Bundled up the block handling into a handleBlock function - means less code gen and more already jit-ed code, hopefully.

lib/handlebars.js

@@ -164,6 +164,22 @@ var Handlebars = {
     } else {
       return value;
     }
+  },
+
+  handleBlock: function(lookup, context, proxy, fn, notFn) {
+    var out = "";
+    if (Handlebars.isFunction(lookup)) {
+      out = out + lookup.call(context, proxy, fn);
+    }
+    else if (typeof lookup != 'undefined') {
+      out = out + Handlebars.helperMissing.call(proxy, lookup, fn);
+    }
+
+    if (notFn != null && Handlebars.isFunction(lookup.not)) {
+      out = out + lookup.not.call(context, proxy, notFn); 
+    }
+
+    return out;
   }
 }
 
@@ -334,16 +350,15 @@ Handlebars.Compiler.prototype = {
     this.fn += "var wrappedContext = Handlebars.buildContext(context);";
     this.fn += "var " + fnId + " = function(context) {" + result + "}; ";
     this.fn += "lookup = " + this.lookupFor(mustache) + "; ";
-    this.fn += "if(Handlebars.isFunction(lookup)) out = out + lookup.call(wrappedContext, proxy, " + fnId + "); ";
-    this.fn += "else if(typeof lookup !== 'undefined') { out = out + Handlebars.helperMissing.call(proxy, lookup, " + fnId + "); }";
-
+    
     if (compiler.continueInverted) {
       var invertedCompiler = this.compileToEndOfBlock(mustache);
-      this.fn += "if (Handlebars.isFunction(lookup.not)) {";
       this.fn += "  var " + fnId + "Not = function(context) { " + invertedCompiler.fn + " };";
-      this.fn += "  out = out + lookup.not.call(wrappedContext, proxy, " + fnId + "Not);";
-      this.fn += "}";
     }
+    else {
+      this.fn += " var " + fnId + "Not = null;";
+    }
+    this.fn += "out = out + Handlebars.handleBlock(lookup, wrappedContext, proxy, " + fnId + ", " + fnId + "Not);"
 
     this.fn += "stack.pop();";
     this.openBlock = false;