Reduce heavy runtime calls from debug mirrors.

src/mirror-debugger.js

 // Copyright 2006-2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 871 matching lines @@
 
 /**
  * Returns the script object for the function.
  * @return {ScriptMirror or undefined} Script object for the function or
  *     undefined if the function has no script
  */
 FunctionMirror.prototype.script = function() {
   // Return script if function is resolved. Otherwise just fall through
   // to return undefined.
   if (this.resolved()) {
+    if (this.script_) {
+      return this.script_;
+    }
     var script = %FunctionGetScript(this.value_);
     if (script) {
-      return MakeMirror(script);
+      return this.script_ = MakeMirror(script);
     }
   }
 };
 
 
 /**
  * Returns the script source position for the function. Only makes sense
  * for functions which has a script defined.
  * @return {Number or undefined} in-script position for the function
  */
 FunctionMirror.prototype.sourcePosition_ = function() {
   // Return script if function is resolved. Otherwise just fall through
   // to return undefined.
   if (this.resolved()) {
     return %FunctionGetScriptSourcePosition(this.value_);
   }
 };
 
 
 /**
  * Returns the script source location object for the function. Only makes sense
  * for functions which has a script defined.
  * @return {Location or undefined} in-script location for the function begin
  */
 FunctionMirror.prototype.sourceLocation = function() {
-  if (this.resolved() && this.script()) {
-    return this.script().locationFromPosition(this.sourcePosition_(),
-                                              true);
+  if (this.resolved()) {
+    var script = this.script();
+    if (script) {
+      return script.locationFromPosition(this.sourcePosition_(), true);
+    }
   }
 };
 
 
 /**
  * Returns objects constructed by this function.
  * @param {number} opt_max_instances Optional parameter specifying the maximum
  *     number of instances to return.
  * @return {Array or undefined} The objects constructed by this function.
  */
 FunctionMirror.prototype.constructedBy = function(opt_max_instances) {
   if (this.resolved()) {
     // Find all objects constructed from this function.
     var result = %DebugConstructedBy(this.value_, opt_max_instances || 0);
 
     // Make mirrors for all the instances found.
     for (var i = 0; i < result.length; i++) {
       result[i] = MakeMirror(result[i]);
     }
 
     return result;
   } else {
     return [];
   }
 };
 
 
 FunctionMirror.prototype.scopeCount = function() {
   if (this.resolved()) {
-    return %GetFunctionScopeCount(this.value());
+    if (IS_UNDEFINED(this.scopeCount_)) {
+      this.scopeCount_ = %GetFunctionScopeCount(this.value());
+    }
+    return this.scopeCount_;
   } else {
     return 0;
   }
 };
 
 
 FunctionMirror.prototype.scope = function(index) {
   if (this.resolved()) {
     return new ScopeMirror(UNDEFINED, this, index);
   }
@@ skipping 536 matching lines @@
   var return_value_offset =
       kFrameDetailsFirstDynamicIndex +
       (this.argumentCount() + this.localCount()) * kFrameDetailsNameValueSize;
   if (this.details_[kFrameDetailsAtReturnIndex]) {
     return this.details_[return_value_offset];
   }
 };
 
 
 FrameDetails.prototype.scopeCount = function() {
-  return %GetScopeCount(this.break_id_, this.frameId());
+  if (IS_UNDEFINED(this.scopeCount_)) {
+    this.scopeCount_ = %GetScopeCount(this.break_id_, this.frameId());
+  }
+  return this.scopeCount_;
 };
 
 
 FrameDetails.prototype.stepInPositionsImpl = function() {
   return %GetStepInPositions(this.break_id_, this.frameId());
 };
 
 
 /**
  * Mirror object for stack frames.
@@ skipping 11 matching lines @@
 }
 inherits(FrameMirror, Mirror);
 
 
 FrameMirror.prototype.index = function() {
   return this.index_;
 };
 
 
 FrameMirror.prototype.func = function() {
+  if (this.func_) {
+    return this.func_;
+  }
+
   // Get the function for this frame from the VM.
   var f = this.details_.func();
 
   // Create a function mirror. NOTE: MakeMirror cannot be used here as the
   // value returned from the VM might be a string if the function for the
   // frame is unresolved.
   if (IS_FUNCTION(f)) {
-    return MakeMirror(f);
+    return this.func_ = MakeMirror(f);
   } else {
     return new UnresolvedFunctionMirror(f);
   }
 };
 
 
 FrameMirror.prototype.receiver = function() {
   return MakeMirror(this.details_.receiver());
 };
 
@@ skipping 62 matching lines @@
   return MakeMirror(this.details_.returnValue());
 };
 
 
 FrameMirror.prototype.sourcePosition = function() {
   return this.details_.sourcePosition();
 };
 
 
 FrameMirror.prototype.sourceLocation = function() {
-  if (this.func().resolved() && this.func().script()) {
-    return this.func().script().locationFromPosition(this.sourcePosition(),
-                                                     true);
+  var func = this.func();
+  if (func.resolved()) {
+    var script = func.script();
+    if (script) {
+      return script.locationFromPosition(this.sourcePosition(), true);
+    }
   }
 };
 
 
 FrameMirror.prototype.sourceLine = function() {
-  if (this.func().resolved()) {
-    var location = this.sourceLocation();
-    if (location) {
-      return location.line;
-    }
+  var location = this.sourceLocation();
+  if (location) {
+    return location.line;
   }
 };
 
 
 FrameMirror.prototype.sourceColumn = function() {
-  if (this.func().resolved()) {
-    var location = this.sourceLocation();
-    if (location) {
-      return location.column;
-    }
+  var location = this.sourceLocation();
+  if (location) {
+    return location.column;
   }
 };
 
 
 FrameMirror.prototype.sourceLineText = function() {
-  if (this.func().resolved()) {
-    var location = this.sourceLocation();
-    if (location) {
-      return location.sourceText();
-    }
+  var location = this.sourceLocation();
+  if (location) {
+    return location.sourceText();
   }
 };
 
 
 FrameMirror.prototype.scopeCount = function() {
   return this.details_.scopeCount();
 };
 
 
 FrameMirror.prototype.scope = function(index) {
@@ skipping 112 matching lines @@
 
   return result;
 };
 
 
 FrameMirror.prototype.sourceAndPositionText = function() {
   // Format source and position.
   var result = '';
   var func = this.func();
   if (func.resolved()) {
-    if (func.script()) {
-      if (func.script().name()) {
-        result += func.script().name();
+    var script = func.script();
+    if (script) {
+      if (script.name()) {
+        result += script.name();
       } else {
         result += '[unnamed]';
       }
       if (!this.isDebuggerFrame()) {
         var location = this.sourceLocation();
         result += ' line ';
         result += !IS_UNDEFINED(location) ? (location.line + 1) : '?';
         result += ' column ';
         result += !IS_UNDEFINED(location) ? (location.column + 1) : '?';
         if (!IS_UNDEFINED(this.sourcePosition())) {
@@ skipping 759 matching lines @@
   }
   return result;
 };
 
 
 JSONProtocolSerializer.prototype.serializeFrame_ = function(mirror, content) {
   content.index = mirror.index();
   content.receiver = this.serializeReference(mirror.receiver());
   var func = mirror.func();
   content.func = this.serializeReference(func);
-  if (func.script()) {
-    content.script = this.serializeReference(func.script());
+  var script = func.script();
+  if (script) {
+    content.script = this.serializeReference(script);
   }
   content.constructCall = mirror.isConstructCall();
   content.atReturn = mirror.isAtReturn();
   if (mirror.isAtReturn()) {
     content.returnValue = this.serializeReference(mirror.returnValue());
   }
   content.debuggerFrame = mirror.isDebuggerFrame();
   var x = new Array(mirror.argumentCount());
   for (var i = 0; i < mirror.argumentCount(); i++) {
     var arg = {};
@@ skipping 55 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }