Changeset 173626 in webkit for trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp

Timestamp:

Sep 15, 2014, 12:32:01 PM (11 years ago)

Author:

[email protected]

Message:

DFG ref count calculation should be reusable
​https://bugs.webkit.org/show_bug.cgi?id=136811

Reviewed by Oliver Hunt.

Henceforth if you call Graph::computeRefCounts(), a nifty O(n) operation, every Node
will be able to tell you how many places it is used from. Currently only DCE uses this,
but it will be useful for ​https://bugs.webkit.org/show_bug.cgi?id=136330.

• dfg/DFGDCEPhase.cpp:

(JSC::DFG::DCEPhase::run):
(JSC::DFG::DCEPhase::findTypeCheckRoot): Deleted.
(JSC::DFG::DCEPhase::countNode): Deleted.
(JSC::DFG::DCEPhase::countEdge): Deleted.

• dfg/DFGGraph.cpp:

(JSC::DFG::Graph::computeRefCounts):

• dfg/DFGGraph.h:

File:

• trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp (modified) (3 diffs)

trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp

@@ -49 +49 @@
         ASSERT(m_graph.m_form == ThreadedCPS || m_graph.m_form == SSA);
         
-        // First reset the counts to 0 for all nodes.
-        //
-        // Also take this opportunity to pretend that Check nodes are not NodeMustGenerate. Check
-        // nodes are MustGenerate because they are executed for effect, but they follow the same
-        // DCE rules as nodes that aren't MustGenerate: they only contribute to the ref count of
-        // their children if the edges require checks. Non-checking edges are removed. Note that
-        // for any Checks left over, this phase will turn them back into NodeMustGenerate.
-        for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
-            BasicBlock* block = m_graph.block(blockIndex);
-            if (!block)
-                continue;
-            for (unsigned indexInBlock = block->size(); indexInBlock--;) {
-                Node* node = block->at(indexInBlock);
-                if (node->op() == Check)
-                    node->clearFlags(NodeMustGenerate);
-                node->setRefCount(0);
-            }
-            for (unsigned phiIndex = block->phis.size(); phiIndex--;)
-                block->phis[phiIndex]->setRefCount(0);
-        }
-    
-        // Now find the roots:
-        // - Nodes that are must-generate.
-        // - Nodes that are reachable from type checks.
-        // Set their ref counts to 1 and put them on the worklist.
-        for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
-            BasicBlock* block = m_graph.block(blockIndex);
-            if (!block)
-                continue;
-            for (unsigned indexInBlock = block->size(); indexInBlock--;) {
-                Node* node = block->at(indexInBlock);
-                DFG_NODE_DO_TO_CHILDREN(m_graph, node, findTypeCheckRoot);
-                if (!(node->flags() & NodeMustGenerate))
-                    continue;
-                if (!node->postfixRef())
-                    m_worklist.append(node);
-            }
-        }
-        
-        while (!m_worklist.isEmpty()) {
-            while (!m_worklist.isEmpty()) {
-                Node* node = m_worklist.last();
-                m_worklist.removeLast();
-                ASSERT(node->shouldGenerate()); // It should not be on the worklist unless it's ref'ed.
-                DFG_NODE_DO_TO_CHILDREN(m_graph, node, countEdge);
-            }
-            
-            if (m_graph.m_form == SSA) {
-                // Find Phi->Upsilon edges, which are represented as meta-data in the
-                // Upsilon.
-                for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
-                    BasicBlock* block = m_graph.block(blockIndex);
-                    if (!block)
-                        continue;
-                    for (unsigned nodeIndex = block->size(); nodeIndex--;) {
-                        Node* node = block->at(nodeIndex);
-                        if (node->op() != Upsilon)
-                            continue;
-                        if (node->shouldGenerate())
-                            continue;
-                        if (node->phi()->shouldGenerate())
-                            countNode(node);
-                    }
-                }
-            }
-        }
+        m_graph.computeRefCounts();
         
         if (m_graph.m_form == SSA) {
@@ -158 +93 @@
 
 private:
-    void findTypeCheckRoot(Node*, Edge edge)
-    {
-        // We may have an "unproved" untyped use for code that is unreachable. The CFA
-        // will just not have gotten around to it.
-        if (edge.isProved() || edge.willNotHaveCheck())
-            return;
-        if (!edge->postfixRef())
-            m_worklist.append(edge.node());
-    }
-    
-    void countNode(Node* node)
-    {
-        if (node->postfixRef())
-            return;
-        m_worklist.append(node);
-    }
-    
-    void countEdge(Node*, Edge edge)
-    {
-        // Don't count edges that are already counted for their type checks.
-        if (!(edge.isProved() || edge.willNotHaveCheck()))
-            return;
-        countNode(edge.node());
-    }
-    
     void fixupBlock(BasicBlock* block)
     {
@@ -328 +238 @@
     }
     
-    Vector<Node*, 128> m_worklist;
     InsertionSet m_insertionSet;
 };