Continue work on cleaning up helpers

lib/handlebars/compiler/compiler.js

@@ -28,7 +28,8 @@ Handlebars.JavaScriptCompiler = function() {};
     lookupOnContext: 19,
     resolvePossibleLambda: 20,
     invokeHelper: 21,
-    pushLiteral: 22
+    pushLiteral: 22,
+    invokeKnownHelper: 23
   };
 
   Compiler.MULTI_PARAM_OPCODES = {
@@ -50,7 +51,8 @@ Handlebars.JavaScriptCompiler = function() {};
     lookupOnContext: 1,
     resolvePossibleLambda: 0,
     invokeHelper: 2,
-    pushLiteral: 1
+    pushLiteral: 1,
+    invokeKnownHelper: 2
   };
 
   Compiler.DISASSEMBLE_MAP = {};
@@ -278,7 +280,13 @@ Handlebars.JavaScriptCompiler = function() {};
       var params = this.setupMustacheParams(mustache),
           name = mustache.id.parts[0];
 
-      this.opcode('invokeHelper', params.length, name);
+      if (this.options.knownHelpers[name]) {
+        this.opcode('invokeKnownHelper', params.length, name);
+      } else if (this.knownHelpersOnly) {
+        throw new Error("You specified knownHelpersOnly, but used the unknown helper " + name);
+      } else {
+        this.opcode('invokeHelper', params.length, name);
+      }
     },
 
     ID: function(id) {
@@ -677,17 +685,30 @@ Handlebars.JavaScriptCompiler = function() {};
     invokeHelper: function(paramSize, name) {
       this.context.aliases.helperMissing = 'helpers.helperMissing';
 
-      var params = [], contexts = [];
-      this.setupParams(paramSize, params, contexts);
-      this.register('foundHelper', this.nameLookup('helpers', name, 'helper'));
+      var helper = this.setupHelper(paramSize, name);
+      this.register('foundHelper', helper.name);
 
-      var main = ["depth0"].concat(params).join(", ");
-      var helperMissing = ["depth0", this.quotedString(name)].concat(params).join(", ");
-      this.pushStack("foundHelper ? foundHelper.call(" + main + ") " +
-             ": helperMissing.call(" + helperMissing + ")");
+      this.pushStack("foundHelper ? foundHelper.call(" +
+        helper.callParams + ") " + ": helperMissing.call(" +
+        helper.helperMissingParams + ")");
+    },
 
-      //this.replaceStack(function(current) {
-      //});
+    invokeKnownHelper: function(paramSize, name) {
+      var helper = this.setupHelper(paramSize, name);
+      this.pushStack(helper.name + ".call(" + helper.callParams + ")");
+    },
+
+    setupHelper: function(paramSize, name) {
+      var params = [];
+      this.setupParams(paramSize, params);
+      var foundHelper = this.nameLookup('helpers', name, 'helper');
+
+      return {
+        params: params,
+        name: foundHelper,
+        callParams: ["depth0"].concat(params).join(", "),
+        helperMissingParams: ["depth0", this.quotedString(name)].concat(params).join(", ")
+      };
     },
 
     // the params and contexts arguments are passed in arrays