@Override
	public long maxValue() {
		long res = -1;
		res <<= (endbit - startbit);
		res <<= 1;
		return ~res;
	}
Contiguous bits in the non-instruction part of the context interpreted
as an integer value
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/processors/sleigh/expression/ContextField.java