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