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Copy pathDFGDominators.cpp
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135 lines (110 loc) · 4.15 KB
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/*
* Copyright (C) 2011 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 "DFGDominators.h"
#if ENABLE(DFG_JIT)
#include "DFGGraph.h"
#include "JSCInlines.h"
namespace JSC { namespace DFG {
Dominators::Dominators()
{
}
Dominators::~Dominators()
{
}
void Dominators::compute(Graph& graph)
{
// This implements a naive dominator solver.
ASSERT(graph.block(0)->predecessors.isEmpty());
unsigned numBlocks = graph.numBlocks();
// Allocate storage for the dense dominance matrix.
if (numBlocks > m_results.size()) {
m_results.grow(numBlocks);
for (unsigned i = numBlocks; i--;)
m_results[i].resize(numBlocks);
m_scratch.resize(numBlocks);
}
// We know that the entry block is only dominated by itself.
m_results[0].clearAll();
m_results[0].set(0);
// Find all of the valid blocks.
m_scratch.clearAll();
for (unsigned i = numBlocks; i--;) {
if (!graph.block(i))
continue;
m_scratch.set(i);
}
// Mark all nodes as dominated by everything.
for (unsigned i = numBlocks; i-- > 1;) {
if (!graph.block(i) || graph.block(i)->predecessors.isEmpty())
m_results[i].clearAll();
else
m_results[i].set(m_scratch);
}
// Iteratively eliminate nodes that are not dominator.
bool changed;
do {
changed = false;
// Prune dominators in all non entry blocks: forward scan.
for (unsigned i = 1; i < numBlocks; ++i)
changed |= pruneDominators(graph, i);
if (!changed)
break;
// Prune dominators in all non entry blocks: backward scan.
changed = false;
for (unsigned i = numBlocks; i-- > 1;)
changed |= pruneDominators(graph, i);
} while (changed);
}
bool Dominators::pruneDominators(Graph& graph, BlockIndex idx)
{
BasicBlock* block = graph.block(idx);
if (!block || block->predecessors.isEmpty())
return false;
// Find the intersection of dom(preds).
m_scratch.set(m_results[block->predecessors[0]->index]);
for (unsigned j = block->predecessors.size(); j-- > 1;)
m_scratch.filter(m_results[block->predecessors[j]->index]);
// The block is also dominated by itself.
m_scratch.set(idx);
return m_results[idx].setAndCheck(m_scratch);
}
void Dominators::dump(Graph& graph, PrintStream& out) const
{
for (BlockIndex blockIndex = 0; blockIndex < graph.numBlocks(); ++blockIndex) {
BasicBlock* block = graph.block(blockIndex);
if (!block)
continue;
out.print(" Block ", *block, ":");
for (BlockIndex otherIndex = 0; otherIndex < graph.numBlocks(); ++otherIndex) {
if (!dominates(block->index, otherIndex))
continue;
out.print(" #", otherIndex);
}
out.print("\n");
}
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)