/**
* 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");
}
}
/**
* 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;
}
}
/**
* 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;
}
/**
* 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());
// }
}
}
}