protected int getFirstUseOffset() {
		Address pcaddr = entryList[0].pcaddr;
		if (pcaddr == null) {
			return 0;
		}
		return (int) pcaddr.subtract(getHighFunction().getFunction().getEntryPoint());
	}
Get the first code Address (expressed as a different in bytes from the starting address of the
function) where this symbol's storage actually holds the value of the symbol. A value of 0 indicates
that the storage is valid across the entire function.  A negative value indicates the storage is
an input to the function.
@return the first-use offset of this symbol's storage
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/HighSymbol.java