Changeset 204355 in webkit for trunk/Source/JavaScriptCore/dfg/DFGGraph.h

Timestamp:

Aug 10, 2016, 2:25:28 PM (9 years ago)

Author:

[email protected]

Message:

[JSC] Speed up SparseCollection & related maps
​https://bugs.webkit.org/show_bug.cgi?id=160733

Patch by Benjamin Poulain <​[email protected]> on 2016-08-10
Reviewed by Saam Barati.

On MBA, Graph::addNode() shows up in profiles due to SparseCollection::add().
This is unfortunate.

The first improvement is to build the new unique_ptr in the empty slot
instead of moving a new value into it.

Previously, the code would load the previous value, test if it is null
then invoke the destructor and finally fastFree(). The initial test
obviously fails so that's a whole bunch of code that is never executed.

With the new code, we just have a store.

I also removed the bounds checking on our maps based on node index.
Those bounds checks are never eliminated by clang because the index
is always loaded from memory instead of being computed.
There are unfortunately too many nodes processed and the bounds checks
get costly.

• b3/B3SparseCollection.h:

(JSC::B3::SparseCollection::add):

• dfg/DFGGraph.h:

(JSC::DFG::Graph::abstractValuesCache):

• dfg/DFGInPlaceAbstractState.h:

File:

• trunk/Source/JavaScriptCore/dfg/DFGGraph.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/dfg/DFGGraph.h

@@ -200 +200 @@
     void packNodeIndices();
 
-    Vector<AbstractValue>& abstractValuesCache() { return m_abstractValuesCache; }
+    Vector<AbstractValue, 0, UnsafeVectorOverflow>& abstractValuesCache() { return m_abstractValuesCache; }
 
     void dethread();
@@ -958 +958 @@
 
     B3::SparseCollection<Node> m_nodes;
-    Vector<AbstractValue> m_abstractValuesCache;
+    Vector<AbstractValue, 0, UnsafeVectorOverflow> m_abstractValuesCache;
 };