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//===- llvm/ADT/SetVector.h - Set with insert order iteration ---*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements a set that has insertion order iteration
/// characteristics. This is useful for keeping a set of things that need to be
/// visited later but in a deterministic order (insertion order). The interface
/// is purposefully minimal.
///
/// This file defines SetVector and SmallSetVector, which performs no
/// allocations if the SetVector has less than a certain number of elements.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_SETVECTOR_H
#define LLVM_ADT_SETVECTOR_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Compiler.h"
#include <cassert>
#include <iterator>
namespace llvm {
/// A vector that has set insertion semantics.
///
/// This adapter class provides a way to keep a set of things that also has the
/// property of a deterministic iteration order. The order of iteration is the
/// order of insertion.
///
/// The key and value types are derived from the Set and Vector types
/// respectively. This allows the vector-type operations and set-type operations
/// to have different types. In particular, this is useful when storing pointers
/// as "Foo *" values but looking them up as "const Foo *" keys.
///
/// No constraint is placed on the key and value types, although it is assumed
/// that value_type can be converted into key_type for insertion. Users must be
/// aware of any loss of information in this conversion. For example, setting
/// value_type to float and key_type to int can produce very surprising results,
/// but it is not explicitly disallowed.
///
/// The parameter N specifies the "small" size of the container, which is the
/// number of elements upto which a linear scan over the Vector will be used
/// when searching for elements instead of checking Set, due to it being better
/// for performance. A value of 0 means that this mode of operation is not used,
/// and is the default value.
template <typename T, typename Vector = SmallVector<T, 0>,
typename Set = DenseSet<T>, unsigned N = 0>
class SetVector {
// Much like in SmallPtrSet, this value should not be too high to prevent
// excessively long linear scans from occuring.
static_assert(N <= 32, "Small size should be less than or equal to 32!");
public:
using value_type = typename Vector::value_type;
using key_type = typename Set::key_type;
using reference = value_type &;
using const_reference = const value_type &;
using set_type = Set;
using vector_type = Vector;
using iterator = typename vector_type::const_iterator;
using const_iterator = typename vector_type::const_iterator;
using reverse_iterator = typename vector_type::const_reverse_iterator;
using const_reverse_iterator = typename vector_type::const_reverse_iterator;
using size_type = typename vector_type::size_type;
/// Construct an empty SetVector
SetVector() = default;
/// Initialize a SetVector with a range of elements
template<typename It>
SetVector(It Start, It End) {
insert(Start, End);
}
ArrayRef<value_type> getArrayRef() const { return vector_; }
/// Clear the SetVector and return the underlying vector.
Vector takeVector() {
set_.clear();
return std::move(vector_);
}
/// Determine if the SetVector is empty or not.
bool empty() const {
return vector_.empty();
}
/// Determine the number of elements in the SetVector.
size_type size() const {
return vector_.size();
}
/// Get an iterator to the beginning of the SetVector.
iterator begin() {
return vector_.begin();
}
/// Get a const_iterator to the beginning of the SetVector.
const_iterator begin() const {
return vector_.begin();
}
/// Get an iterator to the end of the SetVector.
iterator end() {
return vector_.end();
}
/// Get a const_iterator to the end of the SetVector.
const_iterator end() const {
return vector_.end();
}
/// Get an reverse_iterator to the end of the SetVector.
reverse_iterator rbegin() {
return vector_.rbegin();
}
/// Get a const_reverse_iterator to the end of the SetVector.
const_reverse_iterator rbegin() const {
return vector_.rbegin();
}
/// Get a reverse_iterator to the beginning of the SetVector.
reverse_iterator rend() {
return vector_.rend();
}
/// Get a const_reverse_iterator to the beginning of the SetVector.
const_reverse_iterator rend() const {
return vector_.rend();
}
/// Return the first element of the SetVector.
const value_type &front() const {
assert(!empty() && "Cannot call front() on empty SetVector!");
return vector_.front();
}
/// Return the last element of the SetVector.
const value_type &back() const {
assert(!empty() && "Cannot call back() on empty SetVector!");
return vector_.back();
}
/// Index into the SetVector.
const_reference operator[](size_type n) const {
assert(n < vector_.size() && "SetVector access out of range!");
return vector_[n];
}
/// Insert a new element into the SetVector.
/// \returns true if the element was inserted into the SetVector.
bool insert(const value_type &X) {
if constexpr (canBeSmall())
if (isSmall()) {
if (!llvm::is_contained(vector_, X)) {
vector_.push_back(X);
if (vector_.size() > N)
makeBig();
return true;
}
return false;
}
bool result = set_.insert(X).second;
if (result)
vector_.push_back(X);
return result;
}
/// Insert a range of elements into the SetVector.
template<typename It>
void insert(It Start, It End) {
for (; Start != End; ++Start)
insert(*Start);
}
/// Remove an item from the set vector.
bool remove(const value_type& X) {
if constexpr (canBeSmall())
if (isSmall()) {
typename vector_type::iterator I = find(vector_, X);
if (I != vector_.end()) {
vector_.erase(I);
return true;
}
return false;
}
if (set_.erase(X)) {
typename vector_type::iterator I = find(vector_, X);
assert(I != vector_.end() && "Corrupted SetVector instances!");
vector_.erase(I);
return true;
}
return false;
}
/// Erase a single element from the set vector.
/// \returns an iterator pointing to the next element that followed the
/// element erased. This is the end of the SetVector if the last element is
/// erased.
iterator erase(const_iterator I) {
if constexpr (canBeSmall())
if (isSmall())
return vector_.erase(I);
const key_type &V = *I;
assert(set_.count(V) && "Corrupted SetVector instances!");
set_.erase(V);
return vector_.erase(I);
}
/// Remove items from the set vector based on a predicate function.
///
/// This is intended to be equivalent to the following code, if we could
/// write it:
///
/// \code
/// V.erase(remove_if(V, P), V.end());
/// \endcode
///
/// However, SetVector doesn't expose non-const iterators, making any
/// algorithm like remove_if impossible to use.
///
/// \returns true if any element is removed.
template <typename UnaryPredicate>
bool remove_if(UnaryPredicate P) {
typename vector_type::iterator I = [this, P] {
if constexpr (canBeSmall())
if (isSmall())
return llvm::remove_if(vector_, P);
return llvm::remove_if(vector_,
TestAndEraseFromSet<UnaryPredicate>(P, set_));
}();
if (I == vector_.end())
return false;
vector_.erase(I, vector_.end());
return true;
}
/// Check if the SetVector contains the given key.
bool contains(const key_type &key) const {
if constexpr (canBeSmall())
if (isSmall())
return is_contained(vector_, key);
return set_.find(key) != set_.end();
}
/// Count the number of elements of a given key in the SetVector.
/// \returns 0 if the element is not in the SetVector, 1 if it is.
size_type count(const key_type &key) const {
if constexpr (canBeSmall())
if (isSmall())
return is_contained(vector_, key);
return set_.count(key);
}
/// Completely clear the SetVector
void clear() {
set_.clear();
vector_.clear();
}
/// Remove the last element of the SetVector.
void pop_back() {
assert(!empty() && "Cannot remove an element from an empty SetVector!");
set_.erase(back());
vector_.pop_back();
}
[[nodiscard]] value_type pop_back_val() {
value_type Ret = back();
pop_back();
return Ret;
}
bool operator==(const SetVector &that) const {
return vector_ == that.vector_;
}
bool operator!=(const SetVector &that) const {
return vector_ != that.vector_;
}
/// Compute This := This u S, return whether 'This' changed.
/// TODO: We should be able to use set_union from SetOperations.h, but
/// SetVector interface is inconsistent with DenseSet.
template <class STy>
bool set_union(const STy &S) {
bool Changed = false;
for (typename STy::const_iterator SI = S.begin(), SE = S.end(); SI != SE;
++SI)
if (insert(*SI))
Changed = true;
return Changed;
}
/// Compute This := This - B
/// TODO: We should be able to use set_subtract from SetOperations.h, but
/// SetVector interface is inconsistent with DenseSet.
template <class STy>
void set_subtract(const STy &S) {
for (typename STy::const_iterator SI = S.begin(), SE = S.end(); SI != SE;
++SI)
remove(*SI);
}
void swap(SetVector<T, Vector, Set, N> &RHS) {
set_.swap(RHS.set_);
vector_.swap(RHS.vector_);
}
private:
/// A wrapper predicate designed for use with std::remove_if.
///
/// This predicate wraps a predicate suitable for use with std::remove_if to
/// call set_.erase(x) on each element which is slated for removal.
template <typename UnaryPredicate>
class TestAndEraseFromSet {
UnaryPredicate P;
set_type &set_;
public:
TestAndEraseFromSet(UnaryPredicate P, set_type &set_)
: P(std::move(P)), set_(set_) {}
template <typename ArgumentT>
bool operator()(const ArgumentT &Arg) {
if (P(Arg)) {
set_.erase(Arg);
return true;
}
return false;
}
};
[[nodiscard]] static constexpr bool canBeSmall() { return N != 0; }
[[nodiscard]] bool isSmall() const { return set_.empty(); }
void makeBig() {
if constexpr (canBeSmall())
for (const auto &entry : vector_)
set_.insert(entry);
}
set_type set_; ///< The set.
vector_type vector_; ///< The vector.
};
/// A SetVector that performs no allocations if smaller than
/// a certain size.
template <typename T, unsigned N>
class SmallSetVector : public SetVector<T, SmallVector<T, N>, DenseSet<T>, N> {
public:
SmallSetVector() = default;
/// Initialize a SmallSetVector with a range of elements
template<typename It>
SmallSetVector(It Start, It End) {
this->insert(Start, End);
}
};
} // end namespace llvm
namespace std {
/// Implement std::swap in terms of SetVector swap.
template <typename T, typename V, typename S, unsigned N>
inline void swap(llvm::SetVector<T, V, S, N> &LHS,
llvm::SetVector<T, V, S, N> &RHS) {
LHS.swap(RHS);
}
/// Implement std::swap in terms of SmallSetVector swap.
template<typename T, unsigned N>
inline void
swap(llvm::SmallSetVector<T, N> &LHS, llvm::SmallSetVector<T, N> &RHS) {
LHS.swap(RHS);
}
} // end namespace std
#endif // LLVM_ADT_SETVECTOR_H
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