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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/173626">173626</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2014-09-15 12:32:01 -0700 (Mon, 15 Sep 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>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:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGDCEPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGGraphcpp">trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGGraphh">trunk/Source/JavaScriptCore/dfg/DFGGraph.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (173625 => 173626)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-09-15 18:45:28 UTC (rev 173625)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-09-15 19:32:01 UTC (rev 173626)
</span><span class="lines">@@ -1,3 +1,23 @@
</span><ins>+2014-09-14 Filip Pizlo <fpizlo@apple.com>
+
+ 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:
+
</ins><span class="cx"> 2014-09-12 Michael Saboff <msaboff@apple.com>
</span><span class="cx">
</span><span class="cx"> Merge JSGlobalObject::reset() into ::init()
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGDCEPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp (173625 => 173626)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp 2014-09-15 18:45:28 UTC (rev 173625)
+++ trunk/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp 2014-09-15 19:32:01 UTC (rev 173626)
</span><span class="lines">@@ -48,73 +48,8 @@
</span><span class="cx"> {
</span><span class="cx"> ASSERT(m_graph.m_form == ThreadedCPS || m_graph.m_form == SSA);
</span><span class="cx">
</span><del>- // 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);
- }
- }
</del><ins>+ m_graph.computeRefCounts();
</ins><span class="cx">
</span><del>- 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);
- }
- }
- }
- }
-
</del><span class="cx"> if (m_graph.m_form == SSA) {
</span><span class="cx"> for (BasicBlock* block : m_graph.blocksInPreOrder())
</span><span class="cx"> fixupBlock(block);
</span><span class="lines">@@ -157,31 +92,6 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> private:
</span><del>- 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());
- }
-
</del><span class="cx"> void fixupBlock(BasicBlock* block)
</span><span class="cx"> {
</span><span class="cx"> if (!block)
</span><span class="lines">@@ -327,7 +237,6 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><del>- Vector<Node*, 128> m_worklist;
</del><span class="cx"> InsertionSet m_insertionSet;
</span><span class="cx"> };
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGGraphcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp (173625 => 173626)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp 2014-09-15 18:45:28 UTC (rev 173625)
+++ trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp 2014-09-15 19:32:01 UTC (rev 173626)
</span><span class="lines">@@ -562,6 +562,124 @@
</span><span class="cx"> determineReachability();
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+namespace {
+
+class RefCountCalculator {
+public:
+ RefCountCalculator(Graph& graph)
+ : m_graph(graph)
+ {
+ }
+
+ void calculate()
+ {
+ // 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--;)
+ block->at(indexInBlock)->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->op() == Check) {
+ // We don't treat Check nodes as MustGenerate. We will gladly
+ // kill them off in this phase.
+ 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);
+ }
+ }
+ }
+ }
+ }
+
+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());
+ }
+
+ Graph& m_graph;
+ Vector<Node*, 128> m_worklist;
+};
+
+} // anonymous namespace
+
+void Graph::computeRefCounts()
+{
+ RefCountCalculator calculator(*this);
+ calculator.calculate();
+}
+
</ins><span class="cx"> void Graph::killBlockAndItsContents(BasicBlock* block)
</span><span class="cx"> {
</span><span class="cx"> for (unsigned phiIndex = block->phis.size(); phiIndex--;)
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGGraphh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGGraph.h (173625 => 173626)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGGraph.h 2014-09-15 18:45:28 UTC (rev 173625)
+++ trunk/Source/JavaScriptCore/dfg/DFGGraph.h 2014-09-15 19:32:01 UTC (rev 173626)
</span><span class="lines">@@ -570,6 +570,8 @@
</span><span class="cx"> void determineReachability();
</span><span class="cx"> void resetReachability();
</span><span class="cx">
</span><ins>+ void computeRefCounts();
+
</ins><span class="cx"> unsigned varArgNumChildren(Node* node)
</span><span class="cx"> {
</span><span class="cx"> ASSERT(node->flags() & NodeHasVarArgs);
</span></span></pre>
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