Simplify size test in PackWriter

Clip the configured limit to Integer.MAX_VALUE at the top of the
loop, saving a compare branch per object considered. This can cut
2M branches out of a repacking of the Linux kernel.

Rewrite the logic so the primary path is to match the conditional;
most objects are larger than BLKSZ (16 bytes) and less than limit.
This may help branch prediction on CPUs if the CPU tries to assume
execution takes the side of the branch and not the second.

Change-Id: I5133d1651640939afe9fbcfd8cfdb59965c57d5a

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java

@@ -1147,7 +1147,9 @@ public class PackWriter {
 		AsyncObjectSizeQueue<ObjectToPack> sizeQueue = reader.getObjectSize(
 				Arrays.<ObjectToPack> asList(list).subList(0, cnt), false);
 		try {
-			final long limit = config.getBigFileThreshold();
+			final long limit = Math.min(
+					config.getBigFileThreshold(),
+					Integer.MAX_VALUE);
 			for (;;) {
 				try {
 					if (!sizeQueue.next())
@@ -1175,14 +1177,10 @@ public class PackWriter {
 					otp = objectsMap.get(sizeQueue.getObjectId());
 
 				long sz = sizeQueue.getSize();
-				if (limit <= sz || Integer.MAX_VALUE <= sz)
-					otp.setDoNotDelta(); // too big, avoid costly files
-
-				else if (sz <= DeltaIndex.BLKSZ)
-					otp.setDoNotDelta(); // too small, won't work
-
-				else
+				if (DeltaIndex.BLKSZ < sz && sz < limit)
 					otp.setWeight((int) sz);
+				else
+					otp.setDoNotDelta(); // too small, or too big
 				monitor.update(1);
 			}
 		} finally {