From c2d0cf1a7edc918d59267eaed5d65403f7ad4c9b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder@redhat.com>
Date: Mon, 3 Mar 2025 13:33:45 +0100
Subject: [PATCH] [clang][bytecode] Don't narrow() when dereferencing to array
 type

It doesn't make sense to do this if the result is supposed to be
an array.
---
 clang/lib/AST/ByteCode/Compiler.cpp           |   6 +-
 .../AST/ByteCode/libcxx/deref-to-array.cpp    | 391 ++++++++++++++++++
 2 files changed, 393 insertions(+), 4 deletions(-)
 create mode 100644 clang/test/AST/ByteCode/libcxx/deref-to-array.cpp

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 74f5d6ebd9ca6..aff931a1ec939 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -6028,14 +6028,12 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
     // We should already have a pointer when we get here.
     return this->delegate(SubExpr);
   case UO_Deref: // *x
-    if (DiscardResult) {
-      // assert(false);
+    if (DiscardResult)
       return this->discard(SubExpr);
-    }
 
     if (!this->visit(SubExpr))
       return false;
-    if (classifyPrim(SubExpr) == PT_Ptr)
+    if (classifyPrim(SubExpr) == PT_Ptr && !E->getType()->isArrayType())
       return this->emitNarrowPtr(E);
     return true;
 
diff --git a/clang/test/AST/ByteCode/libcxx/deref-to-array.cpp b/clang/test/AST/ByteCode/libcxx/deref-to-array.cpp
new file mode 100644
index 0000000000000..2a527ab336a0d
--- /dev/null
+++ b/clang/test/AST/ByteCode/libcxx/deref-to-array.cpp
@@ -0,0 +1,391 @@
+// RUN: %clang_cc1 -std=c++2c -fexperimental-new-constant-interpreter -verify=expected,both %s
+// RUN: %clang_cc1 -std=c++2c  -verify=ref,both %s
+
+// both-no-diagnostics
+
+namespace std {
+inline namespace {
+template <class _Tp, _Tp __v> struct integral_constant {
+  static const _Tp value = __v;
+};
+template <bool _Val> using _BoolConstant = integral_constant<bool, _Val>;
+template <class _Tp> using __remove_cv_t = __remove_cv(_Tp);
+template <class _Tp> using remove_cv_t = __remove_cv_t<_Tp>;
+template <class _From, class _To>
+constexpr bool is_convertible_v = __is_convertible(_From, _To);
+template <class _Tp> _Tp __declval(long);
+template <class _Tp> decltype(__declval<_Tp>(0)) declval();
+template <class _From, class _To>
+concept convertible_to = is_convertible_v<_From, _To> &&
+                         requires { static_cast<_To>(declval<_From>()); };
+template <class _Tp> constexpr bool is_reference_v = __is_reference(_Tp);
+template <class _Tp>
+constexpr bool is_lvalue_reference_v = __is_lvalue_reference(_Tp);
+template <class>
+constexpr bool is_nothrow_destructible_v =
+    integral_constant<bool, __is_nothrow_destructible(int)>::value;
+template <class _Tp>
+concept destructible = is_nothrow_destructible_v<_Tp>;
+template <class _Tp, class _Up>
+using _IsSame = _BoolConstant<__is_same(_Tp, _Up)>;
+template <class... _Args>
+constexpr bool is_constructible_v = __is_constructible(_Args...);
+template <class _Tp, class... _Args>
+concept constructible_from = destructible<_Tp> && is_constructible_v<_Tp>;
+template <class _Tp>
+concept move_constructible =
+    constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
+template <class _Tp, class _Up>
+concept __same_as_impl = _IsSame<_Tp, _Up>::value;
+template <class _Tp, class _Up>
+concept same_as = __same_as_impl<_Tp, _Up> && __same_as_impl<_Up, _Tp>;
+template <bool> struct _IfImpl;
+template <> struct _IfImpl<false> {
+  template <class, class _ElseRes> using _Select = _ElseRes;
+};
+template <bool _Cond, class _IfRes, class _ElseRes>
+using _If = _IfImpl<_Cond>::template _Select<_IfRes, _ElseRes>;
+template <class _If> struct conditional {
+  using type = _If;
+};
+template <bool, class _IfRes, class>
+using conditional_t = conditional<_IfRes>::type;
+template <class _Tp>
+using __libcpp_remove_reference_t = __remove_reference_t(_Tp);
+template <class _Tp>
+using remove_reference_t = __libcpp_remove_reference_t<_Tp>;
+template <class _Tp> using __decay_t = __decay(_Tp);
+template <class _Tp> using __remove_cvref_t = __remove_cvref(_Tp);
+template <class _Tp> using remove_cvref_t = __remove_cvref_t<_Tp>;
+struct __copy_cv {
+  template <class _To> using __apply = _To;
+};
+template <class, class _To> using __copy_cv_t = __copy_cv::__apply<_To>;
+template <class _Xp, class _Yp>
+using __cond_res =
+    decltype(false ? std::declval<_Xp (&)()>()() : std::declval<_Yp (&)()>()());
+template <class _Ap, class _Bp, class = remove_reference_t<_Ap>,
+          class = remove_reference_t<_Bp>>
+struct __common_ref;
+template <class _Ap, class _Bp, class, class>
+struct __common_ref : __common_ref<_Bp, _Ap> {};
+template <class _Xp, class _Yp>
+using __common_ref_t = __common_ref<_Xp, _Yp>::__type;
+template <class _Xp, class _Yp>
+using __cv_cond_res =
+    __cond_res<__copy_cv_t<_Xp, _Yp> &, __copy_cv_t<_Yp, _Xp> &>;
+template <class _Ap, class _Bp, class _Xp, class _Yp>
+  requires requires { typename __cv_cond_res<_Xp, _Yp>; } &&
+           is_reference_v<__cv_cond_res<_Xp, _Yp>>
+struct __common_ref<_Ap, _Bp &, _Xp, _Yp> {
+  using __type = __cv_cond_res<_Xp, _Yp>;
+};
+template <class _Tp, class _Up>
+using __common_ref_D = __common_ref_t<const _Tp, _Up &>;
+template <class _Ap, class _Bp, class _Xp, class _Yp>
+  requires requires { typename __common_ref_D<_Xp, _Yp>; } &&
+           is_convertible_v<_Ap, __common_ref_D<_Xp, _Yp>>
+struct __common_ref<_Ap &&, _Bp &, _Xp, _Yp> {
+  using __type = __common_ref_D<_Xp, _Yp>;
+};
+template <class...> struct common_reference;
+template <class... _Types>
+using common_reference_t = common_reference<_Types...>::type;
+template <class, class> struct __common_reference_sub_bullet1;
+template <class _Tp, class _Up>
+struct common_reference<_Tp, _Up> : __common_reference_sub_bullet1<_Tp, _Up> {};
+template <class _Tp, class _Up>
+  requires is_reference_v<_Tp> && is_reference_v<_Up> &&
+           requires { typename __common_ref_t<_Tp, _Up>; }
+struct __common_reference_sub_bullet1<_Tp, _Up> {
+  using type = __common_ref_t<_Tp, _Up>;
+};
+template <class _Tp, class _Up>
+concept common_reference_with =
+    same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>> &&
+    convertible_to<_Tp, common_reference_t<_Tp, _Up>> &&
+    convertible_to<_Up, common_reference_t<_Tp, _Up>>;
+template <class _Tp>
+using __make_const_lvalue_ref = __libcpp_remove_reference_t<_Tp> &;
+template <class _Lhs, class _Rhs>
+concept assignable_from =
+    is_lvalue_reference_v<_Lhs> &&
+    common_reference_with<__make_const_lvalue_ref<_Lhs>,
+                          __make_const_lvalue_ref<_Rhs>> &&
+    requires(_Lhs __lhs, _Rhs __rhs) {
+      { __rhs } -> same_as<_Lhs>;
+    };
+template <class _Tp> constexpr __libcpp_remove_reference_t<_Tp> &&move(_Tp &&);
+typedef int type;
+template <bool, class = void> using __enable_if_t = type;
+namespace ranges {
+inline namespace {
+auto swap = int{};
+}
+} // namespace ranges
+template <class _Tp> constexpr bool is_object_v = __is_object(_Tp);
+template <class _Tp>
+concept movable = is_object_v<_Tp> && move_constructible<_Tp> &&
+                  assignable_from<_Tp &, _Tp>;
+template <decltype(sizeof(int)), class> struct tuple_element;
+template <class...> class tuple;
+template <template <class> class _Templ, class... _Args,
+          class = _Templ<_Args...>>
+integral_constant<bool, true> __sfinae_test_impl(int);
+template <template <class> class, class>
+integral_constant<bool, false> __sfinae_test_impl(...);
+template <template <class> class _Templ, class... _Args>
+using _IsValidExpansion =
+    decltype(std::__sfinae_test_impl<_Templ, _Args...>(0));
+template <class _Tp>
+using __test_for_primary_template =
+    __enable_if_t<_IsSame<_Tp, typename _Tp::__primary_template>::value>;
+template <class _Tp>
+using __is_primary_template =
+    _IsValidExpansion<__test_for_primary_template, _Tp>;
+template <class> struct iterator_traits;
+template <class> struct __cond_value_type;
+template <class _Tp>
+  requires is_object_v<_Tp>
+struct __cond_value_type<_Tp> {
+  using value_type = remove_cv_t<_Tp>;
+};
+template <class> struct indirectly_readable_traits;
+template <class _Tp>
+struct indirectly_readable_traits<_Tp *> : __cond_value_type<_Tp> {};
+template <bool> struct _OrImpl;
+template <> struct _OrImpl<true> {
+  template <class, class _First, class... _Rest>
+  using _Result = _OrImpl<!(_First::value) &&
+                          sizeof...(_Rest)>::template _Result<_First, _Rest...>;
+};
+template <> struct _OrImpl<false> {
+  template <class _Res, class...> using _Result = _Res;
+};
+template <class... _Args>
+using _Or =
+    _OrImpl<sizeof...(_Args) !=
+            0>::template _Result<integral_constant<bool, false>, _Args...>;
+template <class _Tp> using __with_reference = _Tp;
+template <class _Tp>
+concept __can_reference = requires { typename __with_reference<_Tp>; };
+template <class _Tp>
+concept __dereferenceable = requires(_Tp __t) {
+  { __t };
+};
+template <__dereferenceable _Tp>
+using iter_reference_t = decltype(*std::declval<_Tp>());
+struct input_iterator_tag {};
+struct contiguous_iterator_tag : input_iterator_tag {};
+template <class> struct __iter_traits_cache {
+  using type = _If<__is_primary_template<iterator_traits<int>>::value, int,
+                   iterator_traits<int>>;
+};
+template <class _Iter> using _ITER_TRAITS = __iter_traits_cache<_Iter>::type;
+struct __iter_concept_concept_test {
+  template <class _Iter> using _Apply = _ITER_TRAITS<_Iter>::iterator_concept;
+};
+template <class, class _Tester>
+struct __test_iter_concept : _IsValidExpansion<_Tester::template _Apply, int>,
+                             _Tester {};
+template <class _Iter> struct __iter_concept_cache {
+  using type =
+      _Or<__test_iter_concept<_Iter, __iter_concept_concept_test>,
+          __test_iter_concept<_Iter, int>, __test_iter_concept<_Iter, int>>;
+};
+template <class _Iter>
+using _ITER_CONCEPT = __iter_concept_cache<_Iter>::type::template _Apply<_Iter>;
+template <class _Tp>
+  requires is_object_v<_Tp>
+struct iterator_traits<_Tp> {
+  typedef contiguous_iterator_tag iterator_concept;
+};
+template <class _Ip>
+using iter_value_t = conditional_t<
+    __is_primary_template<iterator_traits<remove_cvref_t<_Ip>>>::value,
+    indirectly_readable_traits<remove_cvref_t<_Ip>>,
+    iterator_traits<remove_cvref_t<_Ip>>>::value_type;
+template <class _Tp> _Tp *addressof(_Tp &);
+template <class _Bp, class _Dp>
+constexpr bool is_base_of_v = __is_base_of(_Bp, _Dp);
+template <class _Dp, class _Bp>
+concept derived_from = is_base_of_v<_Bp, _Dp> && is_convertible_v<_Dp *, _Bp *>;
+namespace ranges {
+struct Trans_NS___iter_move___fn {
+  template <class _Ip>
+  auto operator()(_Ip __i) -> decltype(std::move(*__i));
+};
+auto iter_move = Trans_NS___iter_move___fn{};
+} // namespace ranges
+template <__dereferenceable _Tp>
+  requires requires {
+    { ranges::iter_move };
+  }
+using iter_rvalue_reference_t =
+    decltype(ranges::iter_move(std::declval<_Tp>()));
+template <class _In>
+concept __indirectly_readable_impl =
+    requires { typename iter_value_t<_In>; } &&
+    common_reference_with<iter_reference_t<_In>, iter_value_t<_In> &> &&
+    common_reference_with<iter_reference_t<_In>,
+                          iter_rvalue_reference_t<_In>> &&
+    common_reference_with<iter_rvalue_reference_t<_In>, iter_value_t<_In> &>;
+template <class _In>
+concept indirectly_readable = __indirectly_readable_impl<remove_cvref_t<_In>>;
+template <class _Ip>
+concept weakly_incrementable =
+    !same_as<_Ip, bool> && movable<_Ip> && requires(_Ip __i) { __i; };
+template <class _Ip>
+concept input_or_output_iterator = requires(_Ip __i) {
+  { __i };
+} && weakly_incrementable<_Ip>;
+template <class _Ip>
+concept input_iterator =
+    input_or_output_iterator<_Ip> && indirectly_readable<_Ip> && requires {
+      typename _ITER_CONCEPT<_Ip>;
+    } && derived_from<_ITER_CONCEPT<_Ip>, input_iterator_tag>;
+namespace ranges {
+struct __fn {
+  template <class _Tp, decltype(sizeof(int)) _Np>
+  constexpr auto operator()(_Tp (&__t)[_Np]) const
+  {
+    return __t;
+  }
+  template <class _Tp> constexpr auto operator()(_Tp __t) const {
+    return static_cast<std::__decay_t<decltype((__t.begin()))>>(__t.begin());
+  }
+};
+inline namespace {
+auto begin = __fn{};
+}
+template <class _Tp>
+using iterator_t = decltype(ranges::begin(std::declval<_Tp &>()));
+inline namespace {
+auto end = int{};
+}
+template <class _Derived>
+class view_interface;
+template <class _Op, class _Yp>
+  requires is_convertible_v<_Op, view_interface<_Yp>>
+void __is_derived_from_view_interface();
+template <class _Tp>
+bool enable_view = derived_from<_Tp, int> ||
+                   requires { ranges::__is_derived_from_view_interface; };
+template <class>
+concept range = requires { ranges::end; };
+template <class _Tp>
+concept input_range = range<_Tp> && input_iterator<iterator_t<_Tp>>;
+template <class _Tp>
+concept view = range<_Tp> && movable<_Tp> && enable_view<_Tp>;
+template <class _Tp>
+concept viewable_range =
+    range<_Tp> &&
+    ((view<remove_cvref_t<_Tp>> && constructible_from<remove_cvref_t<_Tp>>) ||
+     (!view<remove_cvref_t<_Tp>> && (is_lvalue_reference_v<_Tp>)));
+} // namespace ranges
+template <decltype(sizeof(int))...> struct __tuple_indices;
+template <class _IdxType, _IdxType... _Values> struct __integer_sequence {
+  template <decltype(sizeof(int)) _Sp>
+  using __to_tuple_indices = __tuple_indices<(_Values)...>;
+};
+template <decltype(sizeof(int)) _Ep, decltype(sizeof(int)) _Sp>
+using __make_indices_imp =
+    __make_integer_seq<__integer_sequence, decltype(sizeof(int)),
+                       _Sp>::template __to_tuple_indices<_Sp>;
+template <int _Ep, decltype(sizeof(int)) _Sp = 0> struct __make_tuple_indices {
+  typedef __make_indices_imp<_Ep, _Sp> type;
+};
+template <class...> struct __tuple_types;
+namespace ranges {
+template <class _Derived>
+class view_interface {};
+} // namespace ranges
+template <decltype(sizeof(int)) _Ip, class... _Types>
+struct tuple_element<_Ip, __tuple_types<_Types...>> {
+  using type = __type_pack_element<_Ip, _Types...>;
+};
+template <decltype(sizeof(int)) _Ip, class... _Tp>
+struct tuple_element<_Ip, tuple<_Tp...>> {
+  using type = tuple_element<_Ip, __tuple_types<_Tp...>>::type;
+};
+
+template <class... _Tp> struct tuple {
+  int __value_;
+  constexpr int get() { return __value_; }
+};
+template <int _Ip, class... _Tp> constexpr void get(tuple<_Tp...> __t) {
+  __t.get();
+}
+namespace ranges {
+template <class _Tp>
+struct __range_adaptor_closure {};
+template <range _Range>
+  requires is_object_v<_Range>
+struct ref_view : view_interface<ref_view<_Range>> {
+  _Range *__range_;
+
+  template <class _Tp>
+  constexpr ref_view(_Tp &&__t)
+      : __range_(std::addressof(static_cast<_Range &>(__t))) {}
+  constexpr iterator_t<_Range> begin() { return ranges::begin(*__range_); }
+};
+template <class _Range> ref_view(_Range &) -> ref_view<_Range>;
+} // namespace ranges
+namespace ranges::views {
+struct __fn : __range_adaptor_closure<__fn> {
+  template <class _Tp> auto operator()(_Tp &&__t) const {
+    return ranges::ref_view{__t};
+  }
+};
+inline namespace {
+auto all = __fn{};
+}
+template <ranges::viewable_range _Range>
+using all_t = decltype(views::all(std::declval<_Range>()));
+} // namespace ranges::views
+namespace ranges {
+template <input_range _View, decltype(sizeof(int)) _Np>
+struct elements_view : view_interface<elements_view<_View, _Np>> {
+  class __iterator;
+
+  constexpr elements_view(_View __base) : __base_(std::move(__base)) {}
+  constexpr auto begin() const { return __iterator(ranges::begin(__base_)); }
+
+  _View __base_ = _View();
+};
+template <input_range _View, decltype(sizeof(int)) _Np>
+struct elements_view<_View, _Np>::__iterator {
+  iterator_t<_View> __current_;
+
+  constexpr void operator*() {
+    auto a = *__current_;
+  }
+};
+namespace views {
+namespace __elements {
+template <int _Np> struct __fn : __range_adaptor_closure<__fn<_Np>> {
+  template <class _Range>
+  constexpr auto operator()(_Range &&__range) const
+      -> decltype(elements_view<all_t<_Range>, _Np>(__range)) {
+    return elements_view<all_t<_Range>, _Np>(__range);
+  }
+};
+} // namespace __elements
+inline namespace {
+template <decltype(sizeof(int)) _Np> auto elements = __elements::__fn<_Np>{};
+}
+} // namespace views
+} // namespace ranges
+} // namespace
+} // namespace std
+constexpr bool test() {
+  std::tuple<short, long> ts[]{{}};
+
+
+  auto ev = std::ranges::views::elements<1>(ts);
+  auto it = ev.begin();
+
+  *it;
+  return true;
+}
+static_assert(test());