Bug 1404897: Allow storing Servo selector lists in the document's selector cache. r=heycam

MozReview-Commit-ID: GtIWGN2zEGT

--HG--
extra : rebase_source : 90d4a61bcc65995ca8a130cd24582e4f20d52276

dom/base/nsDocument.cpp

@@ -1406,13 +1406,39 @@ nsIDocument::SelectorCache::~SelectorCache()
   AgeAllGenerations();
 }
 
+void
+nsIDocument::SelectorCache::SelectorList::Reset()
+{
+  if (mIsServo) {
+    if (mServo) {
+      Servo_SelectorList_Drop(mServo);
+      mServo = nullptr;
+    }
+  } else {
+    if (mGecko) {
+      delete mGecko;
+      mGecko = nullptr;
+    }
+  }
+}
+
 // CacheList takes ownership of aSelectorList.
 void nsIDocument::SelectorCache::CacheList(const nsAString& aSelector,
-                                           nsCSSSelectorList* aSelectorList)
+                                           mozilla::UniquePtr<nsCSSSelectorList>&& aSelectorList)
 {
   MOZ_ASSERT(NS_IsMainThread());
   SelectorCacheKey* key = new SelectorCacheKey(aSelector);
-  mTable.Put(key->mKey, aSelectorList);
+  mTable.Put(key->mKey, SelectorList(Move(aSelectorList)));
+  AddObject(key);
+}
+
+void nsIDocument::SelectorCache::CacheList(
+  const nsAString& aSelector,
+  UniquePtr<RawServoSelectorList>&& aSelectorList)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  SelectorCacheKey* key = new SelectorCacheKey(aSelector);
+  mTable.Put(key->mKey, SelectorList(Move(aSelectorList)));
   AddObject(key);
 }
 

dom/base/nsIDocument.h

@@ -37,6 +37,7 @@
 #include "mozilla/LinkedList.h"
 #include "mozilla/NotNull.h"
 #include "mozilla/SegmentedVector.h"
+#include "mozilla/ServoBindingTypes.h"
 #include "mozilla/StyleBackendType.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/TimeStamp.h"
@@ -1148,27 +1149,106 @@ public:
     : public nsExpirationTracker<SelectorCacheKey, 4>
   {
     public:
+      class SelectorList
+      {
+      public:
+        SelectorList()
+          : mIsServo(false)
+          , mGecko(nullptr)
+        {}
+
+        SelectorList(SelectorList&& aOther)
+        {
+          *this = mozilla::Move(aOther);
+        }
+
+        SelectorList& operator=(SelectorList&& aOther)
+        {
+          Reset();
+          mIsServo = aOther.mIsServo;
+          if (mIsServo) {
+            mServo = aOther.mServo;
+            aOther.mServo = nullptr;
+          } else {
+            mGecko = aOther.mGecko;
+            aOther.mGecko = nullptr;
+          }
+          return *this;
+        }
+
+        SelectorList(const SelectorList& aOther) = delete;
+
+        explicit SelectorList(mozilla::UniquePtr<RawServoSelectorList>&& aList)
+          : mIsServo(true)
+          , mServo(aList.release())
+        {}
+
+        explicit SelectorList(mozilla::UniquePtr<nsCSSSelectorList>&& aList)
+          : mIsServo(false)
+          , mGecko(aList.release())
+        {}
+
+        ~SelectorList() {
+          Reset();
+        }
+
+        bool IsServo() const { return mIsServo; }
+        bool IsGecko() const { return !IsServo(); }
+
+        explicit operator bool() const
+        {
+          return IsServo() ? !!AsServo() : !!AsGecko();
+        }
+
+        nsCSSSelectorList* AsGecko() const
+        {
+          MOZ_ASSERT(IsGecko());
+          return mGecko;
+        }
+
+        RawServoSelectorList* AsServo() const
+        {
+          MOZ_ASSERT(IsServo());
+          return mServo;
+        }
+
+      private:
+        void Reset();
+
+        bool mIsServo;
+
+        union {
+          nsCSSSelectorList* mGecko;
+          RawServoSelectorList* mServo;
+        };
+      };
+
       explicit SelectorCache(nsIEventTarget* aEventTarget);
 
       // CacheList takes ownership of aSelectorList.
-      void CacheList(const nsAString& aSelector, nsCSSSelectorList* aSelectorList);
+      void CacheList(const nsAString& aSelector,
+                     mozilla::UniquePtr<nsCSSSelectorList>&& aSelectorList);
+      void CacheList(const nsAString& aSelector,
+                     mozilla::UniquePtr<RawServoSelectorList>&& aSelectorList);
 
       virtual void NotifyExpired(SelectorCacheKey* aSelector) override;
 
       // We do not call MarkUsed because it would just slow down lookups and
       // because we're OK expiring things after a few seconds even if they're
       // being used.  Returns whether we actually had an entry for aSelector.
-      // If we have an entry and *aList is null, that indicates that aSelector
+      //
+      // If we have an entry and the selector list returned has a null
+      // nsCSSSelectorList*/RawServoSelectorList*, that indicates that aSelector
       // has already been parsed and is not a syntactically valid selector.
-      bool GetList(const nsAString& aSelector, nsCSSSelectorList** aList)
+      SelectorList* GetList(const nsAString& aSelector)
       {
-        return mTable.Get(aSelector, aList);
+        return mTable.GetValue(aSelector);
       }
 
       ~SelectorCache();
 
     private:
-      nsClassHashtable<nsStringHashKey, nsCSSSelectorList> mTable;
+      nsDataHashtable<nsStringHashKey, SelectorList> mTable;
   };
 
   SelectorCache& GetSelectorCache() {

dom/base/nsINode.cpp

@@ -2682,21 +2682,23 @@ nsINode::ParseSelectorList(const nsAString& aSelectorString,
 {
   nsIDocument* doc = OwnerDoc();
   nsIDocument::SelectorCache& cache = doc->GetSelectorCache();
-  nsCSSSelectorList* selectorList = nullptr;
-  bool haveCachedList = cache.GetList(aSelectorString, &selectorList);
-  if (haveCachedList) {
-    if (!selectorList) {
+  nsIDocument::SelectorCache::SelectorList* list =
+    cache.GetList(aSelectorString);
+  if (list) {
+    if (!*list) {
       // Invalid selector.
       aRv.ThrowDOMException(NS_ERROR_DOM_SYNTAX_ERR,
         NS_LITERAL_CSTRING("'") + NS_ConvertUTF16toUTF8(aSelectorString) +
         NS_LITERAL_CSTRING("' is not a valid selector")
       );
     }
-    return selectorList;
+    MOZ_ASSERT(list->IsGecko(), "We haven't done anything with Servo yet");
+    return list->AsGecko();
   }
 
   nsCSSParser parser(doc->CSSLoader());
 
+  nsCSSSelectorList* selectorList = nullptr;
   aRv = parser.ParseSelectorString(aSelectorString,
                                    doc->GetDocumentURI(),
                                    0, // XXXbz get the line number!
@@ -2714,7 +2716,7 @@ nsINode::ParseSelectorList(const nsAString& aSelectorString,
       NS_LITERAL_CSTRING("' is not a valid selector")
     );
 
-    cache.CacheList(aSelectorString, nullptr);
+    cache.CacheList(aSelectorString, UniquePtr<nsCSSSelectorList>());
     return nullptr;
   }
 
@@ -2734,7 +2736,7 @@ nsINode::ParseSelectorList(const nsAString& aSelectorString,
   if (selectorList) {
     NS_ASSERTION(selectorList->mSelectors,
                  "How can we not have any selectors?");
-    cache.CacheList(aSelectorString, selectorList);
+    cache.CacheList(aSelectorString, UniquePtr<nsCSSSelectorList>(selectorList));
   } else {
     // This is the "only pseudo-element selectors" case, which is
     // not common, so just don't worry about caching it.  That way a