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| 1 | //===-- StatementContext.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 | // Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/ |
| 10 | // |
| 11 | //===----------------------------------------------------------------------===// |
| 12 | |
| 13 | #ifndef FORTRAN_LOWER_STATEMENTCONTEXT_H |
| 14 | #define FORTRAN_LOWER_STATEMENTCONTEXT_H |
| 15 | |
| 16 | #include "llvm/ADT/STLExtras.h" |
| 17 | #include "llvm/ADT/SmallVector.h" |
| 18 | #include <functional> |
| 19 | #include <optional> |
| 20 | |
| 21 | namespace Fortran::lower { |
| 22 | |
| 23 | /// When lowering a statement, temporaries for intermediate results may be |
| 24 | /// allocated on the heap. A StatementContext enables their deallocation |
| 25 | /// with one of several explicit finalize calls, or with an implicit |
| 26 | /// call to finalizeAndPop() at the end of the context. A context may prohibit |
| 27 | /// temporary allocation. Otherwise, an initial "outer" context scope may have |
| 28 | /// nested context scopes, which must make explicit subscope finalize calls. |
| 29 | /// |
| 30 | /// In addition to being useful for individual action statement contexts, a |
| 31 | /// StatementContext is also useful for construct blocks delimited by a pair |
| 32 | /// of statements such as (block-stmt, end-block-stmt), or a program unit |
| 33 | /// delimited by a pair of statements such as (subroutine-stmt, end-subroutine- |
| 34 | /// stmt). Attached cleanup code for these contexts may include stack |
| 35 | /// management code, deallocation code, and finalization of derived type |
| 36 | /// entities in the context. |
| 37 | class StatementContext { |
| 38 | public: |
| 39 | explicit StatementContext(bool cleanupProhibited = false) { |
| 40 | if (cleanupProhibited) |
| 41 | return; |
| 42 | cufs.push_back({}); |
| 43 | } |
| 44 | |
| 45 | ~StatementContext() { |
| 46 | if (!cufs.empty()) |
| 47 | finalizeAndPop(); |
| 48 | assert(cufs.empty() && "invalid StatementContext destructor call"); |
| 49 | } |
| 50 | |
| 51 | using CleanupFunction = std::function<void()>; |
| 52 | |
| 53 | /// Push a context subscope. |
| 54 | void pushScope() { |
| 55 | assert(!cufs.empty() && "invalid pushScope statement context"); |
| 56 | cufs.push_back({}); |
| 57 | } |
| 58 | |
| 59 | /// Append a cleanup function to the "list" of cleanup functions. |
| 60 | void attachCleanup(CleanupFunction cuf) { |
| 61 | assert(!cufs.empty() && "invalid attachCleanup statement context"); |
| 62 | if (cufs.back()) { |
| 63 | CleanupFunction oldCleanup = *cufs.back(); |
| 64 | cufs.back() = [=]() { |
| 65 | cuf(); |
| 66 | oldCleanup(); |
| 67 | }; |
| 68 | } else { |
| 69 | cufs.back() = cuf; |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | /// Make cleanup calls. Retain the stack top list for a repeat call. |
| 74 | void finalizeAndKeep() { |
| 75 | assert(!cufs.empty() && "invalid finalize statement context"); |
| 76 | if (cufs.back()) |
| 77 | (*cufs.back())(); |
| 78 | } |
| 79 | |
| 80 | /// Make cleanup calls. Clear the stack top list. |
| 81 | void finalizeAndReset() { |
| 82 | finalizeAndKeep(); |
| 83 | cufs.back().reset(); |
| 84 | } |
| 85 | |
| 86 | /// Make cleanup calls. Pop the stack top list. |
| 87 | void finalizeAndPop() { |
| 88 | finalizeAndKeep(); |
| 89 | cufs.pop_back(); |
| 90 | } |
| 91 | |
| 92 | bool hasCode() const { |
| 93 | return !cufs.empty() && llvm::any_of(cufs, [](auto &opt) -> bool { |
| 94 | return opt.has_value(); |
| 95 | }); |
| 96 | } |
| 97 | |
| 98 | private: |
| 99 | // A statement context should never be copied or moved. |
| 100 | StatementContext(const StatementContext &) = delete; |
| 101 | StatementContext &operator=(const StatementContext &) = delete; |
| 102 | StatementContext(StatementContext &&) = delete; |
| 103 | |
| 104 | // Stack of cleanup function "lists" (nested cleanup function calls). |
| 105 | llvm::SmallVector<std::optional<CleanupFunction>> cufs; |
| 106 | }; |
| 107 | |
| 108 | } // namespace Fortran::lower |
| 109 | |
| 110 | #endif // FORTRAN_LOWER_STATEMENTCONTEXT_H |
| 111 |
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