diff options
Diffstat (limited to 'src/proguard/optimize/peephole/GotoCommonCodeReplacer.java')
| -rw-r--r-- | src/proguard/optimize/peephole/GotoCommonCodeReplacer.java | 263 |
1 files changed, 0 insertions, 263 deletions
diff --git a/src/proguard/optimize/peephole/GotoCommonCodeReplacer.java b/src/proguard/optimize/peephole/GotoCommonCodeReplacer.java deleted file mode 100644 index a1f422f..0000000 --- a/src/proguard/optimize/peephole/GotoCommonCodeReplacer.java +++ /dev/null @@ -1,263 +0,0 @@ -/* - * ProGuard -- shrinking, optimization, obfuscation, and preverification - * of Java bytecode. - * - * Copyright (c) 2002-2014 Eric Lafortune (eric@graphics.cornell.edu) - * - * This program is free software; you can redistribute it and/or modify it - * under the terms of the GNU General Public License as published by the Free - * Software Foundation; either version 2 of the License, or (at your option) - * any later version. - * - * This program is distributed in the hope that it will be useful, but WITHOUT - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or - * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for - * more details. - * - * You should have received a copy of the GNU General Public License along - * with this program; if not, write to the Free Software Foundation, Inc., - * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA - */ -package proguard.optimize.peephole; - -import proguard.classfile.*; -import proguard.classfile.attribute.*; -import proguard.classfile.attribute.visitor.AttributeVisitor; -import proguard.classfile.editor.CodeAttributeEditor; -import proguard.classfile.instruction.*; -import proguard.classfile.instruction.visitor.InstructionVisitor; -import proguard.classfile.util.SimplifiedVisitor; - -/** - * This AttributeVisitor redirects unconditional branches so any common code - * is shared, and the code preceding the branch can be removed, in the code - * attributes that it visits. - * - * @author Eric Lafortune - */ -public class GotoCommonCodeReplacer -extends SimplifiedVisitor -implements AttributeVisitor, - InstructionVisitor -{ - //* - private static final boolean DEBUG = false; - /*/ - private static boolean DEBUG = true; - //*/ - - - private final InstructionVisitor extraInstructionVisitor; - - private final BranchTargetFinder branchTargetFinder = new BranchTargetFinder(); - private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor(true, false); - - - /** - * Creates a new GotoCommonCodeReplacer. - * @param extraInstructionVisitor an optional extra visitor for all replaced - * goto instructions. - */ - public GotoCommonCodeReplacer(InstructionVisitor extraInstructionVisitor) - { - this.extraInstructionVisitor = extraInstructionVisitor; - } - - - // Implementations for AttributeVisitor. - - public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} - - - public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) - { -// DEBUG = -// clazz.getName().equals("abc/Def") && -// method.getName(clazz).equals("abc"); - - // Mark all branch targets. - branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute); - - // Reset the code attribute editor. - codeAttributeEditor.reset(codeAttribute.u4codeLength); - - // Remap the variables of the instructions. - codeAttribute.instructionsAccept(clazz, method, this); - - // Apply the code atribute editor. - codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute); - } - - - // Implementations for InstructionVisitor. - - public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {} - - - public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, BranchInstruction branchInstruction) - { - // Check if the instruction is an unconditional goto instruction that - // isn't the target of a branch itself. - byte opcode = branchInstruction.opcode; - if ((opcode == InstructionConstants.OP_GOTO || - opcode == InstructionConstants.OP_GOTO_W) && - !branchTargetFinder.isBranchTarget(offset)) - { - int branchOffset = branchInstruction.branchOffset; - int targetOffset = offset + branchOffset; - - // Get the number of common bytes. - int commonCount = commonByteCodeCount(codeAttribute, offset, targetOffset); - - if (commonCount > 0 && - !exceptionBoundary(codeAttribute, offset, targetOffset)) - { - if (DEBUG) - { - System.out.println("GotoCommonCodeReplacer: "+clazz.getName()+"."+method.getName(clazz)+" (["+(offset-commonCount)+"] - "+branchInstruction.toString(offset)+" -> "+targetOffset+")"); - } - - // Delete the common instructions. - for (int delta = 0; delta <= commonCount; delta++) - { - int deleteOffset = offset - delta; - if (branchTargetFinder.isInstruction(deleteOffset)) - { - codeAttributeEditor.clearModifications(deleteOffset); - codeAttributeEditor.deleteInstruction(deleteOffset); - } - } - - // Redirect the goto instruction, if it is still necessary. - int newBranchOffset = branchOffset - commonCount; - if (newBranchOffset != branchInstruction.length(offset)) - { - Instruction newGotoInstruction = - new BranchInstruction(opcode, newBranchOffset).shrink(); - codeAttributeEditor.replaceInstruction(offset, - newGotoInstruction); - } - - // Visit the instruction, if required. - if (extraInstructionVisitor != null) - { - extraInstructionVisitor.visitBranchInstruction(clazz, method, codeAttribute, offset, branchInstruction); - } - } - } - } - - - // Small utility methods. - - /** - * Returns the number of common bytes preceding the given offsets, - * avoiding branches and exception blocks. - */ - private int commonByteCodeCount(CodeAttribute codeAttribute, int offset1, int offset2) - { - // Find the block of common instructions preceding it. - byte[] code = codeAttribute.code; - - int successfulDelta = 0; - - for (int delta = 1; - delta <= offset1 && - delta <= offset2 && - offset2 - delta != offset1; - delta++) - { - int newOffset1 = offset1 - delta; - int newOffset2 = offset2 - delta; - - // Is the code identical at both offsets? - if (code[newOffset1] != code[newOffset2]) - { - break; - } - - // Are there instructions at either offset but not both? - if (branchTargetFinder.isInstruction(newOffset1) ^ - branchTargetFinder.isInstruction(newOffset2)) - { - break; - } - - // Are there instructions at both offsets? - if (branchTargetFinder.isInstruction(newOffset1) && - branchTargetFinder.isInstruction(newOffset2)) - { - // Are the offsets involved in some branches? - // Note that the preverifier doesn't like initializer - // invocations to be moved around. - // Also note that the preverifier doesn't like pop instructions - // that work on different operands. - if (branchTargetFinder.isBranchOrigin(newOffset1) || - branchTargetFinder.isBranchTarget(newOffset1) || - branchTargetFinder.isExceptionStart(newOffset1) || - branchTargetFinder.isExceptionEnd(newOffset1) || - branchTargetFinder.isInitializer(newOffset1) || - branchTargetFinder.isExceptionStart(newOffset2) || - branchTargetFinder.isExceptionEnd(newOffset2) || - isPop(code[newOffset1])) - { - break; - } - - // Make sure the new branch target was a branch target before, - // in order not to introduce new entries in the stack map table. - if (branchTargetFinder.isBranchTarget(newOffset2)) - { - successfulDelta = delta; - } - - if (branchTargetFinder.isBranchTarget(newOffset1)) - { - break; - } - } - } - - return successfulDelta; - } - - - /** - * Returns whether the given opcode represents a pop instruction that must - * get a consistent type (pop, pop2, arraylength). - */ - private boolean isPop(byte opcode) - { - return opcode == InstructionConstants.OP_POP || - opcode == InstructionConstants.OP_POP2 || - opcode == InstructionConstants.OP_ARRAYLENGTH; - } - - - /** - * Returns the whether there is a boundary of an exception block between - * the given offsets (including both). - */ - private boolean exceptionBoundary(CodeAttribute codeAttribute, int offset1, int offset2) - { - // Swap the offsets if the second one is smaller than the first one. - if (offset2 < offset1) - { - int offset = offset1; - offset1 = offset2; - offset2 = offset; - } - - // Check if there is a boundary of an exception block. - for (int offset = offset1; offset <= offset2; offset++) - { - if (branchTargetFinder.isExceptionStart(offset) || - branchTargetFinder.isExceptionEnd(offset)) - { - return true; - } - } - - return false; - } -} |