1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * ASM: a very small and fast Java bytecode manipulation framework
32 * Copyright (c) 2000-2011 INRIA, France Telecom
33 * All rights reserved.
34 *
35 * Redistribution and use in source and binary forms, with or without
36 * modification, are permitted provided that the following conditions
37 * are met:
38 * 1. Redistributions of source code must retain the above copyright
39 * notice, this list of conditions and the following disclaimer.
40 * 2. Redistributions in binary form must reproduce the above copyright
41 * notice, this list of conditions and the following disclaimer in the
42 * documentation and/or other materials provided with the distribution.
43 * 3. Neither the name of the copyright holders nor the names of its
44 * contributors may be used to endorse or promote products derived from
45 * this software without specific prior written permission.
46 *
47 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
48 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
49 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
50 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
51 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
52 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
53 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
54 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
55 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
56 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
57 * THE POSSIBILITY OF SUCH DAMAGE.
58 */
59 package jdk.internal.org.objectweb.asm;
60
61 /**
62 * Information about the input and output stack map frames of a basic block.
63 *
64 * @author Eric Bruneton
65 */
66 final class Frame {
67
68 /*
69 * Frames are computed in a two steps process: during the visit of each
70 * instruction, the state of the frame at the end of current basic block is
71 * updated by simulating the action of the instruction on the previous state
72 * of this so called "output frame". In visitMaxs, a fix point algorithm is
73 * used to compute the "input frame" of each basic block, i.e. the stack map
74 * frame at the beginning of the basic block, starting from the input frame
75 * of the first basic block (which is computed from the method descriptor),
76 * and by using the previously computed output frames to compute the input
77 * state of the other blocks.
78 *
79 * All output and input frames are stored as arrays of integers. Reference
80 * and array types are represented by an index into a type table (which is
81 * not the same as the constant pool of the class, in order to avoid adding
82 * unnecessary constants in the pool - not all computed frames will end up
83 * being stored in the stack map table). This allows very fast type
84 * comparisons.
85 *
86 * Output stack map frames are computed relatively to the input frame of the
87 * basic block, which is not yet known when output frames are computed. It
88 * is therefore necessary to be able to represent abstract types such as
89 * "the type at position x in the input frame locals" or "the type at
90 * position x from the top of the input frame stack" or even "the type at
91 * position x in the input frame, with y more (or less) array dimensions".
92 * This explains the rather complicated type format used in output frames.
93 *
94 * This format is the following: DIM KIND VALUE (4, 4 and 24 bits). DIM is a
95 * signed number of array dimensions (from -8 to 7). KIND is either BASE,
96 * LOCAL or STACK. BASE is used for types that are not relative to the input
97 * frame. LOCAL is used for types that are relative to the input local
98 * variable types. STACK is used for types that are relative to the input
99 * stack types. VALUE depends on KIND. For LOCAL types, it is an index in
100 * the input local variable types. For STACK types, it is a position
101 * relatively to the top of input frame stack. For BASE types, it is either
102 * one of the constants defined below, or for OBJECT and UNINITIALIZED
103 * types, a tag and an index in the type table.
104 *
105 * Output frames can contain types of any kind and with a positive or
106 * negative dimension (and even unassigned types, represented by 0 - which
107 * does not correspond to any valid type value). Input frames can only
108 * contain BASE types of positive or null dimension. In all cases the type
109 * table contains only internal type names (array type descriptors are
110 * forbidden - dimensions must be represented through the DIM field).
111 *
112 * The LONG and DOUBLE types are always represented by using two slots (LONG
113 * + TOP or DOUBLE + TOP), for local variable types as well as in the
114 * operand stack. This is necessary to be able to simulate DUPx_y
115 * instructions, whose effect would be dependent on the actual type values
116 * if types were always represented by a single slot in the stack (and this
117 * is not possible, since actual type values are not always known - cf LOCAL
118 * and STACK type kinds).
119 */
120
121 /**
122 * Mask to get the dimension of a frame type. This dimension is a signed
123 * integer between -8 and 7.
124 */
125 static final int DIM = 0xF0000000;
126
127 /**
128 * Constant to be added to a type to get a type with one more dimension.
129 */
130 static final int ARRAY_OF = 0x10000000;
131
132 /**
133 * Constant to be added to a type to get a type with one less dimension.
134 */
135 static final int ELEMENT_OF = 0xF0000000;
136
137 /**
138 * Mask to get the kind of a frame type.
139 *
140 * @see #BASE
141 * @see #LOCAL
142 * @see #STACK
143 */
144 static final int KIND = 0xF000000;
145
146 /**
147 * Flag used for LOCAL and STACK types. Indicates that if this type happens
148 * to be a long or double type (during the computations of input frames),
149 * then it must be set to TOP because the second word of this value has been
150 * reused to store other data in the basic block. Hence the first word no
151 * longer stores a valid long or double value.
152 */
153 static final int TOP_IF_LONG_OR_DOUBLE = 0x800000;
154
155 /**
156 * Mask to get the value of a frame type.
157 */
158 static final int VALUE = 0x7FFFFF;
159
160 /**
161 * Mask to get the kind of base types.
162 */
163 static final int BASE_KIND = 0xFF00000;
164
165 /**
166 * Mask to get the value of base types.
167 */
168 static final int BASE_VALUE = 0xFFFFF;
169
170 /**
171 * Kind of the types that are not relative to an input stack map frame.
172 */
173 static final int BASE = 0x1000000;
174
175 /**
176 * Base kind of the base reference types. The BASE_VALUE of such types is an
177 * index into the type table.
178 */
179 static final int OBJECT = BASE | 0x700000;
180
181 /**
182 * Base kind of the uninitialized base types. The BASE_VALUE of such types
183 * in an index into the type table (the Item at that index contains both an
184 * instruction offset and an internal class name).
185 */
186 static final int UNINITIALIZED = BASE | 0x800000;
187
188 /**
189 * Kind of the types that are relative to the local variable types of an
190 * input stack map frame. The value of such types is a local variable index.
191 */
192 private static final int LOCAL = 0x2000000;
193
194 /**
195 * Kind of the the types that are relative to the stack of an input stack
196 * map frame. The value of such types is a position relatively to the top of
197 * this stack.
198 */
199 private static final int STACK = 0x3000000;
200
201 /**
202 * The TOP type. This is a BASE type.
203 */
204 static final int TOP = BASE | 0;
205
206 /**
207 * The BOOLEAN type. This is a BASE type mainly used for array types.
208 */
209 static final int BOOLEAN = BASE | 9;
210
211 /**
212 * The BYTE type. This is a BASE type mainly used for array types.
213 */
214 static final int BYTE = BASE | 10;
215
216 /**
217 * The CHAR type. This is a BASE type mainly used for array types.
218 */
219 static final int CHAR = BASE | 11;
220
221 /**
222 * The SHORT type. This is a BASE type mainly used for array types.
223 */
224 static final int SHORT = BASE | 12;
225
226 /**
227 * The INTEGER type. This is a BASE type.
228 */
229 static final int INTEGER = BASE | 1;
230
231 /**
232 * The FLOAT type. This is a BASE type.
233 */
234 static final int FLOAT = BASE | 2;
235
236 /**
237 * The DOUBLE type. This is a BASE type.
238 */
239 static final int DOUBLE = BASE | 3;
240
241 /**
242 * The LONG type. This is a BASE type.
243 */
244 static final int LONG = BASE | 4;
245
246 /**
247 * The NULL type. This is a BASE type.
248 */
249 static final int NULL = BASE | 5;
250
251 /**
252 * The UNINITIALIZED_THIS type. This is a BASE type.
253 */
254 static final int UNINITIALIZED_THIS = BASE | 6;
255
256 /**
257 * The stack size variation corresponding to each JVM instruction. This
258 * stack variation is equal to the size of the values produced by an
259 * instruction, minus the size of the values consumed by this instruction.
260 */
261 static final int[] SIZE;
262
263 /**
264 * Computes the stack size variation corresponding to each JVM instruction.
265 */
266 static {
267 int i;
268 int[] b = new int[202];
269 String s = "EFFFFFFFFGGFFFGGFFFEEFGFGFEEEEEEEEEEEEEEEEEEEEDEDEDDDDD"
270 + "CDCDEEEEEEEEEEEEEEEEEEEEBABABBBBDCFFFGGGEDCDCDCDCDCDCDCDCD"
271 + "CDCEEEEDDDDDDDCDCDCEFEFDDEEFFDEDEEEBDDBBDDDDDDCCCCCCCCEFED"
272 + "DDCDCDEEEEEEEEEEFEEEEEEDDEEDDEE";
273 for (i = 0; i < b.length; ++i) {
274 b[i] = s.charAt(i) - 'E';
275 }
276 SIZE = b;
277
278 // code to generate the above string
279 //
280 // int NA = 0; // not applicable (unused opcode or variable size opcode)
281 //
282 // b = new int[] {
283 // 0, //NOP, // visitInsn
284 // 1, //ACONST_NULL, // -
285 // 1, //ICONST_M1, // -
286 // 1, //ICONST_0, // -
287 // 1, //ICONST_1, // -
288 // 1, //ICONST_2, // -
289 // 1, //ICONST_3, // -
290 // 1, //ICONST_4, // -
291 // 1, //ICONST_5, // -
292 // 2, //LCONST_0, // -
293 // 2, //LCONST_1, // -
294 // 1, //FCONST_0, // -
295 // 1, //FCONST_1, // -
296 // 1, //FCONST_2, // -
297 // 2, //DCONST_0, // -
298 // 2, //DCONST_1, // -
299 // 1, //BIPUSH, // visitIntInsn
300 // 1, //SIPUSH, // -
301 // 1, //LDC, // visitLdcInsn
302 // NA, //LDC_W, // -
303 // NA, //LDC2_W, // -
304 // 1, //ILOAD, // visitVarInsn
305 // 2, //LLOAD, // -
306 // 1, //FLOAD, // -
307 // 2, //DLOAD, // -
308 // 1, //ALOAD, // -
309 // NA, //ILOAD_0, // -
310 // NA, //ILOAD_1, // -
311 // NA, //ILOAD_2, // -
312 // NA, //ILOAD_3, // -
313 // NA, //LLOAD_0, // -
314 // NA, //LLOAD_1, // -
315 // NA, //LLOAD_2, // -
316 // NA, //LLOAD_3, // -
317 // NA, //FLOAD_0, // -
318 // NA, //FLOAD_1, // -
319 // NA, //FLOAD_2, // -
320 // NA, //FLOAD_3, // -
321 // NA, //DLOAD_0, // -
322 // NA, //DLOAD_1, // -
323 // NA, //DLOAD_2, // -
324 // NA, //DLOAD_3, // -
325 // NA, //ALOAD_0, // -
326 // NA, //ALOAD_1, // -
327 // NA, //ALOAD_2, // -
328 // NA, //ALOAD_3, // -
329 // -1, //IALOAD, // visitInsn
330 // 0, //LALOAD, // -
331 // -1, //FALOAD, // -
332 // 0, //DALOAD, // -
333 // -1, //AALOAD, // -
334 // -1, //BALOAD, // -
335 // -1, //CALOAD, // -
336 // -1, //SALOAD, // -
337 // -1, //ISTORE, // visitVarInsn
338 // -2, //LSTORE, // -
339 // -1, //FSTORE, // -
340 // -2, //DSTORE, // -
341 // -1, //ASTORE, // -
342 // NA, //ISTORE_0, // -
343 // NA, //ISTORE_1, // -
344 // NA, //ISTORE_2, // -
345 // NA, //ISTORE_3, // -
346 // NA, //LSTORE_0, // -
347 // NA, //LSTORE_1, // -
348 // NA, //LSTORE_2, // -
349 // NA, //LSTORE_3, // -
350 // NA, //FSTORE_0, // -
351 // NA, //FSTORE_1, // -
352 // NA, //FSTORE_2, // -
353 // NA, //FSTORE_3, // -
354 // NA, //DSTORE_0, // -
355 // NA, //DSTORE_1, // -
356 // NA, //DSTORE_2, // -
357 // NA, //DSTORE_3, // -
358 // NA, //ASTORE_0, // -
359 // NA, //ASTORE_1, // -
360 // NA, //ASTORE_2, // -
361 // NA, //ASTORE_3, // -
362 // -3, //IASTORE, // visitInsn
363 // -4, //LASTORE, // -
364 // -3, //FASTORE, // -
365 // -4, //DASTORE, // -
366 // -3, //AASTORE, // -
367 // -3, //BASTORE, // -
368 // -3, //CASTORE, // -
369 // -3, //SASTORE, // -
370 // -1, //POP, // -
371 // -2, //POP2, // -
372 // 1, //DUP, // -
373 // 1, //DUP_X1, // -
374 // 1, //DUP_X2, // -
375 // 2, //DUP2, // -
376 // 2, //DUP2_X1, // -
377 // 2, //DUP2_X2, // -
378 // 0, //SWAP, // -
379 // -1, //IADD, // -
380 // -2, //LADD, // -
381 // -1, //FADD, // -
382 // -2, //DADD, // -
383 // -1, //ISUB, // -
384 // -2, //LSUB, // -
385 // -1, //FSUB, // -
386 // -2, //DSUB, // -
387 // -1, //IMUL, // -
388 // -2, //LMUL, // -
389 // -1, //FMUL, // -
390 // -2, //DMUL, // -
391 // -1, //IDIV, // -
392 // -2, //LDIV, // -
393 // -1, //FDIV, // -
394 // -2, //DDIV, // -
395 // -1, //IREM, // -
396 // -2, //LREM, // -
397 // -1, //FREM, // -
398 // -2, //DREM, // -
399 // 0, //INEG, // -
400 // 0, //LNEG, // -
401 // 0, //FNEG, // -
402 // 0, //DNEG, // -
403 // -1, //ISHL, // -
404 // -1, //LSHL, // -
405 // -1, //ISHR, // -
406 // -1, //LSHR, // -
407 // -1, //IUSHR, // -
408 // -1, //LUSHR, // -
409 // -1, //IAND, // -
410 // -2, //LAND, // -
411 // -1, //IOR, // -
412 // -2, //LOR, // -
413 // -1, //IXOR, // -
414 // -2, //LXOR, // -
415 // 0, //IINC, // visitIincInsn
416 // 1, //I2L, // visitInsn
417 // 0, //I2F, // -
418 // 1, //I2D, // -
419 // -1, //L2I, // -
420 // -1, //L2F, // -
421 // 0, //L2D, // -
422 // 0, //F2I, // -
423 // 1, //F2L, // -
424 // 1, //F2D, // -
425 // -1, //D2I, // -
426 // 0, //D2L, // -
427 // -1, //D2F, // -
428 // 0, //I2B, // -
429 // 0, //I2C, // -
430 // 0, //I2S, // -
431 // -3, //LCMP, // -
432 // -1, //FCMPL, // -
433 // -1, //FCMPG, // -
434 // -3, //DCMPL, // -
435 // -3, //DCMPG, // -
436 // -1, //IFEQ, // visitJumpInsn
437 // -1, //IFNE, // -
438 // -1, //IFLT, // -
439 // -1, //IFGE, // -
440 // -1, //IFGT, // -
441 // -1, //IFLE, // -
442 // -2, //IF_ICMPEQ, // -
443 // -2, //IF_ICMPNE, // -
444 // -2, //IF_ICMPLT, // -
445 // -2, //IF_ICMPGE, // -
446 // -2, //IF_ICMPGT, // -
447 // -2, //IF_ICMPLE, // -
448 // -2, //IF_ACMPEQ, // -
449 // -2, //IF_ACMPNE, // -
450 // 0, //GOTO, // -
451 // 1, //JSR, // -
452 // 0, //RET, // visitVarInsn
453 // -1, //TABLESWITCH, // visiTableSwitchInsn
454 // -1, //LOOKUPSWITCH, // visitLookupSwitch
455 // -1, //IRETURN, // visitInsn
456 // -2, //LRETURN, // -
457 // -1, //FRETURN, // -
458 // -2, //DRETURN, // -
459 // -1, //ARETURN, // -
460 // 0, //RETURN, // -
461 // NA, //GETSTATIC, // visitFieldInsn
462 // NA, //PUTSTATIC, // -
463 // NA, //GETFIELD, // -
464 // NA, //PUTFIELD, // -
465 // NA, //INVOKEVIRTUAL, // visitMethodInsn
466 // NA, //INVOKESPECIAL, // -
467 // NA, //INVOKESTATIC, // -
468 // NA, //INVOKEINTERFACE, // -
469 // NA, //INVOKEDYNAMIC, // visitInvokeDynamicInsn
470 // 1, //NEW, // visitTypeInsn
471 // 0, //NEWARRAY, // visitIntInsn
472 // 0, //ANEWARRAY, // visitTypeInsn
473 // 0, //ARRAYLENGTH, // visitInsn
474 // NA, //ATHROW, // -
475 // 0, //CHECKCAST, // visitTypeInsn
476 // 0, //INSTANCEOF, // -
477 // -1, //MONITORENTER, // visitInsn
478 // -1, //MONITOREXIT, // -
479 // NA, //WIDE, // NOT VISITED
480 // NA, //MULTIANEWARRAY, // visitMultiANewArrayInsn
481 // -1, //IFNULL, // visitJumpInsn
482 // -1, //IFNONNULL, // -
483 // NA, //GOTO_W, // -
484 // NA, //JSR_W, // -
485 // };
486 // for (i = 0; i < b.length; ++i) {
487 // System.err.print((char)('E' + b[i]));
488 // }
489 // System.err.println();
490 }
491
492 /**
493 * The label (i.e. basic block) to which these input and output stack map
494 * frames correspond.
495 */
496 Label owner;
497
498 /**
499 * The input stack map frame locals.
500 */
501 int[] inputLocals;
502
503 /**
504 * The input stack map frame stack.
505 */
506 int[] inputStack;
507
508 /**
509 * The output stack map frame locals.
510 */
511 private int[] outputLocals;
512
513 /**
514 * The output stack map frame stack.
515 */
516 private int[] outputStack;
517
518 /**
519 * Relative size of the output stack. The exact semantics of this field
520 * depends on the algorithm that is used.
521 *
522 * When only the maximum stack size is computed, this field is the size of
523 * the output stack relatively to the top of the input stack.
524 *
525 * When the stack map frames are completely computed, this field is the
526 * actual number of types in {@link #outputStack}.
527 */
528 private int outputStackTop;
529
530 /**
531 * Number of types that are initialized in the basic block.
532 *
533 * @see #initializations
534 */
535 private int initializationCount;
536
537 /**
538 * The types that are initialized in the basic block. A constructor
539 * invocation on an UNINITIALIZED or UNINITIALIZED_THIS type must replace
540 * <i>every occurence</i> of this type in the local variables and in the
541 * operand stack. This cannot be done during the first phase of the
542 * algorithm since, during this phase, the local variables and the operand
543 * stack are not completely computed. It is therefore necessary to store the
544 * types on which constructors are invoked in the basic block, in order to
545 * do this replacement during the second phase of the algorithm, where the
546 * frames are fully computed. Note that this array can contain types that
547 * are relative to input locals or to the input stack (see below for the
548 * description of the algorithm).
549 */
550 private int[] initializations;
551
552 /**
553 * Returns the output frame local variable type at the given index.
554 *
555 * @param local
556 * the index of the local that must be returned.
557 * @return the output frame local variable type at the given index.
558 */
559 private int get(final int local) {
560 if (outputLocals == null || local >= outputLocals.length) {
561 // this local has never been assigned in this basic block,
562 // so it is still equal to its value in the input frame
563 return LOCAL | local;
564 } else {
565 int type = outputLocals[local];
566 if (type == 0) {
567 // this local has never been assigned in this basic block,
568 // so it is still equal to its value in the input frame
569 type = outputLocals[local] = LOCAL | local;
570 }
571 return type;
572 }
573 }
574
575 /**
576 * Sets the output frame local variable type at the given index.
577 *
578 * @param local
579 * the index of the local that must be set.
580 * @param type
581 * the value of the local that must be set.
582 */
583 private void set(final int local, final int type) {
584 // creates and/or resizes the output local variables array if necessary
585 if (outputLocals == null) {
586 outputLocals = new int[10];
587 }
588 int n = outputLocals.length;
589 if (local >= n) {
590 int[] t = new int[Math.max(local + 1, 2 * n)];
591 System.arraycopy(outputLocals, 0, t, 0, n);
592 outputLocals = t;
593 }
594 // sets the local variable
595 outputLocals[local] = type;
596 }
597
598 /**
599 * Pushes a new type onto the output frame stack.
600 *
601 * @param type
602 * the type that must be pushed.
603 */
604 private void push(final int type) {
605 // creates and/or resizes the output stack array if necessary
606 if (outputStack == null) {
607 outputStack = new int[10];
608 }
609 int n = outputStack.length;
610 if (outputStackTop >= n) {
611 int[] t = new int[Math.max(outputStackTop + 1, 2 * n)];
612 System.arraycopy(outputStack, 0, t, 0, n);
613 outputStack = t;
614 }
615 // pushes the type on the output stack
616 outputStack[outputStackTop++] = type;
617 // updates the maximun height reached by the output stack, if needed
618 int top = owner.inputStackTop + outputStackTop;
619 if (top > owner.outputStackMax) {
620 owner.outputStackMax = top;
621 }
622 }
623
624 /**
625 * Pushes a new type onto the output frame stack.
626 *
627 * @param cw
628 * the ClassWriter to which this label belongs.
629 * @param desc
630 * the descriptor of the type to be pushed. Can also be a method
631 * descriptor (in this case this method pushes its return type
632 * onto the output frame stack).
633 */
634 private void push(final ClassWriter cw, final String desc) {
635 int type = type(cw, desc);
636 if (type != 0) {
637 push(type);
638 if (type == LONG || type == DOUBLE) {
639 push(TOP);
640 }
641 }
642 }
643
644 /**
645 * Returns the int encoding of the given type.
646 *
647 * @param cw
648 * the ClassWriter to which this label belongs.
649 * @param desc
650 * a type descriptor.
651 * @return the int encoding of the given type.
652 */
653 private static int type(final ClassWriter cw, final String desc) {
654 String t;
655 int index = desc.charAt(0) == '(' ? desc.indexOf(')') + 1 : 0;
656 switch (desc.charAt(index)) {
657 case 'V':
658 return 0;
659 case 'Z':
660 case 'C':
661 case 'B':
662 case 'S':
663 case 'I':
664 return INTEGER;
665 case 'F':
666 return FLOAT;
667 case 'J':
668 return LONG;
669 case 'D':
670 return DOUBLE;
671 case 'L':
672 // stores the internal name, not the descriptor!
673 t = desc.substring(index + 1, desc.length() - 1);
674 return OBJECT | cw.addType(t);
675 // case '[':
676 default:
677 // extracts the dimensions and the element type
678 int data;
679 int dims = index + 1;
680 while (desc.charAt(dims) == '[') {
681 ++dims;
682 }
683 switch (desc.charAt(dims)) {
684 case 'Z':
685 data = BOOLEAN;
686 break;
687 case 'C':
688 data = CHAR;
689 break;
690 case 'B':
691 data = BYTE;
692 break;
693 case 'S':
694 data = SHORT;
695 break;
696 case 'I':
697 data = INTEGER;
698 break;
699 case 'F':
700 data = FLOAT;
701 break;
702 case 'J':
703 data = LONG;
704 break;
705 case 'D':
706 data = DOUBLE;
707 break;
708 // case 'L':
709 default:
710 // stores the internal name, not the descriptor
711 t = desc.substring(dims + 1, desc.length() - 1);
712 data = OBJECT | cw.addType(t);
713 }
714 return (dims - index) << 28 | data;
715 }
716 }
717
718 /**
719 * Pops a type from the output frame stack and returns its value.
720 *
721 * @return the type that has been popped from the output frame stack.
722 */
723 private int pop() {
724 if (outputStackTop > 0) {
725 return outputStack[--outputStackTop];
726 } else {
727 // if the output frame stack is empty, pops from the input stack
728 return STACK | -(--owner.inputStackTop);
729 }
730 }
731
732 /**
733 * Pops the given number of types from the output frame stack.
734 *
735 * @param elements
736 * the number of types that must be popped.
737 */
738 private void pop(final int elements) {
739 if (outputStackTop >= elements) {
740 outputStackTop -= elements;
741 } else {
742 // if the number of elements to be popped is greater than the number
743 // of elements in the output stack, clear it, and pops the remaining
744 // elements from the input stack.
745 owner.inputStackTop -= elements - outputStackTop;
746 outputStackTop = 0;
747 }
748 }
749
750 /**
751 * Pops a type from the output frame stack.
752 *
753 * @param desc
754 * the descriptor of the type to be popped. Can also be a method
755 * descriptor (in this case this method pops the types
756 * corresponding to the method arguments).
757 */
758 private void pop(final String desc) {
759 char c = desc.charAt(0);
760 if (c == '(') {
761 pop((Type.getArgumentsAndReturnSizes(desc) >> 2) - 1);
762 } else if (c == 'J' || c == 'D') {
763 pop(2);
764 } else {
765 pop(1);
766 }
767 }
768
769 /**
770 * Adds a new type to the list of types on which a constructor is invoked in
771 * the basic block.
772 *
773 * @param var
774 * a type on a which a constructor is invoked.
775 */
776 private void init(final int var) {
777 // creates and/or resizes the initializations array if necessary
778 if (initializations == null) {
779 initializations = new int[2];
780 }
781 int n = initializations.length;
782 if (initializationCount >= n) {
783 int[] t = new int[Math.max(initializationCount + 1, 2 * n)];
784 System.arraycopy(initializations, 0, t, 0, n);
785 initializations = t;
786 }
787 // stores the type to be initialized
788 initializations[initializationCount++] = var;
789 }
790
791 /**
792 * Replaces the given type with the appropriate type if it is one of the
793 * types on which a constructor is invoked in the basic block.
794 *
795 * @param cw
796 * the ClassWriter to which this label belongs.
797 * @param t
798 * a type
799 * @return t or, if t is one of the types on which a constructor is invoked
800 * in the basic block, the type corresponding to this constructor.
801 */
802 private int init(final ClassWriter cw, final int t) {
803 int s;
804 if (t == UNINITIALIZED_THIS) {
805 s = OBJECT | cw.addType(cw.thisName);
806 } else if ((t & (DIM | BASE_KIND)) == UNINITIALIZED) {
807 String type = cw.typeTable[t & BASE_VALUE].strVal1;
808 s = OBJECT | cw.addType(type);
809 } else {
810 return t;
811 }
812 for (int j = 0; j < initializationCount; ++j) {
813 int u = initializations[j];
814 int dim = u & DIM;
815 int kind = u & KIND;
816 if (kind == LOCAL) {
817 u = dim + inputLocals[u & VALUE];
818 } else if (kind == STACK) {
819 u = dim + inputStack[inputStack.length - (u & VALUE)];
820 }
821 if (t == u) {
822 return s;
823 }
824 }
825 return t;
826 }
827
828 /**
829 * Initializes the input frame of the first basic block from the method
830 * descriptor.
831 *
832 * @param cw
833 * the ClassWriter to which this label belongs.
834 * @param access
835 * the access flags of the method to which this label belongs.
836 * @param args
837 * the formal parameter types of this method.
838 * @param maxLocals
839 * the maximum number of local variables of this method.
840 */
841 void initInputFrame(final ClassWriter cw, final int access,
842 final Type[] args, final int maxLocals) {
843 inputLocals = new int[maxLocals];
844 inputStack = new int[0];
845 int i = 0;
846 if ((access & Opcodes.ACC_STATIC) == 0) {
847 if ((access & MethodWriter.ACC_CONSTRUCTOR) == 0) {
848 inputLocals[i++] = OBJECT | cw.addType(cw.thisName);
849 } else {
850 inputLocals[i++] = UNINITIALIZED_THIS;
851 }
852 }
853 for (int j = 0; j < args.length; ++j) {
854 int t = type(cw, args[j].getDescriptor());
855 inputLocals[i++] = t;
856 if (t == LONG || t == DOUBLE) {
857 inputLocals[i++] = TOP;
858 }
859 }
860 while (i < maxLocals) {
861 inputLocals[i++] = TOP;
862 }
863 }
864
865 /**
866 * Simulates the action of the given instruction on the output stack frame.
867 *
868 * @param opcode
869 * the opcode of the instruction.
870 * @param arg
871 * the operand of the instruction, if any.
872 * @param cw
873 * the class writer to which this label belongs.
874 * @param item
875 * the operand of the instructions, if any.
876 */
877 void execute(final int opcode, final int arg, final ClassWriter cw,
878 final Item item) {
879 int t1, t2, t3, t4;
880 switch (opcode) {
881 case Opcodes.NOP:
882 case Opcodes.INEG:
883 case Opcodes.LNEG:
884 case Opcodes.FNEG:
885 case Opcodes.DNEG:
886 case Opcodes.I2B:
887 case Opcodes.I2C:
888 case Opcodes.I2S:
889 case Opcodes.GOTO:
890 case Opcodes.RETURN:
891 break;
892 case Opcodes.ACONST_NULL:
893 push(NULL);
894 break;
895 case Opcodes.ICONST_M1:
896 case Opcodes.ICONST_0:
897 case Opcodes.ICONST_1:
898 case Opcodes.ICONST_2:
899 case Opcodes.ICONST_3:
900 case Opcodes.ICONST_4:
901 case Opcodes.ICONST_5:
902 case Opcodes.BIPUSH:
903 case Opcodes.SIPUSH:
904 case Opcodes.ILOAD:
905 push(INTEGER);
906 break;
907 case Opcodes.LCONST_0:
908 case Opcodes.LCONST_1:
909 case Opcodes.LLOAD:
910 push(LONG);
911 push(TOP);
912 break;
913 case Opcodes.FCONST_0:
914 case Opcodes.FCONST_1:
915 case Opcodes.FCONST_2:
916 case Opcodes.FLOAD:
917 push(FLOAT);
918 break;
919 case Opcodes.DCONST_0:
920 case Opcodes.DCONST_1:
921 case Opcodes.DLOAD:
922 push(DOUBLE);
923 push(TOP);
924 break;
925 case Opcodes.LDC:
926 switch (item.type) {
927 case ClassWriter.INT:
928 push(INTEGER);
929 break;
930 case ClassWriter.LONG:
931 push(LONG);
932 push(TOP);
933 break;
934 case ClassWriter.FLOAT:
935 push(FLOAT);
936 break;
937 case ClassWriter.DOUBLE:
938 push(DOUBLE);
939 push(TOP);
940 break;
941 case ClassWriter.CLASS:
942 push(OBJECT | cw.addType("java/lang/Class"));
943 break;
944 case ClassWriter.STR:
945 push(OBJECT | cw.addType("java/lang/String"));
946 break;
947 case ClassWriter.MTYPE:
948 push(OBJECT | cw.addType("java/lang/invoke/MethodType"));
949 break;
950 // case ClassWriter.HANDLE_BASE + [1..9]:
951 default:
952 push(OBJECT | cw.addType("java/lang/invoke/MethodHandle"));
953 }
954 break;
955 case Opcodes.ALOAD:
956 push(get(arg));
957 break;
958 case Opcodes.IALOAD:
959 case Opcodes.BALOAD:
960 case Opcodes.CALOAD:
961 case Opcodes.SALOAD:
962 pop(2);
963 push(INTEGER);
964 break;
965 case Opcodes.LALOAD:
966 case Opcodes.D2L:
967 pop(2);
968 push(LONG);
969 push(TOP);
970 break;
971 case Opcodes.FALOAD:
972 pop(2);
973 push(FLOAT);
974 break;
975 case Opcodes.DALOAD:
976 case Opcodes.L2D:
977 pop(2);
978 push(DOUBLE);
979 push(TOP);
980 break;
981 case Opcodes.AALOAD:
982 pop(1);
983 t1 = pop();
984 push(ELEMENT_OF + t1);
985 break;
986 case Opcodes.ISTORE:
987 case Opcodes.FSTORE:
988 case Opcodes.ASTORE:
989 t1 = pop();
990 set(arg, t1);
991 if (arg > 0) {
992 t2 = get(arg - 1);
993 // if t2 is of kind STACK or LOCAL we cannot know its size!
994 if (t2 == LONG || t2 == DOUBLE) {
995 set(arg - 1, TOP);
996 } else if ((t2 & KIND) != BASE) {
997 set(arg - 1, t2 | TOP_IF_LONG_OR_DOUBLE);
998 }
999 }
1000 break;
1001 case Opcodes.LSTORE:
1002 case Opcodes.DSTORE:
1003 pop(1);
1004 t1 = pop();
1005 set(arg, t1);
1006 set(arg + 1, TOP);
1007 if (arg > 0) {
1008 t2 = get(arg - 1);
1009 // if t2 is of kind STACK or LOCAL we cannot know its size!
1010 if (t2 == LONG || t2 == DOUBLE) {
1011 set(arg - 1, TOP);
1012 } else if ((t2 & KIND) != BASE) {
1013 set(arg - 1, t2 | TOP_IF_LONG_OR_DOUBLE);
1014 }
1015 }
1016 break;
1017 case Opcodes.IASTORE:
1018 case Opcodes.BASTORE:
1019 case Opcodes.CASTORE:
1020 case Opcodes.SASTORE:
1021 case Opcodes.FASTORE:
1022 case Opcodes.AASTORE:
1023 pop(3);
1024 break;
1025 case Opcodes.LASTORE:
1026 case Opcodes.DASTORE:
1027 pop(4);
1028 break;
1029 case Opcodes.POP:
1030 case Opcodes.IFEQ:
1031 case Opcodes.IFNE:
1032 case Opcodes.IFLT:
1033 case Opcodes.IFGE:
1034 case Opcodes.IFGT:
1035 case Opcodes.IFLE:
1036 case Opcodes.IRETURN:
1037 case Opcodes.FRETURN:
1038 case Opcodes.ARETURN:
1039 case Opcodes.TABLESWITCH:
1040 case Opcodes.LOOKUPSWITCH:
1041 case Opcodes.ATHROW:
1042 case Opcodes.MONITORENTER:
1043 case Opcodes.MONITOREXIT:
1044 case Opcodes.IFNULL:
1045 case Opcodes.IFNONNULL:
1046 pop(1);
1047 break;
1048 case Opcodes.POP2:
1049 case Opcodes.IF_ICMPEQ:
1050 case Opcodes.IF_ICMPNE:
1051 case Opcodes.IF_ICMPLT:
1052 case Opcodes.IF_ICMPGE:
1053 case Opcodes.IF_ICMPGT:
1054 case Opcodes.IF_ICMPLE:
1055 case Opcodes.IF_ACMPEQ:
1056 case Opcodes.IF_ACMPNE:
1057 case Opcodes.LRETURN:
1058 case Opcodes.DRETURN:
1059 pop(2);
1060 break;
1061 case Opcodes.DUP:
1062 t1 = pop();
1063 push(t1);
1064 push(t1);
1065 break;
1066 case Opcodes.DUP_X1:
1067 t1 = pop();
1068 t2 = pop();
1069 push(t1);
1070 push(t2);
1071 push(t1);
1072 break;
1073 case Opcodes.DUP_X2:
1074 t1 = pop();
1075 t2 = pop();
1076 t3 = pop();
1077 push(t1);
1078 push(t3);
1079 push(t2);
1080 push(t1);
1081 break;
1082 case Opcodes.DUP2:
1083 t1 = pop();
1084 t2 = pop();
1085 push(t2);
1086 push(t1);
1087 push(t2);
1088 push(t1);
1089 break;
1090 case Opcodes.DUP2_X1:
1091 t1 = pop();
1092 t2 = pop();
1093 t3 = pop();
1094 push(t2);
1095 push(t1);
1096 push(t3);
1097 push(t2);
1098 push(t1);
1099 break;
1100 case Opcodes.DUP2_X2:
1101 t1 = pop();
1102 t2 = pop();
1103 t3 = pop();
1104 t4 = pop();
1105 push(t2);
1106 push(t1);
1107 push(t4);
1108 push(t3);
1109 push(t2);
1110 push(t1);
1111 break;
1112 case Opcodes.SWAP:
1113 t1 = pop();
1114 t2 = pop();
1115 push(t1);
1116 push(t2);
1117 break;
1118 case Opcodes.IADD:
1119 case Opcodes.ISUB:
1120 case Opcodes.IMUL:
1121 case Opcodes.IDIV:
1122 case Opcodes.IREM:
1123 case Opcodes.IAND:
1124 case Opcodes.IOR:
1125 case Opcodes.IXOR:
1126 case Opcodes.ISHL:
1127 case Opcodes.ISHR:
1128 case Opcodes.IUSHR:
1129 case Opcodes.L2I:
1130 case Opcodes.D2I:
1131 case Opcodes.FCMPL:
1132 case Opcodes.FCMPG:
1133 pop(2);
1134 push(INTEGER);
1135 break;
1136 case Opcodes.LADD:
1137 case Opcodes.LSUB:
1138 case Opcodes.LMUL:
1139 case Opcodes.LDIV:
1140 case Opcodes.LREM:
1141 case Opcodes.LAND:
1142 case Opcodes.LOR:
1143 case Opcodes.LXOR:
1144 pop(4);
1145 push(LONG);
1146 push(TOP);
1147 break;
1148 case Opcodes.FADD:
1149 case Opcodes.FSUB:
1150 case Opcodes.FMUL:
1151 case Opcodes.FDIV:
1152 case Opcodes.FREM:
1153 case Opcodes.L2F:
1154 case Opcodes.D2F:
1155 pop(2);
1156 push(FLOAT);
1157 break;
1158 case Opcodes.DADD:
1159 case Opcodes.DSUB:
1160 case Opcodes.DMUL:
1161 case Opcodes.DDIV:
1162 case Opcodes.DREM:
1163 pop(4);
1164 push(DOUBLE);
1165 push(TOP);
1166 break;
1167 case Opcodes.LSHL:
1168 case Opcodes.LSHR:
1169 case Opcodes.LUSHR:
1170 pop(3);
1171 push(LONG);
1172 push(TOP);
1173 break;
1174 case Opcodes.IINC:
1175 set(arg, INTEGER);
1176 break;
1177 case Opcodes.I2L:
1178 case Opcodes.F2L:
1179 pop(1);
1180 push(LONG);
1181 push(TOP);
1182 break;
1183 case Opcodes.I2F:
1184 pop(1);
1185 push(FLOAT);
1186 break;
1187 case Opcodes.I2D:
1188 case Opcodes.F2D:
1189 pop(1);
1190 push(DOUBLE);
1191 push(TOP);
1192 break;
1193 case Opcodes.F2I:
1194 case Opcodes.ARRAYLENGTH:
1195 case Opcodes.INSTANCEOF:
1196 pop(1);
1197 push(INTEGER);
1198 break;
1199 case Opcodes.LCMP:
1200 case Opcodes.DCMPL:
1201 case Opcodes.DCMPG:
1202 pop(4);
1203 push(INTEGER);
1204 break;
1205 case Opcodes.JSR:
1206 case Opcodes.RET:
1207 throw new RuntimeException(
1208 "JSR/RET are not supported with computeFrames option");
1209 case Opcodes.GETSTATIC:
1210 push(cw, item.strVal3);
1211 break;
1212 case Opcodes.PUTSTATIC:
1213 pop(item.strVal3);
1214 break;
1215 case Opcodes.GETFIELD:
1216 pop(1);
1217 push(cw, item.strVal3);
1218 break;
1219 case Opcodes.PUTFIELD:
1220 pop(item.strVal3);
1221 pop();
1222 break;
1223 case Opcodes.INVOKEVIRTUAL:
1224 case Opcodes.INVOKESPECIAL:
1225 case Opcodes.INVOKESTATIC:
1226 case Opcodes.INVOKEINTERFACE:
1227 pop(item.strVal3);
1228 if (opcode != Opcodes.INVOKESTATIC) {
1229 t1 = pop();
1230 if (opcode == Opcodes.INVOKESPECIAL
1231 && item.strVal2.charAt(0) == '<') {
1232 init(t1);
1233 }
1234 }
1235 push(cw, item.strVal3);
1236 break;
1237 case Opcodes.INVOKEDYNAMIC:
1238 pop(item.strVal2);
1239 push(cw, item.strVal2);
1240 break;
1241 case Opcodes.NEW:
1242 push(UNINITIALIZED | cw.addUninitializedType(item.strVal1, arg));
1243 break;
1244 case Opcodes.NEWARRAY:
1245 pop();
1246 switch (arg) {
1247 case Opcodes.T_BOOLEAN:
1248 push(ARRAY_OF | BOOLEAN);
1249 break;
1250 case Opcodes.T_CHAR:
1251 push(ARRAY_OF | CHAR);
1252 break;
1253 case Opcodes.T_BYTE:
1254 push(ARRAY_OF | BYTE);
1255 break;
1256 case Opcodes.T_SHORT:
1257 push(ARRAY_OF | SHORT);
1258 break;
1259 case Opcodes.T_INT:
1260 push(ARRAY_OF | INTEGER);
1261 break;
1262 case Opcodes.T_FLOAT:
1263 push(ARRAY_OF | FLOAT);
1264 break;
1265 case Opcodes.T_DOUBLE:
1266 push(ARRAY_OF | DOUBLE);
1267 break;
1268 // case Opcodes.T_LONG:
1269 default:
1270 push(ARRAY_OF | LONG);
1271 break;
1272 }
1273 break;
1274 case Opcodes.ANEWARRAY:
1275 String s = item.strVal1;
1276 pop();
1277 if (s.charAt(0) == '[') {
1278 push(cw, '[' + s);
1279 } else {
1280 push(ARRAY_OF | OBJECT | cw.addType(s));
1281 }
1282 break;
1283 case Opcodes.CHECKCAST:
1284 s = item.strVal1;
1285 pop();
1286 if (s.charAt(0) == '[') {
1287 push(cw, s);
1288 } else {
1289 push(OBJECT | cw.addType(s));
1290 }
1291 break;
1292 // case Opcodes.MULTIANEWARRAY:
1293 default:
1294 pop(arg);
1295 push(cw, item.strVal1);
1296 break;
1297 }
1298 }
1299
1300 /**
1301 * Merges the input frame of the given basic block with the input and output
1302 * frames of this basic block. Returns <tt>true</tt> if the input frame of
1303 * the given label has been changed by this operation.
1304 *
1305 * @param cw
1306 * the ClassWriter to which this label belongs.
1307 * @param frame
1308 * the basic block whose input frame must be updated.
1309 * @param edge
1310 * the kind of the {@link Edge} between this label and 'label'.
1311 * See {@link Edge#info}.
1312 * @return <tt>true</tt> if the input frame of the given label has been
1313 * changed by this operation.
1314 */
1315 boolean merge(final ClassWriter cw, final Frame frame, final int edge) {
1316 boolean changed = false;
1317 int i, s, dim, kind, t;
1318
1319 int nLocal = inputLocals.length;
1320 int nStack = inputStack.length;
1321 if (frame.inputLocals == null) {
1322 frame.inputLocals = new int[nLocal];
1323 changed = true;
1324 }
1325
1326 for (i = 0; i < nLocal; ++i) {
1327 if (outputLocals != null && i < outputLocals.length) {
1328 s = outputLocals[i];
1329 if (s == 0) {
1330 t = inputLocals[i];
1331 } else {
1332 dim = s & DIM;
1333 kind = s & KIND;
1334 if (kind == BASE) {
1335 t = s;
1336 } else {
1337 if (kind == LOCAL) {
1338 t = dim + inputLocals[s & VALUE];
1339 } else {
1340 t = dim + inputStack[nStack - (s & VALUE)];
1341 }
1342 if ((s & TOP_IF_LONG_OR_DOUBLE) != 0
1343 && (t == LONG || t == DOUBLE)) {
1344 t = TOP;
1345 }
1346 }
1347 }
1348 } else {
1349 t = inputLocals[i];
1350 }
1351 if (initializations != null) {
1352 t = init(cw, t);
1353 }
1354 changed |= merge(cw, t, frame.inputLocals, i);
1355 }
1356
1357 if (edge > 0) {
1358 for (i = 0; i < nLocal; ++i) {
1359 t = inputLocals[i];
1360 changed |= merge(cw, t, frame.inputLocals, i);
1361 }
1362 if (frame.inputStack == null) {
1363 frame.inputStack = new int[1];
1364 changed = true;
1365 }
1366 changed |= merge(cw, edge, frame.inputStack, 0);
1367 return changed;
1368 }
1369
1370 int nInputStack = inputStack.length + owner.inputStackTop;
1371 if (frame.inputStack == null) {
1372 frame.inputStack = new int[nInputStack + outputStackTop];
1373 changed = true;
1374 }
1375
1376 for (i = 0; i < nInputStack; ++i) {
1377 t = inputStack[i];
1378 if (initializations != null) {
1379 t = init(cw, t);
1380 }
1381 changed |= merge(cw, t, frame.inputStack, i);
1382 }
1383 for (i = 0; i < outputStackTop; ++i) {
1384 s = outputStack[i];
1385 dim = s & DIM;
1386 kind = s & KIND;
1387 if (kind == BASE) {
1388 t = s;
1389 } else {
1390 if (kind == LOCAL) {
1391 t = dim + inputLocals[s & VALUE];
1392 } else {
1393 t = dim + inputStack[nStack - (s & VALUE)];
1394 }
1395 if ((s & TOP_IF_LONG_OR_DOUBLE) != 0
1396 && (t == LONG || t == DOUBLE)) {
1397 t = TOP;
1398 }
1399 }
1400 if (initializations != null) {
1401 t = init(cw, t);
1402 }
1403 changed |= merge(cw, t, frame.inputStack, nInputStack + i);
1404 }
1405 return changed;
1406 }
1407
1408 /**
1409 * Merges the type at the given index in the given type array with the given
1410 * type. Returns <tt>true</tt> if the type array has been modified by this
1411 * operation.
1412 *
1413 * @param cw
1414 * the ClassWriter to which this label belongs.
1415 * @param t
1416 * the type with which the type array element must be merged.
1417 * @param types
1418 * an array of types.
1419 * @param index
1420 * the index of the type that must be merged in 'types'.
1421 * @return <tt>true</tt> if the type array has been modified by this
1422 * operation.
1423 */
1424 private static boolean merge(final ClassWriter cw, int t,
1425 final int[] types, final int index) {
1426 int u = types[index];
1427 if (u == t) {
1428 // if the types are equal, merge(u,t)=u, so there is no change
1429 return false;
1430 }
1431 if ((t & ~DIM) == NULL) {
1432 if (u == NULL) {
1433 return false;
1434 }
1435 t = NULL;
1436 }
1437 if (u == 0) {
1438 // if types[index] has never been assigned, merge(u,t)=t
1439 types[index] = t;
1440 return true;
1441 }
1442 int v;
1443 if ((u & BASE_KIND) == OBJECT || (u & DIM) != 0) {
1444 // if u is a reference type of any dimension
1445 if (t == NULL) {
1446 // if t is the NULL type, merge(u,t)=u, so there is no change
1447 return false;
1448 } else if ((t & (DIM | BASE_KIND)) == (u & (DIM | BASE_KIND))) {
1449 // if t and u have the same dimension and same base kind
1450 if ((u & BASE_KIND) == OBJECT) {
1451 // if t is also a reference type, and if u and t have the
1452 // same dimension merge(u,t) = dim(t) | common parent of the
1453 // element types of u and t
1454 v = (t & DIM) | OBJECT
1455 | cw.getMergedType(t & BASE_VALUE, u & BASE_VALUE);
1456 } else {
1457 // if u and t are array types, but not with the same element
1458 // type, merge(u,t) = dim(u) - 1 | java/lang/Object
1459 int vdim = ELEMENT_OF + (u & DIM);
1460 v = vdim | OBJECT | cw.addType("java/lang/Object");
1461 }
1462 } else if ((t & BASE_KIND) == OBJECT || (t & DIM) != 0) {
1463 // if t is any other reference or array type, the merged type
1464 // is min(udim, tdim) | java/lang/Object, where udim is the
1465 // array dimension of u, minus 1 if u is an array type with a
1466 // primitive element type (and similarly for tdim).
1467 int tdim = (((t & DIM) == 0 || (t & BASE_KIND) == OBJECT) ? 0
1468 : ELEMENT_OF) + (t & DIM);
1469 int udim = (((u & DIM) == 0 || (u & BASE_KIND) == OBJECT) ? 0
1470 : ELEMENT_OF) + (u & DIM);
1471 v = Math.min(tdim, udim) | OBJECT
1472 | cw.addType("java/lang/Object");
1473 } else {
1474 // if t is any other type, merge(u,t)=TOP
1475 v = TOP;
1476 }
1477 } else if (u == NULL) {
1478 // if u is the NULL type, merge(u,t)=t,
1479 // or TOP if t is not a reference type
1480 v = (t & BASE_KIND) == OBJECT || (t & DIM) != 0 ? t : TOP;
1481 } else {
1482 // if u is any other type, merge(u,t)=TOP whatever t
1483 v = TOP;
1484 }
1485 if (u != v) {
1486 types[index] = v;
1487 return true;
1488 }
1489 return false;
1490 }
1491 }