/**
* Analyzes the given method.
*
* @param owner the internal name of the class to which the method belongs.
* @param m the method to be analyzed.
* @return the symbolic state of the execution stack frame at each bytecode instruction of the
* method. The size of the returned array is equal to the number of instructions (and labels)
* of the method. A given frame is <tt>null</tt> if and only if the corresponding instruction
* cannot be reached (dead code).
* @throws AnalyzerException if a problem occurs during the analysis.
*/
public Frame[] analyze(final String owner, final MethodNode m) throws AnalyzerException {
if ((m.access & (ACC_ABSTRACT | ACC_NATIVE)) != 0) {
frames = new Frame[0];
return frames;
}
n = m.instructions.size();
insns = m.instructions;
handlers = new List[n];
frames = new Frame[n];
subroutines = new Subroutine[n];
queued = new boolean[n];
queue = new int[n];
top = 0;
// computes exception handlers for each instruction
for (int i = 0; i < m.tryCatchBlocks.size(); ++i) {
TryCatchBlockNode tcb = (TryCatchBlockNode) m.tryCatchBlocks.get(i);
int begin = insns.indexOf(tcb.start);
int end = insns.indexOf(tcb.end);
for (int j = begin; j < end; ++j) {
List insnHandlers = handlers[j];
if (insnHandlers == null) {
insnHandlers = new ArrayList();
handlers[j] = insnHandlers;
}
insnHandlers.add(tcb);
}
}
// computes the subroutine for each instruction:
Subroutine main = new Subroutine(null, m.maxLocals, null);
List subroutineCalls = new ArrayList();
Map subroutineHeads = new HashMap();
findSubroutine(0, main, subroutineCalls);
while (!subroutineCalls.isEmpty()) {
JumpInsnNode jsr = (JumpInsnNode) subroutineCalls.remove(0);
Subroutine sub = (Subroutine) subroutineHeads.get(jsr.label);
if (sub == null) {
sub = new Subroutine(jsr.label, m.maxLocals, jsr);
subroutineHeads.put(jsr.label, sub);
findSubroutine(insns.indexOf(jsr.label), sub, subroutineCalls);
} else {
sub.callers.add(jsr);
}
}
for (int i = 0; i < n; ++i) {
if (subroutines[i] != null && subroutines[i].start == null) {
subroutines[i] = null;
}
}
// initializes the data structures for the control flow analysis
Frame current = newFrame(m.maxLocals, m.maxStack);
Frame handler = newFrame(m.maxLocals, m.maxStack);
Type[] args = Type.getArgumentTypes(m.desc);
int local = 0;
if ((m.access & ACC_STATIC) == 0) {
Type ctype = Type.getObjectType(owner);
current.setLocal(local++, interpreter.newValue(ctype));
}
for (int i = 0; i < args.length; ++i) {
current.setLocal(local++, interpreter.newValue(args[i]));
if (args[i].getSize() == 2) {
current.setLocal(local++, interpreter.newValue(null));
}
}
while (local < m.maxLocals) {
current.setLocal(local++, interpreter.newValue(null));
}
merge(0, current, null);
// control flow analysis
while (top > 0) {
int insn = queue[--top];
Frame f = frames[insn];
Subroutine subroutine = subroutines[insn];
queued[insn] = false;
try {
AbstractInsnNode insnNode = m.instructions.get(insn);
int insnOpcode = insnNode.getOpcode();
int insnType = insnNode.getType();
if (insnType == AbstractInsnNode.LABEL
|| insnType == AbstractInsnNode.LINE
|| insnType == AbstractInsnNode.FRAME) {
merge(insn + 1, f, subroutine);
newControlFlowEdge(insn, insn + 1);
} else {
current.init(f).execute(insnNode, interpreter);
subroutine = subroutine == null ? null : subroutine.copy();
if (insnNode instanceof JumpInsnNode) {
JumpInsnNode j = (JumpInsnNode) insnNode;
if (insnOpcode != GOTO && insnOpcode != JSR) {
merge(insn + 1, current, subroutine);
newControlFlowEdge(insn, insn + 1);
}
int jump = insns.indexOf(j.label);
if (insnOpcode == JSR) {
merge(jump, current, new Subroutine(j.label, m.maxLocals, j));
} else {
merge(jump, current, subroutine);
}
newControlFlowEdge(insn, jump);
} else if (insnNode instanceof LookupSwitchInsnNode) {
LookupSwitchInsnNode lsi = (LookupSwitchInsnNode) insnNode;
int jump = insns.indexOf(lsi.dflt);
merge(jump, current, subroutine);
newControlFlowEdge(insn, jump);
for (int j = 0; j < lsi.labels.size(); ++j) {
LabelNode label = (LabelNode) lsi.labels.get(j);
jump = insns.indexOf(label);
merge(jump, current, subroutine);
newControlFlowEdge(insn, jump);
}
} else if (insnNode instanceof TableSwitchInsnNode) {
TableSwitchInsnNode tsi = (TableSwitchInsnNode) insnNode;
int jump = insns.indexOf(tsi.dflt);
merge(jump, current, subroutine);
newControlFlowEdge(insn, jump);
for (int j = 0; j < tsi.labels.size(); ++j) {
LabelNode label = (LabelNode) tsi.labels.get(j);
jump = insns.indexOf(label);
merge(jump, current, subroutine);
newControlFlowEdge(insn, jump);
}
} else if (insnOpcode == RET) {
if (subroutine == null) {
throw new AnalyzerException("RET instruction outside of a sub routine");
}
for (int i = 0; i < subroutine.callers.size(); ++i) {
Object caller = subroutine.callers.get(i);
int call = insns.indexOf((AbstractInsnNode) caller);
if (frames[call] != null) {
merge(call + 1, frames[call], current, subroutines[call], subroutine.access);
newControlFlowEdge(insn, call + 1);
}
}
} else if (insnOpcode != ATHROW && (insnOpcode < IRETURN || insnOpcode > RETURN)) {
if (subroutine != null) {
if (insnNode instanceof VarInsnNode) {
int var = ((VarInsnNode) insnNode).var;
subroutine.access[var] = true;
if (insnOpcode == LLOAD
|| insnOpcode == DLOAD
|| insnOpcode == LSTORE
|| insnOpcode == DSTORE) {
subroutine.access[var + 1] = true;
}
} else if (insnNode instanceof IincInsnNode) {
int var = ((IincInsnNode) insnNode).var;
subroutine.access[var] = true;
}
}
merge(insn + 1, current, subroutine);
newControlFlowEdge(insn, insn + 1);
}
}
List insnHandlers = handlers[insn];
if (insnHandlers != null) {
for (int i = 0; i < insnHandlers.size(); ++i) {
TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
Type type;
if (tcb.type == null) {
type = Type.getObjectType("java/lang/Throwable");
} else {
type = Type.getObjectType(tcb.type);
}
int jump = insns.indexOf(tcb.handler);
if (newControlFlowExceptionEdge(insn, jump)) {
handler.init(f);
handler.clearStack();
handler.push(interpreter.newValue(type));
merge(jump, handler, subroutine);
}
}
}
} catch (AnalyzerException e) {
throw new AnalyzerException("Error at instruction " + insn + ": " + e.getMessage(), e);
} catch (Exception e) {
throw new AnalyzerException("Error at instruction " + insn + ": " + e.getMessage(), e);
}
}
return frames;
}
private void findSubroutine(int insn, final Subroutine sub, final List calls)
throws AnalyzerException {
while (true) {
if (insn < 0 || insn >= n) {
throw new AnalyzerException("Execution can fall off end of the code");
}
if (subroutines[insn] != null) {
return;
}
subroutines[insn] = sub.copy();
AbstractInsnNode node = insns.get(insn);
// calls findSubroutine recursively on normal successors
if (node instanceof JumpInsnNode) {
if (node.getOpcode() == JSR) {
// do not follow a JSR, it leads to another subroutine!
calls.add(node);
} else {
JumpInsnNode jnode = (JumpInsnNode) node;
findSubroutine(insns.indexOf(jnode.label), sub, calls);
}
} else if (node instanceof TableSwitchInsnNode) {
TableSwitchInsnNode tsnode = (TableSwitchInsnNode) node;
findSubroutine(insns.indexOf(tsnode.dflt), sub, calls);
for (int i = tsnode.labels.size() - 1; i >= 0; --i) {
LabelNode l = (LabelNode) tsnode.labels.get(i);
findSubroutine(insns.indexOf(l), sub, calls);
}
} else if (node instanceof LookupSwitchInsnNode) {
LookupSwitchInsnNode lsnode = (LookupSwitchInsnNode) node;
findSubroutine(insns.indexOf(lsnode.dflt), sub, calls);
for (int i = lsnode.labels.size() - 1; i >= 0; --i) {
LabelNode l = (LabelNode) lsnode.labels.get(i);
findSubroutine(insns.indexOf(l), sub, calls);
}
}
// calls findSubroutine recursively on exception handler successors
List insnHandlers = handlers[insn];
if (insnHandlers != null) {
for (int i = 0; i < insnHandlers.size(); ++i) {
TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
findSubroutine(insns.indexOf(tcb.handler), sub, calls);
}
}
// if insn does not falls through to the next instruction, return.
switch (node.getOpcode()) {
case GOTO:
case RET:
case TABLESWITCH:
case LOOKUPSWITCH:
case IRETURN:
case LRETURN:
case FRETURN:
case DRETURN:
case ARETURN:
case RETURN:
case ATHROW:
return;
}
insn++;
}
}