/**
* Write the local variable table. The necessary constants have already been added to the constant
* table by the collect() method. The flowFields method is used to determine which variables are
* alive at each pc.
*/
public void writeLocalVariableTable(
Environment env, MemberDefinition field, DataOutputStream out, ConstantPool tab)
throws IOException {
MemberDefinition locals[] = new MemberDefinition[maxvar];
int i = 0;
// Initialize arguments
if ((field != null) && (field.getArguments() != null)) {
int reg = 0;
Vector v = field.getArguments();
for (Enumeration e = v.elements(); e.hasMoreElements(); ) {
MemberDefinition f = ((MemberDefinition) e.nextElement());
locals[reg] = f;
reg += f.getType().stackSize();
}
}
flowFields(env, first, locals);
LocalVariableTable lvtab = new LocalVariableTable();
// Initialize arguments again
for (i = 0; i < maxvar; i++) locals[i] = null;
if ((field != null) && (field.getArguments() != null)) {
int reg = 0;
Vector v = field.getArguments();
for (Enumeration e = v.elements(); e.hasMoreElements(); ) {
MemberDefinition f = ((MemberDefinition) e.nextElement());
locals[reg] = f;
lvtab.define(f, reg, 0, maxpc);
reg += f.getType().stackSize();
}
}
int pcs[] = new int[maxvar];
for (Instruction inst = first; inst != null; inst = inst.next) {
switch (inst.opc) {
case opc_istore:
case opc_istore_0:
case opc_istore_1:
case opc_istore_2:
case opc_istore_3:
case opc_fstore:
case opc_fstore_0:
case opc_fstore_1:
case opc_fstore_2:
case opc_fstore_3:
case opc_astore:
case opc_astore_0:
case opc_astore_1:
case opc_astore_2:
case opc_astore_3:
case opc_lstore:
case opc_lstore_0:
case opc_lstore_1:
case opc_lstore_2:
case opc_lstore_3:
case opc_dstore:
case opc_dstore_0:
case opc_dstore_1:
case opc_dstore_2:
case opc_dstore_3:
if (inst.value instanceof LocalVariable) {
LocalVariable v = (LocalVariable) inst.value;
int pc = (inst.next != null) ? inst.next.pc : inst.pc;
if (locals[v.slot] != null) {
lvtab.define(locals[v.slot], v.slot, pcs[v.slot], pc);
}
pcs[v.slot] = pc;
locals[v.slot] = v.field;
}
break;
case opc_label:
{
// flush previous labels
for (i = 0; i < maxvar; i++) {
if (locals[i] != null) {
lvtab.define(locals[i], i, pcs[i], inst.pc);
}
}
// init new labels
int pc = inst.pc;
MemberDefinition[] labelLocals = ((Label) inst).locals;
if (labelLocals == null) { // unreachable code??
for (i = 0; i < maxvar; i++) locals[i] = null;
} else {
System.arraycopy(labelLocals, 0, locals, 0, maxvar);
}
for (i = 0; i < maxvar; i++) {
pcs[i] = pc;
}
break;
}
}
}
// flush remaining labels
for (i = 0; i < maxvar; i++) {
if (locals[i] != null) {
lvtab.define(locals[i], i, pcs[i], maxpc);
}
}
// write the local variable table
lvtab.write(env, out, tab);
}
/**
* Figure out when registers contain a legal value. This is done using a simple data flow
* algorithm. This information is later used to generate the local variable table.
*/
void flowFields(Environment env, Label lbl, MemberDefinition locals[]) {
if (lbl.locals != null) {
// Been here before. Erase any conflicts.
MemberDefinition f[] = lbl.locals;
for (int i = 0; i < maxvar; i++) {
if (f[i] != locals[i]) {
f[i] = null;
}
}
return;
}
// Remember the set of active registers at this point
lbl.locals = new MemberDefinition[maxvar];
System.arraycopy(locals, 0, lbl.locals, 0, maxvar);
MemberDefinition newlocals[] = new MemberDefinition[maxvar];
System.arraycopy(locals, 0, newlocals, 0, maxvar);
locals = newlocals;
for (Instruction inst = lbl.next; inst != null; inst = inst.next) {
switch (inst.opc) {
case opc_istore:
case opc_istore_0:
case opc_istore_1:
case opc_istore_2:
case opc_istore_3:
case opc_fstore:
case opc_fstore_0:
case opc_fstore_1:
case opc_fstore_2:
case opc_fstore_3:
case opc_astore:
case opc_astore_0:
case opc_astore_1:
case opc_astore_2:
case opc_astore_3:
case opc_lstore:
case opc_lstore_0:
case opc_lstore_1:
case opc_lstore_2:
case opc_lstore_3:
case opc_dstore:
case opc_dstore_0:
case opc_dstore_1:
case opc_dstore_2:
case opc_dstore_3:
if (inst.value instanceof LocalVariable) {
LocalVariable v = (LocalVariable) inst.value;
locals[v.slot] = v.field;
}
break;
case opc_label:
flowFields(env, (Label) inst, locals);
return;
case opc_ifeq:
case opc_ifne:
case opc_ifgt:
case opc_ifge:
case opc_iflt:
case opc_ifle:
case opc_if_icmpeq:
case opc_if_icmpne:
case opc_if_icmpgt:
case opc_if_icmpge:
case opc_if_icmplt:
case opc_if_icmple:
case opc_if_acmpeq:
case opc_if_acmpne:
case opc_ifnull:
case opc_ifnonnull:
case opc_jsr:
flowFields(env, (Label) inst.value, locals);
break;
case opc_goto:
flowFields(env, (Label) inst.value, locals);
return;
case opc_return:
case opc_ireturn:
case opc_lreturn:
case opc_freturn:
case opc_dreturn:
case opc_areturn:
case opc_athrow:
case opc_ret:
return;
case opc_tableswitch:
case opc_lookupswitch:
{
SwitchData sw = (SwitchData) inst.value;
flowFields(env, sw.defaultLabel, locals);
for (Enumeration e = sw.tab.elements(); e.hasMoreElements(); ) {
flowFields(env, (Label) e.nextElement(), locals);
}
return;
}
case opc_try:
{
Vector catches = ((TryData) inst.value).catches;
for (Enumeration e = catches.elements(); e.hasMoreElements(); ) {
CatchData cd = (CatchData) e.nextElement();
flowFields(env, cd.getLabel(), locals);
}
break;
}
}
}
}
