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Diffstat (limited to 'asm/src/main/java/org/objectweb/asm/Frame.java')
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1 files changed, 1473 insertions, 0 deletions
diff --git a/asm/src/main/java/org/objectweb/asm/Frame.java b/asm/src/main/java/org/objectweb/asm/Frame.java new file mode 100644 index 00000000..07f256e5 --- /dev/null +++ b/asm/src/main/java/org/objectweb/asm/Frame.java @@ -0,0 +1,1473 @@ +// ASM: a very small and fast Java bytecode manipulation framework +// Copyright (c) 2000-2011 INRIA, France Telecom +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions +// are met: +// 1. Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// 2. Redistributions in binary form must reproduce the above copyright +// notice, this list of conditions and the following disclaimer in the +// documentation and/or other materials provided with the distribution. +// 3. Neither the name of the copyright holders nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE +// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF +// THE POSSIBILITY OF SUCH DAMAGE. +package org.objectweb.asm; + +/** + * The input and output stack map frames of a basic block. + * + * <p>Stack map frames are computed in two steps: + * + * <ul> + * <li>During the visit of each instruction in MethodWriter, the state of the frame at the end of + * the current basic block is updated by simulating the action of the instruction on the + * previous state of this so called "output frame". + * <li>After all instructions have been visited, a fix point algorithm is used in MethodWriter to + * compute the "input frame" of each basic block (i.e. the stack map frame at the beginning of + * the basic block). See {@link MethodWriter#computeAllFrames}. + * </ul> + * + * <p>Output stack map frames are computed relatively to the input frame of the basic block, which + * is not yet known when output frames are computed. It is therefore necessary to be able to + * represent abstract types such as "the type at position x in the input frame locals" or "the type + * at position x from the top of the input frame stack" or even "the type at position x in the input + * frame, with y more (or less) array dimensions". This explains the rather complicated type format + * used in this class, explained below. + * + * <p>The local variables and the operand stack of input and output frames contain values called + * "abstract types" hereafter. An abstract type is represented with 4 fields named DIM, KIND, FLAGS + * and VALUE, packed in a single int value for better performance and memory efficiency: + * + * <pre> + * ===================================== + * |...DIM|KIND|.F|...............VALUE| + * ===================================== + * </pre> + * + * <ul> + * <li>the DIM field, stored in the 6 most significant bits, is a signed number of array + * dimensions (from -32 to 31, included). It can be retrieved with {@link #DIM_MASK} and a + * right shift of {@link #DIM_SHIFT}. + * <li>the KIND field, stored in 4 bits, indicates the kind of VALUE used. These 4 bits can be + * retrieved with {@link #KIND_MASK} and, without any shift, must be equal to {@link + * #CONSTANT_KIND}, {@link #REFERENCE_KIND}, {@link #UNINITIALIZED_KIND}, {@link #LOCAL_KIND} + * or {@link #STACK_KIND}. + * <li>the FLAGS field, stored in 2 bits, contains up to 2 boolean flags. Currently only one flag + * is defined, namely {@link #TOP_IF_LONG_OR_DOUBLE_FLAG}. + * <li>the VALUE field, stored in the remaining 20 bits, contains either + * <ul> + * <li>one of the constants {@link #ITEM_TOP}, {@link #ITEM_ASM_BOOLEAN}, {@link + * #ITEM_ASM_BYTE}, {@link #ITEM_ASM_CHAR} or {@link #ITEM_ASM_SHORT}, {@link + * #ITEM_INTEGER}, {@link #ITEM_FLOAT}, {@link #ITEM_LONG}, {@link #ITEM_DOUBLE}, {@link + * #ITEM_NULL} or {@link #ITEM_UNINITIALIZED_THIS}, if KIND is equal to {@link + * #CONSTANT_KIND}. + * <li>the index of a {@link Symbol#TYPE_TAG} {@link Symbol} in the type table of a {@link + * SymbolTable}, if KIND is equal to {@link #REFERENCE_KIND}. + * <li>the index of an {@link Symbol#UNINITIALIZED_TYPE_TAG} {@link Symbol} in the type + * table of a SymbolTable, if KIND is equal to {@link #UNINITIALIZED_KIND}. + * <li>the index of a local variable in the input stack frame, if KIND is equal to {@link + * #LOCAL_KIND}. + * <li>a position relatively to the top of the stack of the input stack frame, if KIND is + * equal to {@link #STACK_KIND}, + * </ul> + * </ul> + * + * <p>Output frames can contain abstract types of any kind and with a positive or negative array + * dimension (and even unassigned types, represented by 0 - which does not correspond to any valid + * abstract type value). Input frames can only contain CONSTANT_KIND, REFERENCE_KIND or + * UNINITIALIZED_KIND abstract types of positive or {@literal null} array dimension. In all cases + * the type table contains only internal type names (array type descriptors are forbidden - array + * dimensions must be represented through the DIM field). + * + * <p>The LONG and DOUBLE types are always represented by using two slots (LONG + TOP or DOUBLE + + * TOP), for local variables as well as in the operand stack. This is necessary to be able to + * simulate DUPx_y instructions, whose effect would be dependent on the concrete types represented + * by the abstract types in the stack (which are not always known). + * + * @author Eric Bruneton + */ +class Frame { + + // Constants used in the StackMapTable attribute. + // See https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.4. + + static final int SAME_FRAME = 0; + static final int SAME_LOCALS_1_STACK_ITEM_FRAME = 64; + static final int RESERVED = 128; + static final int SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED = 247; + static final int CHOP_FRAME = 248; + static final int SAME_FRAME_EXTENDED = 251; + static final int APPEND_FRAME = 252; + static final int FULL_FRAME = 255; + + static final int ITEM_TOP = 0; + static final int ITEM_INTEGER = 1; + static final int ITEM_FLOAT = 2; + static final int ITEM_DOUBLE = 3; + static final int ITEM_LONG = 4; + static final int ITEM_NULL = 5; + static final int ITEM_UNINITIALIZED_THIS = 6; + static final int ITEM_OBJECT = 7; + static final int ITEM_UNINITIALIZED = 8; + // Additional, ASM specific constants used in abstract types below. + private static final int ITEM_ASM_BOOLEAN = 9; + private static final int ITEM_ASM_BYTE = 10; + private static final int ITEM_ASM_CHAR = 11; + private static final int ITEM_ASM_SHORT = 12; + + // The size and offset in bits of each field of an abstract type. + + private static final int DIM_SIZE = 6; + private static final int KIND_SIZE = 4; + private static final int FLAGS_SIZE = 2; + private static final int VALUE_SIZE = 32 - DIM_SIZE - KIND_SIZE - FLAGS_SIZE; + + private static final int DIM_SHIFT = KIND_SIZE + FLAGS_SIZE + VALUE_SIZE; + private static final int KIND_SHIFT = FLAGS_SIZE + VALUE_SIZE; + private static final int FLAGS_SHIFT = VALUE_SIZE; + + // Bitmasks to get each field of an abstract type. + + private static final int DIM_MASK = ((1 << DIM_SIZE) - 1) << DIM_SHIFT; + private static final int KIND_MASK = ((1 << KIND_SIZE) - 1) << KIND_SHIFT; + private static final int VALUE_MASK = (1 << VALUE_SIZE) - 1; + + // Constants to manipulate the DIM field of an abstract type. + + /** The constant to be added to an abstract type to get one with one more array dimension. */ + private static final int ARRAY_OF = +1 << DIM_SHIFT; + + /** The constant to be added to an abstract type to get one with one less array dimension. */ + private static final int ELEMENT_OF = -1 << DIM_SHIFT; + + // Possible values for the KIND field of an abstract type. + + private static final int CONSTANT_KIND = 1 << KIND_SHIFT; + private static final int REFERENCE_KIND = 2 << KIND_SHIFT; + private static final int UNINITIALIZED_KIND = 3 << KIND_SHIFT; + private static final int LOCAL_KIND = 4 << KIND_SHIFT; + private static final int STACK_KIND = 5 << KIND_SHIFT; + + // Possible flags for the FLAGS field of an abstract type. + + /** + * A flag used for LOCAL_KIND and STACK_KIND abstract types, indicating that if the resolved, + * concrete type is LONG or DOUBLE, TOP should be used instead (because the value has been + * partially overridden with an xSTORE instruction). + */ + private static final int TOP_IF_LONG_OR_DOUBLE_FLAG = 1 << FLAGS_SHIFT; + + // Useful predefined abstract types (all the possible CONSTANT_KIND types). + + private static final int TOP = CONSTANT_KIND | ITEM_TOP; + private static final int BOOLEAN = CONSTANT_KIND | ITEM_ASM_BOOLEAN; + private static final int BYTE = CONSTANT_KIND | ITEM_ASM_BYTE; + private static final int CHAR = CONSTANT_KIND | ITEM_ASM_CHAR; + private static final int SHORT = CONSTANT_KIND | ITEM_ASM_SHORT; + private static final int INTEGER = CONSTANT_KIND | ITEM_INTEGER; + private static final int FLOAT = CONSTANT_KIND | ITEM_FLOAT; + private static final int LONG = CONSTANT_KIND | ITEM_LONG; + private static final int DOUBLE = CONSTANT_KIND | ITEM_DOUBLE; + private static final int NULL = CONSTANT_KIND | ITEM_NULL; + private static final int UNINITIALIZED_THIS = CONSTANT_KIND | ITEM_UNINITIALIZED_THIS; + + // ----------------------------------------------------------------------------------------------- + // Instance fields + // ----------------------------------------------------------------------------------------------- + + /** The basic block to which these input and output stack map frames correspond. */ + Label owner; + + /** The input stack map frame locals. This is an array of abstract types. */ + private int[] inputLocals; + + /** The input stack map frame stack. This is an array of abstract types. */ + private int[] inputStack; + + /** The output stack map frame locals. This is an array of abstract types. */ + private int[] outputLocals; + + /** The output stack map frame stack. This is an array of abstract types. */ + private int[] outputStack; + + /** + * The start of the output stack, relatively to the input stack. This offset is always negative or + * null. A null offset means that the output stack must be appended to the input stack. A -n + * offset means that the first n output stack elements must replace the top n input stack + * elements, and that the other elements must be appended to the input stack. + */ + private short outputStackStart; + + /** The index of the top stack element in {@link #outputStack}. */ + private short outputStackTop; + + /** The number of types that are initialized in the basic block. See {@link #initializations}. */ + private int initializationCount; + + /** + * The abstract types that are initialized in the basic block. A constructor invocation on an + * UNINITIALIZED or UNINITIALIZED_THIS abstract type must replace <i>every occurrence</i> of this + * type in the local variables and in the operand stack. This cannot be done during the first step + * of the algorithm since, during this step, the local variables and the operand stack types are + * still abstract. It is therefore necessary to store the abstract types of the constructors which + * are invoked in the basic block, in order to do this replacement during the second step of the + * algorithm, where the frames are fully computed. Note that this array can contain abstract types + * that are relative to the input locals or to the input stack. + */ + private int[] initializations; + + // ----------------------------------------------------------------------------------------------- + // Constructor + // ----------------------------------------------------------------------------------------------- + + /** + * Constructs a new Frame. + * + * @param owner the basic block to which these input and output stack map frames correspond. + */ + Frame(final Label owner) { + this.owner = owner; + } + + /** + * Sets this frame to the value of the given frame. + * + * <p>WARNING: after this method is called the two frames share the same data structures. It is + * recommended to discard the given frame to avoid unexpected side effects. + * + * @param frame The new frame value. + */ + final void copyFrom(final Frame frame) { + inputLocals = frame.inputLocals; + inputStack = frame.inputStack; + outputStackStart = 0; + outputLocals = frame.outputLocals; + outputStack = frame.outputStack; + outputStackTop = frame.outputStackTop; + initializationCount = frame.initializationCount; + initializations = frame.initializations; + } + + // ----------------------------------------------------------------------------------------------- + // Static methods to get abstract types from other type formats + // ----------------------------------------------------------------------------------------------- + + /** + * Returns the abstract type corresponding to the given public API frame element type. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param type a frame element type described using the same format as in {@link + * MethodVisitor#visitFrame}, i.e. either {@link Opcodes#TOP}, {@link Opcodes#INTEGER}, {@link + * Opcodes#FLOAT}, {@link Opcodes#LONG}, {@link Opcodes#DOUBLE}, {@link Opcodes#NULL}, or + * {@link Opcodes#UNINITIALIZED_THIS}, or the internal name of a class, or a Label designating + * a NEW instruction (for uninitialized types). + * @return the abstract type corresponding to the given frame element type. + */ + static int getAbstractTypeFromApiFormat(final SymbolTable symbolTable, final Object type) { + if (type instanceof Integer) { + return CONSTANT_KIND | ((Integer) type).intValue(); + } else if (type instanceof String) { + String descriptor = Type.getObjectType((String) type).getDescriptor(); + return getAbstractTypeFromDescriptor(symbolTable, descriptor, 0); + } else { + return UNINITIALIZED_KIND + | symbolTable.addUninitializedType("", ((Label) type).bytecodeOffset); + } + } + + /** + * Returns the abstract type corresponding to the internal name of a class. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param internalName the internal name of a class. This must <i>not</i> be an array type + * descriptor. + * @return the abstract type value corresponding to the given internal name. + */ + static int getAbstractTypeFromInternalName( + final SymbolTable symbolTable, final String internalName) { + return REFERENCE_KIND | symbolTable.addType(internalName); + } + + /** + * Returns the abstract type corresponding to the given type descriptor. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param buffer a string ending with a type descriptor. + * @param offset the start offset of the type descriptor in buffer. + * @return the abstract type corresponding to the given type descriptor. + */ + private static int getAbstractTypeFromDescriptor( + final SymbolTable symbolTable, final String buffer, final int offset) { + String internalName; + switch (buffer.charAt(offset)) { + case 'V': + return 0; + case 'Z': + case 'C': + case 'B': + case 'S': + case 'I': + return INTEGER; + case 'F': + return FLOAT; + case 'J': + return LONG; + case 'D': + return DOUBLE; + case 'L': + internalName = buffer.substring(offset + 1, buffer.length() - 1); + return REFERENCE_KIND | symbolTable.addType(internalName); + case '[': + int elementDescriptorOffset = offset + 1; + while (buffer.charAt(elementDescriptorOffset) == '[') { + ++elementDescriptorOffset; + } + int typeValue; + switch (buffer.charAt(elementDescriptorOffset)) { + case 'Z': + typeValue = BOOLEAN; + break; + case 'C': + typeValue = CHAR; + break; + case 'B': + typeValue = BYTE; + break; + case 'S': + typeValue = SHORT; + break; + case 'I': + typeValue = INTEGER; + break; + case 'F': + typeValue = FLOAT; + break; + case 'J': + typeValue = LONG; + break; + case 'D': + typeValue = DOUBLE; + break; + case 'L': + internalName = buffer.substring(elementDescriptorOffset + 1, buffer.length() - 1); + typeValue = REFERENCE_KIND | symbolTable.addType(internalName); + break; + default: + throw new IllegalArgumentException(); + } + return ((elementDescriptorOffset - offset) << DIM_SHIFT) | typeValue; + default: + throw new IllegalArgumentException(); + } + } + + // ----------------------------------------------------------------------------------------------- + // Methods related to the input frame + // ----------------------------------------------------------------------------------------------- + + /** + * Sets the input frame from the given method description. This method is used to initialize the + * first frame of a method, which is implicit (i.e. not stored explicitly in the StackMapTable + * attribute). + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param access the method's access flags. + * @param descriptor the method descriptor. + * @param maxLocals the maximum number of local variables of the method. + */ + final void setInputFrameFromDescriptor( + final SymbolTable symbolTable, + final int access, + final String descriptor, + final int maxLocals) { + inputLocals = new int[maxLocals]; + inputStack = new int[0]; + int inputLocalIndex = 0; + if ((access & Opcodes.ACC_STATIC) == 0) { + if ((access & Constants.ACC_CONSTRUCTOR) == 0) { + inputLocals[inputLocalIndex++] = + REFERENCE_KIND | symbolTable.addType(symbolTable.getClassName()); + } else { + inputLocals[inputLocalIndex++] = UNINITIALIZED_THIS; + } + } + for (Type argumentType : Type.getArgumentTypes(descriptor)) { + int abstractType = + getAbstractTypeFromDescriptor(symbolTable, argumentType.getDescriptor(), 0); + inputLocals[inputLocalIndex++] = abstractType; + if (abstractType == LONG || abstractType == DOUBLE) { + inputLocals[inputLocalIndex++] = TOP; + } + } + while (inputLocalIndex < maxLocals) { + inputLocals[inputLocalIndex++] = TOP; + } + } + + /** + * Sets the input frame from the given public API frame description. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param numLocal the number of local variables. + * @param local the local variable types, described using the same format as in {@link + * MethodVisitor#visitFrame}. + * @param numStack the number of operand stack elements. + * @param stack the operand stack types, described using the same format as in {@link + * MethodVisitor#visitFrame}. + */ + final void setInputFrameFromApiFormat( + final SymbolTable symbolTable, + final int numLocal, + final Object[] local, + final int numStack, + final Object[] stack) { + int inputLocalIndex = 0; + for (int i = 0; i < numLocal; ++i) { + inputLocals[inputLocalIndex++] = getAbstractTypeFromApiFormat(symbolTable, local[i]); + if (local[i] == Opcodes.LONG || local[i] == Opcodes.DOUBLE) { + inputLocals[inputLocalIndex++] = TOP; + } + } + while (inputLocalIndex < inputLocals.length) { + inputLocals[inputLocalIndex++] = TOP; + } + int numStackTop = 0; + for (int i = 0; i < numStack; ++i) { + if (stack[i] == Opcodes.LONG || stack[i] == Opcodes.DOUBLE) { + ++numStackTop; + } + } + inputStack = new int[numStack + numStackTop]; + int inputStackIndex = 0; + for (int i = 0; i < numStack; ++i) { + inputStack[inputStackIndex++] = getAbstractTypeFromApiFormat(symbolTable, stack[i]); + if (stack[i] == Opcodes.LONG || stack[i] == Opcodes.DOUBLE) { + inputStack[inputStackIndex++] = TOP; + } + } + outputStackTop = 0; + initializationCount = 0; + } + + final int getInputStackSize() { + return inputStack.length; + } + + // ----------------------------------------------------------------------------------------------- + // Methods related to the output frame + // ----------------------------------------------------------------------------------------------- + + /** + * Returns the abstract type stored at the given local variable index in the output frame. + * + * @param localIndex the index of the local variable whose value must be returned. + * @return the abstract type stored at the given local variable index in the output frame. + */ + private int getLocal(final int localIndex) { + if (outputLocals == null || localIndex >= outputLocals.length) { + // If this local has never been assigned in this basic block, it is still equal to its value + // in the input frame. + return LOCAL_KIND | localIndex; + } else { + int abstractType = outputLocals[localIndex]; + if (abstractType == 0) { + // If this local has never been assigned in this basic block, so it is still equal to its + // value in the input frame. + abstractType = outputLocals[localIndex] = LOCAL_KIND | localIndex; + } + return abstractType; + } + } + + /** + * Replaces the abstract type stored at the given local variable index in the output frame. + * + * @param localIndex the index of the output frame local variable that must be set. + * @param abstractType the value that must be set. + */ + private void setLocal(final int localIndex, final int abstractType) { + // Create and/or resize the output local variables array if necessary. + if (outputLocals == null) { + outputLocals = new int[10]; + } + int outputLocalsLength = outputLocals.length; + if (localIndex >= outputLocalsLength) { + int[] newOutputLocals = new int[Math.max(localIndex + 1, 2 * outputLocalsLength)]; + System.arraycopy(outputLocals, 0, newOutputLocals, 0, outputLocalsLength); + outputLocals = newOutputLocals; + } + // Set the local variable. + outputLocals[localIndex] = abstractType; + } + + /** + * Pushes the given abstract type on the output frame stack. + * + * @param abstractType an abstract type. + */ + private void push(final int abstractType) { + // Create and/or resize the output stack array if necessary. + if (outputStack == null) { + outputStack = new int[10]; + } + int outputStackLength = outputStack.length; + if (outputStackTop >= outputStackLength) { + int[] newOutputStack = new int[Math.max(outputStackTop + 1, 2 * outputStackLength)]; + System.arraycopy(outputStack, 0, newOutputStack, 0, outputStackLength); + outputStack = newOutputStack; + } + // Pushes the abstract type on the output stack. + outputStack[outputStackTop++] = abstractType; + // Updates the maximum size reached by the output stack, if needed (note that this size is + // relative to the input stack size, which is not known yet). + short outputStackSize = (short) (outputStackStart + outputStackTop); + if (outputStackSize > owner.outputStackMax) { + owner.outputStackMax = outputStackSize; + } + } + + /** + * Pushes the abstract type corresponding to the given descriptor on the output frame stack. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param descriptor a type or method descriptor (in which case its return type is pushed). + */ + private void push(final SymbolTable symbolTable, final String descriptor) { + int typeDescriptorOffset = + descriptor.charAt(0) == '(' ? Type.getReturnTypeOffset(descriptor) : 0; + int abstractType = getAbstractTypeFromDescriptor(symbolTable, descriptor, typeDescriptorOffset); + if (abstractType != 0) { + push(abstractType); + if (abstractType == LONG || abstractType == DOUBLE) { + push(TOP); + } + } + } + + /** + * Pops an abstract type from the output frame stack and returns its value. + * + * @return the abstract type that has been popped from the output frame stack. + */ + private int pop() { + if (outputStackTop > 0) { + return outputStack[--outputStackTop]; + } else { + // If the output frame stack is empty, pop from the input stack. + return STACK_KIND | -(--outputStackStart); + } + } + + /** + * Pops the given number of abstract types from the output frame stack. + * + * @param elements the number of abstract types that must be popped. + */ + private void pop(final int elements) { + if (outputStackTop >= elements) { + outputStackTop -= elements; + } else { + // If the number of elements to be popped is greater than the number of elements in the output + // stack, clear it, and pop the remaining elements from the input stack. + outputStackStart -= elements - outputStackTop; + outputStackTop = 0; + } + } + + /** + * Pops as many abstract types from the output frame stack as described by the given descriptor. + * + * @param descriptor a type or method descriptor (in which case its argument types are popped). + */ + private void pop(final String descriptor) { + char firstDescriptorChar = descriptor.charAt(0); + if (firstDescriptorChar == '(') { + pop((Type.getArgumentsAndReturnSizes(descriptor) >> 2) - 1); + } else if (firstDescriptorChar == 'J' || firstDescriptorChar == 'D') { + pop(2); + } else { + pop(1); + } + } + + // ----------------------------------------------------------------------------------------------- + // Methods to handle uninitialized types + // ----------------------------------------------------------------------------------------------- + + /** + * Adds an abstract type to the list of types on which a constructor is invoked in the basic + * block. + * + * @param abstractType an abstract type on a which a constructor is invoked. + */ + private void addInitializedType(final int abstractType) { + // Create and/or resize the initializations array if necessary. + if (initializations == null) { + initializations = new int[2]; + } + int initializationsLength = initializations.length; + if (initializationCount >= initializationsLength) { + int[] newInitializations = + new int[Math.max(initializationCount + 1, 2 * initializationsLength)]; + System.arraycopy(initializations, 0, newInitializations, 0, initializationsLength); + initializations = newInitializations; + } + // Store the abstract type. + initializations[initializationCount++] = abstractType; + } + + /** + * Returns the "initialized" abstract type corresponding to the given abstract type. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param abstractType an abstract type. + * @return the REFERENCE_KIND abstract type corresponding to abstractType if it is + * UNINITIALIZED_THIS or an UNINITIALIZED_KIND abstract type for one of the types on which a + * constructor is invoked in the basic block. Otherwise returns abstractType. + */ + private int getInitializedType(final SymbolTable symbolTable, final int abstractType) { + if (abstractType == UNINITIALIZED_THIS + || (abstractType & (DIM_MASK | KIND_MASK)) == UNINITIALIZED_KIND) { + for (int i = 0; i < initializationCount; ++i) { + int initializedType = initializations[i]; + int dim = initializedType & DIM_MASK; + int kind = initializedType & KIND_MASK; + int value = initializedType & VALUE_MASK; + if (kind == LOCAL_KIND) { + initializedType = dim + inputLocals[value]; + } else if (kind == STACK_KIND) { + initializedType = dim + inputStack[inputStack.length - value]; + } + if (abstractType == initializedType) { + if (abstractType == UNINITIALIZED_THIS) { + return REFERENCE_KIND | symbolTable.addType(symbolTable.getClassName()); + } else { + return REFERENCE_KIND + | symbolTable.addType(symbolTable.getType(abstractType & VALUE_MASK).value); + } + } + } + } + return abstractType; + } + + // ----------------------------------------------------------------------------------------------- + // Main method, to simulate the execution of each instruction on the output frame + // ----------------------------------------------------------------------------------------------- + + /** + * Simulates the action of the given instruction on the output stack frame. + * + * @param opcode the opcode of the instruction. + * @param arg the numeric operand of the instruction, if any. + * @param argSymbol the Symbol operand of the instruction, if any. + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + */ + void execute( + final int opcode, final int arg, final Symbol argSymbol, final SymbolTable symbolTable) { + // Abstract types popped from the stack or read from local variables. + int abstractType1; + int abstractType2; + int abstractType3; + int abstractType4; + switch (opcode) { + case Opcodes.NOP: + case Opcodes.INEG: + case Opcodes.LNEG: + case Opcodes.FNEG: + case Opcodes.DNEG: + case Opcodes.I2B: + case Opcodes.I2C: + case Opcodes.I2S: + case Opcodes.GOTO: + case Opcodes.RETURN: + break; + case Opcodes.ACONST_NULL: + push(NULL); + break; + case Opcodes.ICONST_M1: + case Opcodes.ICONST_0: + case Opcodes.ICONST_1: + case Opcodes.ICONST_2: + case Opcodes.ICONST_3: + case Opcodes.ICONST_4: + case Opcodes.ICONST_5: + case Opcodes.BIPUSH: + case Opcodes.SIPUSH: + case Opcodes.ILOAD: + push(INTEGER); + break; + case Opcodes.LCONST_0: + case Opcodes.LCONST_1: + case Opcodes.LLOAD: + push(LONG); + push(TOP); + break; + case Opcodes.FCONST_0: + case Opcodes.FCONST_1: + case Opcodes.FCONST_2: + case Opcodes.FLOAD: + push(FLOAT); + break; + case Opcodes.DCONST_0: + case Opcodes.DCONST_1: + case Opcodes.DLOAD: + push(DOUBLE); + push(TOP); + break; + case Opcodes.LDC: + switch (argSymbol.tag) { + case Symbol.CONSTANT_INTEGER_TAG: + push(INTEGER); + break; + case Symbol.CONSTANT_LONG_TAG: + push(LONG); + push(TOP); + break; + case Symbol.CONSTANT_FLOAT_TAG: + push(FLOAT); + break; + case Symbol.CONSTANT_DOUBLE_TAG: + push(DOUBLE); + push(TOP); + break; + case Symbol.CONSTANT_CLASS_TAG: + push(REFERENCE_KIND | symbolTable.addType("java/lang/Class")); + break; + case Symbol.CONSTANT_STRING_TAG: + push(REFERENCE_KIND | symbolTable.addType("java/lang/String")); + break; + case Symbol.CONSTANT_METHOD_TYPE_TAG: + push(REFERENCE_KIND | symbolTable.addType("java/lang/invoke/MethodType")); + break; + case Symbol.CONSTANT_METHOD_HANDLE_TAG: + push(REFERENCE_KIND | symbolTable.addType("java/lang/invoke/MethodHandle")); + break; + case Symbol.CONSTANT_DYNAMIC_TAG: + push(symbolTable, argSymbol.value); + break; + default: + throw new AssertionError(); + } + break; + case Opcodes.ALOAD: + push(getLocal(arg)); + break; + case Opcodes.LALOAD: + case Opcodes.D2L: + pop(2); + push(LONG); + push(TOP); + break; + case Opcodes.DALOAD: + case Opcodes.L2D: + pop(2); + push(DOUBLE); + push(TOP); + break; + case Opcodes.AALOAD: + pop(1); + abstractType1 = pop(); + push(abstractType1 == NULL ? abstractType1 : ELEMENT_OF + abstractType1); + break; + case Opcodes.ISTORE: + case Opcodes.FSTORE: + case Opcodes.ASTORE: + abstractType1 = pop(); + setLocal(arg, abstractType1); + if (arg > 0) { + int previousLocalType = getLocal(arg - 1); + if (previousLocalType == LONG || previousLocalType == DOUBLE) { + setLocal(arg - 1, TOP); + } else if ((previousLocalType & KIND_MASK) == LOCAL_KIND + || (previousLocalType & KIND_MASK) == STACK_KIND) { + // The type of the previous local variable is not known yet, but if it later appears + // to be LONG or DOUBLE, we should then use TOP instead. + setLocal(arg - 1, previousLocalType | TOP_IF_LONG_OR_DOUBLE_FLAG); + } + } + break; + case Opcodes.LSTORE: + case Opcodes.DSTORE: + pop(1); + abstractType1 = pop(); + setLocal(arg, abstractType1); + setLocal(arg + 1, TOP); + if (arg > 0) { + int previousLocalType = getLocal(arg - 1); + if (previousLocalType == LONG || previousLocalType == DOUBLE) { + setLocal(arg - 1, TOP); + } else if ((previousLocalType & KIND_MASK) == LOCAL_KIND + || (previousLocalType & KIND_MASK) == STACK_KIND) { + // The type of the previous local variable is not known yet, but if it later appears + // to be LONG or DOUBLE, we should then use TOP instead. + setLocal(arg - 1, previousLocalType | TOP_IF_LONG_OR_DOUBLE_FLAG); + } + } + break; + case Opcodes.IASTORE: + case Opcodes.BASTORE: + case Opcodes.CASTORE: + case Opcodes.SASTORE: + case Opcodes.FASTORE: + case Opcodes.AASTORE: + pop(3); + break; + case Opcodes.LASTORE: + case Opcodes.DASTORE: + pop(4); + break; + case Opcodes.POP: + case Opcodes.IFEQ: + case Opcodes.IFNE: + case Opcodes.IFLT: + case Opcodes.IFGE: + case Opcodes.IFGT: + case Opcodes.IFLE: + case Opcodes.IRETURN: + case Opcodes.FRETURN: + case Opcodes.ARETURN: + case Opcodes.TABLESWITCH: + case Opcodes.LOOKUPSWITCH: + case Opcodes.ATHROW: + case Opcodes.MONITORENTER: + case Opcodes.MONITOREXIT: + case Opcodes.IFNULL: + case Opcodes.IFNONNULL: + pop(1); + break; + case Opcodes.POP2: + case Opcodes.IF_ICMPEQ: + case Opcodes.IF_ICMPNE: + case Opcodes.IF_ICMPLT: + case Opcodes.IF_ICMPGE: + case Opcodes.IF_ICMPGT: + case Opcodes.IF_ICMPLE: + case Opcodes.IF_ACMPEQ: + case Opcodes.IF_ACMPNE: + case Opcodes.LRETURN: + case Opcodes.DRETURN: + pop(2); + break; + case Opcodes.DUP: + abstractType1 = pop(); + push(abstractType1); + push(abstractType1); + break; + case Opcodes.DUP_X1: + abstractType1 = pop(); + abstractType2 = pop(); + push(abstractType1); + push(abstractType2); + push(abstractType1); + break; + case Opcodes.DUP_X2: + abstractType1 = pop(); + abstractType2 = pop(); + abstractType3 = pop(); + push(abstractType1); + push(abstractType3); + push(abstractType2); + push(abstractType1); + break; + case Opcodes.DUP2: + abstractType1 = pop(); + abstractType2 = pop(); + push(abstractType2); + push(abstractType1); + push(abstractType2); + push(abstractType1); + break; + case Opcodes.DUP2_X1: + abstractType1 = pop(); + abstractType2 = pop(); + abstractType3 = pop(); + push(abstractType2); + push(abstractType1); + push(abstractType3); + push(abstractType2); + push(abstractType1); + break; + case Opcodes.DUP2_X2: + abstractType1 = pop(); + abstractType2 = pop(); + abstractType3 = pop(); + abstractType4 = pop(); + push(abstractType2); + push(abstractType1); + push(abstractType4); + push(abstractType3); + push(abstractType2); + push(abstractType1); + break; + case Opcodes.SWAP: + abstractType1 = pop(); + abstractType2 = pop(); + push(abstractType1); + push(abstractType2); + break; + case Opcodes.IALOAD: + case Opcodes.BALOAD: + case Opcodes.CALOAD: + case Opcodes.SALOAD: + case Opcodes.IADD: + case Opcodes.ISUB: + case Opcodes.IMUL: + case Opcodes.IDIV: + case Opcodes.IREM: + case Opcodes.IAND: + case Opcodes.IOR: + case Opcodes.IXOR: + case Opcodes.ISHL: + case Opcodes.ISHR: + case Opcodes.IUSHR: + case Opcodes.L2I: + case Opcodes.D2I: + case Opcodes.FCMPL: + case Opcodes.FCMPG: + pop(2); + push(INTEGER); + break; + case Opcodes.LADD: + case Opcodes.LSUB: + case Opcodes.LMUL: + case Opcodes.LDIV: + case Opcodes.LREM: + case Opcodes.LAND: + case Opcodes.LOR: + case Opcodes.LXOR: + pop(4); + push(LONG); + push(TOP); + break; + case Opcodes.FALOAD: + case Opcodes.FADD: + case Opcodes.FSUB: + case Opcodes.FMUL: + case Opcodes.FDIV: + case Opcodes.FREM: + case Opcodes.L2F: + case Opcodes.D2F: + pop(2); + push(FLOAT); + break; + case Opcodes.DADD: + case Opcodes.DSUB: + case Opcodes.DMUL: + case Opcodes.DDIV: + case Opcodes.DREM: + pop(4); + push(DOUBLE); + push(TOP); + break; + case Opcodes.LSHL: + case Opcodes.LSHR: + case Opcodes.LUSHR: + pop(3); + push(LONG); + push(TOP); + break; + case Opcodes.IINC: + setLocal(arg, INTEGER); + break; + case Opcodes.I2L: + case Opcodes.F2L: + pop(1); + push(LONG); + push(TOP); + break; + case Opcodes.I2F: + pop(1); + push(FLOAT); + break; + case Opcodes.I2D: + case Opcodes.F2D: + pop(1); + push(DOUBLE); + push(TOP); + break; + case Opcodes.F2I: + case Opcodes.ARRAYLENGTH: + case Opcodes.INSTANCEOF: + pop(1); + push(INTEGER); + break; + case Opcodes.LCMP: + case Opcodes.DCMPL: + case Opcodes.DCMPG: + pop(4); + push(INTEGER); + break; + case Opcodes.JSR: + case Opcodes.RET: + throw new IllegalArgumentException("JSR/RET are not supported with computeFrames option"); + case Opcodes.GETSTATIC: + push(symbolTable, argSymbol.value); + break; + case Opcodes.PUTSTATIC: + pop(argSymbol.value); + break; + case Opcodes.GETFIELD: + pop(1); + push(symbolTable, argSymbol.value); + break; + case Opcodes.PUTFIELD: + pop(argSymbol.value); + pop(); + break; + case Opcodes.INVOKEVIRTUAL: + case Opcodes.INVOKESPECIAL: + case Opcodes.INVOKESTATIC: + case Opcodes.INVOKEINTERFACE: + pop(argSymbol.value); + if (opcode != Opcodes.INVOKESTATIC) { + abstractType1 = pop(); + if (opcode == Opcodes.INVOKESPECIAL && argSymbol.name.charAt(0) == '<') { + addInitializedType(abstractType1); + } + } + push(symbolTable, argSymbol.value); + break; + case Opcodes.INVOKEDYNAMIC: + pop(argSymbol.value); + push(symbolTable, argSymbol.value); + break; + case Opcodes.NEW: + push(UNINITIALIZED_KIND | symbolTable.addUninitializedType(argSymbol.value, arg)); + break; + case Opcodes.NEWARRAY: + pop(); + switch (arg) { + case Opcodes.T_BOOLEAN: + push(ARRAY_OF | BOOLEAN); + break; + case Opcodes.T_CHAR: + push(ARRAY_OF | CHAR); + break; + case Opcodes.T_BYTE: + push(ARRAY_OF | BYTE); + break; + case Opcodes.T_SHORT: + push(ARRAY_OF | SHORT); + break; + case Opcodes.T_INT: + push(ARRAY_OF | INTEGER); + break; + case Opcodes.T_FLOAT: + push(ARRAY_OF | FLOAT); + break; + case Opcodes.T_DOUBLE: + push(ARRAY_OF | DOUBLE); + break; + case Opcodes.T_LONG: + push(ARRAY_OF | LONG); + break; + default: + throw new IllegalArgumentException(); + } + break; + case Opcodes.ANEWARRAY: + String arrayElementType = argSymbol.value; + pop(); + if (arrayElementType.charAt(0) == '[') { + push(symbolTable, '[' + arrayElementType); + } else { + push(ARRAY_OF | REFERENCE_KIND | symbolTable.addType(arrayElementType)); + } + break; + case Opcodes.CHECKCAST: + String castType = argSymbol.value; + pop(); + if (castType.charAt(0) == '[') { + push(symbolTable, castType); + } else { + push(REFERENCE_KIND | symbolTable.addType(castType)); + } + break; + case Opcodes.MULTIANEWARRAY: + pop(arg); + push(symbolTable, argSymbol.value); + break; + default: + throw new IllegalArgumentException(); + } + } + + // ----------------------------------------------------------------------------------------------- + // Frame merging methods, used in the second step of the stack map frame computation algorithm + // ----------------------------------------------------------------------------------------------- + + /** + * Computes the concrete output type corresponding to a given abstract output type. + * + * @param abstractOutputType an abstract output type. + * @param numStack the size of the input stack, used to resolve abstract output types of + * STACK_KIND kind. + * @return the concrete output type corresponding to 'abstractOutputType'. + */ + private int getConcreteOutputType(final int abstractOutputType, final int numStack) { + int dim = abstractOutputType & DIM_MASK; + int kind = abstractOutputType & KIND_MASK; + if (kind == LOCAL_KIND) { + // By definition, a LOCAL_KIND type designates the concrete type of a local variable at + // the beginning of the basic block corresponding to this frame (which is known when + // this method is called, but was not when the abstract type was computed). + int concreteOutputType = dim + inputLocals[abstractOutputType & VALUE_MASK]; + if ((abstractOutputType & TOP_IF_LONG_OR_DOUBLE_FLAG) != 0 + && (concreteOutputType == LONG || concreteOutputType == DOUBLE)) { + concreteOutputType = TOP; + } + return concreteOutputType; + } else if (kind == STACK_KIND) { + // By definition, a STACK_KIND type designates the concrete type of a local variable at + // the beginning of the basic block corresponding to this frame (which is known when + // this method is called, but was not when the abstract type was computed). + int concreteOutputType = dim + inputStack[numStack - (abstractOutputType & VALUE_MASK)]; + if ((abstractOutputType & TOP_IF_LONG_OR_DOUBLE_FLAG) != 0 + && (concreteOutputType == LONG || concreteOutputType == DOUBLE)) { + concreteOutputType = TOP; + } + return concreteOutputType; + } else { + return abstractOutputType; + } + } + + /** + * Merges the input frame of the given {@link Frame} with the input and output frames of this + * {@link Frame}. Returns {@literal true} if the given frame has been changed by this operation + * (the input and output frames of this {@link Frame} are never changed). + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param dstFrame the {@link Frame} whose input frame must be updated. This should be the frame + * of a successor, in the control flow graph, of the basic block corresponding to this frame. + * @param catchTypeIndex if 'frame' corresponds to an exception handler basic block, the type + * table index of the caught exception type, otherwise 0. + * @return {@literal true} if the input frame of 'frame' has been changed by this operation. + */ + final boolean merge( + final SymbolTable symbolTable, final Frame dstFrame, final int catchTypeIndex) { + boolean frameChanged = false; + + // Compute the concrete types of the local variables at the end of the basic block corresponding + // to this frame, by resolving its abstract output types, and merge these concrete types with + // those of the local variables in the input frame of dstFrame. + int numLocal = inputLocals.length; + int numStack = inputStack.length; + if (dstFrame.inputLocals == null) { + dstFrame.inputLocals = new int[numLocal]; + frameChanged = true; + } + for (int i = 0; i < numLocal; ++i) { + int concreteOutputType; + if (outputLocals != null && i < outputLocals.length) { + int abstractOutputType = outputLocals[i]; + if (abstractOutputType == 0) { + // If the local variable has never been assigned in this basic block, it is equal to its + // value at the beginning of the block. + concreteOutputType = inputLocals[i]; + } else { + concreteOutputType = getConcreteOutputType(abstractOutputType, numStack); + } + } else { + // If the local variable has never been assigned in this basic block, it is equal to its + // value at the beginning of the block. + concreteOutputType = inputLocals[i]; + } + // concreteOutputType might be an uninitialized type from the input locals or from the input + // stack. However, if a constructor has been called for this class type in the basic block, + // then this type is no longer uninitialized at the end of basic block. + if (initializations != null) { + concreteOutputType = getInitializedType(symbolTable, concreteOutputType); + } + frameChanged |= merge(symbolTable, concreteOutputType, dstFrame.inputLocals, i); + } + + // If dstFrame is an exception handler block, it can be reached from any instruction of the + // basic block corresponding to this frame, in particular from the first one. Therefore, the + // input locals of dstFrame should be compatible (i.e. merged) with the input locals of this + // frame (and the input stack of dstFrame should be compatible, i.e. merged, with a one + // element stack containing the caught exception type). + if (catchTypeIndex > 0) { + for (int i = 0; i < numLocal; ++i) { + frameChanged |= merge(symbolTable, inputLocals[i], dstFrame.inputLocals, i); + } + if (dstFrame.inputStack == null) { + dstFrame.inputStack = new int[1]; + frameChanged = true; + } + frameChanged |= merge(symbolTable, catchTypeIndex, dstFrame.inputStack, 0); + return frameChanged; + } + + // Compute the concrete types of the stack operands at the end of the basic block corresponding + // to this frame, by resolving its abstract output types, and merge these concrete types with + // those of the stack operands in the input frame of dstFrame. + int numInputStack = inputStack.length + outputStackStart; + if (dstFrame.inputStack == null) { + dstFrame.inputStack = new int[numInputStack + outputStackTop]; + frameChanged = true; + } + // First, do this for the stack operands that have not been popped in the basic block + // corresponding to this frame, and which are therefore equal to their value in the input + // frame (except for uninitialized types, which may have been initialized). + for (int i = 0; i < numInputStack; ++i) { + int concreteOutputType = inputStack[i]; + if (initializations != null) { + concreteOutputType = getInitializedType(symbolTable, concreteOutputType); + } + frameChanged |= merge(symbolTable, concreteOutputType, dstFrame.inputStack, i); + } + // Then, do this for the stack operands that have pushed in the basic block (this code is the + // same as the one above for local variables). + for (int i = 0; i < outputStackTop; ++i) { + int abstractOutputType = outputStack[i]; + int concreteOutputType = getConcreteOutputType(abstractOutputType, numStack); + if (initializations != null) { + concreteOutputType = getInitializedType(symbolTable, concreteOutputType); + } + frameChanged |= + merge(symbolTable, concreteOutputType, dstFrame.inputStack, numInputStack + i); + } + return frameChanged; + } + + /** + * Merges the type at the given index in the given abstract type array with the given type. + * Returns {@literal true} if the type array has been modified by this operation. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param sourceType the abstract type with which the abstract type array element must be merged. + * This type should be of {@link #CONSTANT_KIND}, {@link #REFERENCE_KIND} or {@link + * #UNINITIALIZED_KIND} kind, with positive or {@literal null} array dimensions. + * @param dstTypes an array of abstract types. These types should be of {@link #CONSTANT_KIND}, + * {@link #REFERENCE_KIND} or {@link #UNINITIALIZED_KIND} kind, with positive or {@literal + * null} array dimensions. + * @param dstIndex the index of the type that must be merged in dstTypes. + * @return {@literal true} if the type array has been modified by this operation. + */ + private static boolean merge( + final SymbolTable symbolTable, + final int sourceType, + final int[] dstTypes, + final int dstIndex) { + int dstType = dstTypes[dstIndex]; + if (dstType == sourceType) { + // If the types are equal, merge(sourceType, dstType) = dstType, so there is no change. + return false; + } + int srcType = sourceType; + if ((sourceType & ~DIM_MASK) == NULL) { + if (dstType == NULL) { + return false; + } + srcType = NULL; + } + if (dstType == 0) { + // If dstTypes[dstIndex] has never been assigned, merge(srcType, dstType) = srcType. + dstTypes[dstIndex] = srcType; + return true; + } + int mergedType; + if ((dstType & DIM_MASK) != 0 || (dstType & KIND_MASK) == REFERENCE_KIND) { + // If dstType is a reference type of any array dimension. + if (srcType == NULL) { + // If srcType is the NULL type, merge(srcType, dstType) = dstType, so there is no change. + return false; + } else if ((srcType & (DIM_MASK | KIND_MASK)) == (dstType & (DIM_MASK | KIND_MASK))) { + // If srcType has the same array dimension and the same kind as dstType. + if ((dstType & KIND_MASK) == REFERENCE_KIND) { + // If srcType and dstType are reference types with the same array dimension, + // merge(srcType, dstType) = dim(srcType) | common super class of srcType and dstType. + mergedType = + (srcType & DIM_MASK) + | REFERENCE_KIND + | symbolTable.addMergedType(srcType & VALUE_MASK, dstType & VALUE_MASK); + } else { + // If srcType and dstType are array types of equal dimension but different element types, + // merge(srcType, dstType) = dim(srcType) - 1 | java/lang/Object. + int mergedDim = ELEMENT_OF + (srcType & DIM_MASK); + mergedType = mergedDim | REFERENCE_KIND | symbolTable.addType("java/lang/Object"); + } + } else if ((srcType & DIM_MASK) != 0 || (srcType & KIND_MASK) == REFERENCE_KIND) { + // If srcType is any other reference or array type, + // merge(srcType, dstType) = min(srcDdim, dstDim) | java/lang/Object + // where srcDim is the array dimension of srcType, minus 1 if srcType is an array type + // with a non reference element type (and similarly for dstDim). + int srcDim = srcType & DIM_MASK; + if (srcDim != 0 && (srcType & KIND_MASK) != REFERENCE_KIND) { + srcDim = ELEMENT_OF + srcDim; + } + int dstDim = dstType & DIM_MASK; + if (dstDim != 0 && (dstType & KIND_MASK) != REFERENCE_KIND) { + dstDim = ELEMENT_OF + dstDim; + } + mergedType = + Math.min(srcDim, dstDim) | REFERENCE_KIND | symbolTable.addType("java/lang/Object"); + } else { + // If srcType is any other type, merge(srcType, dstType) = TOP. + mergedType = TOP; + } + } else if (dstType == NULL) { + // If dstType is the NULL type, merge(srcType, dstType) = srcType, or TOP if srcType is not a + // an array type or a reference type. + mergedType = + (srcType & DIM_MASK) != 0 || (srcType & KIND_MASK) == REFERENCE_KIND ? srcType : TOP; + } else { + // If dstType is any other type, merge(srcType, dstType) = TOP whatever srcType. + mergedType = TOP; + } + if (mergedType != dstType) { + dstTypes[dstIndex] = mergedType; + return true; + } + return false; + } + + // ----------------------------------------------------------------------------------------------- + // Frame output methods, to generate StackMapFrame attributes + // ----------------------------------------------------------------------------------------------- + + /** + * Makes the given {@link MethodWriter} visit the input frame of this {@link Frame}. The visit is + * done with the {@link MethodWriter#visitFrameStart}, {@link MethodWriter#visitAbstractType} and + * {@link MethodWriter#visitFrameEnd} methods. + * + * @param methodWriter the {@link MethodWriter} that should visit the input frame of this {@link + * Frame}. + */ + final void accept(final MethodWriter methodWriter) { + // Compute the number of locals, ignoring TOP types that are just after a LONG or a DOUBLE, and + // all trailing TOP types. + int[] localTypes = inputLocals; + int numLocal = 0; + int numTrailingTop = 0; + int i = 0; + while (i < localTypes.length) { + int localType = localTypes[i]; + i += (localType == LONG || localType == DOUBLE) ? 2 : 1; + if (localType == TOP) { + numTrailingTop++; + } else { + numLocal += numTrailingTop + 1; + numTrailingTop = 0; + } + } + // Compute the stack size, ignoring TOP types that are just after a LONG or a DOUBLE. + int[] stackTypes = inputStack; + int numStack = 0; + i = 0; + while (i < stackTypes.length) { + int stackType = stackTypes[i]; + i += (stackType == LONG || stackType == DOUBLE) ? 2 : 1; + numStack++; + } + // Visit the frame and its content. + int frameIndex = methodWriter.visitFrameStart(owner.bytecodeOffset, numLocal, numStack); + i = 0; + while (numLocal-- > 0) { + int localType = localTypes[i]; + i += (localType == LONG || localType == DOUBLE) ? 2 : 1; + methodWriter.visitAbstractType(frameIndex++, localType); + } + i = 0; + while (numStack-- > 0) { + int stackType = stackTypes[i]; + i += (stackType == LONG || stackType == DOUBLE) ? 2 : 1; + methodWriter.visitAbstractType(frameIndex++, stackType); + } + methodWriter.visitFrameEnd(); + } + + /** + * Put the given abstract type in the given ByteVector, using the JVMS verification_type_info + * format used in StackMapTable attributes. + * + * @param symbolTable the type table to use to lookup and store type {@link Symbol}. + * @param abstractType an abstract type, restricted to {@link Frame#CONSTANT_KIND}, {@link + * Frame#REFERENCE_KIND} or {@link Frame#UNINITIALIZED_KIND} types. + * @param output where the abstract type must be put. + * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.4">JVMS + * 4.7.4</a> + */ + static void putAbstractType( + final SymbolTable symbolTable, final int abstractType, final ByteVector output) { + int arrayDimensions = (abstractType & Frame.DIM_MASK) >> DIM_SHIFT; + if (arrayDimensions == 0) { + int typeValue = abstractType & VALUE_MASK; + switch (abstractType & KIND_MASK) { + case CONSTANT_KIND: + output.putByte(typeValue); + break; + case REFERENCE_KIND: + output + .putByte(ITEM_OBJECT) + .putShort(symbolTable.addConstantClass(symbolTable.getType(typeValue).value).index); + break; + case UNINITIALIZED_KIND: + output.putByte(ITEM_UNINITIALIZED).putShort((int) symbolTable.getType(typeValue).data); + break; + default: + throw new AssertionError(); + } + } else { + // Case of an array type, we need to build its descriptor first. + StringBuilder typeDescriptor = new StringBuilder(); + while (arrayDimensions-- > 0) { + typeDescriptor.append('['); + } + if ((abstractType & KIND_MASK) == REFERENCE_KIND) { + typeDescriptor + .append('L') + .append(symbolTable.getType(abstractType & VALUE_MASK).value) + .append(';'); + } else { + switch (abstractType & VALUE_MASK) { + case Frame.ITEM_ASM_BOOLEAN: + typeDescriptor.append('Z'); + break; + case Frame.ITEM_ASM_BYTE: + typeDescriptor.append('B'); + break; + case Frame.ITEM_ASM_CHAR: + typeDescriptor.append('C'); + break; + case Frame.ITEM_ASM_SHORT: + typeDescriptor.append('S'); + break; + case Frame.ITEM_INTEGER: + typeDescriptor.append('I'); + break; + case Frame.ITEM_FLOAT: + typeDescriptor.append('F'); + break; + case Frame.ITEM_LONG: + typeDescriptor.append('J'); + break; + case Frame.ITEM_DOUBLE: + typeDescriptor.append('D'); + break; + default: + throw new AssertionError(); + } + } + output + .putByte(ITEM_OBJECT) + .putShort(symbolTable.addConstantClass(typeDescriptor.toString()).index); + } + } +} |