| /*** |
| * 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.apache.tajo.org.objectweb.asm; |
| |
| /** |
| * A label represents a position in the bytecode of a method. Labels are used |
| * for jump, goto, and switch instructions, and for try catch blocks. A label |
| * designates the <i>instruction</i> that is just after. Note however that there |
| * can be other elements between a label and the instruction it designates (such |
| * as other labels, stack map frames, line numbers, etc.). |
| * |
| * @author Eric Bruneton |
| */ |
| public class Label { |
| |
| /** |
| * Indicates if this label is only used for debug attributes. Such a label |
| * is not the start of a basic block, the target of a jump instruction, or |
| * an exception handler. It can be safely ignored in control flow graph |
| * analysis algorithms (for optimization purposes). |
| */ |
| static final int DEBUG = 1; |
| |
| /** |
| * Indicates if the position of this label is known. |
| */ |
| static final int RESOLVED = 2; |
| |
| /** |
| * Indicates if this label has been updated, after instruction resizing. |
| */ |
| static final int RESIZED = 4; |
| |
| /** |
| * Indicates if this basic block has been pushed in the basic block stack. |
| * See {@link MethodWriter#visitMaxs visitMaxs}. |
| */ |
| static final int PUSHED = 8; |
| |
| /** |
| * Indicates if this label is the target of a jump instruction, or the start |
| * of an exception handler. |
| */ |
| static final int TARGET = 16; |
| |
| /** |
| * Indicates if a stack map frame must be stored for this label. |
| */ |
| static final int STORE = 32; |
| |
| /** |
| * Indicates if this label corresponds to a reachable basic block. |
| */ |
| static final int REACHABLE = 64; |
| |
| /** |
| * Indicates if this basic block ends with a JSR instruction. |
| */ |
| static final int JSR = 128; |
| |
| /** |
| * Indicates if this basic block ends with a RET instruction. |
| */ |
| static final int RET = 256; |
| |
| /** |
| * Indicates if this basic block is the start of a subroutine. |
| */ |
| static final int SUBROUTINE = 512; |
| |
| /** |
| * Indicates if this subroutine basic block has been visited by a |
| * visitSubroutine(null, ...) call. |
| */ |
| static final int VISITED = 1024; |
| |
| /** |
| * Indicates if this subroutine basic block has been visited by a |
| * visitSubroutine(!null, ...) call. |
| */ |
| static final int VISITED2 = 2048; |
| |
| /** |
| * Field used to associate user information to a label. Warning: this field |
| * is used by the ASM tree package. In order to use it with the ASM tree |
| * package you must override the |
| * {@link org.apache.tajo.org.objectweb.asm.tree.MethodNode#getLabelNode} method. |
| */ |
| public Object info; |
| |
| /** |
| * Flags that indicate the status of this label. |
| * |
| * @see #DEBUG |
| * @see #RESOLVED |
| * @see #RESIZED |
| * @see #PUSHED |
| * @see #TARGET |
| * @see #STORE |
| * @see #REACHABLE |
| * @see #JSR |
| * @see #RET |
| */ |
| int status; |
| |
| /** |
| * The line number corresponding to this label, if known. |
| */ |
| int line; |
| |
| /** |
| * The position of this label in the code, if known. |
| */ |
| int position; |
| |
| /** |
| * Number of forward references to this label, times two. |
| */ |
| private int referenceCount; |
| |
| /** |
| * Informations about forward references. Each forward reference is |
| * described by two consecutive integers in this array: the first one is the |
| * position of the first byte of the bytecode instruction that contains the |
| * forward reference, while the second is the position of the first byte of |
| * the forward reference itself. In fact the sign of the first integer |
| * indicates if this reference uses 2 or 4 bytes, and its absolute value |
| * gives the position of the bytecode instruction. This array is also used |
| * as a bitset to store the subroutines to which a basic block belongs. This |
| * information is needed in {@linked MethodWriter#visitMaxs}, after all |
| * forward references have been resolved. Hence the same array can be used |
| * for both purposes without problems. |
| */ |
| private int[] srcAndRefPositions; |
| |
| // ------------------------------------------------------------------------ |
| |
| /* |
| * Fields for the control flow and data flow graph analysis algorithms (used |
| * to compute the maximum stack size or the stack map frames). A control |
| * flow graph contains one node per "basic block", and one edge per "jump" |
| * from one basic block to another. Each node (i.e., each basic block) is |
| * represented by the Label object that corresponds to the first instruction |
| * of this basic block. Each node also stores the list of its successors in |
| * the graph, as a linked list of Edge objects. |
| * |
| * The control flow analysis algorithms used to compute the maximum stack |
| * size or the stack map frames are similar and use two steps. The first |
| * step, during the visit of each instruction, builds information about the |
| * state of the local variables and the operand stack at the end of each |
| * basic block, called the "output frame", <i>relatively</i> to the frame |
| * state at the beginning of the basic block, which is called the "input |
| * frame", and which is <i>unknown</i> during this step. The second step, in |
| * {@link MethodWriter#visitMaxs}, is a fix point algorithm that computes |
| * information about the input frame of each basic block, from the input |
| * state of the first basic block (known from the method signature), and by |
| * the using the previously computed relative output frames. |
| * |
| * The algorithm used to compute the maximum stack size only computes the |
| * relative output and absolute input stack heights, while the algorithm |
| * used to compute stack map frames computes relative output frames and |
| * absolute input frames. |
| */ |
| |
| /** |
| * Start of the output stack relatively to the input stack. The exact |
| * semantics of this field depends on the algorithm that is used. |
| * |
| * When only the maximum stack size is computed, this field is the number of |
| * elements in the input stack. |
| * |
| * When the stack map frames are completely computed, this field is the |
| * offset of the first output stack element relatively to the top of 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. |
| */ |
| int inputStackTop; |
| |
| /** |
| * Maximum height reached by the output stack, relatively to the top of the |
| * input stack. This maximum is always positive or null. |
| */ |
| int outputStackMax; |
| |
| /** |
| * Information about the input and output stack map frames of this basic |
| * block. This field is only used when {@link ClassWriter#COMPUTE_FRAMES} |
| * option is used. |
| */ |
| Frame frame; |
| |
| /** |
| * The successor of this label, in the order they are visited. This linked |
| * list does not include labels used for debug info only. If |
| * {@link ClassWriter#COMPUTE_FRAMES} option is used then, in addition, it |
| * does not contain successive labels that denote the same bytecode position |
| * (in this case only the first label appears in this list). |
| */ |
| Label successor; |
| |
| /** |
| * The successors of this node in the control flow graph. These successors |
| * are stored in a linked list of {@link Edge Edge} objects, linked to each |
| * other by their {@link Edge#next} field. |
| */ |
| Edge successors; |
| |
| /** |
| * The next basic block in the basic block stack. This stack is used in the |
| * main loop of the fix point algorithm used in the second step of the |
| * control flow analysis algorithms. It is also used in |
| * {@link #visitSubroutine} to avoid using a recursive method. |
| * |
| * @see MethodWriter#visitMaxs |
| */ |
| Label next; |
| |
| // ------------------------------------------------------------------------ |
| // Constructor |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Constructs a new label. |
| */ |
| public Label() { |
| } |
| |
| // ------------------------------------------------------------------------ |
| // Methods to compute offsets and to manage forward references |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Returns the offset corresponding to this label. This offset is computed |
| * from the start of the method's bytecode. <i>This method is intended for |
| * {@link Attribute} sub classes, and is normally not needed by class |
| * generators or adapters.</i> |
| * |
| * @return the offset corresponding to this label. |
| * @throws IllegalStateException |
| * if this label is not resolved yet. |
| */ |
| public int getOffset() { |
| if ((status & RESOLVED) == 0) { |
| throw new IllegalStateException( |
| "Label offset position has not been resolved yet"); |
| } |
| return position; |
| } |
| |
| /** |
| * Puts a reference to this label in the bytecode of a method. If the |
| * position of the label is known, the offset is computed and written |
| * directly. Otherwise, a null offset is written and a new forward reference |
| * is declared for this label. |
| * |
| * @param owner |
| * the code writer that calls this method. |
| * @param out |
| * the bytecode of the method. |
| * @param source |
| * the position of first byte of the bytecode instruction that |
| * contains this label. |
| * @param wideOffset |
| * <tt>true</tt> if the reference must be stored in 4 bytes, or |
| * <tt>false</tt> if it must be stored with 2 bytes. |
| * @throws IllegalArgumentException |
| * if this label has not been created by the given code writer. |
| */ |
| void put(final MethodWriter owner, final ByteVector out, final int source, |
| final boolean wideOffset) { |
| if ((status & RESOLVED) == 0) { |
| if (wideOffset) { |
| addReference(-1 - source, out.length); |
| out.putInt(-1); |
| } else { |
| addReference(source, out.length); |
| out.putShort(-1); |
| } |
| } else { |
| if (wideOffset) { |
| out.putInt(position - source); |
| } else { |
| out.putShort(position - source); |
| } |
| } |
| } |
| |
| /** |
| * Adds a forward reference to this label. This method must be called only |
| * for a true forward reference, i.e. only if this label is not resolved |
| * yet. For backward references, the offset of the reference can be, and |
| * must be, computed and stored directly. |
| * |
| * @param sourcePosition |
| * the position of the referencing instruction. This position |
| * will be used to compute the offset of this forward reference. |
| * @param referencePosition |
| * the position where the offset for this forward reference must |
| * be stored. |
| */ |
| private void addReference(final int sourcePosition, |
| final int referencePosition) { |
| if (srcAndRefPositions == null) { |
| srcAndRefPositions = new int[6]; |
| } |
| if (referenceCount >= srcAndRefPositions.length) { |
| int[] a = new int[srcAndRefPositions.length + 6]; |
| System.arraycopy(srcAndRefPositions, 0, a, 0, |
| srcAndRefPositions.length); |
| srcAndRefPositions = a; |
| } |
| srcAndRefPositions[referenceCount++] = sourcePosition; |
| srcAndRefPositions[referenceCount++] = referencePosition; |
| } |
| |
| /** |
| * Resolves all forward references to this label. This method must be called |
| * when this label is added to the bytecode of the method, i.e. when its |
| * position becomes known. This method fills in the blanks that where left |
| * in the bytecode by each forward reference previously added to this label. |
| * |
| * @param owner |
| * the code writer that calls this method. |
| * @param position |
| * the position of this label in the bytecode. |
| * @param data |
| * the bytecode of the method. |
| * @return <tt>true</tt> if a blank that was left for this label was to |
| * small to store the offset. In such a case the corresponding jump |
| * instruction is replaced with a pseudo instruction (using unused |
| * opcodes) using an unsigned two bytes offset. These pseudo |
| * instructions will need to be replaced with true instructions with |
| * wider offsets (4 bytes instead of 2). This is done in |
| * {@link MethodWriter#resizeInstructions}. |
| * @throws IllegalArgumentException |
| * if this label has already been resolved, or if it has not |
| * been created by the given code writer. |
| */ |
| boolean resolve(final MethodWriter owner, final int position, |
| final byte[] data) { |
| boolean needUpdate = false; |
| this.status |= RESOLVED; |
| this.position = position; |
| int i = 0; |
| while (i < referenceCount) { |
| int source = srcAndRefPositions[i++]; |
| int reference = srcAndRefPositions[i++]; |
| int offset; |
| if (source >= 0) { |
| offset = position - source; |
| if (offset < Short.MIN_VALUE || offset > Short.MAX_VALUE) { |
| /* |
| * changes the opcode of the jump instruction, in order to |
| * be able to find it later (see resizeInstructions in |
| * MethodWriter). These temporary opcodes are similar to |
| * jump instruction opcodes, except that the 2 bytes offset |
| * is unsigned (and can therefore represent values from 0 to |
| * 65535, which is sufficient since the size of a method is |
| * limited to 65535 bytes). |
| */ |
| int opcode = data[reference - 1] & 0xFF; |
| if (opcode <= Opcodes.JSR) { |
| // changes IFEQ ... JSR to opcodes 202 to 217 |
| data[reference - 1] = (byte) (opcode + 49); |
| } else { |
| // changes IFNULL and IFNONNULL to opcodes 218 and 219 |
| data[reference - 1] = (byte) (opcode + 20); |
| } |
| needUpdate = true; |
| } |
| data[reference++] = (byte) (offset >>> 8); |
| data[reference] = (byte) offset; |
| } else { |
| offset = position + source + 1; |
| data[reference++] = (byte) (offset >>> 24); |
| data[reference++] = (byte) (offset >>> 16); |
| data[reference++] = (byte) (offset >>> 8); |
| data[reference] = (byte) offset; |
| } |
| } |
| return needUpdate; |
| } |
| |
| /** |
| * Returns the first label of the series to which this label belongs. For an |
| * isolated label or for the first label in a series of successive labels, |
| * this method returns the label itself. For other labels it returns the |
| * first label of the series. |
| * |
| * @return the first label of the series to which this label belongs. |
| */ |
| Label getFirst() { |
| return !ClassReader.FRAMES || frame == null ? this : frame.owner; |
| } |
| |
| // ------------------------------------------------------------------------ |
| // Methods related to subroutines |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Returns true is this basic block belongs to the given subroutine. |
| * |
| * @param id |
| * a subroutine id. |
| * @return true is this basic block belongs to the given subroutine. |
| */ |
| boolean inSubroutine(final long id) { |
| if ((status & Label.VISITED) != 0) { |
| return (srcAndRefPositions[(int) (id >>> 32)] & (int) id) != 0; |
| } |
| return false; |
| } |
| |
| /** |
| * Returns true if this basic block and the given one belong to a common |
| * subroutine. |
| * |
| * @param block |
| * another basic block. |
| * @return true if this basic block and the given one belong to a common |
| * subroutine. |
| */ |
| boolean inSameSubroutine(final Label block) { |
| if ((status & VISITED) == 0 || (block.status & VISITED) == 0) { |
| return false; |
| } |
| for (int i = 0; i < srcAndRefPositions.length; ++i) { |
| if ((srcAndRefPositions[i] & block.srcAndRefPositions[i]) != 0) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Marks this basic block as belonging to the given subroutine. |
| * |
| * @param id |
| * a subroutine id. |
| * @param nbSubroutines |
| * the total number of subroutines in the method. |
| */ |
| void addToSubroutine(final long id, final int nbSubroutines) { |
| if ((status & VISITED) == 0) { |
| status |= VISITED; |
| srcAndRefPositions = new int[(nbSubroutines - 1) / 32 + 1]; |
| } |
| srcAndRefPositions[(int) (id >>> 32)] |= (int) id; |
| } |
| |
| /** |
| * Finds the basic blocks that belong to a given subroutine, and marks these |
| * blocks as belonging to this subroutine. This method follows the control |
| * flow graph to find all the blocks that are reachable from the current |
| * block WITHOUT following any JSR target. |
| * |
| * @param JSR |
| * a JSR block that jumps to this subroutine. If this JSR is not |
| * null it is added to the successor of the RET blocks found in |
| * the subroutine. |
| * @param id |
| * the id of this subroutine. |
| * @param nbSubroutines |
| * the total number of subroutines in the method. |
| */ |
| void visitSubroutine(final Label JSR, final long id, final int nbSubroutines) { |
| // user managed stack of labels, to avoid using a recursive method |
| // (recursivity can lead to stack overflow with very large methods) |
| Label stack = this; |
| while (stack != null) { |
| // removes a label l from the stack |
| Label l = stack; |
| stack = l.next; |
| l.next = null; |
| |
| if (JSR != null) { |
| if ((l.status & VISITED2) != 0) { |
| continue; |
| } |
| l.status |= VISITED2; |
| // adds JSR to the successors of l, if it is a RET block |
| if ((l.status & RET) != 0) { |
| if (!l.inSameSubroutine(JSR)) { |
| Edge e = new Edge(); |
| e.info = l.inputStackTop; |
| e.successor = JSR.successors.successor; |
| e.next = l.successors; |
| l.successors = e; |
| } |
| } |
| } else { |
| // if the l block already belongs to subroutine 'id', continue |
| if (l.inSubroutine(id)) { |
| continue; |
| } |
| // marks the l block as belonging to subroutine 'id' |
| l.addToSubroutine(id, nbSubroutines); |
| } |
| // pushes each successor of l on the stack, except JSR targets |
| Edge e = l.successors; |
| while (e != null) { |
| // if the l block is a JSR block, then 'l.successors.next' leads |
| // to the JSR target (see {@link #visitJumpInsn}) and must |
| // therefore not be followed |
| if ((l.status & Label.JSR) == 0 || e != l.successors.next) { |
| // pushes e.successor on the stack if it not already added |
| if (e.successor.next == null) { |
| e.successor.next = stack; |
| stack = e.successor; |
| } |
| } |
| e = e.next; |
| } |
| } |
| } |
| |
| // ------------------------------------------------------------------------ |
| // Overriden Object methods |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Returns a string representation of this label. |
| * |
| * @return a string representation of this label. |
| */ |
| @Override |
| public String toString() { |
| return "L" + System.identityHashCode(this); |
| } |
| } |