public void visitBranchInstruction(
Clazz clazz,
Method method,
CodeAttribute codeAttribute,
int offset,
BranchInstruction branchInstruction) {
byte opcode = branchInstruction.opcode;
// Evaluate the target instruction blocks.
evaluateInstructionBlock(clazz, method, codeAttribute, offset + branchInstruction.branchOffset);
// Evaluate the instructions after a subroutine branch.
if (opcode == InstructionConstants.OP_JSR || opcode == InstructionConstants.OP_JSR_W) {
// We assume subroutine calls (jsr and jsr_w instructions) don't
// change the stack, other than popping the return value.
stackSize -= 1;
evaluateInstructionBlock(
clazz, method, codeAttribute, offset + branchInstruction.length(offset));
}
// Some branch instructions always end the current instruction block.
exitInstructionBlock =
opcode == InstructionConstants.OP_GOTO
|| opcode == InstructionConstants.OP_GOTO_W
|| opcode == InstructionConstants.OP_JSR
|| opcode == InstructionConstants.OP_JSR_W;
}
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);
}
}
}
}
}
