Speed up table.sort.

src/core/org/luaj/vm2/LuaTable.java

@@ -789,17 +789,21 @@ public class LuaTable extends LuaValue implements Metatable {
 		if (m_metatable != null && m_metatable.useWeakValues()) {
 			dropWeakArrayValues();
 		}
+		LuaValue[] array = this.array;
 		int n = array.length;
 		while ( n > 0 && array[n-1] == null )
 			--n;
 		if ( n > 1 )
-			heapSort(n, comparator);
+			heapSort(n, comparator.isnil() ? null : comparator);
 	}
 
 	private void heapSort(int count, LuaValue cmpfunc) {
 		heapify(count, cmpfunc);
+		LuaValue[] array = this.array;
 		for ( int end=count-1; end>0; ) {
-			swap(end, 0);
+			LuaValue a = array[end]; // swap(end, 0)
+			array[end] = array[0];
+			array[0] = a;
 			siftDown(0, --end, cmpfunc);
 		}
 	}
@@ -810,12 +814,15 @@ public class LuaTable extends LuaValue implements Metatable {
 	}
 
 	private void siftDown(int start, int end, LuaValue cmpfunc) {
+		LuaValue[] array = this.array;
 		for ( int root=start; root*2+1 <= end; ) {
 			int child = root*2+1;
 			if (child < end && compare(child, child + 1, cmpfunc))
 				++child;
 			if (compare(root, child, cmpfunc)) {
-				swap(root, child);
+				LuaValue a = array[root]; // swap(root, child)
+				array[root] = array[child];
+				array[child] = a;
 				root = child;
 			} else
 				return;
@@ -824,6 +831,8 @@ public class LuaTable extends LuaValue implements Metatable {
 
 	private boolean compare(int i, int j, LuaValue cmpfunc) {
 		LuaValue a, b;
+		LuaValue[] array = this.array;
+		Metatable m_metatable = this.m_metatable;
 		if (m_metatable == null) {
 			a = array[i];
 			b = array[j];
@@ -833,19 +842,13 @@ public class LuaTable extends LuaValue implements Metatable {
 		}
 		if ( a == null || b == null )
 			return false;
-		if ( ! cmpfunc.isnil() ) {
+		if ( cmpfunc != null ) {
 			return cmpfunc.call(a,b).toboolean();
 		} else {
 			return a.lt_b(b);
 		}
 	}
 	
-	private void swap(int i, int j) {
-		LuaValue a = array[i];
-		array[i] = array[j];
-		array[j] = a;
-	}
-	
 	/** This may be deprecated in a future release.
 	 * It is recommended to count via iteration over next() instead
 	 * @return count of keys in the table