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/*
* 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 "DFGLoopPreHeaderCreationPhase.h"
#if ENABLE(DFG_JIT)
#include "DFGBasicBlockInlines.h"
#include "DFGBlockInsertionSet.h"
#include "DFGGraph.h"
#include "DFGPhase.h"
#include "JSCInlines.h"
#include <wtf/HashMap.h>
namespace JSC { namespace DFG {
BasicBlock* createPreHeader(Graph& graph, BlockInsertionSet& insertionSet, BasicBlock* block)
{
// Don't bother to preserve execution frequencies for now.
BasicBlock* preHeader = insertionSet.insertBefore(block, PNaN);
preHeader->appendNode(
graph, SpecNone, Jump, block->at(0)->origin, OpInfo(block));
for (unsigned predecessorIndex = 0; predecessorIndex < block->predecessors.size(); predecessorIndex++) {
BasicBlock* predecessor = block->predecessors[predecessorIndex];
if (graph.m_dominators.dominates(block, predecessor))
continue;
block->predecessors[predecessorIndex--] = block->predecessors.last();
block->predecessors.removeLast();
for (unsigned successorIndex = predecessor->numSuccessors(); successorIndex--;) {
BasicBlock*& successor = predecessor->successor(successorIndex);
if (successor != block)
continue;
successor = preHeader;
preHeader->predecessors.append(predecessor);
}
}
block->predecessors.append(preHeader);
return preHeader;
}
class LoopPreHeaderCreationPhase : public Phase {
public:
LoopPreHeaderCreationPhase(Graph& graph)
: Phase(graph, "loop pre-header creation")
, m_insertionSet(graph)
{
}
bool run()
{
m_graph.m_dominators.computeIfNecessary(m_graph);
m_graph.m_naturalLoops.computeIfNecessary(m_graph);
for (unsigned loopIndex = m_graph.m_naturalLoops.numLoops(); loopIndex--;) {
const NaturalLoop& loop = m_graph.m_naturalLoops.loop(loopIndex);
BasicBlock* existingPreHeader = 0;
bool needsNewPreHeader = false;
for (unsigned predecessorIndex = loop.header()->predecessors.size(); predecessorIndex--;) {
BasicBlock* predecessor = loop.header()->predecessors[predecessorIndex];
if (m_graph.m_dominators.dominates(loop.header(), predecessor))
continue;
if (!existingPreHeader) {
existingPreHeader = predecessor;
continue;
}
if (existingPreHeader == predecessor)
continue;
needsNewPreHeader = true;
break;
}
if (!needsNewPreHeader)
continue;
createPreHeader(m_graph, m_insertionSet, loop.header());
}
return m_insertionSet.execute();
}
BlockInsertionSet m_insertionSet;
};
bool performLoopPreHeaderCreation(Graph& graph)
{
SamplingRegion samplingRegion("DFG Loop Pre-Header Creation Phase");
return runPhase<LoopPreHeaderCreationPhase>(graph);
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)
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