of instructions matching the requested pattern
    310          * @return true if the matched area is really useful
    311          */
    312         public boolean checkCode( InstructionHandle[] match );
    313     }
    314
    315     // Initialize pattern map
    316     static {
    317         map
    318                 .put(
    319                         "arithmeticinstruction",
    320                         "(irem|lrem|iand|ior|ineg|isub|lneg|fneg|fmul|ldiv|fadd|lxor|frem|idiv|land|ixor|ishr|fsub|lshl|fdiv|iadd|lor|dmul|lsub|ishl|imul|lmul|lushr|dneg|iushr|lshr|ddiv|drem|dadd|ladd|dsub)");
    321         map.put("invokeinstruction", "(invokevirtual|invokeinterface|invokestatic|invokespecial)");
    322         map
    323                 .put(
    324                         "arrayinstruction",
    325                         "(baload|aastore|saload|caload|fastore|lastore|iaload|castore|iastore|aaload|bastore|sastore|faload|laload|daload|dastore)");
    326         map.put("gotoinstruction", "(goto|goto_w)");
    327         map.put("conversioninstruction",
    328                 "(d2l|l2d|i2s|d2i|l2i|i2b|l2f|d2f|f2i|i2d|i2l|f2d|i2c|f2l|i2f)");
    329         map.put("localvariableinstruction",
    330                 "(fstore|iinc|lload|dstore|dload|iload|aload|astore|istore|fload|lstore)");
    331         map.put("loadinstruction", "(fload|dload|lload|iload|aload)");
    332         map.put("fieldinstruction", "(getfield|putstatic|getstatic|putfield)");
    333         map
    334                 .put(
    335                         "cpinstruction",
    336                         "(ldc2_w|invokeinterface|multianewarray|putstatic|instanceof|getstatic|checkcast|getfield|invokespecial|ldc_w|invokestatic|invokevirtual|putfield|ldc|new|anewarray)");
    337         map.put("stackinstruction", "(dup2|swap|dup2_x2|pop|pop2|dup|dup2_x1|dup_x2|dup_x1)");
    338         map
    339                 .put(
    340                         "branchinstruction",
    341                         "(ifle|if_acmpne|if_icmpeq|if_acmpeq|ifnonnull|goto_w|iflt|ifnull|if_icmpne|tableswitch|if_icmple|ifeq|if_icmplt|jsr_w|if_icmpgt|ifgt|jsr|goto|ifne|ifge|lookupswitch|if_icmpge)");
    342         map.put("returninstruction", "(lreturn|ireturn|freturn|dreturn|areturn|return)");
    343         map.put("storeinstruction", "(istore|fstore|dstore|astore|lstore)");
    344         map.put("select", "(tableswitch|lookupswitch)");
    345         map
    346                 .put(
    347                         "ifinstruction",
    348                         "(ifeq|ifgt|if_icmpne|if_icmpeq|ifge|ifnull|ifne|if_icmple|if_icmpge|if_acmpeq|if_icmplt|if_acmpne|ifnonnull|iflt|if_icmpgt|ifle)");
    349         map.put("jsrinstruction", "(jsr|jsr_w)");
    350         map.put("variablelengthinstruction", "(tableswitch|jsr|goto|lookupswitch)");
    351         map.put("unconditionalbranch", "(goto|jsr|jsr_w|athrow|goto_w)");
    352         map.put("constantpushinstruction", "(dconst|bipush|sipush|fconst|iconst|lconst)");
    353         map
    354                 .put(
    355                         "typedinstruction",
    356                         "(imul|lsub|aload|fload|lor|new|aaload|fcmpg|iand|iaload|lrem|idiv|d2l|isub|dcmpg|dastore|ret|f2d|f2i|drem|iinc|i2c|checkcast|frem|lreturn|astore|lushr|daload|dneg|fastore|istore|lshl|ldiv|lstore|areturn|ishr|ldc_w|invokeinterface|aastore|lxor|ishl|l2d|i2f|return|faload|sipush|iushr|caload|instanceof|invokespecial|putfield|fmul|ireturn|laload|d2f|lneg|ixor|i2l|fdiv|lastore|multianewarray|i2b|getstatic|i2d|putstatic|fcmpl|saload|ladd|irem|dload|jsr_w|dconst|dcmpl|fsub|freturn|ldc|aconst_null|castore|lmul|ldc2_w|dadd|iconst|f2l|ddiv|dstore|land|jsr|anewarray|dmul|bipush|dsub|sastore|d2i|i2s|lshr|iadd|l2i|lload|bastore|fstore|fneg|iload|fadd|baload|fconst|ior|ineg|dreturn|l2f|lconst|getfield|invokevirtual|invokestatic|iastore)");
    357         map.put("popinstruction", "(fstore|dstore|pop|pop2|astore|putstatic|istore|lstore)");
    358         map.put("allocationinstruction", "(multianewarray|new|anewarray|newarray)");
    359         map
    360                 .put(
    361                         "indexedinstruction",
    362                         "(lload|lstore|fload|ldc2_w|invokeinterface|multianewarray|astore|dload|putstatic|instanceof|getstatic|checkcast|getfield|invokespecial|dstore|istore|iinc|ldc_w|ret|fstore|invokestatic|iload|putfield|invokevirtual|ldc|new|aload|anewarray)");
    363         map
    364                 .put(
    365                         "pushinstruction",
    366                         "(dup|lload|dup2|bipush|fload|ldc2_w|sipush|lconst|fconst|dload|getstatic|ldc_w|aconst_null|dconst|iload|ldc|iconst|aload)");
    367         map
    368                 .put(
    369                         "stackproducer",
    370                         "(imul|lsub|aload|fload|lor|new|aaload|fcmpg|iand|iaload|lrem|idiv|d2l|isub|dcmpg|dup|f2d|f2i|drem|i2c|checkcast|frem|lushr|daload|dneg|lshl|ldiv|ishr|ldc_w|invokeinterface|lxor|ishl|l2d|i2f|faload|sipush|iushr|caload|instanceof|invokespecial|fmul|laload|d2f|lneg|ixor|i2l|fdiv|getstatic|i2b|swap|i2d|dup2|fcmpl|saload|ladd|irem|dload|jsr_w|dconst|dcmpl|fsub|ldc|arraylength|aconst_null|tableswitch|lmul|ldc2_w|iconst|dadd|f2l|ddiv|land|jsr|anewarray|dmul|bipush|dsub|d2i|newarray|i2s|lshr|iadd|lload|l2i|fneg|iload|fadd|baload|fconst|lookupswitch|ior|ineg|lconst|l2f|getfield|invokevirtual|invokestatic)");
    371         map
    372                 .put(
    373                         "stackconsumer",
    374                         "(imul|lsub|lor|iflt|fcmpg|if_icmpgt|iand|ifeq|if_icmplt|lrem|ifnonnull|idiv|d2l|isub|dcmpg|dastore|if_icmpeq|f2d|f2i|drem|i2c|checkcast|frem|lreturn|astore|lushr|pop2|monitorexit|dneg|fastore|istore|lshl|ldiv|lstore|areturn|if_icmpge|ishr|monitorenter|invokeinterface|aastore|lxor|ishl|l2d|i2f|return|iushr|instanceof|invokespecial|fmul|ireturn|d2f|lneg|ixor|pop|i2l|ifnull|fdiv|lastore|i2b|if_acmpeq|ifge|swap|i2d|putstatic|fcmpl|ladd|irem|dcmpl|fsub|freturn|ifgt|castore|lmul|dadd|f2l|ddiv|dstore|land|if_icmpne|if_acmpne|dmul|dsub|sastore|ifle|d2i|i2s|lshr|iadd|l2i|bastore|fstore|fneg|fadd|ior|ineg|ifne|dreturn|l2f|if_icmple|getfield|invokevirtual|invokestatic|iastore)");
    375         map
    376                 .put(
    377                         "exceptionthrower",
    378                         "(irem|lrem|laload|putstatic|baload|dastore|areturn|getstatic|ldiv|anewarray|iastore|castore|idiv|saload|lastore|fastore|putfield|lreturn|caload|getfield|return|aastore|freturn|newarray|instanceof|multianewarray|athrow|faload|iaload|aaload|dreturn|monitorenter|checkcast|bastore|arraylength|new|invokevirtual|sastore|ldc_w|ireturn|invokespecial|monitorexit|invokeinterface|ldc|invokestatic|daload)");
    379         map
    380                 .put(
    381                         "loadclass",
    382                         "(multianewarray|invokeinterface|instanceof|invokespecial|putfield|checkcast|putstatic|invokevirtual|new|getstatic|invokestatic|getfield|anewarray)");
    383         map
    384                 .put(
    385                         "instructiontargeter",
    386                         "(ifle|if_acmpne|if_icmpeq|if_acmpeq|ifnonnull|goto_w|iflt|ifnull|if_icmpne|tableswitch|if_icmple|ifeq|if_icmplt|jsr_w|if_icmpgt|ifgt|jsr|goto|ifne|ifge|lookupswitch|if_icmpge)");
    387         // Some aliases
    388         map.put("if_icmp", "(if_icmpne|if_icmpeq|if_icmple|if_icmpge|if_icmplt|if_icmpgt)");
    389         map.put("if_acmp", "(if_acmpeq|if_acmpne)");
    390         map.put("if", "(ifeq|ifne|iflt|ifge|ifgt|ifle)");
    391         // Precompile some aliases first
    392         map.put("iconst", precompile(Constants.ICONST_0, Constants.ICONST_5, Constants.ICONST_M1));
    393         map.put("lconst", new String(new char[] {
    394                 '(', makeChar(Constants.LCONST_0), '|', makeChar(Constants.LCONST_1), ')'
    395         }));
    396         map.put("dconst", new String(new char[] {
    397                 '(', makeChar(Constants.DCONST_0), '|', makeChar(Constants.DCONST_1), ')'
    398         }));
    399         map.put("fconst", new String(new char[] {
    400                 '(', makeChar(Constants.FCONST_0), '|', makeChar(Constants.FCONST_1), ')'
    401         }));
    402         map.put("iload", precompile(Constants.ILOAD_0, Constants.ILOAD_3, Constants.ILOAD));
    403         map.put("dload", precompile(Constants.DLOAD_0, Constants.DLOAD_3, Constants.DLOAD));
    404         map.put("fload", precompile(Constants.FLOAD_0, Constants.FLOAD_3, Constants.FLOAD));
    405         map.put("aload", precompile(Constants.ALOAD_0, Constants.ALOAD_3, Constants.ALOAD));
    406         map.put("istore", precompile(Constants.ISTORE_0, Constants.ISTORE_3, Constants.ISTORE));
    407         map.put("dstore", precompile(Constants.DSTORE_0, Constants.DSTORE_3, Constants.DSTORE));
    408         map.put("fstore", precompile(Constants.FSTORE_0, Constants.FSTORE_3, Constants.FSTORE));
    409         map.put("astore", precompile(Constants.ASTORE_0, Constants.ASTORE_3, Constants.ASTORE));
    410         // Compile strings
    411         for (Iterator i = map.keySet().iterator(); i.hasNext();) {
    412             String key = (String) i.next();
    413             String value = (String) map.get(key);
    414             char ch = value.charAt(1); // Omit already precompiled patterns
    415             if (ch < OFFSET) {
    416                 map.put(key, compilePattern(value)); // precompile all patterns
    417             }
    418         }
    419         // Add instruction alias to match anything
    420         StringBuffer buf = new StringBuffer("(");
    421         for (short i = 0; i < NO_OPCODES; i++) {
    422             if (Constants.NO_OF_OPERANDS[i] != Constants.UNDEFINED) { // Not an
    423                 // invalid
    424                 // opcode
    425                 buf.append(makeChar(i));
    426                 if (i < NO_OPCODES - 1) {
    427                     buf.append('|');
    428                 }
    429             }
    430         }
    431         buf.append(')');
    432         map.put("instruction", buf.toString());
    433     }
    434
    435
    436     private static String precompile( short from, short to, short extra ) {
    437         StringBuffer buf = new StringBuffer("(");
    438         for (short i = from; i <= to; i++) {
    439             buf.append(makeChar(i));
    440             buf.append('|');
    441         }
    442         buf.append(makeChar(extra));
    443         buf.append(")");
    444         return buf.toString();
    445     }
    446
    447
    448     /*
    449      * Internal debugging routines.
    450      */
    451     private static final String pattern2string( String pattern ) {
    452         return pattern2string(pattern, true);
    453     }
    454
    455
    456     private static final String pattern2string( String pattern, boolean make_string ) {
    457         StringBuffer buf = new StringBuffer();
    458         for (int i = 0; i < pattern.length(); i++) {
    459             char ch = pattern.charAt(i);
    460             if (ch >= OFFSET) {
    461                 if (make_string) {
    462                     buf.append(Constants.OPCODE_NAMES[ch - OFFSET]);
    463                 } else {
    464                     buf.append((ch - OFFSET));
    465                 }
    466             } else {
    467                 buf.append(ch);
    468             }
    469         }
    470         return buf.toString();
    471     }
    472 }