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/*
* Copyright (C) 2013-2015 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 "DFGGraph.h"
#include "DFGInsertionSet.h"
#include "DFGPhase.h"
#include "JSCJSValueInlines.h"
namespace JSC { namespace DFG {
class DCEPhase : public Phase {
public:
DCEPhase(Graph& graph)
: Phase(graph, "dead code elimination")
, m_insertionSet(graph)
{
}
bool run()
{
ASSERT(m_graph.m_form == ThreadedCPS || m_graph.m_form == SSA);
m_graph.computeRefCounts();
for (BasicBlock* block : m_graph.blocksInPreOrder())
fixupBlock(block);
for (auto& argumentsVector : m_graph.m_rootToArguments.values())
cleanVariables(argumentsVector);
// Just do a basic Phantom/Check clean-up.
for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
BasicBlock* block = m_graph.block(blockIndex);
if (!block)
continue;
unsigned sourceIndex = 0;
unsigned targetIndex = 0;
while (sourceIndex < block->size()) {
Node* node = block->at(sourceIndex++);
switch (node->op()) {
case Check:
case Phantom:
if (node->children.isEmpty())
continue;
break;
case CheckVarargs: {
bool isEmpty = true;
m_graph.doToChildren(node, [&] (Edge edge) {
isEmpty &= !edge;
});
if (isEmpty)
continue;
break;
}
default:
break;
}
block->at(targetIndex++) = node;
}
block->resize(targetIndex);
}
m_graph.m_refCountState = ExactRefCount;
return true;
}
private:
void fixupBlock(BasicBlock* block)
{
if (!block)
return;
if (m_graph.m_form == ThreadedCPS) {
for (unsigned phiIndex = 0; phiIndex < block->phis.size(); ++phiIndex) {
Node* phi = block->phis[phiIndex];
if (!phi->shouldGenerate()) {
m_graph.deleteNode(phi);
block->phis[phiIndex--] = block->phis.last();
block->phis.removeLast();
}
}
cleanVariables(block->variablesAtHead);
cleanVariables(block->variablesAtTail);
}
// This has to be a forward loop because we are using the insertion set.
for (unsigned indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) {
Node* node = block->at(indexInBlock);
if (node->shouldGenerate())
continue;
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.willNotHaveCheck())
continue;
m_insertionSet.insertNode(indexInBlock, SpecNone, Check, node->origin, edge);
}
node->setOpAndDefaultFlags(Check);
node->children.reset();
node->setRefCount(1);
continue;
}
node->remove(m_graph);
node->setRefCount(1);
}
m_insertionSet.execute(block);
}
template<typename VariablesVectorType>
void cleanVariables(VariablesVectorType& variables)
{
for (unsigned i = variables.size(); i--;) {
Node* node = variables[i];
if (!node)
continue;
if (node->op() != Check && node->shouldGenerate())
continue;
variables[i] = nullptr;
}
}
InsertionSet m_insertionSet;
};
bool performDCE(Graph& graph)
{
return runPhase<DCEPhase>(graph);
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)