public int getNumFixedBits() {
		int popcnt = 0;
		for (byte dit : dits) {
			popcnt += popcount[0xff & dit];
		}
		return popcnt;
	}
Get number of bits that must be 0/1

@return number of bits that are not don't care (ditted)
Ghidra/Features/Base/src/main/java/ghidra/util/bytesearch/DittedBitSequence.java