/*******************************************************************************
* Copyright (c) 2002 - 2006 IBM Corporation.
* 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 com.ibm.wala.ssa;
import java.util.Collection;
import java.util.Collections;
import com.ibm.wala.types.TypeReference;
/**
* An instruction in SSA form.
*/
public abstract class SSAInstruction {
public static final int NO_INDEX = -1;
public final int iindex;
/**
* prevent instantiation by the outside
*/
protected SSAInstruction(int iindex) {
this.iindex = iindex;
}
/**
* This method is meant to be used during SSA conversion for an IR that is not in SSA form. It creates a new SSAInstruction of the
* same type as the receiver, with a combination of the receiver's uses and defs and those from the method parameters.
*
* In particular, if the 'defs' parameter is null, then the new instruction has the same defs as the receiver. If 'defs' is not
* null, it must be an array with a size equal to the number of defs that the receiver instruction has. In this case, the new
* instruction has defs taken from the array. The uses of the new instruction work in the same way with the 'uses' parameter.
*
* Note that this only applies to CAst-based IR translation, since Java bytecode-based IR generation uses a different SSA
* construction mechanism.
*
* TODO: move this into the SSAInstructionFactory
*/
public abstract SSAInstruction copyForSSA(SSAInstructionFactory insts, int[] defs, int[] uses);
public abstract String toString(SymbolTable symbolTable);
@Override
public String toString() {
return toString(null);
}
protected String getValueString(SymbolTable symbolTable, int valueNumber) {
if (symbolTable == null) {
return Integer.toString(valueNumber);
} else {
return symbolTable.getValueString(valueNumber);
}
}
/**
* Apply an IVisitor to this instruction. We invoke the appropriate IVisitor method according to the type of this instruction.
*/
public abstract void visit(IVisitor v);
/**
* This interface is used by Instruction.visit to dispatch based on the instruction type.
*/
public static interface IVisitor {
void visitGoto(SSAGotoInstruction instruction);
void visitArrayLoad(SSAArrayLoadInstruction instruction);
void visitArrayStore(SSAArrayStoreInstruction instruction);
void visitBinaryOp(SSABinaryOpInstruction instruction);
void visitUnaryOp(SSAUnaryOpInstruction instruction);
void visitConversion(SSAConversionInstruction instruction);
void visitComparison(SSAComparisonInstruction instruction);
void visitConditionalBranch(SSAConditionalBranchInstruction instruction);
void visitSwitch(SSASwitchInstruction instruction);
void visitReturn(SSAReturnInstruction instruction);
void visitGet(SSAGetInstruction instruction);
void visitPut(SSAPutInstruction instruction);
void visitInvoke(SSAInvokeInstruction instruction);
void visitNew(SSANewInstruction instruction);
void visitArrayLength(SSAArrayLengthInstruction instruction);
void visitThrow(SSAThrowInstruction instruction);
void visitMonitor(SSAMonitorInstruction instruction);
void visitCheckCast(SSACheckCastInstruction instruction);
void visitInstanceof(SSAInstanceofInstruction instruction);
void visitPhi(SSAPhiInstruction instruction);
void visitPi(SSAPiInstruction instruction);
void visitGetCaughtException(SSAGetCaughtExceptionInstruction instruction);
void visitLoadMetadata(SSALoadMetadataInstruction instruction);
}
/**
* A base visitor implementation that does nothing.
*/
public static abstract class Visitor implements IVisitor {
@Override
public void visitGoto(SSAGotoInstruction instruction) {
}
@Override
public void visitArrayLoad(SSAArrayLoadInstruction instruction) {
}
@Override
public void visitArrayStore(SSAArrayStoreInstruction instruction) {
}
@Override
public void visitBinaryOp(SSABinaryOpInstruction instruction) {
}
@Override
public void visitUnaryOp(SSAUnaryOpInstruction instruction) {
}
@Override
public void visitConversion(SSAConversionInstruction instruction) {
}
@Override
public void visitComparison(SSAComparisonInstruction instruction) {
}
@Override
public void visitConditionalBranch(SSAConditionalBranchInstruction instruction) {
}
@Override
public void visitSwitch(SSASwitchInstruction instruction) {
}
@Override
public void visitReturn(SSAReturnInstruction instruction) {
}
@Override
public void visitGet(SSAGetInstruction instruction) {
}
@Override
public void visitPut(SSAPutInstruction instruction) {
}
@Override
public void visitInvoke(SSAInvokeInstruction instruction) {
}
@Override
public void visitNew(SSANewInstruction instruction) {
}
@Override
public void visitArrayLength(SSAArrayLengthInstruction instruction) {
}
@Override
public void visitThrow(SSAThrowInstruction instruction) {
}
@Override
public void visitMonitor(SSAMonitorInstruction instruction) {
}
@Override
public void visitCheckCast(SSACheckCastInstruction instruction) {
}
@Override
public void visitInstanceof(SSAInstanceofInstruction instruction) {
}
@Override
public void visitPhi(SSAPhiInstruction instruction) {
}
@Override
public void visitPi(SSAPiInstruction instruction) {
}
@Override
public void visitGetCaughtException(SSAGetCaughtExceptionInstruction instruction) {
}
@Override
public void visitLoadMetadata(SSALoadMetadataInstruction instruction) {
}
}
/**
* Does this instruction define a normal value, as distinct from a set of exceptions possibly thrown by it (e.g. for invoke
* instructions).
*
* @return true if the instruction does define a proper value.
*/
public boolean hasDef() {
return false;
}
public int getDef() {
return -1;
}
/**
* Return the ith def
*
* @param i number of the def, starting at 0.
*/
public int getDef(int i) {
return -1;
}
public int getNumberOfDefs() {
return 0;
}
public int getNumberOfUses() {
return 0;
}
/**
* @return value number representing the jth use in this instruction. -1 means TOP (i.e., the value doesn't matter)
*/
public int getUse(int j) throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
@Override
public abstract int hashCode();
/**
* @return true iff this instruction may throw an exception.
*/
public boolean isPEI() {
return false;
}
/**
* This method should never return null.
*
* @return the set of exception types that an instruction might throw ... disregarding athrows and invokes.
*/
public Collection<TypeReference> getExceptionTypes() {
assert !isPEI();
return Collections.emptySet();
}
/**
* @return true iff this instruction may fall through to the next
*/
public abstract boolean isFallThrough();
/**
* We assume these instructions are canonical and managed by a governing IR object. Be careful.
*
* Depending on the caching policy (see {@link com.ibm.wala.ssa.SSACache}), the governing IR may be deleted
* to reclaim memory and recomputed as needed. When an IR is recomputed, it also creates fresh SSAInstruction
* objects that will not equal old ones. Thus, do not compare for identity SSAInstructions obtained from
* distinct calls that retrieve cached values (e.g. distinct CGNode.getIR() calls).
* See <a href="https://github.com/wala/WALA/issues/6"> the github issue </a> for details.
*
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public final boolean equals(Object obj) {
if (this == obj)
return true;
if (obj != null && obj instanceof SSAInstruction)
return this.iindex == ((SSAInstruction) obj).iindex;
else
return false;
}
}