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| 1 | //===-- include/flang/Evaluate/fold.h ---------------------------*- C++ -*-===// |
|---|---|
| 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 | #ifndef FORTRAN_EVALUATE_FOLD_H_ |
| 10 | #define FORTRAN_EVALUATE_FOLD_H_ |
| 11 | |
| 12 | // Implements expression tree rewriting, particularly constant expression |
| 13 | // and designator reference evaluation. |
| 14 | |
| 15 | #include "common.h" |
| 16 | #include "constant.h" |
| 17 | #include "expression.h" |
| 18 | #include "tools.h" |
| 19 | #include "type.h" |
| 20 | #include <variant> |
| 21 | |
| 22 | namespace Fortran::evaluate::characteristics { |
| 23 | class TypeAndShape; |
| 24 | } |
| 25 | |
| 26 | namespace Fortran::evaluate { |
| 27 | |
| 28 | using namespace Fortran::parser::literals; |
| 29 | |
| 30 | // Fold() rewrites an expression and returns it. When the rewritten expression |
| 31 | // is a constant, UnwrapConstantValue() and GetScalarConstantValue() below will |
| 32 | // be able to extract it. |
| 33 | // Note the rvalue reference argument: the rewrites are performed in place |
| 34 | // for efficiency. |
| 35 | template <typename T> Expr<T> Fold(FoldingContext &context, Expr<T> &&expr) { |
| 36 | return Expr<T>::Rewrite(context, std::move(expr)); |
| 37 | } |
| 38 | |
| 39 | characteristics::TypeAndShape Fold( |
| 40 | FoldingContext &, characteristics::TypeAndShape &&); |
| 41 | |
| 42 | template <typename A> |
| 43 | std::optional<A> Fold(FoldingContext &context, std::optional<A> &&x) { |
| 44 | if (x) { |
| 45 | return Fold(context, std::move(*x)); |
| 46 | } else { |
| 47 | return std::nullopt; |
| 48 | } |
| 49 | } |
| 50 | |
| 51 | // UnwrapConstantValue() isolates the known constant value of |
| 52 | // an expression, if it has one. It returns a pointer, which is |
| 53 | // const-qualified when the expression is so. The value can be |
| 54 | // parenthesized. |
| 55 | template <typename T, typename EXPR> |
| 56 | auto UnwrapConstantValue(EXPR &expr) -> common::Constify<Constant<T>, EXPR> * { |
| 57 | if (auto *c{UnwrapExpr<Constant<T>>(expr)}) { |
| 58 | return c; |
| 59 | } else { |
| 60 | if (auto *parens{UnwrapExpr<Parentheses<T>>(expr)}) { |
| 61 | return UnwrapConstantValue<T>(parens->left()); |
| 62 | } |
| 63 | return nullptr; |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | // GetScalarConstantValue() extracts the known scalar constant value of |
| 68 | // an expression, if it has one. The value can be parenthesized. |
| 69 | template <typename T, typename EXPR> |
| 70 | constexpr auto GetScalarConstantValue(const EXPR &expr) |
| 71 | -> std::optional<Scalar<T>> { |
| 72 | if (const Constant<T> *constant{UnwrapConstantValue<T>(expr)}) { |
| 73 | return constant->GetScalarValue(); |
| 74 | } else { |
| 75 | return std::nullopt; |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | // When an expression is a constant integer, ToInt64() extracts its value. |
| 80 | // Ensure that the expression has been folded beforehand when folding might |
| 81 | // be required. |
| 82 | template <int KIND> |
| 83 | constexpr std::optional<std::int64_t> ToInt64( |
| 84 | const Expr<Type<TypeCategory::Integer, KIND>> &expr) { |
| 85 | if (auto scalar{ |
| 86 | GetScalarConstantValue<Type<TypeCategory::Integer, KIND>>(expr)}) { |
| 87 | return scalar->ToInt64(); |
| 88 | } else { |
| 89 | return std::nullopt; |
| 90 | } |
| 91 | } |
| 92 | |
| 93 | std::optional<std::int64_t> ToInt64(const Expr<SomeInteger> &); |
| 94 | std::optional<std::int64_t> ToInt64(const Expr<SomeType> &); |
| 95 | std::optional<std::int64_t> ToInt64(const ActualArgument &); |
| 96 | |
| 97 | template <typename A> |
| 98 | std::optional<std::int64_t> ToInt64(const std::optional<A> &x) { |
| 99 | if (x) { |
| 100 | return ToInt64(*x); |
| 101 | } else { |
| 102 | return std::nullopt; |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | template <typename A> std::optional<std::int64_t> ToInt64(A *p) { |
| 107 | if (p) { |
| 108 | return ToInt64(std::as_const(*p)); |
| 109 | } else { |
| 110 | return std::nullopt; |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | } // namespace Fortran::evaluate |
| 115 | #endif // FORTRAN_EVALUATE_FOLD_H_ |
| 116 |
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