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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.
*/
#ifndef DFGNaturalLoops_h
#define DFGNaturalLoops_h
#if ENABLE(DFG_JIT)
#include "DFGBasicBlock.h"
#include "DFGCommon.h"
#include "DFGDominators.h"
#include <wtf/FastMalloc.h>
#include <wtf/Noncopyable.h>
namespace JSC { namespace DFG {
class NaturalLoops;
class NaturalLoop {
public:
NaturalLoop()
: m_header(0)
, m_outerLoopIndex(UINT_MAX)
{
}
NaturalLoop(BasicBlock* header, unsigned index)
: m_header(header)
, m_outerLoopIndex(UINT_MAX)
, m_index(index)
{
}
BasicBlock* header() const { return m_header; }
unsigned size() const { return m_body.size(); }
BasicBlock* at(unsigned i) const { return m_body[i]; }
BasicBlock* operator[](unsigned i) const { return at(i); }
// This is the slower, but simpler, way of asking if a block belongs to
// a natural loop. It's faster to call NaturalLoops::belongsTo(), which
// tries to be O(loop depth) rather than O(loop size). Loop depth is
// almost always smaller than loop size. A *lot* smaller.
bool contains(BasicBlock* block) const
{
for (unsigned i = m_body.size(); i--;) {
if (m_body[i] == block)
return true;
}
ASSERT(block != header()); // Header should be contained.
return false;
}
// The index of this loop in NaturalLoops.
unsigned index() const { return m_index; }
bool isOuterMostLoop() const { return m_outerLoopIndex == UINT_MAX; }
void dump(PrintStream&) const;
private:
friend class NaturalLoops;
void addBlock(BasicBlock* block) { m_body.append(block); }
BasicBlock* m_header;
Vector<BasicBlock*, 4> m_body;
unsigned m_outerLoopIndex;
unsigned m_index;
};
class NaturalLoops {
WTF_MAKE_NONCOPYABLE(NaturalLoops);
WTF_MAKE_FAST_ALLOCATED;
public:
NaturalLoops(Graph&);
~NaturalLoops();
unsigned numLoops() const
{
return m_loops.size();
}
const NaturalLoop& loop(unsigned i) const
{
return m_loops[i];
}
// Return either null if the block isn't a loop header, or the
// loop it belongs to.
const NaturalLoop* headerOf(BasicBlock* block) const
{
const NaturalLoop* loop = innerMostLoopOf(block);
if (!loop)
return 0;
if (loop->header() == block)
return loop;
if (!ASSERT_DISABLED) {
for (; loop; loop = innerMostOuterLoop(*loop))
ASSERT(loop->header() != block);
}
return 0;
}
const NaturalLoop* innerMostLoopOf(BasicBlock* block) const
{
unsigned index = block->innerMostLoopIndices[0];
if (index == UINT_MAX)
return 0;
return &m_loops[index];
}
const NaturalLoop* innerMostOuterLoop(const NaturalLoop& loop) const
{
if (loop.m_outerLoopIndex == UINT_MAX)
return 0;
return &m_loops[loop.m_outerLoopIndex];
}
bool belongsTo(BasicBlock* block, const NaturalLoop& candidateLoop) const
{
// It's faster to do this test using the loop itself, if it's small.
if (candidateLoop.size() < 4)
return candidateLoop.contains(block);
for (const NaturalLoop* loop = innerMostLoopOf(block); loop; loop = innerMostOuterLoop(*loop)) {
if (loop == &candidateLoop)
return true;
}
return false;
}
unsigned loopDepth(BasicBlock* block) const
{
unsigned depth = 0;
for (const NaturalLoop* loop = innerMostLoopOf(block); loop; loop = innerMostOuterLoop(*loop))
depth++;
return depth;
}
// Return the indices of all loops this belongs to.
Vector<const NaturalLoop*> loopsOf(BasicBlock*) const;
void dump(PrintStream&) const;
private:
// If we ever had a scalability problem in our natural loop finder, we could
// use some HashMap's here. But it just feels a heck of a lot less convenient.
Vector<NaturalLoop, 4> m_loops;
};
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)
#endif // DFGNaturalLoops_h
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