diff options
Diffstat (limited to 'src/proguard/classfile/editor/VariableCleaner.java')
| -rw-r--r-- | src/proguard/classfile/editor/VariableCleaner.java | 208 |
1 files changed, 172 insertions, 36 deletions
diff --git a/src/proguard/classfile/editor/VariableCleaner.java b/src/proguard/classfile/editor/VariableCleaner.java index 1e93c15..63b7d4a 100644 --- a/src/proguard/classfile/editor/VariableCleaner.java +++ b/src/proguard/classfile/editor/VariableCleaner.java @@ -2,7 +2,7 @@ * ProGuard -- shrinking, optimization, obfuscation, and preverification * of Java bytecode. * - * Copyright (c) 2002-2009 Eric Lafortune (eric@graphics.cornell.edu) + * Copyright (c) 2002-2013 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 @@ -22,15 +22,15 @@ package proguard.classfile.editor; import proguard.classfile.*; import proguard.classfile.attribute.*; -import proguard.classfile.attribute.visitor.*; -import proguard.classfile.instruction.*; -import proguard.classfile.instruction.visitor.InstructionVisitor; +import proguard.classfile.attribute.visitor.AttributeVisitor; import proguard.classfile.util.SimplifiedVisitor; -import proguard.optimize.info.VariableUsageMarker; + +import java.util.Arrays; /** - * This AttributeVisitor cleans up unused variables in all attributes that it - * visits. + * This AttributeVisitor cleans up variable tables in all code attributes that + * it visits. It trims overlapping local variables. It removes empty local + * variables and empty local variable tables. * * @author Eric Lafortune */ @@ -38,7 +38,8 @@ public class VariableCleaner extends SimplifiedVisitor implements AttributeVisitor { - private final VariableUsageMarker variableUsageMarker = new VariableUsageMarker(); + private boolean deleteLocalVariableTableAttribute; + private boolean deleteLocalVariableTypeTableAttribute; // Implementations for AttributeVisitor. @@ -48,11 +49,35 @@ implements AttributeVisitor public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) { - // Figure out the local variables that are used by the code. - variableUsageMarker.visitCodeAttribute(clazz, method, codeAttribute); + deleteLocalVariableTableAttribute = false; + deleteLocalVariableTypeTableAttribute = false; - // Clean up the variables of the attributes. + // Trim the local variable table and the local variable type table. codeAttribute.attributesAccept(clazz, method, this); + + // Delete the local variable table if it ended up empty. + if (deleteLocalVariableTableAttribute) + { + AttributesEditor editor = + new AttributesEditor((ProgramClass)clazz, + (ProgramMember)method, + codeAttribute, + true); + + editor.deleteAttribute(ClassConstants.ATTR_LocalVariableTable); + } + + // Delete the local variable type table if it ended up empty. + if (deleteLocalVariableTypeTableAttribute) + { + AttributesEditor editor = + new AttributesEditor((ProgramClass)clazz, + (ProgramMember)method, + codeAttribute, + true); + + editor.deleteAttribute(ClassConstants.ATTR_LocalVariableTypeTable); + } } @@ -60,9 +85,20 @@ implements AttributeVisitor { // Clean up local variables that aren't used. localVariableTableAttribute.u2localVariableTableLength = - removeEmptyLocalVariables(localVariableTableAttribute.localVariableTable, - localVariableTableAttribute.u2localVariableTableLength, - codeAttribute.u2maxLocals); + removeUnusedLocalVariables(localVariableTableAttribute.localVariableTable, + localVariableTableAttribute.u2localVariableTableLength, + codeAttribute.u2maxLocals); + + // Trim the code blocks of the local variables. + trimLocalVariables(localVariableTableAttribute.localVariableTable, + localVariableTableAttribute.u2localVariableTableLength, + codeAttribute.u2maxLocals); + + // Delete the attribute in a moment, if it is empty. + if (localVariableTableAttribute.u2localVariableTableLength == 0) + { + deleteLocalVariableTableAttribute = true; + } } @@ -70,9 +106,20 @@ implements AttributeVisitor { // Clean up local variables that aren't used. localVariableTypeTableAttribute.u2localVariableTypeTableLength = - removeEmptyLocalVariableTypes(localVariableTypeTableAttribute.localVariableTypeTable, - localVariableTypeTableAttribute.u2localVariableTypeTableLength, - codeAttribute.u2maxLocals); + removeUnusedLocalVariableTypes(localVariableTypeTableAttribute.localVariableTypeTable, + localVariableTypeTableAttribute.u2localVariableTypeTableLength, + codeAttribute.u2maxLocals); + + // Trim the code blocks of the local variables. + trimLocalVariableTypes(localVariableTypeTableAttribute.localVariableTypeTable, + localVariableTypeTableAttribute.u2localVariableTypeTableLength, + codeAttribute.u2maxLocals); + + // Delete the attribute in a moment, if it is empty. + if (localVariableTypeTableAttribute.u2localVariableTypeTableLength == 0) + { + deleteLocalVariableTypeTableAttribute = true; + } } @@ -80,27 +127,30 @@ implements AttributeVisitor /** * Returns the given list of local variables, without the ones that aren't - * used + * used. */ - private int removeEmptyLocalVariables(LocalVariableInfo[] localVariableInfos, - int localVariableInfoCount, - int maxLocals) + private int removeUnusedLocalVariables(LocalVariableInfo[] localVariableInfos, + int localVariableInfoCount, + int maxLocals) { // Overwrite all empty local variable entries. + // Do keep parameter entries. int newIndex = 0; - for (int index = 0; index < localVariableInfoCount && index < maxLocals; index++) + for (int index = 0; index < localVariableInfoCount; index++) { - if (variableUsageMarker.isVariableUsed(index)) + LocalVariableInfo localVariableInfo = localVariableInfos[index]; + + if (localVariableInfo.u2index >= 0 && + localVariableInfo.u2index < maxLocals && + (localVariableInfo.u2startPC == 0 || + localVariableInfo.u2length > 0)) { localVariableInfos[newIndex++] = localVariableInfos[index]; } } // Clean up any remaining array elements. - for (int index = newIndex; index < localVariableInfoCount; index++) - { - localVariableInfos[index] = null; - } + Arrays.fill(localVariableInfos, newIndex, localVariableInfoCount, null); return newIndex; } @@ -108,28 +158,114 @@ implements AttributeVisitor /** * Returns the given list of local variable types, without the ones that - * aren't used + * aren't used. */ - private int removeEmptyLocalVariableTypes(LocalVariableTypeInfo[] localVariableTypeInfos, - int localVariableTypeInfoCount, - int maxLocals) + private int removeUnusedLocalVariableTypes(LocalVariableTypeInfo[] localVariableTypeInfos, + int localVariableTypeInfoCount, + int maxLocals) { // Overwrite all empty local variable type entries. + // Do keep parameter entries. int newIndex = 0; - for (int index = 0; index < localVariableTypeInfoCount && index < maxLocals; index++) + for (int index = 0; index < localVariableTypeInfoCount; index++) { - if (variableUsageMarker.isVariableUsed(index)) + LocalVariableTypeInfo localVariableTypeInfo = localVariableTypeInfos[index]; + + if (localVariableTypeInfo.u2index >= 0 && + localVariableTypeInfo.u2index < maxLocals && + (localVariableTypeInfo.u2startPC == 0 || + localVariableTypeInfo.u2length > 0)) { localVariableTypeInfos[newIndex++] = localVariableTypeInfos[index]; } } // Clean up any remaining array elements. - for (int index = newIndex; index < localVariableTypeInfoCount; index++) + Arrays.fill(localVariableTypeInfos, newIndex, localVariableTypeInfoCount, null); + + return newIndex; + } + + + /** + * Sorts the given list of local variables and trims their code blocks + * when necessary. The block is trimmed at the end, which is a bit + * arbitrary. + */ + private void trimLocalVariables(LocalVariableInfo[] localVariableInfos, + int localVariableInfoCount, + int maxLocals) + { + // Sort the local variable entries. + Arrays.sort(localVariableInfos, 0, localVariableInfoCount); + + int[] startPCs = createMaxArray(maxLocals); + + // Trim the local variable entries, starting at the last one. + for (int index = localVariableInfoCount-1; index >= 0; index--) { - localVariableTypeInfos[index] = null; + LocalVariableInfo localVariableInfo = localVariableInfos[index]; + + // Make sure the variable's code block doesn't overlap with the + // next one for the same variable. + int maxLength = startPCs[localVariableInfo.u2index] - + localVariableInfo.u2startPC; + + if (localVariableInfo.u2length > maxLength) + { + localVariableInfo.u2length = maxLength; + } + + startPCs[localVariableInfo.u2index] = localVariableInfo.u2startPC; } + } - return newIndex; + + /** + * Sorts the given list of local variable types and trims their code blocks + * when necessary. The block is trimmed at the end, which is a bit + * arbitrary. + */ + private void trimLocalVariableTypes(LocalVariableTypeInfo[] localVariableTypeInfos, + int localVariableTypeInfoCount, + int maxLocals) + { + // Sort the local variable entries. + Arrays.sort(localVariableTypeInfos, 0, localVariableTypeInfoCount); + + int[] startPCs = createMaxArray(maxLocals); + + // Trim the local variable entries, starting at the last one. + for (int index = localVariableTypeInfoCount-1; index >= 0; index--) + { + LocalVariableTypeInfo localVariableTypeInfo = localVariableTypeInfos[index]; + + // Make sure the variable's code block doesn't overlap with the + // next one for the same variable. + int maxLength = startPCs[localVariableTypeInfo.u2index] - + localVariableTypeInfo.u2startPC; + + if (localVariableTypeInfo.u2length > maxLength) + { + localVariableTypeInfo.u2length = maxLength; + } + + startPCs[localVariableTypeInfo.u2index] = localVariableTypeInfo.u2startPC; + } + } + + + /** + * Creates an integer array of the given length, initialized with + * Integer.MAX_VALUE. + */ + private int[] createMaxArray(int length) + { + int[] startPCs = new int[length]; + for (int index = 0; index < length; index++) + { + startPCs[index] = Integer.MAX_VALUE; + } + return startPCs; } }
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