1 //===-- lib/Evaluate/initial-image.cpp ------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "flang/Evaluate/initial-image.h"
10 #include "flang/Semantics/scope.h"
11 #include "flang/Semantics/tools.h"
12 #include <cstring>
13 
14 namespace Fortran::evaluate {
15 
16 auto InitialImage::Add(ConstantSubscript offset, std::size_t bytes,
17     const Constant<SomeDerived> &x, FoldingContext &context) -> Result {
18   if (offset < 0 || offset + bytes > data_.size()) {
19     return OutOfRange;
20   } else {
21     auto elements{TotalElementCount(x.shape())};
22     auto elementBytes{bytes > 0 ? bytes / elements : 0};
23     if (elements * elementBytes != bytes) {
24       return SizeMismatch;
25     } else {
26       auto at{x.lbounds()};
27       for (auto elements{TotalElementCount(x.shape())}; elements-- > 0;
28            x.IncrementSubscripts(at)) {
29         auto scalar{x.At(at)};
30         // TODO: length type parameter values?
31         for (const auto &[symbolRef, indExpr] : scalar) {
32           const Symbol &component{*symbolRef};
33           if (component.offset() + component.size() > elementBytes) {
34             return SizeMismatch;
35           } else if (IsPointer(component)) {
36             AddPointer(offset + component.offset(), indExpr.value());
37           } else {
38             Result added{Add(offset + component.offset(), component.size(),
39                 indExpr.value(), context)};
40             if (added != Ok) {
41               return Ok;
42             }
43           }
44         }
45         offset += elementBytes;
46       }
47     }
48     return Ok;
49   }
50 }
51 
52 void InitialImage::AddPointer(
53     ConstantSubscript offset, const Expr<SomeType> &pointer) {
54   pointers_.emplace(offset, pointer);
55 }
56 
57 void InitialImage::Incorporate(ConstantSubscript toOffset,
58     const InitialImage &from, ConstantSubscript fromOffset,
59     ConstantSubscript bytes) {
60   CHECK(from.pointers_.empty()); // pointers are not allowed in EQUIVALENCE
61   CHECK(fromOffset >= 0 && bytes >= 0 &&
62       static_cast<std::size_t>(fromOffset + bytes) <= from.size());
63   CHECK(static_cast<std::size_t>(toOffset + bytes) <= size());
64   std::memcpy(&data_[toOffset], &from.data_[fromOffset], bytes);
65 }
66 
67 // Classes used with common::SearchTypes() to (re)construct Constant<> values
68 // of the right type to initialize each symbol from the values that have
69 // been placed into its initialization image by DATA statements.
70 class AsConstantHelper {
71 public:
72   using Result = std::optional<Expr<SomeType>>;
73   using Types = AllTypes;
74   AsConstantHelper(FoldingContext &context, const DynamicType &type,
75       const ConstantSubscripts &extents, const InitialImage &image,
76       ConstantSubscript offset = 0)
77       : context_{context}, type_{type}, image_{image}, extents_{extents},
78         offset_{offset} {
79     CHECK(!type.IsPolymorphic());
80   }
81   template <typename T> Result Test() {
82     if (T::category != type_.category()) {
83       return std::nullopt;
84     }
85     if constexpr (T::category != TypeCategory::Derived) {
86       if (T::kind != type_.kind()) {
87         return std::nullopt;
88       }
89     }
90     using Const = Constant<T>;
91     using Scalar = typename Const::Element;
92     std::size_t elements{TotalElementCount(extents_)};
93     std::vector<Scalar> typedValue(elements);
94     auto elemBytes{
95         ToInt64(type_.MeasureSizeInBytes(context_, GetRank(extents_) > 0))};
96     CHECK(elemBytes && *elemBytes >= 0);
97     std::size_t stride{static_cast<std::size_t>(*elemBytes)};
98     CHECK(offset_ + elements * stride <= image_.data_.size());
99     if constexpr (T::category == TypeCategory::Derived) {
100       const semantics::DerivedTypeSpec &derived{type_.GetDerivedTypeSpec()};
101       for (auto iter : DEREF(derived.scope())) {
102         const Symbol &component{*iter.second};
103         bool isProcPtr{IsProcedurePointer(component)};
104         if (isProcPtr || component.has<semantics::ObjectEntityDetails>()) {
105           auto at{offset_ + component.offset()};
106           if (isProcPtr) {
107             for (std::size_t j{0}; j < elements; ++j, at += stride) {
108               if (Result value{image_.AsConstantPointer(at)}) {
109                 typedValue[j].emplace(component, std::move(*value));
110               }
111             }
112           } else if (IsPointer(component)) {
113             for (std::size_t j{0}; j < elements; ++j, at += stride) {
114               if (Result value{image_.AsConstantPointer(at)}) {
115                 typedValue[j].emplace(component, std::move(*value));
116               }
117             }
118           } else {
119             auto componentType{DynamicType::From(component)};
120             CHECK(componentType.has_value());
121             auto componentExtents{GetConstantExtents(context_, component)};
122             CHECK(componentExtents.has_value());
123             for (std::size_t j{0}; j < elements; ++j, at += stride) {
124               if (Result value{image_.AsConstant(
125                       context_, *componentType, *componentExtents, at)}) {
126                 typedValue[j].emplace(component, std::move(*value));
127               }
128             }
129           }
130         }
131       }
132       return AsGenericExpr(
133           Const{derived, std::move(typedValue), std::move(extents_)});
134     } else if constexpr (T::category == TypeCategory::Character) {
135       auto length{static_cast<ConstantSubscript>(stride) / T::kind};
136       for (std::size_t j{0}; j < elements; ++j) {
137         using Char = typename Scalar::value_type;
138         const Char *data{reinterpret_cast<const Char *>(
139             &image_.data_[offset_ + j * stride])};
140         typedValue[j].assign(data, length);
141       }
142       return AsGenericExpr(
143           Const{length, std::move(typedValue), std::move(extents_)});
144     } else {
145       // Lengthless intrinsic type
146       CHECK(sizeof(Scalar) <= stride);
147       for (std::size_t j{0}; j < elements; ++j) {
148         std::memcpy(&typedValue[j], &image_.data_[offset_ + j * stride],
149             sizeof(Scalar));
150       }
151       return AsGenericExpr(Const{std::move(typedValue), std::move(extents_)});
152     }
153   }
154 
155 private:
156   FoldingContext &context_;
157   const DynamicType &type_;
158   const InitialImage &image_;
159   ConstantSubscripts extents_; // a copy
160   ConstantSubscript offset_;
161 };
162 
163 std::optional<Expr<SomeType>> InitialImage::AsConstant(FoldingContext &context,
164     const DynamicType &type, const ConstantSubscripts &extents,
165     ConstantSubscript offset) const {
166   return common::SearchTypes(
167       AsConstantHelper{context, type, extents, *this, offset});
168 }
169 
170 std::optional<Expr<SomeType>> InitialImage::AsConstantPointer(
171     ConstantSubscript offset) const {
172   auto iter{pointers_.find(offset)};
173   return iter == pointers_.end() ? std::optional<Expr<SomeType>>{}
174                                  : iter->second;
175 }
176 
177 } // namespace Fortran::evaluate
178