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34a3716b46
This patch removes all uses of `std::iterator`, which was deprecated in C++17. While this isn't currently an issue while compiling LLVM, it's useful for those using LLVM as a library. For some reason there're a few places that were seemingly able to use `std` functions unqualified, which no longer works after this patch. I've updated those places, but I'm not really sure why it worked in the first place. Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D67586
451 lines
15 KiB
C++
451 lines
15 KiB
C++
//===- llvm/ADT/CoalescingBitVector.h - A coalescing bitvector --*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file A bitvector that uses an IntervalMap to coalesce adjacent elements
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/// into intervals.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_COALESCINGBITVECTOR_H
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#define LLVM_ADT_COALESCINGBITVECTOR_H
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#include "llvm/ADT/IntervalMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <initializer_list>
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namespace llvm {
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/// A bitvector that, under the hood, relies on an IntervalMap to coalesce
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/// elements into intervals. Good for representing sets which predominantly
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/// contain contiguous ranges. Bad for representing sets with lots of gaps
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/// between elements.
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///
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/// Compared to SparseBitVector, CoalescingBitVector offers more predictable
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/// performance for non-sequential find() operations.
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///
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/// \tparam IndexT - The type of the index into the bitvector.
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template <typename IndexT> class CoalescingBitVector {
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static_assert(std::is_unsigned<IndexT>::value,
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"Index must be an unsigned integer.");
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using ThisT = CoalescingBitVector<IndexT>;
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/// An interval map for closed integer ranges. The mapped values are unused.
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using MapT = IntervalMap<IndexT, char>;
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using UnderlyingIterator = typename MapT::const_iterator;
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using IntervalT = std::pair<IndexT, IndexT>;
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public:
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using Allocator = typename MapT::Allocator;
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/// Construct by passing in a CoalescingBitVector<IndexT>::Allocator
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/// reference.
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CoalescingBitVector(Allocator &Alloc)
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: Alloc(&Alloc), Intervals(Alloc) {}
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/// \name Copy/move constructors and assignment operators.
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/// @{
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CoalescingBitVector(const ThisT &Other)
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: Alloc(Other.Alloc), Intervals(*Other.Alloc) {
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set(Other);
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}
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ThisT &operator=(const ThisT &Other) {
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clear();
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set(Other);
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return *this;
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}
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CoalescingBitVector(ThisT &&Other) = delete;
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ThisT &operator=(ThisT &&Other) = delete;
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/// @}
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/// Clear all the bits.
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void clear() { Intervals.clear(); }
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/// Check whether no bits are set.
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bool empty() const { return Intervals.empty(); }
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/// Count the number of set bits.
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unsigned count() const {
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unsigned Bits = 0;
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for (auto It = Intervals.begin(), End = Intervals.end(); It != End; ++It)
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Bits += 1 + It.stop() - It.start();
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return Bits;
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}
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/// Set the bit at \p Index.
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///
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/// This method does /not/ support setting a bit that has already been set,
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/// for efficiency reasons. If possible, restructure your code to not set the
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/// same bit multiple times, or use \ref test_and_set.
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void set(IndexT Index) {
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assert(!test(Index) && "Setting already-set bits not supported/efficient, "
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"IntervalMap will assert");
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insert(Index, Index);
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}
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/// Set the bits set in \p Other.
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///
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/// This method does /not/ support setting already-set bits, see \ref set
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/// for the rationale. For a safe set union operation, use \ref operator|=.
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void set(const ThisT &Other) {
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for (auto It = Other.Intervals.begin(), End = Other.Intervals.end();
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It != End; ++It)
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insert(It.start(), It.stop());
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}
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/// Set the bits at \p Indices. Used for testing, primarily.
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void set(std::initializer_list<IndexT> Indices) {
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for (IndexT Index : Indices)
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set(Index);
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}
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/// Check whether the bit at \p Index is set.
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bool test(IndexT Index) const {
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const auto It = Intervals.find(Index);
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if (It == Intervals.end())
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return false;
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assert(It.stop() >= Index && "Interval must end after Index");
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return It.start() <= Index;
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}
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/// Set the bit at \p Index. Supports setting an already-set bit.
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void test_and_set(IndexT Index) {
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if (!test(Index))
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set(Index);
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}
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/// Reset the bit at \p Index. Supports resetting an already-unset bit.
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void reset(IndexT Index) {
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auto It = Intervals.find(Index);
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if (It == Intervals.end())
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return;
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// Split the interval containing Index into up to two parts: one from
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// [Start, Index-1] and another from [Index+1, Stop]. If Index is equal to
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// either Start or Stop, we create one new interval. If Index is equal to
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// both Start and Stop, we simply erase the existing interval.
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IndexT Start = It.start();
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if (Index < Start)
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// The index was not set.
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return;
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IndexT Stop = It.stop();
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assert(Index <= Stop && "Wrong interval for index");
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It.erase();
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if (Start < Index)
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insert(Start, Index - 1);
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if (Index < Stop)
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insert(Index + 1, Stop);
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}
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/// Set union. If \p RHS is guaranteed to not overlap with this, \ref set may
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/// be a faster alternative.
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void operator|=(const ThisT &RHS) {
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// Get the overlaps between the two interval maps.
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SmallVector<IntervalT, 8> Overlaps;
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getOverlaps(RHS, Overlaps);
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// Insert the non-overlapping parts of all the intervals from RHS.
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for (auto It = RHS.Intervals.begin(), End = RHS.Intervals.end();
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It != End; ++It) {
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IndexT Start = It.start();
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IndexT Stop = It.stop();
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SmallVector<IntervalT, 8> NonOverlappingParts;
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getNonOverlappingParts(Start, Stop, Overlaps, NonOverlappingParts);
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for (IntervalT AdditivePortion : NonOverlappingParts)
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insert(AdditivePortion.first, AdditivePortion.second);
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}
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}
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/// Set intersection.
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void operator&=(const ThisT &RHS) {
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// Get the overlaps between the two interval maps (i.e. the intersection).
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SmallVector<IntervalT, 8> Overlaps;
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getOverlaps(RHS, Overlaps);
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// Rebuild the interval map, including only the overlaps.
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clear();
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for (IntervalT Overlap : Overlaps)
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insert(Overlap.first, Overlap.second);
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}
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/// Reset all bits present in \p Other.
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void intersectWithComplement(const ThisT &Other) {
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SmallVector<IntervalT, 8> Overlaps;
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if (!getOverlaps(Other, Overlaps)) {
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// If there is no overlap with Other, the intersection is empty.
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return;
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}
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// Delete the overlapping intervals. Split up intervals that only partially
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// intersect an overlap.
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for (IntervalT Overlap : Overlaps) {
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IndexT OlapStart, OlapStop;
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std::tie(OlapStart, OlapStop) = Overlap;
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auto It = Intervals.find(OlapStart);
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IndexT CurrStart = It.start();
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IndexT CurrStop = It.stop();
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assert(CurrStart <= OlapStart && OlapStop <= CurrStop &&
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"Expected some intersection!");
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// Split the overlap interval into up to two parts: one from [CurrStart,
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// OlapStart-1] and another from [OlapStop+1, CurrStop]. If OlapStart is
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// equal to CurrStart, the first split interval is unnecessary. Ditto for
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// when OlapStop is equal to CurrStop, we omit the second split interval.
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It.erase();
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if (CurrStart < OlapStart)
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insert(CurrStart, OlapStart - 1);
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if (OlapStop < CurrStop)
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insert(OlapStop + 1, CurrStop);
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}
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}
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bool operator==(const ThisT &RHS) const {
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// We cannot just use std::equal because it checks the dereferenced values
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// of an iterator pair for equality, not the iterators themselves. In our
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// case that results in comparison of the (unused) IntervalMap values.
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auto ItL = Intervals.begin();
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auto ItR = RHS.Intervals.begin();
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while (ItL != Intervals.end() && ItR != RHS.Intervals.end() &&
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ItL.start() == ItR.start() && ItL.stop() == ItR.stop()) {
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++ItL;
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++ItR;
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}
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return ItL == Intervals.end() && ItR == RHS.Intervals.end();
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}
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bool operator!=(const ThisT &RHS) const { return !operator==(RHS); }
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class const_iterator {
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friend class CoalescingBitVector;
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public:
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using iterator_category = std::forward_iterator_tag;
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using value_type = IndexT;
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using difference_type = std::ptrdiff_t;
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using pointer = value_type *;
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using reference = value_type &;
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private:
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// For performance reasons, make the offset at the end different than the
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// one used in \ref begin, to optimize the common `It == end()` pattern.
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static constexpr unsigned kIteratorAtTheEndOffset = ~0u;
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UnderlyingIterator MapIterator;
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unsigned OffsetIntoMapIterator = 0;
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// Querying the start/stop of an IntervalMap iterator can be very expensive.
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// Cache these values for performance reasons.
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IndexT CachedStart = IndexT();
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IndexT CachedStop = IndexT();
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void setToEnd() {
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OffsetIntoMapIterator = kIteratorAtTheEndOffset;
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CachedStart = IndexT();
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CachedStop = IndexT();
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}
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/// MapIterator has just changed, reset the cached state to point to the
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/// start of the new underlying iterator.
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void resetCache() {
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if (MapIterator.valid()) {
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OffsetIntoMapIterator = 0;
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CachedStart = MapIterator.start();
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CachedStop = MapIterator.stop();
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} else {
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setToEnd();
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}
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}
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/// Advance the iterator to \p Index, if it is contained within the current
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/// interval. The public-facing method which supports advancing past the
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/// current interval is \ref advanceToLowerBound.
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void advanceTo(IndexT Index) {
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assert(Index <= CachedStop && "Cannot advance to OOB index");
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if (Index < CachedStart)
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// We're already past this index.
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return;
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OffsetIntoMapIterator = Index - CachedStart;
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}
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const_iterator(UnderlyingIterator MapIt) : MapIterator(MapIt) {
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resetCache();
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}
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public:
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const_iterator() { setToEnd(); }
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bool operator==(const const_iterator &RHS) const {
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// Do /not/ compare MapIterator for equality, as this is very expensive.
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// The cached start/stop values make that check unnecessary.
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return std::tie(OffsetIntoMapIterator, CachedStart, CachedStop) ==
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std::tie(RHS.OffsetIntoMapIterator, RHS.CachedStart,
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RHS.CachedStop);
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}
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bool operator!=(const const_iterator &RHS) const {
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return !operator==(RHS);
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}
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IndexT operator*() const { return CachedStart + OffsetIntoMapIterator; }
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const_iterator &operator++() { // Pre-increment (++It).
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if (CachedStart + OffsetIntoMapIterator < CachedStop) {
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// Keep going within the current interval.
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++OffsetIntoMapIterator;
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} else {
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// We reached the end of the current interval: advance.
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++MapIterator;
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resetCache();
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}
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return *this;
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}
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const_iterator operator++(int) { // Post-increment (It++).
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const_iterator tmp = *this;
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operator++();
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return tmp;
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}
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/// Advance the iterator to the first set bit AT, OR AFTER, \p Index. If
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/// no such set bit exists, advance to end(). This is like std::lower_bound.
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/// This is useful if \p Index is close to the current iterator position.
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/// However, unlike \ref find(), this has worst-case O(n) performance.
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void advanceToLowerBound(IndexT Index) {
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if (OffsetIntoMapIterator == kIteratorAtTheEndOffset)
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return;
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// Advance to the first interval containing (or past) Index, or to end().
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while (Index > CachedStop) {
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++MapIterator;
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resetCache();
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if (OffsetIntoMapIterator == kIteratorAtTheEndOffset)
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return;
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}
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advanceTo(Index);
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}
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};
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const_iterator begin() const { return const_iterator(Intervals.begin()); }
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const_iterator end() const { return const_iterator(); }
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/// Return an iterator pointing to the first set bit AT, OR AFTER, \p Index.
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/// If no such set bit exists, return end(). This is like std::lower_bound.
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/// This has worst-case logarithmic performance (roughly O(log(gaps between
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/// contiguous ranges))).
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const_iterator find(IndexT Index) const {
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auto UnderlyingIt = Intervals.find(Index);
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if (UnderlyingIt == Intervals.end())
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return end();
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auto It = const_iterator(UnderlyingIt);
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It.advanceTo(Index);
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return It;
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}
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/// Return a range iterator which iterates over all of the set bits in the
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/// half-open range [Start, End).
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iterator_range<const_iterator> half_open_range(IndexT Start,
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IndexT End) const {
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assert(Start < End && "Not a valid range");
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auto StartIt = find(Start);
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if (StartIt == end() || *StartIt >= End)
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return {end(), end()};
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auto EndIt = StartIt;
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EndIt.advanceToLowerBound(End);
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return {StartIt, EndIt};
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}
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void print(raw_ostream &OS) const {
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OS << "{";
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for (auto It = Intervals.begin(), End = Intervals.end(); It != End;
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++It) {
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OS << "[" << It.start();
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if (It.start() != It.stop())
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OS << ", " << It.stop();
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OS << "]";
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}
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OS << "}";
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void dump() const {
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// LLDB swallows the first line of output after callling dump(). Add
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// newlines before/after the braces to work around this.
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dbgs() << "\n";
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print(dbgs());
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dbgs() << "\n";
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}
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#endif
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private:
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void insert(IndexT Start, IndexT End) { Intervals.insert(Start, End, 0); }
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/// Record the overlaps between \p this and \p Other in \p Overlaps. Return
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/// true if there is any overlap.
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bool getOverlaps(const ThisT &Other,
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SmallVectorImpl<IntervalT> &Overlaps) const {
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for (IntervalMapOverlaps<MapT, MapT> I(Intervals, Other.Intervals);
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I.valid(); ++I)
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Overlaps.emplace_back(I.start(), I.stop());
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assert(llvm::is_sorted(Overlaps,
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[](IntervalT LHS, IntervalT RHS) {
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return LHS.second < RHS.first;
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}) &&
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"Overlaps must be sorted");
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return !Overlaps.empty();
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}
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/// Given the set of overlaps between this and some other bitvector, and an
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/// interval [Start, Stop] from that bitvector, determine the portions of the
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/// interval which do not overlap with this.
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void getNonOverlappingParts(IndexT Start, IndexT Stop,
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const SmallVectorImpl<IntervalT> &Overlaps,
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SmallVectorImpl<IntervalT> &NonOverlappingParts) {
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IndexT NextUncoveredBit = Start;
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for (IntervalT Overlap : Overlaps) {
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IndexT OlapStart, OlapStop;
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std::tie(OlapStart, OlapStop) = Overlap;
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// [Start;Stop] and [OlapStart;OlapStop] overlap iff OlapStart <= Stop
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// and Start <= OlapStop.
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bool DoesOverlap = OlapStart <= Stop && Start <= OlapStop;
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if (!DoesOverlap)
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continue;
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// Cover the range [NextUncoveredBit, OlapStart). This puts the start of
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// the next uncovered range at OlapStop+1.
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if (NextUncoveredBit < OlapStart)
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NonOverlappingParts.emplace_back(NextUncoveredBit, OlapStart - 1);
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NextUncoveredBit = OlapStop + 1;
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if (NextUncoveredBit > Stop)
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break;
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}
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if (NextUncoveredBit <= Stop)
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NonOverlappingParts.emplace_back(NextUncoveredBit, Stop);
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}
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Allocator *Alloc;
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MapT Intervals;
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};
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} // namespace llvm
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#endif // LLVM_ADT_COALESCINGBITVECTOR_H
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