/** Marks the code starting at the given offset. */
private void markCode(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset) {
boolean oldNext = next;
byte[] code = codeAttribute.code;
// Continue with the current instruction as long as we haven't marked it
// yet.
while (!isReachable[offset]) {
// Get the current instruction.
Instruction instruction = InstructionFactory.create(code, offset);
// Mark it as reachable.
isReachable[offset] = true;
// By default, we'll assume we can continue with the next
// instruction in a moment.
next = true;
// Mark the branch targets, if any.
instruction.accept(clazz, method, codeAttribute, offset, this);
// Can we really continue with the next instruction?
if (!next) {
break;
}
// Go to the next instruction.
offset += instruction.length(offset);
}
next = oldNext;
}
public void visitExceptionInfo(
Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo) {
int startPC = Math.max(exceptionInfo.u2startPC, clipStart);
int endPC = Math.min(exceptionInfo.u2endPC, clipEnd);
int handlerPC = exceptionInfo.u2handlerPC;
int catchType = exceptionInfo.u2catchType;
// Exclude any subroutine invocations that jump out of the try block,
// by adding a try block before (and later on, after) each invocation.
for (int offset = startPC; offset < endPC; offset++) {
if (branchTargetFinder.isSubroutineInvocation(offset)) {
Instruction instruction = InstructionFactory.create(codeAttribute.code, offset);
int instructionLength = instruction.length(offset);
// Is it a subroutine invocation?
if (!exceptionInfo.isApplicable(offset + ((BranchInstruction) instruction).branchOffset)) {
if (DEBUG) {
System.out.println(
" Appending extra exception [" + startPC + " -> " + offset + "] -> " + handlerPC);
}
// Append a try block that ends before the subroutine invocation.
codeAttributeComposer.appendException(
new ExceptionInfo(startPC, offset, handlerPC, catchType));
// The next try block will start after the subroutine invocation.
startPC = offset + instructionLength;
}
}
}
if (DEBUG) {
System.out.println(
" Appending exception [" + startPC + " -> " + endPC + "] -> " + handlerPC);
}
// Append the exception. Note that exceptions with empty try blocks
// are automatically ignored.
codeAttributeComposer.appendException(new ExceptionInfo(startPC, endPC, handlerPC, catchType));
}
public void visitBranchInstruction(
Clazz clazz,
Method method,
CodeAttribute codeAttribute,
int offset,
BranchInstruction branchInstruction) {
// Check if the instruction is an unconditional goto instruction.
byte opcode = branchInstruction.opcode;
if (opcode == InstructionConstants.OP_GOTO || opcode == InstructionConstants.OP_GOTO_W) {
// Check if the goto instruction points to another simple goto
// instruction.
int branchOffset = branchInstruction.branchOffset;
int targetOffset = offset + branchOffset;
if (branchOffset != branchInstruction.length(offset)
&& !codeAttributeEditor.isModified(offset)
&& !codeAttributeEditor.isModified(targetOffset)) {
Instruction targetInstruction = InstructionFactory.create(codeAttribute.code, targetOffset);
if (targetInstruction.opcode == InstructionConstants.OP_GOTO) {
// Simplify the goto instruction.
int targetBranchOffset = ((BranchInstruction) targetInstruction).branchOffset;
Instruction newBranchInstruction =
new BranchInstruction(opcode, (branchOffset + targetBranchOffset));
codeAttributeEditor.replaceInstruction(offset, newBranchInstruction);
// Visit the instruction, if required.
if (extraInstructionVisitor != null) {
extraInstructionVisitor.visitBranchInstruction(
clazz, method, codeAttribute, offset, branchInstruction);
}
}
}
}
}
/**
* Evaluates a block of instructions that hasn't been handled before, starting at the given offset
* and ending at a branch instruction, a return instruction, or a throw instruction. Branch
* instructions are handled recursively.
*/
private void evaluateInstructionBlock(
Clazz clazz, Method method, CodeAttribute codeAttribute, int instructionOffset) {
if (DEBUG) {
if (evaluated[instructionOffset]) {
System.out.println("-- (instruction block at " + instructionOffset + " already evaluated)");
} else {
System.out.println("-- instruction block:");
}
}
// Remember the initial stack size.
int initialStackSize = stackSize;
// Remember the maximum stack size.
if (maxStackSize < stackSize) {
maxStackSize = stackSize;
}
// Evaluate any instructions that haven't been evaluated before.
while (!evaluated[instructionOffset]) {
// Mark the instruction as evaluated.
evaluated[instructionOffset] = true;
Instruction instruction = InstructionFactory.create(codeAttribute.code, instructionOffset);
if (DEBUG) {
int stackPushCount = instruction.stackPushCount(clazz);
int stackPopCount = instruction.stackPopCount(clazz);
System.out.println(
"["
+ instructionOffset
+ "]: "
+ stackSize
+ " - "
+ stackPopCount
+ " + "
+ stackPushCount
+ " = "
+ (stackSize + stackPushCount - stackPopCount)
+ ": "
+ instruction.toString(instructionOffset));
}
// Compute the instruction's effect on the stack size.
stackSize -= instruction.stackPopCount(clazz);
if (stackSize < 0) {
throw new IllegalArgumentException(
"Stack size becomes negative after instruction "
+ instruction.toString(instructionOffset)
+ " in ["
+ clazz.getName()
+ "."
+ method.getName(clazz)
+ method.getDescriptor(clazz)
+ "]");
}
stackSizes[instructionOffset] = stackSize += instruction.stackPushCount(clazz);
// Remember the maximum stack size.
if (maxStackSize < stackSize) {
maxStackSize = stackSize;
}
// Remember the next instruction offset.
int nextInstructionOffset = instructionOffset + instruction.length(instructionOffset);
// Visit the instruction, in order to handle branches.
instruction.accept(clazz, method, codeAttribute, instructionOffset, this);
// Stop evaluating after a branch.
if (exitInstructionBlock) {
break;
}
// Continue with the next instruction.
instructionOffset = nextInstructionOffset;
if (DEBUG) {
if (evaluated[instructionOffset]) {
System.out.println("-- (instruction at " + instructionOffset + " already evaluated)");
}
}
}
// Restore the stack size for possible subsequent instruction blocks.
this.stackSize = initialStackSize;
}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {
// DEBUG =
// clazz.getName().equals("abc/Def") &&
// method.getName(clazz).equals("abc");
if (DEBUG) {
method.accept(clazz, new ClassPrinter());
}
branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute);
// Don't bother if there aren't any subroutines anyway.
if (!containsSubroutines(codeAttribute)) {
return;
}
if (DEBUG) {
System.out.println(
"SubroutineInliner: processing ["
+ clazz.getName()
+ "."
+ method.getName(clazz)
+ method.getDescriptor(clazz)
+ "]");
}
// Append the body of the code.
codeAttributeComposer.reset();
codeAttributeComposer.beginCodeFragment(codeAttribute.u4codeLength);
// Copy the non-subroutine instructions.
int offset = 0;
while (offset < codeAttribute.u4codeLength) {
Instruction instruction = InstructionFactory.create(codeAttribute.code, offset);
int instructionLength = instruction.length(offset);
// Is this returning subroutine?
if (branchTargetFinder.isSubroutine(offset)
&& branchTargetFinder.isSubroutineReturning(offset)) {
// Skip the subroutine.
if (DEBUG) {
System.out.println(
" Skipping original subroutine instruction " + instruction.toString(offset));
}
// Append a label at this offset instead.
codeAttributeComposer.appendLabel(offset);
} else {
// Copy the instruction, inlining any subroutine call recursively.
instruction.accept(clazz, method, codeAttribute, offset, this);
}
offset += instructionLength;
}
// Copy the exceptions. Note that exceptions with empty try blocks
// are automatically removed.
codeAttribute.exceptionsAccept(clazz, method, subroutineExceptionInliner);
if (DEBUG) {
System.out.println(" Appending label after code at [" + offset + "]");
}
// Append a label just after the code.
codeAttributeComposer.appendLabel(codeAttribute.u4codeLength);
// End and update the code attribute.
codeAttributeComposer.endCodeFragment();
codeAttributeComposer.visitCodeAttribute(clazz, method, codeAttribute);
if (DEBUG) {
method.accept(clazz, new ClassPrinter());
}
}