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 
  60 package jdk.internal.org.objectweb.asm;
  61 
  62 /**
  63  * The input and output stack map frames of a basic block.
  64  *
  65  * <p>Stack map frames are computed in two steps:
  66  *
  67  * <ul>
  68  *   <li>During the visit of each instruction in MethodWriter, the state of the frame at the end of
  69  *       the current basic block is updated by simulating the action of the instruction on the
  70  *       previous state of this so called "output frame".
  71  *   <li>After all instructions have been visited, a fix point algorithm is used in MethodWriter to
  72  *       compute the "input frame" of each basic block (i.e. the stack map frame at the beginning of
  73  *       the basic block). See {@link MethodWriter#computeAllFrames}.
  74  * </ul>
  75  *
  76  * <p>Output stack map frames are computed relatively to the input frame of the basic block, which
  77  * is not yet known when output frames are computed. It is therefore necessary to be able to
  78  * represent abstract types such as "the type at position x in the input frame locals" or "the type
  79  * at position x from the top of the input frame stack" or even "the type at position x in the input
  80  * frame, with y more (or less) array dimensions". This explains the rather complicated type format
  81  * used in this class, explained below.
  82  *
  83  * <p>The local variables and the operand stack of input and output frames contain values called
  84  * "abstract types" hereafter. An abstract type is represented with 4 fields named DIM, KIND, FLAGS
  85  * and VALUE, packed in a single int value for better performance and memory efficiency:
  86  *
  87  * <pre>
  88  *   =====================================
  89  *   |...DIM|KIND|.F|...............VALUE|
  90  *   =====================================
  91  * </pre>
  92  *
  93  * <ul>
  94  *   <li>the DIM field, stored in the 6 most significant bits, is a signed number of array
  95  *       dimensions (from -32 to 31, included). It can be retrieved with {@link #DIM_MASK} and a
  96  *       right shift of {@link #DIM_SHIFT}.
  97  *   <li>the KIND field, stored in 4 bits, indicates the kind of VALUE used. These 4 bits can be
  98  *       retrieved with {@link #KIND_MASK} and, without any shift, must be equal to {@link
  99  *       #CONSTANT_KIND}, {@link #REFERENCE_KIND}, {@link #UNINITIALIZED_KIND}, {@link #LOCAL_KIND}
 100  *       or {@link #STACK_KIND}.
 101  *   <li>the FLAGS field, stored in 2 bits, contains up to 2 boolean flags. Currently only one flag
 102  *       is defined, namely {@link #TOP_IF_LONG_OR_DOUBLE_FLAG}.
 103  *   <li>the VALUE field, stored in the remaining 20 bits, contains either
 104  *       <ul>
 105  *         <li>one of the constants {@link #ITEM_TOP}, {@link #ITEM_ASM_BOOLEAN}, {@link
 106  *             #ITEM_ASM_BYTE}, {@link #ITEM_ASM_CHAR} or {@link #ITEM_ASM_SHORT}, {@link
 107  *             #ITEM_INTEGER}, {@link #ITEM_FLOAT}, {@link #ITEM_LONG}, {@link #ITEM_DOUBLE}, {@link
 108  *             #ITEM_NULL} or {@link #ITEM_UNINITIALIZED_THIS}, if KIND is equal to {@link
 109  *             #CONSTANT_KIND}.
 110  *         <li>the index of a {@link Symbol#TYPE_TAG} {@link Symbol} in the type table of a {@link
 111  *             SymbolTable}, if KIND is equal to {@link #REFERENCE_KIND}.
 112  *         <li>the index of an {@link Symbol#UNINITIALIZED_TYPE_TAG} {@link Symbol} in the type
 113  *             table of a SymbolTable, if KIND is equal to {@link #UNINITIALIZED_KIND}.
 114  *         <li>the index of a local variable in the input stack frame, if KIND is equal to {@link
 115  *             #LOCAL_KIND}.
 116  *         <li>a position relatively to the top of the stack of the input stack frame, if KIND is
 117  *             equal to {@link #STACK_KIND},
 118  *       </ul>
 119  * </ul>
 120  *
 121  * <p>Output frames can contain abstract types of any kind and with a positive or negative array
 122  * dimension (and even unassigned types, represented by 0 - which does not correspond to any valid
 123  * abstract type value). Input frames can only contain CONSTANT_KIND, REFERENCE_KIND or
 124  * UNINITIALIZED_KIND abstract types of positive or {@literal null} array dimension. In all cases
 125  * the type table contains only internal type names (array type descriptors are forbidden - array
 126  * dimensions must be represented through the DIM field).
 127  *
 128  * <p>The LONG and DOUBLE types are always represented by using two slots (LONG + TOP or DOUBLE +
 129  * TOP), for local variables as well as in the operand stack. This is necessary to be able to
 130  * simulate DUPx_y instructions, whose effect would be dependent on the concrete types represented
 131  * by the abstract types in the stack (which are not always known).
 132  *
 133  * @author Eric Bruneton
 134  */
 135 class Frame {
 136 
 137     // Constants used in the StackMapTable attribute.
 138     // See https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.4.
 139 
 140     static final int SAME_FRAME = 0;
 141     static final int SAME_LOCALS_1_STACK_ITEM_FRAME = 64;
 142     static final int RESERVED = 128;
 143     static final int SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED = 247;
 144     static final int CHOP_FRAME = 248;
 145     static final int SAME_FRAME_EXTENDED = 251;
 146     static final int APPEND_FRAME = 252;
 147     static final int FULL_FRAME = 255;
 148 
 149     static final int ITEM_TOP = 0;
 150     static final int ITEM_INTEGER = 1;
 151     static final int ITEM_FLOAT = 2;
 152     static final int ITEM_DOUBLE = 3;
 153     static final int ITEM_LONG = 4;
 154     static final int ITEM_NULL = 5;
 155     static final int ITEM_UNINITIALIZED_THIS = 6;
 156     static final int ITEM_OBJECT = 7;
 157     static final int ITEM_UNINITIALIZED = 8;
 158     // Additional, ASM specific constants used in abstract types below.
 159     private static final int ITEM_ASM_BOOLEAN = 9;
 160     private static final int ITEM_ASM_BYTE = 10;
 161     private static final int ITEM_ASM_CHAR = 11;
 162     private static final int ITEM_ASM_SHORT = 12;
 163 
 164     // The size and offset in bits of each field of an abstract type.
 165 
 166     private static final int DIM_SIZE = 6;
 167     private static final int KIND_SIZE = 4;
 168     private static final int FLAGS_SIZE = 2;
 169     private static final int VALUE_SIZE = 32 - DIM_SIZE - KIND_SIZE - FLAGS_SIZE;
 170 
 171     private static final int DIM_SHIFT = KIND_SIZE + FLAGS_SIZE + VALUE_SIZE;
 172     private static final int KIND_SHIFT = FLAGS_SIZE + VALUE_SIZE;
 173     private static final int FLAGS_SHIFT = VALUE_SIZE;
 174 
 175     // Bitmasks to get each field of an abstract type.
 176 
 177     private static final int DIM_MASK = ((1 << DIM_SIZE) - 1) << DIM_SHIFT;
 178     private static final int KIND_MASK = ((1 << KIND_SIZE) - 1) << KIND_SHIFT;
 179     private static final int VALUE_MASK = (1 << VALUE_SIZE) - 1;
 180 
 181     // Constants to manipulate the DIM field of an abstract type.
 182 
 183     /** The constant to be added to an abstract type to get one with one more array dimension. */
 184     private static final int ARRAY_OF = +1 << DIM_SHIFT;
 185 
 186     /** The constant to be added to an abstract type to get one with one less array dimension. */
 187     private static final int ELEMENT_OF = -1 << DIM_SHIFT;
 188 
 189     // Possible values for the KIND field of an abstract type.
 190 
 191     private static final int CONSTANT_KIND = 1 << KIND_SHIFT;
 192     private static final int REFERENCE_KIND = 2 << KIND_SHIFT;
 193     private static final int UNINITIALIZED_KIND = 3 << KIND_SHIFT;
 194     private static final int LOCAL_KIND = 4 << KIND_SHIFT;
 195     private static final int STACK_KIND = 5 << KIND_SHIFT;
 196 
 197     // Possible flags for the FLAGS field of an abstract type.
 198 
 199     /**
 200       * A flag used for LOCAL_KIND and STACK_KIND abstract types, indicating that if the resolved,
 201       * concrete type is LONG or DOUBLE, TOP should be used instead (because the value has been
 202       * partially overridden with an xSTORE instruction).
 203       */
 204     private static final int TOP_IF_LONG_OR_DOUBLE_FLAG = 1 << FLAGS_SHIFT;
 205 
 206     // Useful predefined abstract types (all the possible CONSTANT_KIND types).
 207 
 208     private static final int TOP = CONSTANT_KIND | ITEM_TOP;
 209     private static final int BOOLEAN = CONSTANT_KIND | ITEM_ASM_BOOLEAN;
 210     private static final int BYTE = CONSTANT_KIND | ITEM_ASM_BYTE;
 211     private static final int CHAR = CONSTANT_KIND | ITEM_ASM_CHAR;
 212     private static final int SHORT = CONSTANT_KIND | ITEM_ASM_SHORT;
 213     private static final int INTEGER = CONSTANT_KIND | ITEM_INTEGER;
 214     private static final int FLOAT = CONSTANT_KIND | ITEM_FLOAT;
 215     private static final int LONG = CONSTANT_KIND | ITEM_LONG;
 216     private static final int DOUBLE = CONSTANT_KIND | ITEM_DOUBLE;
 217     private static final int NULL = CONSTANT_KIND | ITEM_NULL;
 218     private static final int UNINITIALIZED_THIS = CONSTANT_KIND | ITEM_UNINITIALIZED_THIS;
 219 
 220     // -----------------------------------------------------------------------------------------------
 221     // Instance fields
 222     // -----------------------------------------------------------------------------------------------
 223 
 224     /** The basic block to which these input and output stack map frames correspond. */
 225     Label owner;
 226 
 227     /** The input stack map frame locals. This is an array of abstract types. */
 228     private int[] inputLocals;
 229 
 230     /** The input stack map frame stack. This is an array of abstract types. */
 231     private int[] inputStack;
 232 
 233     /** The output stack map frame locals. This is an array of abstract types. */
 234     private int[] outputLocals;
 235 
 236     /** The output stack map frame stack. This is an array of abstract types. */
 237     private int[] outputStack;
 238 
 239     /**
 240       * The start of the output stack, relatively to the input stack. This offset is always negative or
 241       * null. A null offset means that the output stack must be appended to the input stack. A -n
 242       * offset means that the first n output stack elements must replace the top n input stack
 243       * elements, and that the other elements must be appended to the input stack.
 244       */
 245     private short outputStackStart;
 246 
 247     /** The index of the top stack element in {@link #outputStack}. */
 248     private short outputStackTop;
 249 
 250     /** The number of types that are initialized in the basic block. See {@link #initializations}. */
 251     private int initializationCount;
 252 
 253     /**
 254       * The abstract types that are initialized in the basic block. A constructor invocation on an
 255       * UNINITIALIZED or UNINITIALIZED_THIS abstract type must replace <i>every occurrence</i> of this
 256       * type in the local variables and in the operand stack. This cannot be done during the first step
 257       * of the algorithm since, during this step, the local variables and the operand stack types are
 258       * still abstract. It is therefore necessary to store the abstract types of the constructors which
 259       * are invoked in the basic block, in order to do this replacement during the second step of the
 260       * algorithm, where the frames are fully computed. Note that this array can contain abstract types
 261       * that are relative to the input locals or to the input stack.
 262       */
 263     private int[] initializations;
 264 
 265     // -----------------------------------------------------------------------------------------------
 266     // Constructor
 267     // -----------------------------------------------------------------------------------------------
 268 
 269     /**
 270       * Constructs a new Frame.
 271       *
 272       * @param owner the basic block to which these input and output stack map frames correspond.
 273       */
 274     Frame(final Label owner) {
 275         this.owner = owner;
 276     }
 277 
 278     /**
 279       * Sets this frame to the value of the given frame.
 280       *
 281       * <p>WARNING: after this method is called the two frames share the same data structures. It is
 282       * recommended to discard the given frame to avoid unexpected side effects.
 283       *
 284       * @param frame The new frame value.
 285       */
 286     final void copyFrom(final Frame frame) {
 287         inputLocals = frame.inputLocals;
 288         inputStack = frame.inputStack;
 289         outputStackStart = 0;
 290         outputLocals = frame.outputLocals;
 291         outputStack = frame.outputStack;
 292         outputStackTop = frame.outputStackTop;
 293         initializationCount = frame.initializationCount;
 294         initializations = frame.initializations;
 295     }
 296 
 297     // -----------------------------------------------------------------------------------------------
 298     // Static methods to get abstract types from other type formats
 299     // -----------------------------------------------------------------------------------------------
 300 
 301     /**
 302       * Returns the abstract type corresponding to the given public API frame element type.
 303       *
 304       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 305       * @param type a frame element type described using the same format as in {@link
 306       *     MethodVisitor#visitFrame}, i.e. either {@link Opcodes#TOP}, {@link Opcodes#INTEGER}, {@link
 307       *     Opcodes#FLOAT}, {@link Opcodes#LONG}, {@link Opcodes#DOUBLE}, {@link Opcodes#NULL}, or
 308       *     {@link Opcodes#UNINITIALIZED_THIS}, or the internal name of a class, or a Label designating
 309       *     a NEW instruction (for uninitialized types).
 310       * @return the abstract type corresponding to the given frame element type.
 311       */
 312     static int getAbstractTypeFromApiFormat(final SymbolTable symbolTable, final Object type) {
 313         if (type instanceof Integer) {
 314             return CONSTANT_KIND | ((Integer) type).intValue();
 315         } else if (type instanceof String) {
 316             String descriptor = Type.getObjectType((String) type).getDescriptor();
 317             return getAbstractTypeFromDescriptor(symbolTable, descriptor, 0);
 318         } else {
 319             return UNINITIALIZED_KIND
 320                     | symbolTable.addUninitializedType("", ((Label) type).bytecodeOffset);
 321         }
 322     }
 323 
 324     /**
 325       * Returns the abstract type corresponding to the internal name of a class.
 326       *
 327       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 328       * @param internalName the internal name of a class. This must <i>not</i> be an array type
 329       *     descriptor.
 330       * @return the abstract type value corresponding to the given internal name.
 331       */
 332     static int getAbstractTypeFromInternalName(
 333             final SymbolTable symbolTable, final String internalName) {
 334         return REFERENCE_KIND | symbolTable.addType(internalName);
 335     }
 336 
 337     /**
 338       * Returns the abstract type corresponding to the given type descriptor.
 339       *
 340       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 341       * @param buffer a string ending with a type descriptor.
 342       * @param offset the start offset of the type descriptor in buffer.
 343       * @return the abstract type corresponding to the given type descriptor.
 344       */
 345     private static int getAbstractTypeFromDescriptor(
 346             final SymbolTable symbolTable, final String buffer, final int offset) {
 347         String internalName;
 348         switch (buffer.charAt(offset)) {
 349             case 'V':
 350                 return 0;
 351             case 'Z':
 352             case 'C':
 353             case 'B':
 354             case 'S':
 355             case 'I':
 356                 return INTEGER;
 357             case 'F':
 358                 return FLOAT;
 359             case 'J':
 360                 return LONG;
 361             case 'D':
 362                 return DOUBLE;
 363             case 'L':
 364                 internalName = buffer.substring(offset + 1, buffer.length() - 1);
 365                 return REFERENCE_KIND | symbolTable.addType(internalName);
 366             case '[':
 367                 int elementDescriptorOffset = offset + 1;
 368                 while (buffer.charAt(elementDescriptorOffset) == '[') {
 369                     ++elementDescriptorOffset;
 370                 }
 371                 int typeValue;
 372                 switch (buffer.charAt(elementDescriptorOffset)) {
 373                     case 'Z':
 374                         typeValue = BOOLEAN;
 375                         break;
 376                     case 'C':
 377                         typeValue = CHAR;
 378                         break;
 379                     case 'B':
 380                         typeValue = BYTE;
 381                         break;
 382                     case 'S':
 383                         typeValue = SHORT;
 384                         break;
 385                     case 'I':
 386                         typeValue = INTEGER;
 387                         break;
 388                     case 'F':
 389                         typeValue = FLOAT;
 390                         break;
 391                     case 'J':
 392                         typeValue = LONG;
 393                         break;
 394                     case 'D':
 395                         typeValue = DOUBLE;
 396                         break;
 397                     case 'L':
 398                         internalName = buffer.substring(elementDescriptorOffset + 1, buffer.length() - 1);
 399                         typeValue = REFERENCE_KIND | symbolTable.addType(internalName);
 400                         break;
 401                     default:
 402                         throw new IllegalArgumentException();
 403                 }
 404                 return ((elementDescriptorOffset - offset) << DIM_SHIFT) | typeValue;
 405             default:
 406                 throw new IllegalArgumentException();
 407         }
 408     }
 409 
 410     // -----------------------------------------------------------------------------------------------
 411     // Methods related to the input frame
 412     // -----------------------------------------------------------------------------------------------
 413 
 414     /**
 415       * Sets the input frame from the given method description. This method is used to initialize the
 416       * first frame of a method, which is implicit (i.e. not stored explicitly in the StackMapTable
 417       * attribute).
 418       *
 419       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 420       * @param access the method's access flags.
 421       * @param descriptor the method descriptor.
 422       * @param maxLocals the maximum number of local variables of the method.
 423       */
 424     final void setInputFrameFromDescriptor(
 425             final SymbolTable symbolTable,
 426             final int access,
 427             final String descriptor,
 428             final int maxLocals) {
 429         inputLocals = new int[maxLocals];
 430         inputStack = new int[0];
 431         int inputLocalIndex = 0;
 432         if ((access & Opcodes.ACC_STATIC) == 0) {
 433             if ((access & Constants.ACC_CONSTRUCTOR) == 0) {
 434                 inputLocals[inputLocalIndex++] =
 435                         REFERENCE_KIND | symbolTable.addType(symbolTable.getClassName());
 436             } else {
 437                 inputLocals[inputLocalIndex++] = UNINITIALIZED_THIS;
 438             }
 439         }
 440         for (Type argumentType : Type.getArgumentTypes(descriptor)) {
 441             int abstractType =
 442                     getAbstractTypeFromDescriptor(symbolTable, argumentType.getDescriptor(), 0);
 443             inputLocals[inputLocalIndex++] = abstractType;
 444             if (abstractType == LONG || abstractType == DOUBLE) {
 445                 inputLocals[inputLocalIndex++] = TOP;
 446             }
 447         }
 448         while (inputLocalIndex < maxLocals) {
 449             inputLocals[inputLocalIndex++] = TOP;
 450         }
 451     }
 452 
 453     /**
 454       * Sets the input frame from the given public API frame description.
 455       *
 456       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 457       * @param numLocal the number of local variables.
 458       * @param local the local variable types, described using the same format as in {@link
 459       *     MethodVisitor#visitFrame}.
 460       * @param numStack the number of operand stack elements.
 461       * @param stack the operand stack types, described using the same format as in {@link
 462       *     MethodVisitor#visitFrame}.
 463       */
 464     final void setInputFrameFromApiFormat(
 465             final SymbolTable symbolTable,
 466             final int numLocal,
 467             final Object[] local,
 468             final int numStack,
 469             final Object[] stack) {
 470         int inputLocalIndex = 0;
 471         for (int i = 0; i < numLocal; ++i) {
 472             inputLocals[inputLocalIndex++] = getAbstractTypeFromApiFormat(symbolTable, local[i]);
 473             if (local[i] == Opcodes.LONG || local[i] == Opcodes.DOUBLE) {
 474                 inputLocals[inputLocalIndex++] = TOP;
 475             }
 476         }
 477         while (inputLocalIndex < inputLocals.length) {
 478             inputLocals[inputLocalIndex++] = TOP;
 479         }
 480         int numStackTop = 0;
 481         for (int i = 0; i < numStack; ++i) {
 482             if (stack[i] == Opcodes.LONG || stack[i] == Opcodes.DOUBLE) {
 483                 ++numStackTop;
 484             }
 485         }
 486         inputStack = new int[numStack + numStackTop];
 487         int inputStackIndex = 0;
 488         for (int i = 0; i < numStack; ++i) {
 489             inputStack[inputStackIndex++] = getAbstractTypeFromApiFormat(symbolTable, stack[i]);
 490             if (stack[i] == Opcodes.LONG || stack[i] == Opcodes.DOUBLE) {
 491                 inputStack[inputStackIndex++] = TOP;
 492             }
 493         }
 494         outputStackTop = 0;
 495         initializationCount = 0;
 496     }
 497 
 498     final int getInputStackSize() {
 499         return inputStack.length;
 500     }
 501 
 502     // -----------------------------------------------------------------------------------------------
 503     // Methods related to the output frame
 504     // -----------------------------------------------------------------------------------------------
 505 
 506     /**
 507       * Returns the abstract type stored at the given local variable index in the output frame.
 508       *
 509       * @param localIndex the index of the local variable whose value must be returned.
 510       * @return the abstract type stored at the given local variable index in the output frame.
 511       */
 512     private int getLocal(final int localIndex) {
 513         if (outputLocals == null || localIndex >= outputLocals.length) {
 514             // If this local has never been assigned in this basic block, it is still equal to its value
 515             // in the input frame.
 516             return LOCAL_KIND | localIndex;
 517         } else {
 518             int abstractType = outputLocals[localIndex];
 519             if (abstractType == 0) {
 520                 // If this local has never been assigned in this basic block, so it is still equal to its
 521                 // value in the input frame.
 522                 abstractType = outputLocals[localIndex] = LOCAL_KIND | localIndex;
 523             }
 524             return abstractType;
 525         }
 526     }
 527 
 528     /**
 529       * Replaces the abstract type stored at the given local variable index in the output frame.
 530       *
 531       * @param localIndex the index of the output frame local variable that must be set.
 532       * @param abstractType the value that must be set.
 533       */
 534     private void setLocal(final int localIndex, final int abstractType) {
 535         // Create and/or resize the output local variables array if necessary.
 536         if (outputLocals == null) {
 537             outputLocals = new int[10];
 538         }
 539         int outputLocalsLength = outputLocals.length;
 540         if (localIndex >= outputLocalsLength) {
 541             int[] newOutputLocals = new int[Math.max(localIndex + 1, 2 * outputLocalsLength)];
 542             System.arraycopy(outputLocals, 0, newOutputLocals, 0, outputLocalsLength);
 543             outputLocals = newOutputLocals;
 544         }
 545         // Set the local variable.
 546         outputLocals[localIndex] = abstractType;
 547     }
 548 
 549     /**
 550       * Pushes the given abstract type on the output frame stack.
 551       *
 552       * @param abstractType an abstract type.
 553       */
 554     private void push(final int abstractType) {
 555         // Create and/or resize the output stack array if necessary.
 556         if (outputStack == null) {
 557             outputStack = new int[10];
 558         }
 559         int outputStackLength = outputStack.length;
 560         if (outputStackTop >= outputStackLength) {
 561             int[] newOutputStack = new int[Math.max(outputStackTop + 1, 2 * outputStackLength)];
 562             System.arraycopy(outputStack, 0, newOutputStack, 0, outputStackLength);
 563             outputStack = newOutputStack;
 564         }
 565         // Pushes the abstract type on the output stack.
 566         outputStack[outputStackTop++] = abstractType;
 567         // Updates the maximum size reached by the output stack, if needed (note that this size is
 568         // relative to the input stack size, which is not known yet).
 569         short outputStackSize = (short) (outputStackStart + outputStackTop);
 570         if (outputStackSize > owner.outputStackMax) {
 571             owner.outputStackMax = outputStackSize;
 572         }
 573     }
 574 
 575     /**
 576       * Pushes the abstract type corresponding to the given descriptor on the output frame stack.
 577       *
 578       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 579       * @param descriptor a type or method descriptor (in which case its return type is pushed).
 580       */
 581     private void push(final SymbolTable symbolTable, final String descriptor) {
 582         int typeDescriptorOffset =
 583                 descriptor.charAt(0) == '(' ? Type.getReturnTypeOffset(descriptor) : 0;
 584         int abstractType = getAbstractTypeFromDescriptor(symbolTable, descriptor, typeDescriptorOffset);
 585         if (abstractType != 0) {
 586             push(abstractType);
 587             if (abstractType == LONG || abstractType == DOUBLE) {
 588                 push(TOP);
 589             }
 590         }
 591     }
 592 
 593     /**
 594       * Pops an abstract type from the output frame stack and returns its value.
 595       *
 596       * @return the abstract type that has been popped from the output frame stack.
 597       */
 598     private int pop() {
 599         if (outputStackTop > 0) {
 600             return outputStack[--outputStackTop];
 601         } else {
 602             // If the output frame stack is empty, pop from the input stack.
 603             return STACK_KIND | -(--outputStackStart);
 604         }
 605     }
 606 
 607     /**
 608       * Pops the given number of abstract types from the output frame stack.
 609       *
 610       * @param elements the number of abstract types that must be popped.
 611       */
 612     private void pop(final int elements) {
 613         if (outputStackTop >= elements) {
 614             outputStackTop -= (short) elements;
 615         } else {
 616             // If the number of elements to be popped is greater than the number of elements in the output
 617             // stack, clear it, and pop the remaining elements from the input stack.
 618             outputStackStart -= (short) (elements - outputStackTop);
 619             outputStackTop = 0;
 620         }
 621     }
 622 
 623     /**
 624       * Pops as many abstract types from the output frame stack as described by the given descriptor.
 625       *
 626       * @param descriptor a type or method descriptor (in which case its argument types are popped).
 627       */
 628     private void pop(final String descriptor) {
 629         char firstDescriptorChar = descriptor.charAt(0);
 630         if (firstDescriptorChar == '(') {
 631             pop((Type.getArgumentsAndReturnSizes(descriptor) >> 2) - 1);
 632         } else if (firstDescriptorChar == 'J' || firstDescriptorChar == 'D') {
 633             pop(2);
 634         } else {
 635             pop(1);
 636         }
 637     }
 638 
 639     // -----------------------------------------------------------------------------------------------
 640     // Methods to handle uninitialized types
 641     // -----------------------------------------------------------------------------------------------
 642 
 643     /**
 644       * Adds an abstract type to the list of types on which a constructor is invoked in the basic
 645       * block.
 646       *
 647       * @param abstractType an abstract type on a which a constructor is invoked.
 648       */
 649     private void addInitializedType(final int abstractType) {
 650         // Create and/or resize the initializations array if necessary.
 651         if (initializations == null) {
 652             initializations = new int[2];
 653         }
 654         int initializationsLength = initializations.length;
 655         if (initializationCount >= initializationsLength) {
 656             int[] newInitializations =
 657                     new int[Math.max(initializationCount + 1, 2 * initializationsLength)];
 658             System.arraycopy(initializations, 0, newInitializations, 0, initializationsLength);
 659             initializations = newInitializations;
 660         }
 661         // Store the abstract type.
 662         initializations[initializationCount++] = abstractType;
 663     }
 664 
 665     /**
 666       * Returns the "initialized" abstract type corresponding to the given abstract type.
 667       *
 668       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 669       * @param abstractType an abstract type.
 670       * @return the REFERENCE_KIND abstract type corresponding to abstractType if it is
 671       *     UNINITIALIZED_THIS or an UNINITIALIZED_KIND abstract type for one of the types on which a
 672       *     constructor is invoked in the basic block. Otherwise returns abstractType.
 673       */
 674     private int getInitializedType(final SymbolTable symbolTable, final int abstractType) {
 675         if (abstractType == UNINITIALIZED_THIS
 676                 || (abstractType & (DIM_MASK | KIND_MASK)) == UNINITIALIZED_KIND) {
 677             for (int i = 0; i < initializationCount; ++i) {
 678                 int initializedType = initializations[i];
 679                 int dim = initializedType & DIM_MASK;
 680                 int kind = initializedType & KIND_MASK;
 681                 int value = initializedType & VALUE_MASK;
 682                 if (kind == LOCAL_KIND) {
 683                     initializedType = dim + inputLocals[value];
 684                 } else if (kind == STACK_KIND) {
 685                     initializedType = dim + inputStack[inputStack.length - value];
 686                 }
 687                 if (abstractType == initializedType) {
 688                     if (abstractType == UNINITIALIZED_THIS) {
 689                         return REFERENCE_KIND | symbolTable.addType(symbolTable.getClassName());
 690                     } else {
 691                         return REFERENCE_KIND
 692                                 | symbolTable.addType(symbolTable.getType(abstractType & VALUE_MASK).value);
 693                     }
 694                 }
 695             }
 696         }
 697         return abstractType;
 698     }
 699 
 700     // -----------------------------------------------------------------------------------------------
 701     // Main method, to simulate the execution of each instruction on the output frame
 702     // -----------------------------------------------------------------------------------------------
 703 
 704     /**
 705       * Simulates the action of the given instruction on the output stack frame.
 706       *
 707       * @param opcode the opcode of the instruction.
 708       * @param arg the numeric operand of the instruction, if any.
 709       * @param argSymbol the Symbol operand of the instruction, if any.
 710       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
 711       */
 712     void execute(
 713             final int opcode, final int arg, final Symbol argSymbol, final SymbolTable symbolTable) {
 714         // Abstract types popped from the stack or read from local variables.
 715         int abstractType1;
 716         int abstractType2;
 717         int abstractType3;
 718         int abstractType4;
 719         switch (opcode) {
 720             case Opcodes.NOP:
 721             case Opcodes.INEG:
 722             case Opcodes.LNEG:
 723             case Opcodes.FNEG:
 724             case Opcodes.DNEG:
 725             case Opcodes.I2B:
 726             case Opcodes.I2C:
 727             case Opcodes.I2S:
 728             case Opcodes.GOTO:
 729             case Opcodes.RETURN:
 730                 break;
 731             case Opcodes.ACONST_NULL:
 732                 push(NULL);
 733                 break;
 734             case Opcodes.ICONST_M1:
 735             case Opcodes.ICONST_0:
 736             case Opcodes.ICONST_1:
 737             case Opcodes.ICONST_2:
 738             case Opcodes.ICONST_3:
 739             case Opcodes.ICONST_4:
 740             case Opcodes.ICONST_5:
 741             case Opcodes.BIPUSH:
 742             case Opcodes.SIPUSH:
 743             case Opcodes.ILOAD:
 744                 push(INTEGER);
 745                 break;
 746             case Opcodes.LCONST_0:
 747             case Opcodes.LCONST_1:
 748             case Opcodes.LLOAD:
 749                 push(LONG);
 750                 push(TOP);
 751                 break;
 752             case Opcodes.FCONST_0:
 753             case Opcodes.FCONST_1:
 754             case Opcodes.FCONST_2:
 755             case Opcodes.FLOAD:
 756                 push(FLOAT);
 757                 break;
 758             case Opcodes.DCONST_0:
 759             case Opcodes.DCONST_1:
 760             case Opcodes.DLOAD:
 761                 push(DOUBLE);
 762                 push(TOP);
 763                 break;
 764             case Opcodes.LDC:
 765                 switch (argSymbol.tag) {
 766                     case Symbol.CONSTANT_INTEGER_TAG:
 767                         push(INTEGER);
 768                         break;
 769                     case Symbol.CONSTANT_LONG_TAG:
 770                         push(LONG);
 771                         push(TOP);
 772                         break;
 773                     case Symbol.CONSTANT_FLOAT_TAG:
 774                         push(FLOAT);
 775                         break;
 776                     case Symbol.CONSTANT_DOUBLE_TAG:
 777                         push(DOUBLE);
 778                         push(TOP);
 779                         break;
 780                     case Symbol.CONSTANT_CLASS_TAG:
 781                         push(REFERENCE_KIND | symbolTable.addType("java/lang/Class"));
 782                         break;
 783                     case Symbol.CONSTANT_STRING_TAG:
 784                         push(REFERENCE_KIND | symbolTable.addType("java/lang/String"));
 785                         break;
 786                     case Symbol.CONSTANT_METHOD_TYPE_TAG:
 787                         push(REFERENCE_KIND | symbolTable.addType("java/lang/invoke/MethodType"));
 788                         break;
 789                     case Symbol.CONSTANT_METHOD_HANDLE_TAG:
 790                         push(REFERENCE_KIND | symbolTable.addType("java/lang/invoke/MethodHandle"));
 791                         break;
 792                     case Symbol.CONSTANT_DYNAMIC_TAG:
 793                         push(symbolTable, argSymbol.value);
 794                         break;
 795                     default:
 796                         throw new AssertionError();
 797                 }
 798                 break;
 799             case Opcodes.ALOAD:
 800                 push(getLocal(arg));
 801                 break;
 802             case Opcodes.LALOAD:
 803             case Opcodes.D2L:
 804                 pop(2);
 805                 push(LONG);
 806                 push(TOP);
 807                 break;
 808             case Opcodes.DALOAD:
 809             case Opcodes.L2D:
 810                 pop(2);
 811                 push(DOUBLE);
 812                 push(TOP);
 813                 break;
 814             case Opcodes.AALOAD:
 815                 pop(1);
 816                 abstractType1 = pop();
 817                 push(abstractType1 == NULL ? abstractType1 : ELEMENT_OF + abstractType1);
 818                 break;
 819             case Opcodes.ISTORE:
 820             case Opcodes.FSTORE:
 821             case Opcodes.ASTORE:
 822                 abstractType1 = pop();
 823                 setLocal(arg, abstractType1);
 824                 if (arg > 0) {
 825                     int previousLocalType = getLocal(arg - 1);
 826                     if (previousLocalType == LONG || previousLocalType == DOUBLE) {
 827                         setLocal(arg - 1, TOP);
 828                     } else if ((previousLocalType & KIND_MASK) == LOCAL_KIND
 829                             || (previousLocalType & KIND_MASK) == STACK_KIND) {
 830                         // The type of the previous local variable is not known yet, but if it later appears
 831                         // to be LONG or DOUBLE, we should then use TOP instead.
 832                         setLocal(arg - 1, previousLocalType | TOP_IF_LONG_OR_DOUBLE_FLAG);
 833                     }
 834                 }
 835                 break;
 836             case Opcodes.LSTORE:
 837             case Opcodes.DSTORE:
 838                 pop(1);
 839                 abstractType1 = pop();
 840                 setLocal(arg, abstractType1);
 841                 setLocal(arg + 1, TOP);
 842                 if (arg > 0) {
 843                     int previousLocalType = getLocal(arg - 1);
 844                     if (previousLocalType == LONG || previousLocalType == DOUBLE) {
 845                         setLocal(arg - 1, TOP);
 846                     } else if ((previousLocalType & KIND_MASK) == LOCAL_KIND
 847                             || (previousLocalType & KIND_MASK) == STACK_KIND) {
 848                         // The type of the previous local variable is not known yet, but if it later appears
 849                         // to be LONG or DOUBLE, we should then use TOP instead.
 850                         setLocal(arg - 1, previousLocalType | TOP_IF_LONG_OR_DOUBLE_FLAG);
 851                     }
 852                 }
 853                 break;
 854             case Opcodes.IASTORE:
 855             case Opcodes.BASTORE:
 856             case Opcodes.CASTORE:
 857             case Opcodes.SASTORE:
 858             case Opcodes.FASTORE:
 859             case Opcodes.AASTORE:
 860                 pop(3);
 861                 break;
 862             case Opcodes.LASTORE:
 863             case Opcodes.DASTORE:
 864                 pop(4);
 865                 break;
 866             case Opcodes.POP:
 867             case Opcodes.IFEQ:
 868             case Opcodes.IFNE:
 869             case Opcodes.IFLT:
 870             case Opcodes.IFGE:
 871             case Opcodes.IFGT:
 872             case Opcodes.IFLE:
 873             case Opcodes.IRETURN:
 874             case Opcodes.FRETURN:
 875             case Opcodes.ARETURN:
 876             case Opcodes.TABLESWITCH:
 877             case Opcodes.LOOKUPSWITCH:
 878             case Opcodes.ATHROW:
 879             case Opcodes.MONITORENTER:
 880             case Opcodes.MONITOREXIT:
 881             case Opcodes.IFNULL:
 882             case Opcodes.IFNONNULL:
 883                 pop(1);
 884                 break;
 885             case Opcodes.POP2:
 886             case Opcodes.IF_ICMPEQ:
 887             case Opcodes.IF_ICMPNE:
 888             case Opcodes.IF_ICMPLT:
 889             case Opcodes.IF_ICMPGE:
 890             case Opcodes.IF_ICMPGT:
 891             case Opcodes.IF_ICMPLE:
 892             case Opcodes.IF_ACMPEQ:
 893             case Opcodes.IF_ACMPNE:
 894             case Opcodes.LRETURN:
 895             case Opcodes.DRETURN:
 896                 pop(2);
 897                 break;
 898             case Opcodes.DUP:
 899                 abstractType1 = pop();
 900                 push(abstractType1);
 901                 push(abstractType1);
 902                 break;
 903             case Opcodes.DUP_X1:
 904                 abstractType1 = pop();
 905                 abstractType2 = pop();
 906                 push(abstractType1);
 907                 push(abstractType2);
 908                 push(abstractType1);
 909                 break;
 910             case Opcodes.DUP_X2:
 911                 abstractType1 = pop();
 912                 abstractType2 = pop();
 913                 abstractType3 = pop();
 914                 push(abstractType1);
 915                 push(abstractType3);
 916                 push(abstractType2);
 917                 push(abstractType1);
 918                 break;
 919             case Opcodes.DUP2:
 920                 abstractType1 = pop();
 921                 abstractType2 = pop();
 922                 push(abstractType2);
 923                 push(abstractType1);
 924                 push(abstractType2);
 925                 push(abstractType1);
 926                 break;
 927             case Opcodes.DUP2_X1:
 928                 abstractType1 = pop();
 929                 abstractType2 = pop();
 930                 abstractType3 = pop();
 931                 push(abstractType2);
 932                 push(abstractType1);
 933                 push(abstractType3);
 934                 push(abstractType2);
 935                 push(abstractType1);
 936                 break;
 937             case Opcodes.DUP2_X2:
 938                 abstractType1 = pop();
 939                 abstractType2 = pop();
 940                 abstractType3 = pop();
 941                 abstractType4 = pop();
 942                 push(abstractType2);
 943                 push(abstractType1);
 944                 push(abstractType4);
 945                 push(abstractType3);
 946                 push(abstractType2);
 947                 push(abstractType1);
 948                 break;
 949             case Opcodes.SWAP:
 950                 abstractType1 = pop();
 951                 abstractType2 = pop();
 952                 push(abstractType1);
 953                 push(abstractType2);
 954                 break;
 955             case Opcodes.IALOAD:
 956             case Opcodes.BALOAD:
 957             case Opcodes.CALOAD:
 958             case Opcodes.SALOAD:
 959             case Opcodes.IADD:
 960             case Opcodes.ISUB:
 961             case Opcodes.IMUL:
 962             case Opcodes.IDIV:
 963             case Opcodes.IREM:
 964             case Opcodes.IAND:
 965             case Opcodes.IOR:
 966             case Opcodes.IXOR:
 967             case Opcodes.ISHL:
 968             case Opcodes.ISHR:
 969             case Opcodes.IUSHR:
 970             case Opcodes.L2I:
 971             case Opcodes.D2I:
 972             case Opcodes.FCMPL:
 973             case Opcodes.FCMPG:
 974                 pop(2);
 975                 push(INTEGER);
 976                 break;
 977             case Opcodes.LADD:
 978             case Opcodes.LSUB:
 979             case Opcodes.LMUL:
 980             case Opcodes.LDIV:
 981             case Opcodes.LREM:
 982             case Opcodes.LAND:
 983             case Opcodes.LOR:
 984             case Opcodes.LXOR:
 985                 pop(4);
 986                 push(LONG);
 987                 push(TOP);
 988                 break;
 989             case Opcodes.FALOAD:
 990             case Opcodes.FADD:
 991             case Opcodes.FSUB:
 992             case Opcodes.FMUL:
 993             case Opcodes.FDIV:
 994             case Opcodes.FREM:
 995             case Opcodes.L2F:
 996             case Opcodes.D2F:
 997                 pop(2);
 998                 push(FLOAT);
 999                 break;
1000             case Opcodes.DADD:
1001             case Opcodes.DSUB:
1002             case Opcodes.DMUL:
1003             case Opcodes.DDIV:
1004             case Opcodes.DREM:
1005                 pop(4);
1006                 push(DOUBLE);
1007                 push(TOP);
1008                 break;
1009             case Opcodes.LSHL:
1010             case Opcodes.LSHR:
1011             case Opcodes.LUSHR:
1012                 pop(3);
1013                 push(LONG);
1014                 push(TOP);
1015                 break;
1016             case Opcodes.IINC:
1017                 setLocal(arg, INTEGER);
1018                 break;
1019             case Opcodes.I2L:
1020             case Opcodes.F2L:
1021                 pop(1);
1022                 push(LONG);
1023                 push(TOP);
1024                 break;
1025             case Opcodes.I2F:
1026                 pop(1);
1027                 push(FLOAT);
1028                 break;
1029             case Opcodes.I2D:
1030             case Opcodes.F2D:
1031                 pop(1);
1032                 push(DOUBLE);
1033                 push(TOP);
1034                 break;
1035             case Opcodes.F2I:
1036             case Opcodes.ARRAYLENGTH:
1037             case Opcodes.INSTANCEOF:
1038                 pop(1);
1039                 push(INTEGER);
1040                 break;
1041             case Opcodes.LCMP:
1042             case Opcodes.DCMPL:
1043             case Opcodes.DCMPG:
1044                 pop(4);
1045                 push(INTEGER);
1046                 break;
1047             case Opcodes.JSR:
1048             case Opcodes.RET:
1049                 throw new IllegalArgumentException("JSR/RET are not supported with computeFrames option");
1050             case Opcodes.GETSTATIC:
1051                 push(symbolTable, argSymbol.value);
1052                 break;
1053             case Opcodes.PUTSTATIC:
1054                 pop(argSymbol.value);
1055                 break;
1056             case Opcodes.GETFIELD:
1057                 pop(1);
1058                 push(symbolTable, argSymbol.value);
1059                 break;
1060             case Opcodes.PUTFIELD:
1061                 pop(argSymbol.value);
1062                 pop();
1063                 break;
1064             case Opcodes.INVOKEVIRTUAL:
1065             case Opcodes.INVOKESPECIAL:
1066             case Opcodes.INVOKESTATIC:
1067             case Opcodes.INVOKEINTERFACE:
1068                 pop(argSymbol.value);
1069                 if (opcode != Opcodes.INVOKESTATIC) {
1070                     abstractType1 = pop();
1071                     if (opcode == Opcodes.INVOKESPECIAL && argSymbol.name.charAt(0) == '<') {
1072                         addInitializedType(abstractType1);
1073                     }
1074                 }
1075                 push(symbolTable, argSymbol.value);
1076                 break;
1077             case Opcodes.INVOKEDYNAMIC:
1078                 pop(argSymbol.value);
1079                 push(symbolTable, argSymbol.value);
1080                 break;
1081             case Opcodes.NEW:
1082                 push(UNINITIALIZED_KIND | symbolTable.addUninitializedType(argSymbol.value, arg));
1083                 break;
1084             case Opcodes.NEWARRAY:
1085                 pop();
1086                 switch (arg) {
1087                     case Opcodes.T_BOOLEAN:
1088                         push(ARRAY_OF | BOOLEAN);
1089                         break;
1090                     case Opcodes.T_CHAR:
1091                         push(ARRAY_OF | CHAR);
1092                         break;
1093                     case Opcodes.T_BYTE:
1094                         push(ARRAY_OF | BYTE);
1095                         break;
1096                     case Opcodes.T_SHORT:
1097                         push(ARRAY_OF | SHORT);
1098                         break;
1099                     case Opcodes.T_INT:
1100                         push(ARRAY_OF | INTEGER);
1101                         break;
1102                     case Opcodes.T_FLOAT:
1103                         push(ARRAY_OF | FLOAT);
1104                         break;
1105                     case Opcodes.T_DOUBLE:
1106                         push(ARRAY_OF | DOUBLE);
1107                         break;
1108                     case Opcodes.T_LONG:
1109                         push(ARRAY_OF | LONG);
1110                         break;
1111                     default:
1112                         throw new IllegalArgumentException();
1113                 }
1114                 break;
1115             case Opcodes.ANEWARRAY:
1116                 String arrayElementType = argSymbol.value;
1117                 pop();
1118                 if (arrayElementType.charAt(0) == '[') {
1119                     push(symbolTable, '[' + arrayElementType);
1120                 } else {
1121                     push(ARRAY_OF | REFERENCE_KIND | symbolTable.addType(arrayElementType));
1122                 }
1123                 break;
1124             case Opcodes.CHECKCAST:
1125                 String castType = argSymbol.value;
1126                 pop();
1127                 if (castType.charAt(0) == '[') {
1128                     push(symbolTable, castType);
1129                 } else {
1130                     push(REFERENCE_KIND | symbolTable.addType(castType));
1131                 }
1132                 break;
1133             case Opcodes.MULTIANEWARRAY:
1134                 pop(arg);
1135                 push(symbolTable, argSymbol.value);
1136                 break;
1137             default:
1138                 throw new IllegalArgumentException();
1139         }
1140     }
1141 
1142     // -----------------------------------------------------------------------------------------------
1143     // Frame merging methods, used in the second step of the stack map frame computation algorithm
1144     // -----------------------------------------------------------------------------------------------
1145 
1146     /**
1147       * Computes the concrete output type corresponding to a given abstract output type.
1148       *
1149       * @param abstractOutputType an abstract output type.
1150       * @param numStack the size of the input stack, used to resolve abstract output types of
1151       *     STACK_KIND kind.
1152       * @return the concrete output type corresponding to 'abstractOutputType'.
1153       */
1154     private int getConcreteOutputType(final int abstractOutputType, final int numStack) {
1155         int dim = abstractOutputType & DIM_MASK;
1156         int kind = abstractOutputType & KIND_MASK;
1157         if (kind == LOCAL_KIND) {
1158             // By definition, a LOCAL_KIND type designates the concrete type of a local variable at
1159             // the beginning of the basic block corresponding to this frame (which is known when
1160             // this method is called, but was not when the abstract type was computed).
1161             int concreteOutputType = dim + inputLocals[abstractOutputType & VALUE_MASK];
1162             if ((abstractOutputType & TOP_IF_LONG_OR_DOUBLE_FLAG) != 0
1163                     && (concreteOutputType == LONG || concreteOutputType == DOUBLE)) {
1164                 concreteOutputType = TOP;
1165             }
1166             return concreteOutputType;
1167         } else if (kind == STACK_KIND) {
1168             // By definition, a STACK_KIND type designates the concrete type of a local variable at
1169             // the beginning of the basic block corresponding to this frame (which is known when
1170             // this method is called, but was not when the abstract type was computed).
1171             int concreteOutputType = dim + inputStack[numStack - (abstractOutputType & VALUE_MASK)];
1172             if ((abstractOutputType & TOP_IF_LONG_OR_DOUBLE_FLAG) != 0
1173                     && (concreteOutputType == LONG || concreteOutputType == DOUBLE)) {
1174                 concreteOutputType = TOP;
1175             }
1176             return concreteOutputType;
1177         } else {
1178             return abstractOutputType;
1179         }
1180     }
1181 
1182     /**
1183       * Merges the input frame of the given {@link Frame} with the input and output frames of this
1184       * {@link Frame}. Returns {@literal true} if the given frame has been changed by this operation
1185       * (the input and output frames of this {@link Frame} are never changed).
1186       *
1187       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
1188       * @param dstFrame the {@link Frame} whose input frame must be updated. This should be the frame
1189       *     of a successor, in the control flow graph, of the basic block corresponding to this frame.
1190       * @param catchTypeIndex if 'frame' corresponds to an exception handler basic block, the type
1191       *     table index of the caught exception type, otherwise 0.
1192       * @return {@literal true} if the input frame of 'frame' has been changed by this operation.
1193       */
1194     final boolean merge(
1195             final SymbolTable symbolTable, final Frame dstFrame, final int catchTypeIndex) {
1196         boolean frameChanged = false;
1197 
1198         // Compute the concrete types of the local variables at the end of the basic block corresponding
1199         // to this frame, by resolving its abstract output types, and merge these concrete types with
1200         // those of the local variables in the input frame of dstFrame.
1201         int numLocal = inputLocals.length;
1202         int numStack = inputStack.length;
1203         if (dstFrame.inputLocals == null) {
1204             dstFrame.inputLocals = new int[numLocal];
1205             frameChanged = true;
1206         }
1207         for (int i = 0; i < numLocal; ++i) {
1208             int concreteOutputType;
1209             if (outputLocals != null && i < outputLocals.length) {
1210                 int abstractOutputType = outputLocals[i];
1211                 if (abstractOutputType == 0) {
1212                     // If the local variable has never been assigned in this basic block, it is equal to its
1213                     // value at the beginning of the block.
1214                     concreteOutputType = inputLocals[i];
1215                 } else {
1216                     concreteOutputType = getConcreteOutputType(abstractOutputType, numStack);
1217                 }
1218             } else {
1219                 // If the local variable has never been assigned in this basic block, it is equal to its
1220                 // value at the beginning of the block.
1221                 concreteOutputType = inputLocals[i];
1222             }
1223             // concreteOutputType might be an uninitialized type from the input locals or from the input
1224             // stack. However, if a constructor has been called for this class type in the basic block,
1225             // then this type is no longer uninitialized at the end of basic block.
1226             if (initializations != null) {
1227                 concreteOutputType = getInitializedType(symbolTable, concreteOutputType);
1228             }
1229             frameChanged |= merge(symbolTable, concreteOutputType, dstFrame.inputLocals, i);
1230         }
1231 
1232         // If dstFrame is an exception handler block, it can be reached from any instruction of the
1233         // basic block corresponding to this frame, in particular from the first one. Therefore, the
1234         // input locals of dstFrame should be compatible (i.e. merged) with the input locals of this
1235         // frame (and the input stack of dstFrame should be compatible, i.e. merged, with a one
1236         // element stack containing the caught exception type).
1237         if (catchTypeIndex > 0) {
1238             for (int i = 0; i < numLocal; ++i) {
1239                 frameChanged |= merge(symbolTable, inputLocals[i], dstFrame.inputLocals, i);
1240             }
1241             if (dstFrame.inputStack == null) {
1242                 dstFrame.inputStack = new int[1];
1243                 frameChanged = true;
1244             }
1245             frameChanged |= merge(symbolTable, catchTypeIndex, dstFrame.inputStack, 0);
1246             return frameChanged;
1247         }
1248 
1249         // Compute the concrete types of the stack operands at the end of the basic block corresponding
1250         // to this frame, by resolving its abstract output types, and merge these concrete types with
1251         // those of the stack operands in the input frame of dstFrame.
1252         int numInputStack = inputStack.length + outputStackStart;
1253         if (dstFrame.inputStack == null) {
1254             dstFrame.inputStack = new int[numInputStack + outputStackTop];
1255             frameChanged = true;
1256         }
1257         // First, do this for the stack operands that have not been popped in the basic block
1258         // corresponding to this frame, and which are therefore equal to their value in the input
1259         // frame (except for uninitialized types, which may have been initialized).
1260         for (int i = 0; i < numInputStack; ++i) {
1261             int concreteOutputType = inputStack[i];
1262             if (initializations != null) {
1263                 concreteOutputType = getInitializedType(symbolTable, concreteOutputType);
1264             }
1265             frameChanged |= merge(symbolTable, concreteOutputType, dstFrame.inputStack, i);
1266         }
1267         // Then, do this for the stack operands that have pushed in the basic block (this code is the
1268         // same as the one above for local variables).
1269         for (int i = 0; i < outputStackTop; ++i) {
1270             int abstractOutputType = outputStack[i];
1271             int concreteOutputType = getConcreteOutputType(abstractOutputType, numStack);
1272             if (initializations != null) {
1273                 concreteOutputType = getInitializedType(symbolTable, concreteOutputType);
1274             }
1275             frameChanged |=
1276                     merge(symbolTable, concreteOutputType, dstFrame.inputStack, numInputStack + i);
1277         }
1278         return frameChanged;
1279     }
1280 
1281     /**
1282       * Merges the type at the given index in the given abstract type array with the given type.
1283       * Returns {@literal true} if the type array has been modified by this operation.
1284       *
1285       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
1286       * @param sourceType the abstract type with which the abstract type array element must be merged.
1287       *     This type should be of {@link #CONSTANT_KIND}, {@link #REFERENCE_KIND} or {@link
1288       *     #UNINITIALIZED_KIND} kind, with positive or {@literal null} array dimensions.
1289       * @param dstTypes an array of abstract types. These types should be of {@link #CONSTANT_KIND},
1290       *     {@link #REFERENCE_KIND} or {@link #UNINITIALIZED_KIND} kind, with positive or {@literal
1291       *     null} array dimensions.
1292       * @param dstIndex the index of the type that must be merged in dstTypes.
1293       * @return {@literal true} if the type array has been modified by this operation.
1294       */
1295     private static boolean merge(
1296             final SymbolTable symbolTable,
1297             final int sourceType,
1298             final int[] dstTypes,
1299             final int dstIndex) {
1300         int dstType = dstTypes[dstIndex];
1301         if (dstType == sourceType) {
1302             // If the types are equal, merge(sourceType, dstType) = dstType, so there is no change.
1303             return false;
1304         }
1305         int srcType = sourceType;
1306         if ((sourceType & ~DIM_MASK) == NULL) {
1307             if (dstType == NULL) {
1308                 return false;
1309             }
1310             srcType = NULL;
1311         }
1312         if (dstType == 0) {
1313             // If dstTypes[dstIndex] has never been assigned, merge(srcType, dstType) = srcType.
1314             dstTypes[dstIndex] = srcType;
1315             return true;
1316         }
1317         int mergedType;
1318         if ((dstType & DIM_MASK) != 0 || (dstType & KIND_MASK) == REFERENCE_KIND) {
1319             // If dstType is a reference type of any array dimension.
1320             if (srcType == NULL) {
1321                 // If srcType is the NULL type, merge(srcType, dstType) = dstType, so there is no change.
1322                 return false;
1323             } else if ((srcType & (DIM_MASK | KIND_MASK)) == (dstType & (DIM_MASK | KIND_MASK))) {
1324                 // If srcType has the same array dimension and the same kind as dstType.
1325                 if ((dstType & KIND_MASK) == REFERENCE_KIND) {
1326                     // If srcType and dstType are reference types with the same array dimension,
1327                     // merge(srcType, dstType) = dim(srcType) | common super class of srcType and dstType.
1328                     mergedType =
1329                             (srcType & DIM_MASK)
1330                                     | REFERENCE_KIND
1331                                     | symbolTable.addMergedType(srcType & VALUE_MASK, dstType & VALUE_MASK);
1332                 } else {
1333                     // If srcType and dstType are array types of equal dimension but different element types,
1334                     // merge(srcType, dstType) = dim(srcType) - 1 | java/lang/Object.
1335                     int mergedDim = ELEMENT_OF + (srcType & DIM_MASK);
1336                     mergedType = mergedDim | REFERENCE_KIND | symbolTable.addType("java/lang/Object");
1337                 }
1338             } else if ((srcType & DIM_MASK) != 0 || (srcType & KIND_MASK) == REFERENCE_KIND) {
1339                 // If srcType is any other reference or array type,
1340                 // merge(srcType, dstType) = min(srcDdim, dstDim) | java/lang/Object
1341                 // where srcDim is the array dimension of srcType, minus 1 if srcType is an array type
1342                 // with a non reference element type (and similarly for dstDim).
1343                 int srcDim = srcType & DIM_MASK;
1344                 if (srcDim != 0 && (srcType & KIND_MASK) != REFERENCE_KIND) {
1345                     srcDim = ELEMENT_OF + srcDim;
1346                 }
1347                 int dstDim = dstType & DIM_MASK;
1348                 if (dstDim != 0 && (dstType & KIND_MASK) != REFERENCE_KIND) {
1349                     dstDim = ELEMENT_OF + dstDim;
1350                 }
1351                 mergedType =
1352                         Math.min(srcDim, dstDim) | REFERENCE_KIND | symbolTable.addType("java/lang/Object");
1353             } else {
1354                 // If srcType is any other type, merge(srcType, dstType) = TOP.
1355                 mergedType = TOP;
1356             }
1357         } else if (dstType == NULL) {
1358             // If dstType is the NULL type, merge(srcType, dstType) = srcType, or TOP if srcType is not a
1359             // an array type or a reference type.
1360             mergedType =
1361                     (srcType & DIM_MASK) != 0 || (srcType & KIND_MASK) == REFERENCE_KIND ? srcType : TOP;
1362         } else {
1363             // If dstType is any other type, merge(srcType, dstType) = TOP whatever srcType.
1364             mergedType = TOP;
1365         }
1366         if (mergedType != dstType) {
1367             dstTypes[dstIndex] = mergedType;
1368             return true;
1369         }
1370         return false;
1371     }
1372 
1373     // -----------------------------------------------------------------------------------------------
1374     // Frame output methods, to generate StackMapFrame attributes
1375     // -----------------------------------------------------------------------------------------------
1376 
1377     /**
1378       * Makes the given {@link MethodWriter} visit the input frame of this {@link Frame}. The visit is
1379       * done with the {@link MethodWriter#visitFrameStart}, {@link MethodWriter#visitAbstractType} and
1380       * {@link MethodWriter#visitFrameEnd} methods.
1381       *
1382       * @param methodWriter the {@link MethodWriter} that should visit the input frame of this {@link
1383       *     Frame}.
1384       */
1385     final void accept(final MethodWriter methodWriter) {
1386         // Compute the number of locals, ignoring TOP types that are just after a LONG or a DOUBLE, and
1387         // all trailing TOP types.
1388         int[] localTypes = inputLocals;
1389         int numLocal = 0;
1390         int numTrailingTop = 0;
1391         int i = 0;
1392         while (i < localTypes.length) {
1393             int localType = localTypes[i];
1394             i += (localType == LONG || localType == DOUBLE) ? 2 : 1;
1395             if (localType == TOP) {
1396                 numTrailingTop++;
1397             } else {
1398                 numLocal += numTrailingTop + 1;
1399                 numTrailingTop = 0;
1400             }
1401         }
1402         // Compute the stack size, ignoring TOP types that are just after a LONG or a DOUBLE.
1403         int[] stackTypes = inputStack;
1404         int numStack = 0;
1405         i = 0;
1406         while (i < stackTypes.length) {
1407             int stackType = stackTypes[i];
1408             i += (stackType == LONG || stackType == DOUBLE) ? 2 : 1;
1409             numStack++;
1410         }
1411         // Visit the frame and its content.
1412         int frameIndex = methodWriter.visitFrameStart(owner.bytecodeOffset, numLocal, numStack);
1413         i = 0;
1414         while (numLocal-- > 0) {
1415             int localType = localTypes[i];
1416             i += (localType == LONG || localType == DOUBLE) ? 2 : 1;
1417             methodWriter.visitAbstractType(frameIndex++, localType);
1418         }
1419         i = 0;
1420         while (numStack-- > 0) {
1421             int stackType = stackTypes[i];
1422             i += (stackType == LONG || stackType == DOUBLE) ? 2 : 1;
1423             methodWriter.visitAbstractType(frameIndex++, stackType);
1424         }
1425         methodWriter.visitFrameEnd();
1426     }
1427 
1428     /**
1429       * Put the given abstract type in the given ByteVector, using the JVMS verification_type_info
1430       * format used in StackMapTable attributes.
1431       *
1432       * @param symbolTable the type table to use to lookup and store type {@link Symbol}.
1433       * @param abstractType an abstract type, restricted to {@link Frame#CONSTANT_KIND}, {@link
1434       *     Frame#REFERENCE_KIND} or {@link Frame#UNINITIALIZED_KIND} types.
1435       * @param output where the abstract type must be put.
1436       * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.4">JVMS
1437       *     4.7.4</a>
1438       */
1439     static void putAbstractType(
1440             final SymbolTable symbolTable, final int abstractType, final ByteVector output) {
1441         int arrayDimensions = (abstractType & Frame.DIM_MASK) >> DIM_SHIFT;
1442         if (arrayDimensions == 0) {
1443             int typeValue = abstractType & VALUE_MASK;
1444             switch (abstractType & KIND_MASK) {
1445                 case CONSTANT_KIND:
1446                     output.putByte(typeValue);
1447                     break;
1448                 case REFERENCE_KIND:
1449                     output
1450                             .putByte(ITEM_OBJECT)
1451                             .putShort(symbolTable.addConstantClass(symbolTable.getType(typeValue).value).index);
1452                     break;
1453                 case UNINITIALIZED_KIND:
1454                     output.putByte(ITEM_UNINITIALIZED).putShort((int) symbolTable.getType(typeValue).data);
1455                     break;
1456                 default:
1457                     throw new AssertionError();
1458             }
1459         } else {
1460             // Case of an array type, we need to build its descriptor first.
1461             StringBuilder typeDescriptor = new StringBuilder();
1462             while (arrayDimensions-- > 0) {
1463                 typeDescriptor.append('[');
1464             }
1465             if ((abstractType & KIND_MASK) == REFERENCE_KIND) {
1466                 typeDescriptor
1467                         .append('L')
1468                         .append(symbolTable.getType(abstractType & VALUE_MASK).value)
1469                         .append(';');
1470             } else {
1471                 switch (abstractType & VALUE_MASK) {
1472                     case Frame.ITEM_ASM_BOOLEAN:
1473                         typeDescriptor.append('Z');
1474                         break;
1475                     case Frame.ITEM_ASM_BYTE:
1476                         typeDescriptor.append('B');
1477                         break;
1478                     case Frame.ITEM_ASM_CHAR:
1479                         typeDescriptor.append('C');
1480                         break;
1481                     case Frame.ITEM_ASM_SHORT:
1482                         typeDescriptor.append('S');
1483                         break;
1484                     case Frame.ITEM_INTEGER:
1485                         typeDescriptor.append('I');
1486                         break;
1487                     case Frame.ITEM_FLOAT:
1488                         typeDescriptor.append('F');
1489                         break;
1490                     case Frame.ITEM_LONG:
1491                         typeDescriptor.append('J');
1492                         break;
1493                     case Frame.ITEM_DOUBLE:
1494                         typeDescriptor.append('D');
1495                         break;
1496                     default:
1497                         throw new AssertionError();
1498                 }
1499             }
1500             output
1501                     .putByte(ITEM_OBJECT)
1502                     .putShort(symbolTable.addConstantClass(typeDescriptor.toString()).index);
1503         }
1504     }
1505 }