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/*
* Copyright (C) 2016 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 WTF_RangeSet_h
#define WTF_RangeSet_h
#include <wtf/ListDump.h>
#include <wtf/MathExtras.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
namespace WTF {
// A RangeSet is a set of numerical ranges. A value belongs to the set if it is within any of the
// ranges. A range belongs to the set if every value in the range belongs to the set. A range overlaps
// the set if any value in the range belongs to the set. You can add ranges and query range
// membership. The internal representation is a list of ranges that gets periodically compacted. This
// representation is optimal so long as the number of distinct ranges tends to be small, and the
// number of range sets tends to be small as well. This works reasonably well in a bunch of compiler
// algorithms, where the top range ends up being used a lot.
//
// The initial user of this is JSC::B3::HeapRange, which is used to perform alias analysis. You can
// model new users on that class. Basically, you need to define:
//
// T::Type - the type of the members of the range. HeapRange uses unsigned.
// T(T::Type begin, T::Type end) - construct a new range.
// T::Type T::begin() const - instance method giving the inclusive beginning of the range.
// T::Type T::end() const - instance method giving the exclusive end of the range.
// void T::dump(PrintStream&) const - some kind of dumping.
template<typename RangeType>
class RangeSet {
public:
typedef RangeType Range;
typedef typename Range::Type Type;
RangeSet()
{
}
~RangeSet()
{
}
void add(const Range& range)
{
if (range.begin() == range.end())
return;
// We expect the range set to become top in a lot of cases. We also expect the same range to
// be added repeatedly. That's why this is here.
if (!m_ranges.isEmpty() && subsumesNonEmpty(m_ranges.last(), range))
return;
m_isCompact = false;
// We append without compacting only if doing so is guaranteed not to resize the vector.
if (m_ranges.size() + 1 < m_ranges.capacity()) {
m_ranges.append(range);
return;
}
m_ranges.append(range);
compact();
}
bool contains(const Range& range) const
{
if (range.begin() == range.end())
return false;
unsigned index = findRange(range);
if (index != UINT_MAX)
return subsumesNonEmpty(m_ranges[index], range);
return false;
}
bool overlaps(const Range& range) const
{
if (range.begin() == range.end())
return false;
return findRange(range) != UINT_MAX;
}
void clear()
{
m_ranges.clear();
m_isCompact = true;
}
void dump(PrintStream& out) const
{
const_cast<RangeSet*>(this)->compact();
out.print(listDump(m_ranges));
}
void dumpRaw(PrintStream& out) const
{
out.print("{", listDump(m_ranges), ", isCompact = ", m_isCompact, "}");
}
private:
void compact()
{
if (m_isCompact)
return;
if (m_ranges.isEmpty()) {
m_isCompact = true;
return;
}
std::sort(
m_ranges.begin(), m_ranges.end(),
[&] (const Range& a, const Range& b) -> bool {
return a.begin() < b.begin();
});
unsigned srcIndex = 1;
unsigned dstIndex = 1;
Range* lastRange = &m_ranges[0];
while (srcIndex < m_ranges.size()) {
Range range = m_ranges[srcIndex++];
ASSERT(range.begin() >= lastRange->begin());
if (range.end() <= lastRange->end())
continue;
if (range.begin() <= lastRange->end()) {
*lastRange = Range(lastRange->begin(), range.end());
continue;
}
ASSERT(!overlapsNonEmpty(*lastRange, range));
lastRange = &m_ranges[dstIndex++];
*lastRange = range;
}
m_ranges.resize(dstIndex);
m_isCompact = true;
}
static bool overlapsNonEmpty(const Range& a, const Range& b)
{
return nonEmptyRangesOverlap(a.begin(), a.end(), b.begin(), b.end());
}
static bool subsumesNonEmpty(const Range& a, const Range& b)
{
return a.begin() <= b.begin() && a.end() >= b.end();
}
unsigned findRange(const Range& range) const
{
const_cast<RangeSet*>(this)->compact();
// FIXME: Once we start using this in anger, we will want this to be a binary search.
for (unsigned i = 0; i < m_ranges.size(); ++i) {
if (overlapsNonEmpty(m_ranges[i], range))
return i;
}
return UINT_MAX;
}
Vector<Range, 8> m_ranges;
bool m_isCompact { true };
};
} // namespace WTF
using WTF::RangeSet;
#endif // WTF_RangeSet_h
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