protected D getPreviousOrSame(D d) {
		D prev = getPrevious(d);
		if (prev == null) {
			return d;
		}
		return prev;
	}
Get the previous bound or this same bound, if the previous doesn't exist

@param d the bound
@return the previous or same bound
Ghidra/Framework/Emulation/src/main/java/generic/RangeMapSetter.java