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org.eclipse.jdt.internal.compiler.ast.IfStatement Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2000, 2009 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;
import org.eclipse.jdt.internal.compiler.ASTVisitor;
import org.eclipse.jdt.internal.compiler.impl.*;
import org.eclipse.jdt.internal.compiler.codegen.*;
import org.eclipse.jdt.internal.compiler.flow.*;
import org.eclipse.jdt.internal.compiler.lookup.*;
public class IfStatement extends Statement {
//this class represents the case of only one statement in
//either else and/or then branches.
public Expression condition;
public Statement thenStatement;
public Statement elseStatement;
// for local variables table attributes
int thenInitStateIndex = -1;
int elseInitStateIndex = -1;
int mergedInitStateIndex = -1;
public IfStatement(Expression condition, Statement thenStatement, int sourceStart, int sourceEnd) {
this.condition = condition;
this.thenStatement = thenStatement;
// remember useful empty statement
if (thenStatement instanceof EmptyStatement) thenStatement.bits |= IsUsefulEmptyStatement;
this.sourceStart = sourceStart;
this.sourceEnd = sourceEnd;
}
public IfStatement(Expression condition, Statement thenStatement, Statement elseStatement, int sourceStart, int sourceEnd) {
this.condition = condition;
this.thenStatement = thenStatement;
// remember useful empty statement
if (thenStatement instanceof EmptyStatement) thenStatement.bits |= IsUsefulEmptyStatement;
this.elseStatement = elseStatement;
if (elseStatement instanceof IfStatement) elseStatement.bits |= IsElseIfStatement;
if (elseStatement instanceof EmptyStatement) elseStatement.bits |= IsUsefulEmptyStatement;
this.sourceStart = sourceStart;
this.sourceEnd = sourceEnd;
}
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
// process the condition
FlowInfo conditionFlowInfo = this.condition.analyseCode(currentScope, flowContext, flowInfo);
int initialComplaintLevel = (flowInfo.reachMode() & FlowInfo.UNREACHABLE) != 0 ? Statement.COMPLAINED_FAKE_REACHABLE : Statement.NOT_COMPLAINED;
Constant cst = this.condition.optimizedBooleanConstant();
boolean isConditionOptimizedTrue = cst != Constant.NotAConstant && cst.booleanValue() == true;
boolean isConditionOptimizedFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;
// process the THEN part
FlowInfo thenFlowInfo = conditionFlowInfo.safeInitsWhenTrue();
if (isConditionOptimizedFalse) {
thenFlowInfo.setReachMode(FlowInfo.UNREACHABLE);
}
FlowInfo elseFlowInfo = conditionFlowInfo.initsWhenFalse();
if (isConditionOptimizedTrue) {
elseFlowInfo.setReachMode(FlowInfo.UNREACHABLE);
}
if (this.thenStatement != null) {
// Save info for code gen
this.thenInitStateIndex = currentScope.methodScope().recordInitializationStates(thenFlowInfo);
if (isConditionOptimizedFalse) {
if (!isKnowDeadCodePattern(this.condition) || currentScope.compilerOptions().reportDeadCodeInTrivialIfStatement) {
this.thenStatement.complainIfUnreachable(thenFlowInfo, currentScope, initialComplaintLevel);
}
}
thenFlowInfo = this.thenStatement.analyseCode(currentScope, flowContext, thenFlowInfo);
}
// code gen: optimizing the jump around the ELSE part
if ((thenFlowInfo.tagBits & FlowInfo.UNREACHABLE) != 0) {
this.bits |= ASTNode.ThenExit;
}
// process the ELSE part
if (this.elseStatement != null) {
// signal else clause unnecessarily nested, tolerate else-if code pattern
if (thenFlowInfo == FlowInfo.DEAD_END
&& (this.bits & IsElseIfStatement) == 0 // else of an else-if
&& !(this.elseStatement instanceof IfStatement)) {
currentScope.problemReporter().unnecessaryElse(this.elseStatement);
}
// Save info for code gen
this.elseInitStateIndex = currentScope.methodScope().recordInitializationStates(elseFlowInfo);
if (isConditionOptimizedTrue) {
if (!isKnowDeadCodePattern(this.condition) || currentScope.compilerOptions().reportDeadCodeInTrivialIfStatement) {
this.elseStatement.complainIfUnreachable(elseFlowInfo, currentScope, initialComplaintLevel);
}
}
elseFlowInfo = this.elseStatement.analyseCode(currentScope, flowContext, elseFlowInfo);
}
// merge THEN & ELSE initializations
FlowInfo mergedInfo = FlowInfo.mergedOptimizedBranches(
thenFlowInfo,
isConditionOptimizedTrue,
elseFlowInfo,
isConditionOptimizedFalse,
true /*if(true){ return; } fake-reachable(); */);
this.mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo);
return mergedInfo;
}
/**
* If code generation
*
* @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
* @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
*/
public void generateCode(BlockScope currentScope, CodeStream codeStream) {
if ((this.bits & IsReachable) == 0) {
return;
}
int pc = codeStream.position;
BranchLabel endifLabel = new BranchLabel(codeStream);
// optimizing the then/else part code gen
Constant cst;
boolean hasThenPart =
!(((cst = this.condition.optimizedBooleanConstant()) != Constant.NotAConstant
&& cst.booleanValue() == false)
|| this.thenStatement == null
|| this.thenStatement.isEmptyBlock());
boolean hasElsePart =
!((cst != Constant.NotAConstant && cst.booleanValue() == true)
|| this.elseStatement == null
|| this.elseStatement.isEmptyBlock());
if (hasThenPart) {
BranchLabel falseLabel = null;
// generate boolean condition
this.condition.generateOptimizedBoolean(
currentScope,
codeStream,
null,
hasElsePart ? (falseLabel = new BranchLabel(codeStream)) : endifLabel,
true/*cst == Constant.NotAConstant*/);
// May loose some local variable initializations : affecting the local variable attributes
if (this.thenInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.thenInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.thenInitStateIndex);
}
// generate then statement
this.thenStatement.generateCode(currentScope, codeStream);
// jump around the else statement
if (hasElsePart) {
if ((this.bits & ASTNode.ThenExit) == 0) {
this.thenStatement.branchChainTo(endifLabel);
int position = codeStream.position;
codeStream.goto_(endifLabel);
//goto is tagged as part of the thenAction block
codeStream.updateLastRecordedEndPC((this.thenStatement instanceof Block) ? ((Block) this.thenStatement).scope : currentScope, position);
// generate else statement
}
// May loose some local variable initializations : affecting the local variable attributes
if (this.elseInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(
currentScope,
this.elseInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.elseInitStateIndex);
}
if (falseLabel != null) falseLabel.place();
this.elseStatement.generateCode(currentScope, codeStream);
}
} else if (hasElsePart) {
// generate boolean condition
this.condition.generateOptimizedBoolean(
currentScope,
codeStream,
endifLabel,
null,
true/*cst == Constant.NotAConstant*/);
// generate else statement
// May loose some local variable initializations : affecting the local variable attributes
if (this.elseInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(
currentScope,
this.elseInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.elseInitStateIndex);
}
this.elseStatement.generateCode(currentScope, codeStream);
} else {
// generate condition side-effects
this.condition.generateCode(currentScope, codeStream, false);
codeStream.recordPositionsFrom(pc, this.sourceStart);
}
// May loose some local variable initializations : affecting the local variable attributes
if (this.mergedInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(
currentScope,
this.mergedInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
}
endifLabel.place();
codeStream.recordPositionsFrom(pc, this.sourceStart);
}
/**
* Answers true if the if is identified as a known coding pattern which
* should be tolerated by dead code analysis.
* e.g. if (DEBUG) print(); // no complaint
* Only invoked when overall condition is known to be optimizeable into false.
*/
public static boolean isKnowDeadCodePattern(Expression expression) {
// if (!DEBUG) print(); - tolerated
if (expression instanceof UnaryExpression) {
expression = ((UnaryExpression) expression).expression;
}
// if (DEBUG) print(); - tolerated
if (expression instanceof Reference) return true;
// if (expression instanceof BinaryExpression) {
// BinaryExpression binary = (BinaryExpression) expression;
// switch ((binary.bits & ASTNode.OperatorMASK) >> ASTNode.OperatorSHIFT/* operator */) {
// case OperatorIds.AND_AND :
// case OperatorIds.OR_OR :
// break;
// default:
// // if (DEBUG_LEVEL > 0) print(); - tolerated
// if ((binary.left instanceof Reference) && binary.right.constant != Constant.NotAConstant)
// return true;
// // if (0 < DEBUG_LEVEL) print(); - tolerated
// if ((binary.right instanceof Reference) && binary.left.constant != Constant.NotAConstant)
// return true;
// }
// }
return false;
}
public StringBuffer printStatement(int indent, StringBuffer output) {
printIndent(indent, output).append("if ("); //$NON-NLS-1$
this.condition.printExpression(0, output).append(")\n"); //$NON-NLS-1$
this.thenStatement.printStatement(indent + 2, output);
if (this.elseStatement != null) {
output.append('\n');
printIndent(indent, output);
output.append("else\n"); //$NON-NLS-1$
this.elseStatement.printStatement(indent + 2, output);
}
return output;
}
public void resolve(BlockScope scope) {
TypeBinding type = this.condition.resolveTypeExpecting(scope, TypeBinding.BOOLEAN);
this.condition.computeConversion(scope, type, type);
if (this.thenStatement != null)
this.thenStatement.resolve(scope);
if (this.elseStatement != null)
this.elseStatement.resolve(scope);
}
public void traverse(ASTVisitor visitor, BlockScope blockScope) {
if (visitor.visit(this, blockScope)) {
this.condition.traverse(visitor, blockScope);
if (this.thenStatement != null)
this.thenStatement.traverse(visitor, blockScope);
if (this.elseStatement != null)
this.elseStatement.traverse(visitor, blockScope);
}
visitor.endVisit(this, blockScope);
}
}
