From 5a302bddef1e02ddc190e0094965e8ec24c3daa8 Mon Sep 17 00:00:00 2001
From: Alex Navasardyan <twokul@users.noreply.github.com>
Date: Fri, 5 Sep 2014 08:15:30 -0400
Subject: [PATCH] [BUGFIX beta] Extracts computed property set into a separate
 function

This is done to work around V8 (it cannot optimize functions with try
blocks).

Some comparisons from a real app:

`defineProperty`

Before:
![defineproperty
deopt](https://cloud.githubusercontent.com/assets/1131196/4164553/ad42a504-34f6-11e4-92cc-fdf17e88cc22.png)

After:
![defineproperty
cp-set](https://cloud.githubusercontent.com/assets/1131196/4164559/bf012a86-34f6-11e4-9bba-e5b2dc378946.png)

`watchKey`

Before:
![watch - key
deopt](https://cloud.githubusercontent.com/assets/1131196/4164570/e518cc88-34f6-11e4-9d66-97901a75161e.png)

After:
![watch-key -
cp-set](https://cloud.githubusercontent.com/assets/1131196/4164573/ec00d28e-34f6-11e4-8798-222b1ee985bf.png)
---
 packages/ember-metal/lib/computed.js | 108 +++++++++++++++------------
 1 file changed, 59 insertions(+), 49 deletions(-)

diff --git a/packages/ember-metal/lib/computed.js b/packages/ember-metal/lib/computed.js
index 5a8c8f5254a..d6026f4141d 100644
--- a/packages/ember-metal/lib/computed.js
+++ b/packages/ember-metal/lib/computed.js
@@ -398,75 +398,85 @@ ComputedPropertyPrototype.get = function(obj, keyName) {
   @param {String} oldValue The old value being replaced.
   @return {Object} The return value of the function backing the CP.
 */
-ComputedPropertyPrototype.set = function(obj, keyName, value) {
-  var cacheable = this._cacheable;
-  var func = this.func;
-  var meta = metaFor(obj, cacheable);
+ComputedPropertyPrototype.set = function computedPropertySetWithSuspend(obj, keyName, value) {
   var oldSuspended = this._suspended;
+
+  this._suspended = obj;
+
+  try {
+    this._set(obj, keyName, value);
+  } finally {
+    this._suspended = oldSuspended;
+  }
+};
+
+ComputedPropertyPrototype._set = function computedPropertySet(obj, keyName, value) {
+  var cacheable      = this._cacheable;
+  var func           = this.func;
+  var meta           = metaFor(obj, cacheable);
+  var cache          = meta.cache;
   var hadCachedValue = false;
-  var cache = meta.cache;
+
   var funcArgLength, cachedValue, ret;
 
   if (this._readOnly) {
     throw new EmberError('Cannot set read-only property "' + keyName + '" on object: ' + inspect(obj));
   }
 
-  this._suspended = obj;
-
-  try {
+  if (cacheable && cache[keyName] !== undefined) {
+    if(cache[keyName] !== UNDEFINED) {
+      cachedValue = cache[keyName];
+    }
 
-    if (cacheable && cache[keyName] !== undefined) {
-      if(cache[keyName] !== UNDEFINED) {
-        cachedValue = cache[keyName];
-      }
+    hadCachedValue = true;
+  }
 
-      hadCachedValue = true;
-    }
+  // Check if the CP has been wrapped. If it has, use the
+  // length from the wrapped function.
 
-    // Check if the CP has been wrapped. If it has, use the
-    // length from the wrapped function.
+  funcArgLength = func.wrappedFunction ? func.wrappedFunction.__ember_arity__ : func.__ember_arity__;
 
-    funcArgLength = func.wrappedFunction ? func.wrappedFunction.__ember_arity__ : func.__ember_arity__;
+  // For backwards-compatibility with computed properties
+  // that check for arguments.length === 2 to determine if
+  // they are being get or set, only pass the old cached
+  // value if the computed property opts into a third
+  // argument.
+  if (funcArgLength === 3) {
+    ret = func.call(obj, keyName, value, cachedValue);
+  } else if (funcArgLength === 2) {
+    ret = func.call(obj, keyName, value);
+  } else {
+    defineProperty(obj, keyName, null, cachedValue);
+    set(obj, keyName, value);
+    return;
+  }
 
-    // For backwards-compatibility with computed properties
-    // that check for arguments.length === 2 to determine if
-    // they are being get or set, only pass the old cached
-    // value if the computed property opts into a third
-    // argument.
-    if (funcArgLength === 3) {
-      ret = func.call(obj, keyName, value, cachedValue);
-    } else if (funcArgLength === 2) {
-      ret = func.call(obj, keyName, value);
-    } else {
-      defineProperty(obj, keyName, null, cachedValue);
-      set(obj, keyName, value);
-      return;
-    }
+  if (hadCachedValue && cachedValue === ret) { return; }
 
-    if (hadCachedValue && cachedValue === ret) { return; }
+  var watched = meta.watching[keyName];
+  if (watched) {
+    propertyWillChange(obj, keyName);
+  }
 
-    var watched = meta.watching[keyName];
-    if (watched) { propertyWillChange(obj, keyName); }
+  if (hadCachedValue) {
+    cache[keyName] = undefined;
+  }
 
-    if (hadCachedValue) {
-      cache[keyName] = undefined;
+  if (cacheable) {
+    if (!hadCachedValue) {
+      addDependentKeys(this, obj, keyName, meta);
     }
-
-    if (cacheable) {
-      if (!hadCachedValue) {
-        addDependentKeys(this, obj, keyName, meta);
-      }
-      if (ret === undefined) {
-        cache[keyName] = UNDEFINED;
-      } else {
-        cache[keyName] = ret;
-      }
+    if (ret === undefined) {
+      cache[keyName] = UNDEFINED;
+    } else {
+      cache[keyName] = ret;
     }
+  }
 
-    if (watched) { propertyDidChange(obj, keyName); }
-  } finally {
-    this._suspended = oldSuspended;
+  if (watched) {
+    propertyDidChange(obj, keyName);
   }
+
   return ret;
 };