--- /dev/null
+/*
+ * Copyright (C) 2013 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "DFGDCEPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlockInlines.h"
+#include "DFGGraph.h"
+#include "DFGInsertionSet.h"
+#include "DFGPhase.h"
+#include "Operations.h"
+
+namespace JSC { namespace DFG {
+
+class DCEPhase : public Phase {
+public:
+ DCEPhase(Graph& graph)
+ : Phase(graph, "dead code elimination")
+ {
+ }
+
+ bool run()
+ {
+ // First reset the counts to 0 for all nodes.
+ for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
+ BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+ 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.m_blocks.size(); ++blockIndex) {
+ BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+ 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()) {
+ 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);
+ }
+
+ for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
+ BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+ if (!block)
+ continue;
+
+ InsertionSet insertionSet(m_graph);
+
+ for (unsigned indexInBlock = block->size(); indexInBlock--;) {
+ Node* node = block->at(indexInBlock);
+ if (node->shouldGenerate())
+ continue;
+
+ switch (node->op()) {
+ case SetLocal: {
+ if (node->child1().isProved() || node->child1().useKind() == UntypedUse) {
+ // Consider the possibility that UInt32ToNumber is dead but its
+ // child isn't; if so then we should MovHint the child.
+ if (!node->child1()->shouldGenerate()
+ && node->child1()->op() == UInt32ToNumber)
+ node->child1() = node->child1()->child1();
+
+ if (!node->child1()->shouldGenerate()) {
+ node->setOpAndDefaultFlags(ZombieHint);
+ node->child1() = Edge();
+ break;
+ }
+ node->setOpAndDefaultFlags(MovHint);
+ break;
+ }
+ node->setOpAndDefaultFlags(MovHintAndCheck);
+ node->setRefCount(1);
+ break;
+ }
+
+ case GetLocal:
+ case SetArgument: {
+ // Leave them as not shouldGenerate.
+ break;
+ }
+
+ default: {
+ if (node->flags() & NodeHasVarArgs) {
+ for (unsigned childIdx = node->firstChild(); childIdx < node->firstChild() + node->numChildren(); childIdx++) {
+ Edge edge = m_graph.m_varArgChildren[childIdx];
+
+ if (!edge || edge.isProved() || edge.useKind() == UntypedUse)
+ continue;
+
+ insertionSet.insertNode(indexInBlock, SpecNone, Phantom, node->codeOrigin, edge);
+ }
+
+ node->convertToPhantomUnchecked();
+ node->children.reset();
+ node->setRefCount(1);
+ break;
+ }
+
+ node->convertToPhantom();
+ eliminateIrrelevantPhantomChildren(node);
+ node->setRefCount(1);
+ break;
+ } }
+ }
+
+ insertionSet.execute(block);
+ }
+
+ m_graph.m_refCountState = ExactRefCount;
+
+ return true;
+ }
+
+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.useKind() == UntypedUse)
+ return;
+ if (!edge->postfixRef())
+ m_worklist.append(edge.node());
+ }
+
+ void countEdge(Node*, Edge edge)
+ {
+ // Don't count edges that are already counted for their type checks.
+ if (!(edge.isProved() || edge.useKind() == UntypedUse))
+ return;
+
+ if (edge->postfixRef())
+ return;
+ m_worklist.append(edge.node());
+ }
+
+ void eliminateIrrelevantPhantomChildren(Node* node)
+ {
+ for (unsigned i = 0; i < AdjacencyList::Size; ++i) {
+ Edge edge = node->children.child(i);
+ if (!edge)
+ continue;
+ if (edge.isProved() || edge.useKind() == UntypedUse)
+ node->children.removeEdge(i--);
+ }
+ }
+
+ Vector<Node*, 128> m_worklist;
+};
+
+bool performDCE(Graph& graph)
+{
+ SamplingRegion samplingRegion("DFG DCE Phase");
+ return runPhase<DCEPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
projects / apple / javascriptcore.git / blobdiff