| //===-- include/flang/Evaluate/fold.h ---------------------------*- 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef FORTRAN_EVALUATE_FOLD_H_ |
| #define FORTRAN_EVALUATE_FOLD_H_ |
| |
| // Implements expression tree rewriting, particularly constant expression |
| // and designator reference evaluation. |
| |
| #include "common.h" |
| #include "constant.h" |
| #include "expression.h" |
| #include "tools.h" |
| #include "type.h" |
| #include <variant> |
| |
| namespace Fortran::evaluate::characteristics { |
| class TypeAndShape; |
| } |
| |
| namespace Fortran::evaluate { |
| |
| using namespace Fortran::parser::literals; |
| |
| // Fold() rewrites an expression and returns it. When the rewritten expression |
| // is a constant, UnwrapConstantValue() and GetScalarConstantValue() below will |
| // be able to extract it. |
| // Note the rvalue reference argument: the rewrites are performed in place |
| // for efficiency. |
| template <typename T> Expr<T> Fold(FoldingContext &context, Expr<T> &&expr) { |
| return Expr<T>::Rewrite(context, std::move(expr)); |
| } |
| |
| characteristics::TypeAndShape Fold( |
| FoldingContext &, characteristics::TypeAndShape &&); |
| |
| template <typename A> |
| std::optional<A> Fold(FoldingContext &context, std::optional<A> &&x) { |
| if (x) { |
| return Fold(context, std::move(*x)); |
| } else { |
| return std::nullopt; |
| } |
| } |
| |
| // UnwrapConstantValue() isolates the known constant value of |
| // an expression, if it has one. It returns a pointer, which is |
| // const-qualified when the expression is so. The value can be |
| // parenthesized. |
| template <typename T, typename EXPR> |
| auto UnwrapConstantValue(EXPR &expr) -> common::Constify<Constant<T>, EXPR> * { |
| if (auto *c{UnwrapExpr<Constant<T>>(expr)}) { |
| return c; |
| } else { |
| if constexpr (!std::is_same_v<T, SomeDerived>) { |
| if (auto *parens{UnwrapExpr<Parentheses<T>>(expr)}) { |
| return UnwrapConstantValue<T>(parens->left()); |
| } |
| } |
| return nullptr; |
| } |
| } |
| |
| // GetScalarConstantValue() extracts the known scalar constant value of |
| // an expression, if it has one. The value can be parenthesized. |
| template <typename T, typename EXPR> |
| auto GetScalarConstantValue(const EXPR &expr) -> std::optional<Scalar<T>> { |
| if (const Constant<T> *constant{UnwrapConstantValue<T>(expr)}) { |
| return constant->GetScalarValue(); |
| } else { |
| return std::nullopt; |
| } |
| } |
| |
| // When an expression is a constant integer, ToInt64() extracts its value. |
| // Ensure that the expression has been folded beforehand when folding might |
| // be required. |
| template <int KIND> |
| std::optional<std::int64_t> ToInt64( |
| const Expr<Type<TypeCategory::Integer, KIND>> &expr) { |
| if (auto scalar{ |
| GetScalarConstantValue<Type<TypeCategory::Integer, KIND>>(expr)}) { |
| return scalar->ToInt64(); |
| } else { |
| return std::nullopt; |
| } |
| } |
| |
| std::optional<std::int64_t> ToInt64(const Expr<SomeInteger> &); |
| std::optional<std::int64_t> ToInt64(const Expr<SomeType> &); |
| |
| template <typename A> |
| std::optional<std::int64_t> ToInt64(const std::optional<A> &x) { |
| if (x) { |
| return ToInt64(*x); |
| } else { |
| return std::nullopt; |
| } |
| } |
| |
| template <typename A> std::optional<std::int64_t> ToInt64(const A *p) { |
| if (p) { |
| return ToInt64(*p); |
| } else { |
| return std::nullopt; |
| } |
| } |
| } // namespace Fortran::evaluate |
| #endif // FORTRAN_EVALUATE_FOLD_H_ |