public void emitSignExtension(String dest, int size, String src) {
		Varnode out = findVarnode(dest, size);
		Varnode[] in = new Varnode[1];
		in[0] = findRegister(src);
		PcodeOp op = new PcodeOp(opAddress, seqnum++, PcodeOp.INT_SEXT, in, out);
		opList.add(op);
	}
Appends the pcode to sign-extend the value src into dest
@param dest target varnode
@param size size of target varnode
@param src size of source varnode
Ghidra/Processors/JVM/src/main/java/ghidra/app/util/pcodeInject/PcodeOpEmitter.java