/*
* fb-contrib - Auxiliary detectors for Java programs
* Copyright (C) 2005-2017 Dave Brosius
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.mebigfatguy.fbcontrib.detect;
import org.apache.bcel.classfile.Code;
import com.mebigfatguy.fbcontrib.collect.MethodInfo;
import com.mebigfatguy.fbcontrib.collect.Statistics;
import com.mebigfatguy.fbcontrib.utils.BugType;
import com.mebigfatguy.fbcontrib.utils.SignatureUtils;
import com.mebigfatguy.fbcontrib.utils.Values;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.OpcodeStack.CustomUserValue;
import edu.umd.cs.findbugs.ba.ClassContext;
/**
* looks for conditional expressions where both simple local variable (in)equalities are used along with method calls, where the method calls are done first. By
* placing the simple local checks first, you eliminate potentially costly calls in some cases. This assumes that the methods called won't have side-effects
* that are desired. At present it only looks for simple sequences of 'and' based conditions.
*/
@CustomUserValue
public class SuboptimalExpressionOrder extends BytecodeScanningDetector {
private static final int NORMAL_WEIGHT_LIMIT = 50;
private BugReporter bugReporter;
private OpcodeStack stack;
private int conditionalTarget;
private int sawMethodWeight;
/**
* constructs a SEO detector given the reporter to report bugs on
*
* @param bugReporter
* the sync of bug reports
*/
public SuboptimalExpressionOrder(BugReporter bugReporter) {
this.bugReporter = bugReporter;
}
/**
* overrides the visitor to setup the opcode stack
*
* @param clsContext
* the context object of the currently parse class
*/
@Override
public void visitClassContext(ClassContext clsContext) {
try {
stack = new OpcodeStack();
super.visitClassContext(clsContext);
} finally {
stack = null;
}
}
/**
* overrides the visitor to reset the opcode stack, and initialize vars
*
* @param obj
* the code object of the currently parsed method
*/
@Override
public void visitCode(Code obj) {
stack.resetForMethodEntry(this);
conditionalTarget = -1;
sawMethodWeight = 0;
super.visitCode(obj);
}
/**
* overrides the visitor to look for chains of expressions joined by 'and' that have method calls before simple local variable conditions
*
* @param seen
* the currently parse opcode
*/
@Override
public void sawOpcode(int seen) {
Integer userValue = null;
if ((conditionalTarget != -1) && (getPC() >= conditionalTarget)) {
conditionalTarget = -1;
sawMethodWeight = 0;
}
try {
switch (seen) {
case INVOKESPECIAL:
case INVOKESTATIC:
case INVOKEINTERFACE:
case INVOKEVIRTUAL:
String signature = getSigConstantOperand();
if (Values.SIG_VOID.equals(SignatureUtils.getReturnSignature(signature))) {
sawMethodWeight = 0;
return;
}
String clsName = getClassConstantOperand();
MethodInfo mi = Statistics.getStatistics().getMethodStatistics(clsName, getNameConstantOperand(), signature);
if ((mi == null) || (mi.getNumBytes() == 0)) {
userValue = Values.ONE;
} else {
userValue = Integer.valueOf(mi.getNumBytes());
}
break;
case LCMP:
case FCMPL:
case FCMPG:
case DCMPL:
case DCMPG:
case IAND:
case IOR:
case IXOR:
if (stack.getStackDepth() >= 2) {
for (int i = 0; i <= 1; i++) {
OpcodeStack.Item itm = stack.getStackItem(i);
userValue = (Integer) itm.getUserValue();
if (userValue != null) {
break;
}
}
} else {
sawMethodWeight = 0;
}
break;
case IF_ICMPEQ:
case IF_ICMPNE:
case IF_ICMPLT:
case IF_ICMPGE:
case IF_ICMPGT:
case IF_ICMPLE:
case IF_ACMPEQ:
case IF_ACMPNE:
if (conditionalTarget < 0) {
conditionalTarget = getBranchTarget();
} else if (conditionalTarget != getBranchTarget()) {
conditionalTarget = -1;
sawMethodWeight = 0;
return;
}
if (stack.getStackDepth() >= 2) {
int expWeight = 0;
for (int i = 0; i <= 1; i++) {
OpcodeStack.Item itm = stack.getStackItem(i);
Integer uv = (Integer) itm.getUserValue();
if (uv != null) {
expWeight = Math.max(uv.intValue(), expWeight);
}
}
if ((expWeight == 0) && (sawMethodWeight > 0)) {
bugReporter.reportBug(new BugInstance(this, BugType.SEO_SUBOPTIMAL_EXPRESSION_ORDER.name(),
sawMethodWeight >= NORMAL_WEIGHT_LIMIT ? NORMAL_PRIORITY : LOW_PRIORITY).addClass(this).addMethod(this)
.addSourceLine(this));
sawMethodWeight = 0;
conditionalTarget = Integer.MAX_VALUE;
} else {
sawMethodWeight = Math.max(sawMethodWeight, expWeight);
}
}
break;
case IFEQ:
case IFNE:
case IFLT:
case IFGE:
case IFGT:
case IFLE:
case IFNULL:
case IFNONNULL:
if (conditionalTarget < 0) {
conditionalTarget = getBranchTarget();
} else if (conditionalTarget != getBranchTarget()) {
conditionalTarget = -1;
sawMethodWeight = 0;
return;
}
if (stack.getStackDepth() >= 1) {
OpcodeStack.Item itm = stack.getStackItem(0);
Integer uv = (Integer) itm.getUserValue();
if (uv == null) {
if (sawMethodWeight > 0) {
bugReporter.reportBug(new BugInstance(this, BugType.SEO_SUBOPTIMAL_EXPRESSION_ORDER.name(),
sawMethodWeight >= NORMAL_WEIGHT_LIMIT ? NORMAL_PRIORITY : LOW_PRIORITY).addClass(this).addMethod(this)
.addSourceLine(this));
sawMethodWeight = 0;
conditionalTarget = Integer.MAX_VALUE;
}
} else {
sawMethodWeight = Math.max(sawMethodWeight, uv.intValue());
}
}
break;
case ISTORE:
case LSTORE:
case FSTORE:
case DSTORE:
case ASTORE:
case ISTORE_0:
case ISTORE_1:
case ISTORE_2:
case ISTORE_3:
case LSTORE_0:
case LSTORE_1:
case LSTORE_2:
case LSTORE_3:
case FSTORE_0:
case FSTORE_1:
case FSTORE_2:
case FSTORE_3:
case DSTORE_0:
case DSTORE_1:
case DSTORE_2:
case DSTORE_3:
case ASTORE_0:
case ASTORE_1:
case ASTORE_2:
case ASTORE_3:
if (stack.getStackDepth() > 0) {
OpcodeStack.Item itm = stack.getStackItem(0);
itm.setUserValue(null);
}
sawMethodWeight = 0;
conditionalTarget = -1;
break;
case ATHROW:
case POP:
case POP2:
case GOTO:
case GOTO_W:
case PUTFIELD:
case PUTSTATIC:
case IINC:
case INSTANCEOF:
case RETURN:
case ARETURN:
case IRETURN:
case LRETURN:
case FRETURN:
case DRETURN:
sawMethodWeight = 0;
conditionalTarget = -1;
break;
case ARRAYLENGTH:
case CHECKCAST:
if (stack.getStackDepth() > 0) {
OpcodeStack.Item itm = stack.getStackItem(0);
userValue = (Integer) itm.getUserValue();
}
break;
}
} finally {
stack.sawOpcode(this, seen);
if ((userValue != null) && (stack.getStackDepth() > 0)) {
OpcodeStack.Item itm = stack.getStackItem(0);
itm.setUserValue(userValue);
}
}
}
}