private void populateSizeMapBigEndian(Register reg) {
		int regSize = reg.getMinimumByteSize();
		for (int i = 1; i <= regSize; i++) {
			Address address = reg.getAddress().add(regSize - i);
			sizeMap.put(new RegisterSizeKey(address, i), reg);
		}
	}
Construct RegisterManager

@param registers all defined registers with appropriate parent-child relationships properly
           established.
@param registerNameMap a complete name-to-register map including all register aliases and
           alternate spellings (e.g., case-variations)
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/RegisterManager.java