f01537b146
Original-commit: flang-compiler/f18@c005e14de9 Reviewed-on: https://github.com/flang-compiler/f18/pull/531 Tree-same-pre-rewrite: false
115 lines
3.7 KiB
C++
115 lines
3.7 KiB
C++
// Copyright (c) 2018-2019, NVIDIA CORPORATION. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef FORTRAN_EVALUATE_FOLD_H_
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#define FORTRAN_EVALUATE_FOLD_H_
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// Implements expression tree rewriting, particularly constant expression
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// evaluation.
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#include "common.h"
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#include "constant.h"
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#include "expression.h"
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#include "tools.h"
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#include "type.h"
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#include <variant>
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namespace Fortran::evaluate {
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using namespace Fortran::parser::literals;
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// Fold() rewrites an expression and returns it. When the rewritten expression
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// is a constant, UnwrapConstantValue() and GetScalarConstantValue() below will
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// be able to extract it.
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// Note the rvalue reference argument: the rewrites are performed in place
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// for efficiency.
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template<typename T> Expr<T> Fold(FoldingContext &context, Expr<T> &&expr) {
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return Expr<T>::Rewrite(context, std::move(expr));
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}
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template<typename T>
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std::optional<Expr<T>> Fold(
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FoldingContext &context, std::optional<Expr<T>> &&expr) {
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if (expr.has_value()) {
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return {Fold(context, std::move(*expr))};
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} else {
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return std::nullopt;
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}
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}
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// UnwrapConstantValue() isolates the known constant value of
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// an expression, if it has one. It returns a pointer, which is
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// const-qualified when the expression is so. The value can be
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// parenthesized.
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template<typename T, typename EXPR>
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auto UnwrapConstantValue(EXPR &expr) -> common::Constify<Constant<T>, EXPR> * {
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if (auto *c{UnwrapExpr<Constant<T>>(expr)}) {
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return c;
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} else {
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if constexpr (!std::is_same_v<T, SomeDerived>) {
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if (auto *parens{UnwrapExpr<Parentheses<T>>(expr)}) {
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return UnwrapConstantValue<T>(parens->left());
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}
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}
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return nullptr;
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}
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}
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// GetScalarConstantValue() extracts the known scalar constant value of
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// an expression, if it has one. The value can be parenthesized.
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template<typename T, typename EXPR>
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auto GetScalarConstantValue(const EXPR &expr) -> std::optional<Scalar<T>> {
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if (const Constant<T> *constant{UnwrapConstantValue<T>(expr)}) {
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return constant->GetScalarValue();
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} else {
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return std::nullopt;
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}
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}
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// Predicate: true when an expression is a constant expression (in the
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// strict sense of the Fortran standard); it may not (yet) be a hard
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// constant value.
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bool IsConstantExpr(const Expr<SomeType> &);
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// Predicate: true when an expression is an object designator with
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// constant addressing and no vector-valued subscript.
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bool IsInitialDataTarget(const Expr<SomeType> &);
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// When an expression is a constant integer, ToInt64() extracts its value.
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// Ensure that the expression has been folded beforehand when folding might
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// be required.
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template<int KIND>
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std::optional<std::int64_t> ToInt64(
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const Expr<Type<TypeCategory::Integer, KIND>> &expr) {
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if (auto scalar{
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GetScalarConstantValue<Type<TypeCategory::Integer, KIND>>(expr)}) {
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return scalar->ToInt64();
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} else {
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return std::nullopt;
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}
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}
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std::optional<std::int64_t> ToInt64(const Expr<SomeInteger> &);
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std::optional<std::int64_t> ToInt64(const Expr<SomeType> &);
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template<typename A>
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std::optional<std::int64_t> ToInt64(const std::optional<A> &x) {
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if (x.has_value()) {
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return ToInt64(*x);
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} else {
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return std::nullopt;
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}
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}
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}
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#endif // FORTRAN_EVALUATE_FOLD_H_
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