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/*
* Copyright (C) 2016-2021 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. AND ITS CONTRIBUTORS ``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 ITS 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 "DFGStoreBarrierClusteringPhase.h"
#if ENABLE(DFG_JIT)
#include "DFGDoesGC.h"
#include "DFGGraph.h"
#include "DFGInsertionSet.h"
#include "DFGMayExit.h"
#include "DFGPhase.h"
#include "JSCJSValueInlines.h"
#include <wtf/FastBitVector.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace JSC { namespace DFG {
namespace {
constexpr bool verbose = false;
class StoreBarrierClusteringPhase : public Phase {
public:
StoreBarrierClusteringPhase(Graph& graph)
: Phase(graph, "store barrier clustering"_s)
, m_insertionSet(graph)
{
}
bool run()
{
size_t maxSize = 0;
for (BasicBlock* block : m_graph.blocksInNaturalOrder())
maxSize = std::max(maxSize, block->size());
m_barrierPoints.resize(maxSize);
for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
size_t blockSize = block->size();
doBlock(block);
m_barrierPoints.clearRange(0, blockSize);
}
return true;
}
private:
// This summarizes everything we need to remember about a barrier.
struct ChildAndOrigin {
ChildAndOrigin() { }
ChildAndOrigin(Node* child, CodeOrigin semanticOrigin)
: child(child)
, semanticOrigin(semanticOrigin)
{
}
Node* child { nullptr };
CodeOrigin semanticOrigin;
};
void doBlock(BasicBlock* block)
{
ASSERT(m_barrierPoints.isEmpty());
// First identify the places where we would want to place all of the barriers based on a
// backwards analysis. We use the futureGC flag to tell us if we had seen a GC. Since this
// is a backwards analysis, when we get to a node, futureGC tells us if a GC will happen
// in the future after that node.
bool futureGC = true;
for (unsigned nodeIndex = block->size(); nodeIndex--;) {
Node* node = block->at(nodeIndex);
// This is a backwards analysis, so exits require conservatism. If we exit, then there
// probably will be a GC in the future! If we needed to then we could lift that
// requirement by either (1) having a StoreBarrierHint that tells OSR exit to barrier that
// value or (2) automatically barriering any DFG-live Node on OSR exit. Either way, it
// would be weird because it would create a new root for OSR availability analysis. I
// don't have evidence that it would be worth it.
if (doesGC(m_graph, node) || mayExit(m_graph, node) != DoesNotExit) {
dataLogLnIf(verbose,
"Possible GC point at ", node, "\n",
" doesGC = ", doesGC(m_graph, node), "\n",
" mayExit = ", mayExit(m_graph, node));
futureGC = true;
continue;
}
if (node->isStoreBarrier() && futureGC) {
m_barrierPoints[nodeIndex] = true;
futureGC = false;
}
}
// Now we run forward and collect the barriers. When we hit a barrier point, insert all of
// them with a fence.
for (unsigned nodeIndex = 0; nodeIndex < block->size(); ++nodeIndex) {
Node* node = block->at(nodeIndex);
if (!node->isStoreBarrier())
continue;
DFG_ASSERT(m_graph, node, !node->origin.wasHoisted);
DFG_ASSERT(m_graph, node, node->child1().useKind() == KnownCellUse, node->op(), node->child1().useKind());
NodeOrigin origin = node->origin;
m_neededBarriers.append(ChildAndOrigin(node->child1().node(), origin.semantic));
node->remove(m_graph);
if (!m_barrierPoints[nodeIndex])
continue;
std::sort(
m_neededBarriers.begin(), m_neededBarriers.end(),
[&] (const ChildAndOrigin& a, const ChildAndOrigin& b) -> bool {
return a.child < b.child;
});
removeRepeatedElements(
m_neededBarriers,
[&] (const ChildAndOrigin& a, const ChildAndOrigin& b) -> bool{
return a.child == b.child;
});
for (auto iter = m_neededBarriers.begin(); iter != m_neededBarriers.end(); ++iter) {
Node* child = iter->child;
CodeOrigin semanticOrigin = iter->semanticOrigin;
NodeType type;
if (iter == m_neededBarriers.begin())
type = FencedStoreBarrier;
else
type = StoreBarrier;
m_insertionSet.insertNode(
nodeIndex, SpecNone, type, origin.withSemantic(semanticOrigin),
Edge(child, KnownCellUse));
}
m_neededBarriers.shrink(0);
}
m_insertionSet.execute(block);
}
InsertionSet m_insertionSet;
FastBitVector m_barrierPoints;
Vector<ChildAndOrigin> m_neededBarriers;
};
} // anonymous namespace
bool performStoreBarrierClustering(Graph& graph)
{
return runPhase<StoreBarrierClusteringPhase>(graph);
}
} } // namespace JSC::DFG
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
#endif // ENABLE(DFG_JIT)
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