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Diffstat (limited to 'src/proguard/optimize/peephole/VariableShrinker.java')
-rw-r--r-- | src/proguard/optimize/peephole/VariableShrinker.java | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/proguard/optimize/peephole/VariableShrinker.java b/src/proguard/optimize/peephole/VariableShrinker.java new file mode 100644 index 0000000..45b694f --- /dev/null +++ b/src/proguard/optimize/peephole/VariableShrinker.java @@ -0,0 +1,129 @@ +/* + * ProGuard -- shrinking, optimization, obfuscation, and preverification + * of Java bytecode. + * + * Copyright (c) 2002-2009 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.VariableEditor; +import proguard.classfile.util.*; +import proguard.classfile.visitor.MemberVisitor; +import proguard.optimize.*; +import proguard.optimize.info.*; + +/** + * This MemberVisitor removes unused local variables from the code of the methods + * that it visits. + * + * @see ParameterUsageMarker + * @see MethodStaticizer + * @see MethodDescriptorShrinker + * @author Eric Lafortune + */ +public class VariableShrinker +extends SimplifiedVisitor +implements AttributeVisitor +{ + private static final boolean DEBUG = false; + + + private final MemberVisitor extraVariableMemberVisitor; + + private final VariableUsageMarker variableUsageMarker = new VariableUsageMarker(); + private final VariableEditor variableEditor = new VariableEditor(); + + + /** + * Creates a new VariableShrinker. + */ + public VariableShrinker() + { + this(null); + } + + + /** + * Creates a new VariableShrinker with an extra visitor. + * @param extraVariableMemberVisitor an optional extra visitor for all + * removed variables. + */ + public VariableShrinker(MemberVisitor extraVariableMemberVisitor) + { + this.extraVariableMemberVisitor = extraVariableMemberVisitor; + } + + + // Implementations for AttributeVisitor. + + public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} + + + public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) + { + if ((method.getAccessFlags() & ClassConstants.INTERNAL_ACC_ABSTRACT) == 0) + { + // Compute the parameter size. + int parameterSize = + ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz), + method.getAccessFlags()); + + // Get the total size of the local variable frame. + int maxLocals = codeAttribute.u2maxLocals; + + if (DEBUG) + { + System.out.println("VariableShrinker: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz)); + System.out.println(" Parameter size = " + parameterSize); + System.out.println(" Max locals = " + maxLocals); + } + + // Figure out the local variables that are used by the code. + variableUsageMarker.visitCodeAttribute(clazz, method, codeAttribute); + + // Delete unused local variables from the local variable frame. + variableEditor.reset(maxLocals); + + for (int variableIndex = parameterSize; variableIndex < maxLocals; variableIndex++) + { + // Is the variable not required? + if (!variableUsageMarker.isVariableUsed(variableIndex)) + { + if (DEBUG) + { + System.out.println(" Deleting local variable #"+variableIndex); + } + + // Delete the unused variable. + variableEditor.deleteVariable(variableIndex); + + // Visit the method, if required. + if (extraVariableMemberVisitor != null) + { + method.accept(clazz, extraVariableMemberVisitor); + } + } + } + + // Shift all remaining parameters and variables in the byte code. + variableEditor.visitCodeAttribute(clazz, method, codeAttribute); + } + } +} |