More P0202 constexpr work. This commit adds fill/fill_n/generate/generate_n/unique/unique_copy. I removed a specialization of fill_n that recognized when we were dealing with raw pointers and 1 byte trivially-assignable types and did a memset, because the compiler will do that optimization for us.

llvm-svn: 323050

9 files changed, 173 insertions, 44 deletions

diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index d51e19c7337..b750616f0e8 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -219,19 +219,19 @@ template <class InputIterator, class OutputIterator, class Predicate, class T>
     replace_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred, const T& new_value);
 
 template <class ForwardIterator, class T>
-    void
+    constexpr void      // constexpr in C++20
     fill(ForwardIterator first, ForwardIterator last, const T& value);
 
 template <class OutputIterator, class Size, class T>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     fill_n(OutputIterator first, Size n, const T& value);
 
 template <class ForwardIterator, class Generator>
-    void
+    constexpr void      // constexpr in C++20
     generate(ForwardIterator first, ForwardIterator last, Generator gen);
 
 template <class OutputIterator, class Size, class Generator>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     generate_n(OutputIterator first, Size n, Generator gen);
 
 template <class ForwardIterator, class T>
@@ -2025,7 +2025,7 @@ replace_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator _
 // fill_n
 
 template <class _OutputIterator, class _Size, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
 {
@@ -2034,24 +2034,8 @@ __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
     return __first;
 }
 
-template <class _Tp, class _Size, class _Up>
-inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
-    is_integral<_Tp>::value && sizeof(_Tp) == 1 &&
-    !is_same<_Tp, bool>::value &&
-    is_integral<_Up>::value && sizeof(_Up) == 1,
-    _Tp*
->::type
-__fill_n(_Tp* __first, _Size __n,_Up __value_)
-{
-    if (__n > 0)
-        _VSTD::memset(__first, (unsigned char)__value_, (size_t)(__n));
-    return __first + __n;
-}
-
 template <class _OutputIterator, class _Size, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
 {
@@ -2061,7 +2045,7 @@ fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
 // fill
 
 template <class _ForwardIterator, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 __fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, forward_iterator_tag)
 {
@@ -2070,7 +2054,7 @@ __fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, f
 }
 
 template <class _RandomAccessIterator, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 __fill(_RandomAccessIterator __first, _RandomAccessIterator __last, const _Tp& __value_, random_access_iterator_tag)
 {
@@ -2078,7 +2062,7 @@ __fill(_RandomAccessIterator __first, _RandomAccessIterator __last, const _Tp& _
 }
 
 template <class _ForwardIterator, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
 {
@@ -2088,7 +2072,7 @@ fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
 // generate
 
 template <class _ForwardIterator, class _Generator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen)
 {
@@ -2099,7 +2083,7 @@ generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen)
 // generate_n
 
 template <class _OutputIterator, class _Size, class _Generator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY  _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 generate_n(_OutputIterator __first, _Size __orig_n, _Generator __gen)
 {
@@ -2194,7 +2178,7 @@ remove_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __
 // unique
 
 template <class _ForwardIterator, class _BinaryPredicate>
-_ForwardIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
 unique(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred)
 {
     __first = _VSTD::adjacent_find<_ForwardIterator, typename add_lvalue_reference<_BinaryPredicate>::type>
@@ -2213,7 +2197,7 @@ unique(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pre
 }
 
 template <class _ForwardIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _ForwardIterator
 unique(_ForwardIterator __first, _ForwardIterator __last)
 {
@@ -2224,7 +2208,7 @@ unique(_ForwardIterator __first, _ForwardIterator __last)
 // unique_copy
 
 template <class _BinaryPredicate, class _InputIterator, class _OutputIterator>
-_OutputIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
 __unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
               input_iterator_tag, output_iterator_tag)
 {
@@ -2247,7 +2231,7 @@ __unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __r
 }
 
 template <class _BinaryPredicate, class _ForwardIterator, class _OutputIterator>
-_OutputIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
 __unique_copy(_ForwardIterator __first, _ForwardIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
               forward_iterator_tag, output_iterator_tag)
 {
@@ -2270,7 +2254,7 @@ __unique_copy(_ForwardIterator __first, _ForwardIterator __last, _OutputIterator
 }
 
 template <class _BinaryPredicate, class _InputIterator, class _ForwardIterator>
-_ForwardIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
 __unique_copy(_InputIterator __first, _InputIterator __last, _ForwardIterator __result, _BinaryPredicate __pred,
               input_iterator_tag, forward_iterator_tag)
 {
@@ -2286,7 +2270,7 @@ __unique_copy(_InputIterator __first, _InputIterator __last, _ForwardIterator __
 }
 
 template <class _InputIterator, class _OutputIterator, class _BinaryPredicate>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred)
 {
@@ -2297,7 +2281,7 @@ unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __res
 }
 
 template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp
index c72adac9e2e..8b9e109d7be 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp
@@ -11,14 +11,26 @@
 
 // template<ForwardIterator Iter, class T>
 //   requires OutputIterator<Iter, const T&>
-//   void
+//   constexpr void      // constexpr after C++17
 //   fill(Iter first, Iter last, const T& value);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+    int ia[] = {0, 1, 2, 3, 4};
+
+    std::fill(std::begin(ia), std::end(ia), 5);
+    
+    return std::all_of(std::begin(ia), std::end(ia), [](int a) {return a == 5; })
+        ;
+    }
+#endif
+
 template <class Iter>
 void
 test_char()
@@ -56,4 +68,8 @@ int main()
     test_int<bidirectional_iterator<int*> >();
     test_int<random_access_iterator<int*> >();
     test_int<int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp
index f39436048ae..fea7165af7b 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp
@@ -11,15 +11,29 @@
 
 // template<class Iter, IntegralLike Size, class T>
 //   requires OutputIterator<Iter, const T&>
-//   OutputIterator
+//   constexpr OutputIterator      // constexpr after C++17
 //   fill_n(Iter first, Size n, const T& value);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 #include "user_defined_integral.hpp"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+    const size_t N = 5;
+    int ib[] = {0, 0, 0, 0, 0, 0}; // one bigger than N
+
+    auto it = std::fill_n(std::begin(ib), N, 5);    
+    return it == (std::begin(ib) + N)
+        && std::all_of(std::begin(ib), it, [](int a) {return a == 5; })
+        && *it == 0 // don't overwrite the last value in the output array
+        ;
+    }
+#endif
+
 typedef UserDefinedIntegral<unsigned> UDI;
 
 template <class Iter>
@@ -153,4 +167,8 @@ int main()
 
     test5();
     test6();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp
index f166d67ba2f..8be501c273b 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp
@@ -12,19 +12,33 @@
 // template<ForwardIterator Iter, Callable Generator>
 //   requires OutputIterator<Iter, Generator::result_type>
 //         && CopyConstructible<Generator>
-//   void
+//   constexpr void      // constexpr after c++17
 //   generate(Iter first, Iter last, Generator gen);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 
 struct gen_test
 {
-    int operator()() const {return 1;}
+    TEST_CONSTEXPR int operator()() const {return 1;}
 };
 
+
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+    int ia[] = {0, 1, 2, 3, 4};
+
+    std::generate(std::begin(ia), std::end(ia), gen_test());
+    
+    return std::all_of(std::begin(ia), std::end(ia), [](int x) { return x == 1; })
+        ;
+    }
+#endif
+
+
 template <class Iter>
 void
 test()
@@ -44,4 +58,8 @@ int main()
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
     test<int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp
index b7322542931..98b7bea653c 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp
@@ -12,7 +12,7 @@
 // template<class Iter, IntegralLike Size, Callable Generator>
 //   requires OutputIterator<Iter, Generator::result_type>
 //         && CopyConstructible<Generator>
-//   void
+//   constexpr void      // constexpr after c++17
 //   generate_n(Iter first, Size n, Generator gen);
 
 #ifdef _MSC_VER
@@ -28,9 +28,25 @@
 
 struct gen_test
 {
-    int operator()() const {return 2;}
+    TEST_CONSTEXPR int operator()() const {return 2;}
 };
 
+
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+    const size_t N = 5;
+    int ib[] = {0, 0, 0, 0, 0, 0}; // one bigger than N
+
+    auto it = std::generate_n(std::begin(ib), N, gen_test());
+    
+    return it == (std::begin(ib) + N)
+        && std::all_of(std::begin(ib), it, [](int x) { return x == 2; })
+        && *it == 0 // don't overwrite the last value in the output array
+        ;
+    }
+#endif
+
+
 template <class Iter, class Size>
 void
 test2()
@@ -64,4 +80,8 @@ int main()
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
     test<int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp
index 049ccfe9871..1c25b480858 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp
@@ -12,7 +12,7 @@
 // template<ForwardIterator Iter>
 //   requires OutputIterator<Iter, Iter::reference>
 //         && EqualityComparable<Iter::value_type>
-//   Iter
+//   constexpr Iter        // constexpr after C++17
 //   unique(Iter first, Iter last);
 
 #include <algorithm>
@@ -22,6 +22,19 @@
 #include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+          int ia[]       = {0, 1, 1, 3, 4};
+    const int expected[] = {0, 1, 3, 4};
+	const size_t N = 4;
+	
+    auto it = std::unique(std::begin(ia), std::end(ia));
+    return it == (std::begin(ia) + N)
+        && std::equal(std::begin(ia), it, std::begin(expected), std::end(expected))
+        ;
+    }
+#endif
+
 template <class Iter>
 void
 test()
@@ -182,4 +195,8 @@ int main()
     test1<random_access_iterator<Ptr*> >();
     test1<Ptr*>();
 #endif
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
index 761dad4ecd0..48ddcf921e4 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
@@ -14,14 +14,29 @@
 //         && EqualityComparable<InIter::value_type>
 //         && HasAssign<InIter::value_type, InIter::reference>
 //         && Constructible<InIter::value_type, InIter::reference>
-//   OutIter
+//   constexpr OutIter        // constexpr after C++17
 //   unique_copy(InIter first, InIter last, OutIter result);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+          int ia[]       = {0, 1, 2, 2, 4};
+          int ib[]       = {0, 0, 0, 0, 0};
+    const int expected[] = {0, 1, 2, 4};
+
+    auto it = std::unique_copy(std::begin(ia), std::end(ia), std::begin(ib));
+    return it == (std::begin(ib) + std::size(expected))
+        && *it == 0 // don't overwrite final value in output
+        && std::equal(std::begin(ib), it, std::begin(expected), std::end(expected))
+        ;
+    }
+#endif
+
 template <class InIter, class OutIter>
 void
 test()
@@ -122,4 +137,8 @@ int main()
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp
index 6819899a114..55bfd36d570 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp
@@ -15,14 +15,30 @@
 //         && HasAssign<InIter::value_type, InIter::reference>
 //         && Constructible<InIter::value_type, InIter::reference>
 //         && CopyConstructible<Pred>
-//   OutIter
+//   constexpr OutIter        // constexpr after C++17
 //   unique_copy(InIter first, InIter last, OutIter result, Pred pred);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+          int ia[]       = {0, 1, 2, 2, 4};
+          int ib[]       = {0, 0, 0, 0, 0};
+    const int expected[] = {0, 1, 2, 4};
+
+    auto it = std::unique_copy(std::begin(ia), std::end(ia), std::begin(ib),
+                         [](int a, int b) {return a == b; });
+    return it == (std::begin(ib) + std::size(expected))
+        && *it == 0 // don't overwrite final value in output
+        && std::equal(std::begin(ib), it, std::begin(expected), std::end(expected))
+        ;
+    }
+#endif
+
 struct count_equal
 {
     static unsigned count;
@@ -149,4 +165,8 @@ int main()
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp
index 1640052058c..539d226e812 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp
@@ -12,7 +12,7 @@
 // template<ForwardIterator Iter, EquivalenceRelation<auto, Iter::value_type> Pred>
 //   requires OutputIterator<Iter, RvalueOf<Iter::reference>::type>
 //         && CopyConstructible<Pred>
-//   Iter
+//   constexpr Iter        // constexpr after C++17
 //   unique(Iter first, Iter last, Pred pred);
 
 #include <algorithm>
@@ -22,6 +22,19 @@
 #include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+          int ia[]       = {0, 1, 1, 3, 4};
+    const int expected[] = {0, 1, 3, 4};
+	const size_t N = 4;
+
+    auto it = std::unique(std::begin(ia), std::end(ia), [](int a, int b) {return a == b; });
+    return it == (std::begin(ia) + N)
+        && std::equal(std::begin(ia), it, std::begin(expected), std::end(expected))
+        ;
+    }
+#endif
+
 struct count_equal
 {
     static unsigned count;
@@ -224,4 +237,8 @@ int main()
     test1<random_access_iterator<Ptr*> >();
     test1<Ptr*>();
 #endif
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }