/**
* Helper method to perform optimizations around jumps when we get a labeling operation. Shared
* with labelNext and labelCurrent methods
*
* @param l the Label object passed into the label operation
* @param kind what kind of labeling operation are we doing (labelNext or labelCurrent)
*/
private void jumpOptimizations(Label l, LabelKind kind) {
// Need to start looking at different indexes for label current vs. label next
// this is because for a label next, the next instruction won't have come in yet.
int idx = kind == LabelKind.LABEL_CURRENT ? 1 : 0;
InstructionInfo prev = previous(idx);
switch (prev.getOpcode()) {
case OP_jump:
{
InstructionInfo prev2 = previous(idx + 1);
Instruction insn = prev2.getInstruction();
if (insn != null && insn.isBranch() && insn.getTarget() == l) {
// If the previous instructions were an if that jumped here, and it
// only jumped over another jump, then we can invert the if instruction
// and save a jump
// iffalse L1, jump L2, L1 -> iftrue L2, L1
Instruction newIf = invertIf(prev2, prev);
if (newIf != null) {
if (kind == LabelKind.LABEL_CURRENT) {
// labelCurrent, so we need to preserve the last instruction
Instruction[] newInsns = {newIf, previous(0).getInstruction()};
replace(idx + 1, newInsns);
} else {
// labelNext so we can just delete the last instruction
replace(idx + 1, newIf);
}
}
}
// If the previous instruction was a jump, and it just jumped
// to the next instruction, then we can remove the jump and just fall
// through
// jump L1, L1 -> L1
else if (prev.getOperand(0) == l) {
if (kind == LabelKind.LABEL_NEXT)
// can just delete the jump because we don't have the next instruction yet
delete(idx);
else
// replace the jump with its target
replace(idx, previous(0).getInstruction());
}
}
}
}
/** @return the immediate for the instruction, or -1 if there is no instruction */
public int getImmediate() {
return insn != null ? insn.getImmediate() : -1;
}
/**
* Get the operand at index i from the underlying instruction
*
* @param i the index of the operand to fetch
* @return the operand at index i, or null if there is no instruction
*/
public Object getOperand(int i) {
return insn != null ? insn.getOperand(i) : null;
}
/** @return the opcode of the Instruction, or -1 if there is no instruction */
public int getOpcode() {
return insn != null ? insn.getOpcode() : -1;
}