Index: selector.js
===================================================================
--- selector.js	(revision 6529)
+++ selector.js	(working copy)
@@ -996,7 +996,40 @@
 	}).length;
 };
 
+var parsedCache = [];
+
 jQuery.filter = jQuery.multiFilter = function( expr, elems, not ) {
+	var parsed = [], split, re, matches = [], match, l, i;
+	// We are looking for simple selectors of the form "div", ".class" or "div.class"
+	// We'll try to minimize the extra-processing for complex selectors
+	
+	// A simple way to quickly exclude many complex selectors
+	if(expr.indexOf(' ') == -1) {
+		// If the selector is not the last parsed one
+		if (expr != parsedCache[0]) {
+			split = expr.split('.');
+			if (split.length < 3) {
+				re = /^(?:[\w\u00c0-\uFFFF-]|\\.)*$/;
+				// The selector begins with a tag (parsed[1] = tag) or with a "." (parsed[1] = true)
+				if (parsed[1] = split[0] != ""? (re.test(split[0])? split[0] : false) : true) {
+					// The second part of the selector is a class (parsed[2] = class) or there is no second part (parsed[2] = true)
+					if(parsed[2] = split[1]? (re.test(split[1])? " " + split[1] + " " : false) : true) {
+						// If we arrived that far, we found a simple selector
+						parsed[0] = expr;
+						parsedCache = parsed;
+					}
+				}
+			}
+		} else parsed = parsedCache;
+	}
+	// If we have succesfully parsed the new selector, or if it was in the cache
+	if(expr == parsed[0]) {
+		for(i = 0, l = elems.length; i < l; ++i) {
+			match = (parsed[1] === true || jQuery.nodeName(elems[i], parsed[1])) && (parsed[2] === true || (" " + elems[i].className + " ").indexOf(parsed[2]) != -1);
+			if(not? !match : match)	matches.push(elems[i]);
+		}
+		return matches;
+	}
 	if ( not ) {
 		expr = ":not(" + expr + ")";
 	}