InstructionFinder


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 }
473
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