/**
* Verifies that the current state of the local variables array matches the state specified by a
* stack map entry.
*
* @param target the target encapsulating a stack map entry specifying what the current state of
* the local variables array should be
* @param replaceWithTarget if true, then the current state of the local variable array is updated
* to reflect the state recorded in the stack map entry
*/
public void mergeLocals(Target target, boolean replaceWithTarget) {
Klass[] recordedTypes = target.getLocals();
if (recordedTypes.length > localTypes.length) {
throw codeParser.verifyError("size of recorded and derived local variable array differs");
}
/*
* Check the locals
*/
for (int i = 0; i < recordedTypes.length; i++) {
Klass recordedType = recordedTypes[i];
Klass derivedType = localTypes[i];
if (!recordedType.isAssignableFrom(derivedType)) {
/*
* For some reason, the preverifier occasionally generates
* stack map entries for local variables even though the
* local variable is dead. What's more, in these cases,
* it determines that the type resulting from merging an
* object type and an interface type is the interface
* type. This makes no sense to me, but the case must be
* allowed.
*/
if (!recordedType.isInterface() || derivedType.isPrimitive()) {
throw codeParser.verifyError("invalid type in local variable");
}
}
if (replaceWithTarget) {
localTypes[i] = recordedType;
}
}
}
/**
* Verify that a local variable index for a given type is not out of bounds.
*
* @param type the type of the local variable at <code>index</code> in the local variables array
* @param index the index of a local variable
*/
public void verifyLocalVariableIndex(Klass type, int index) {
if (index < 0) {
throw codeParser.verifyError("invalid local variable index");
}
if (type.isDoubleWord()) {
index++;
}
if (index >= localTypes.length) {
throw codeParser.verifyError("invalid local variable index");
}
}
/**
* Get a <code>Local</code> instance to represent a value of a given type that will be
* stored/loaded to/from a given local variable.
*
* @param type the type of the value
* @param index the index of the local variable
* @param isParameter true if the local is a parameter
* @return the variable at index <code>index</code> in which values of type <code>type</code> are
* stored
*/
private Local allocateLocalPrim(Klass type, int index, boolean isParameter) {
Assert.that(localTypes.length < 0xFFFF);
Assert.that(
index >= 0 && index < localTypes.length,
"index=" + index + " localTypes.length=" + localTypes.length);
Klass localType = getLocalTypeFor(type);
int key = localType.getSuiteID();
/* We need a hard partition between uses of a slot as a reference vs. an Address, Offset, or UWord.
* The partitioning of java primitives and objects is accomplished not only by the type passed in here, but
* by the bytecode verifier. We can't be sure that some bytecodes are refering to the same local variable
* as both a reference and as a Squawk primitive. Without that kind of support we are conservative here
* and force a clash whenever javac uses the same local index for a reference and a Squawk primitive.
*/
if (localType.isSquawkPrimitive()) {
key = Klass.REFERENCE.getSuiteID();
}
key = key << 16 | index;
if (localValues == null) {
localValues = new IntHashtable();
}
Local local = (Local) localValues.get(key);
if (local == null) {
local = new Local(localType, index, isParameter);
localValues.put(key, local);
}
/*
* Ensure that the original class file does not use the same local variable
* for both a Squawk primitive value and any other reference value. This prevents the
* translator from having to do a complete liveness analysis to de-multiplex
* such a local variable slot. Such de-multiplexing is required as Squawk primitives
* are 'magically' translated into integers (or longs on a 64 bit system).
*/
if (localType.isSquawkPrimitive() || local.getType().isSquawkPrimitive()) {
if (localType != local.getType()) {
throw codeParser.verifyError(
getBadAddressLocalVariableMessage(index, localType, local.getType()));
}
}
// System.out.println("allocated: "+local+" index "+index);
/// *if[SCOPEDLOCALVARIABLES]*/
codeParser.localVariableAllocated(codeParser.getCurrentIP(), local);
/// *end[SCOPEDLOCALVARIABLES]*/
return local;
}
/**
* Pops a value off the operand stack.
*
* @param type the type that the value popped off the operand stack must be assignable to
* @return the instruction that produced the popped value
*/
public StackProducer pop(Klass type) {
StackProducer producer;
if (type.isDoubleWord()) {
if (sp < 2) {
throw codeParser.verifyError("operand stack underflow");
}
if (!isTopDoubleWord()) {
throw codeParser.verifyError("incompatible type on operand stack " + tosKlassName());
}
sp -= 2;
producer = stack[sp];
} else {
if (sp < 1) {
throw codeParser.verifyError("operand stack underflow");
}
if (isTopDoubleWord()) {
throw codeParser.verifyError("incompatible type on operand stack " + tosKlassName());
}
producer = stack[--sp];
/*
* The primitive one-word, non-float types are all assignment compatible with each other
*/
if (type.isPrimitive() && type != Klass.FLOAT) {
type = Klass.INT;
}
}
Assert.that(producer != null);
/*
* Interfaces are treated as java.lang.Object in the verifier.
*/
if (type.isInterface()) {
type = Klass.OBJECT;
}
/*
* Verify that the instruction is producing the correct type.
*/
if (!type.isAssignableFrom(producer.getType())) {
throw codeParser.verifyError(
"incompatible type: '" + type + "' is not assignable from '" + producer.getType() + "'");
}
return producer;
}
/**
* Emulates loading a value of a given type from a local variable.
*
* @param index the index of the local variable being loaded from
* @param localType the expected type of the variable from which the value is loaded
* @return the variable from which the value is loaded
*/
public Local load(int index, Klass localType) {
verifyLocalVariableIndex(localType, index);
Klass derivedType = localTypes[index];
if (!localType.isAssignableFrom(derivedType)) {
throw codeParser.verifyError("incompatible type in local variable");
}
if (localType.isDoubleWord()) {
Klass secondWordType = Klass.getSecondWordType(localType);
if (!secondWordType.isAssignableFrom(localTypes[index + 1])) {
throw codeParser.verifyError("incompatible type in local variable");
}
}
if (derivedType.isSquawkPrimitive()) {
localType = derivedType;
}
return allocateLocal(localType, index);
}
/**
* Merges the current state of the operand stack into the saved state at a control flow target.
* This method also verifies that the current state of the operand stack matches the expected
* state of the operand stack at the target as pecified by a stack map entry.
*
* @param target the target encapsulting the merged state of the operand stack at a distinct
* address
* @param replaceWithTarget if true, then the current state of the operand stack is updated to
* reflect the state recorded in the stack map entry
*/
public void mergeStack(Target target, boolean replaceWithTarget) {
Klass[] recordedTypes = target.getStack();
/*
* Fail if the map sp is different
*/
if (recordedTypes.length != getStackSize()) {
throw codeParser.verifyError("size of recorded and derived stack differs");
}
/*
* Check the stack items
*/
for (int r = 0, d = 0; r < recordedTypes.length; ++r, ++d) {
Klass recordedType = recordedTypes[r];
Klass derivedType = getStackTypeAt(d);
if (!recordedType.isAssignableFrom(derivedType)) {
// Interfaces are treated like java.lang.Object in the verifier according to the CLDC spec.
if (!recordedType.isInterface() || !Klass.OBJECT.isAssignableFrom(derivedType)) {
throw codeParser.verifyError(
"invalid type on operand stack @ "
+ d
+ ": expected "
+ recordedType
+ ", received "
+ derivedType);
}
}
}
/*
* Merge the instructions on the stack
*/
target.merge(this);
if (replaceWithTarget) {
resetStack(target, false);
}
}
/**
* Pushes a value to the operand stack.
*
* @param producer the instruction producing the value being pushed
*/
public void push(StackProducer producer) {
Klass type = producer.getType();
Assert.that(type != Klass.VOID);
/*
* Check for overflow and push the producer.
*/
if (sp == maxStack) {
throw codeParser.verifyError("operand stack overflow");
}
stack[sp++] = producer;
/*
* For long and double check for overflow and then add a null word to the stack.
*/
if (type.isDoubleWord()) {
if (sp == maxStack) {
throw codeParser.verifyError("operand stack overflow");
}
stack[sp++] = null;
}
}
/**
* Creates and returns the detailed error message when a local variable is used as a Squawk
* primitive as well as some value not of exactly the same type. The message includes information
* derived from the LocalVariableTable attribute so that the source code can be easily changed.
*
* @param index the local variable index that is (mis)used
* @return the detailed error message
*/
private String getBadAddressLocalVariableMessage(int index, Klass type1, Klass type2) {
Assert.that(type1.isSquawkPrimitive() || type2.isSquawkPrimitive());
if (type2.isSquawkPrimitive()) {
Klass otherType = type1;
type1 = type2;
type2 = otherType;
}
StringBuffer buf =
new StringBuffer(
"Stack location "
+ index
+ " cannot be used for both a local variable of type "
+ type1.getName()
+ " and of type "
+ type2.getName()
+ ". Try moving the variable of type "
+ type1.getName()
+ " to the top-most scope of the method.");
Enumeration e = codeParser.getLocalVariableTableEntries();
if (e != null) {
buf.append(" (source code usage: ");
while (e.hasMoreElements()) {
LocalVariableTableEntry entry = (LocalVariableTableEntry) e.nextElement();
if (entry.getIndex() == index) {
int start = codeParser.getSourceLineNumber(entry.getStart().getBytecodeOffset());
int end = codeParser.getSourceLineNumber(entry.getEnd().getBytecodeOffset());
buf.append(entry.getType().getName())
.append(' ')
.append(entry.getName())
.append(" from line ")
.append(start)
.append(" to line ")
.append(end)
.append(';');
}
}
}
return buf.toString();
}
/**
* Tests two given types to ensure that they are both {@link Klass#isSquawkPrimitive() Squawk
* primitives} or both not Squawk primitives. If they are both Squawk primitives, then they must
* be exactly the same type. This enforces the constraint that Squawk primitive values cannot be
* assigned to or compared with any other type.
*
* @param type1 the first type to compare
* @param type2 the second type to compare
*/
public void verifyUseOfSquawkPrimitive(Klass type1, Klass type2) {
if (type1.isSquawkPrimitive() || type2.isSquawkPrimitive()) {
if (type1 != type2) {
// Offsets are implemented as Words
// if (type1.getClassID() + type2.getClassID() != CID.UWORD + CID.OFFSET) {
String type = type1.getName();
throw codeParser.verifyError(
type
+ " values can only be written to or compared with other "
+ type
+ " values, not with "
+ type2.getName());
// }
}
}
}
/**
* Traces the frame state at the current verification address.
*
* @param opcode the opcode of the instruction at <code>address</code>
* @param address the current verification address
*/
public void traceFrameState(int opcode, int address) {
/*
* Trace the recorded and derived types
*/
if (Translator.TRACING_ENABLED) {
Target target = null;
try {
target = codeParser.getTarget(address);
} catch (NoClassDefFoundError e) {
/* Just means there is no stack map at this address */
}
Tracer.traceln("Frame state @ " + address + " [ " + Opcode.mnemonics[opcode] + " ]");
traceLocals(target);
traceStack(target);
}
}
/**
* Resets the max stack limit back to the value specified in the class file for the current
* method.
*/
public void resetMaxStack() {
maxStack = codeParser.getMaxStack();
}
/**
* Creates a Frame instance to emulate and verify the execution of a single class file method.
*
* @param codeParser the parser used to parse the "Code" attribute of the method being emulated
* @param extraLocals the number of extra local variables needed
*/
public Frame(CodeParser codeParser, int extraLocals) {
this.maxStack = codeParser.getMaxStack();
this.codeParser = codeParser;
/*
* Initialize the operand stack
*/
stack = new StackProducer[maxStack];
/*
* Initialize the types in the local variables
*/
localTypes = new Klass[codeParser.getMaxLocals() + extraLocals];
Method method = codeParser.getMethod();
Klass[] parameterTypes = method.getParameterTypes();
Local[] parameterLocals = null;
if (Translator.REVERSE_PARAMETERS && method.isInterpreterInvoked()) {
parameterLocals = new Local[parameterTypes.length];
}
int javacIndex = 0;
/*
* Initialize 'this' in non-static methods. The type of 'this' is
* UNINITIALIZED_THIS if this method is a constructor in any class
* except java.lang.Object otherwise it is the class in which the
* method was defined.
*/
if (!method.isStatic() || method.isConstructor()) {
Assert.that(parameterLocals == null);
Klass thisType = method.getDefiningClass();
if (method.isConstructor() && thisType != Klass.OBJECT) {
thisType = Klass.UNINITIALIZED_THIS;
}
Local thisLocal = allocateParameter(thisType, javacIndex);
store(javacIndex, thisType, thisLocal);
javacIndex++;
}
/*
* Initialize locals for the parameters.
*/
int parameterIndex = javacIndex;
for (int i = 0; i < parameterTypes.length; i++) {
Klass parameterType = parameterTypes[i];
Local parameterLocal = allocateParameter(parameterType, javacIndex);
if (parameterLocals != null) {
parameterLocals[i] = parameterLocal;
}
if (Klass.SQUAWK_64) {
if (javacIndex != parameterIndex) {
Assert.that(parameterIndex < javacIndex);
parameterLocal.setParameterIndex(parameterIndex);
}
parameterIndex++;
}
store(javacIndex, parameterType, parameterLocal);
javacIndex += (parameterType.isDoubleWord() ? 2 : 1);
}
parameterLocalsCount = javacIndex;
/*
* Adjust the parameter offsets for parameter order reversal.
*/
if (parameterLocals != null) {
parameterIndex = 0;
for (int i = parameterTypes.length - 1; i >= 0; i--) {
Klass parameterType = parameterTypes[i];
parameterLocals[i].setParameterIndex(parameterIndex++);
if (!Klass.SQUAWK_64 && parameterType.isDoubleWord()) {
parameterIndex++;
}
}
}
/*
* Initialize the remaining local variables to the TOP type
*/
while (javacIndex < localTypes.length) {
localTypes[javacIndex++] = Klass.TOP;
}
}
