public byte[] getBaseMask() {
		if (baseMask == null) {
			synchronized (this) {
				Register base = getBaseRegister();
				int byteLength = (base.getBitLength() + 7) / 8;
				byte[] newBaseMask = new byte[byteLength];
				int endBit = leastSigBitInBaseRegister + bitLength - 1;
				for (int i = leastSigBitInBaseRegister; i <= endBit; i++) {
					setBit(newBaseMask, i);
				}
				baseMask = newBaseMask;
			}
		}
		return baseMask;
	}
Returns the mask that indicates which bits in the base register apply to this register.

@return the mask that indicates which bits in the base register apply to this register
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/Register.java