code: void writeTagNoClear(long bucketIndex, int posInBucket, long tag) {
  		long tagStartIdx = getTagOffset(bucketIndex, posInBucket);
  		// BIT BANGIN YEAAAARRHHHGGGHHH
  		for (int i = 0; i < bitsPerTag; i++) {
  			// second arg just does bit test in tag
  			if ((tag & (1L << i)) != 0) {
  				memBlock.set(tagStartIdx + i);
  			}
  		}
  	}
docs: Writes a tag to a bucket position. Faster than regular write because it
  assumes tag starts with all zeros, but doesn't work properly if the
  position wasn't empty.