/**
* 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;
}
