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[Flang] Add a Fortran Standards Support doc #132195
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[Flang] Add a Fortran Standards Support doc
kiranchandramohan 8499992
Address review comments
kiranchandramohan 6c4b380
Add support tables for Fortran 2023 and Fortran 2018 standards
kiranchandramohan 84165a7
Move MIN MAX extension to Fortran 2003 table
kiranchandramohan 8f9db84
Remove line about extending support for Fortran 2018 and Fortran 2023
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Address review comments
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Address review comment about multi-image execution
kiranchandramohan 66199ad
Partially address comments from Mark
kiranchandramohan 04fb498
Address Steve's comments
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| <!--===- docs/FortranStandardsSupport.md | ||
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| 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 | ||
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| --> | ||
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| # Flang Fortran Standards Support | ||
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| ```{contents} | ||
| --- | ||
| local: | ||
| --- | ||
| ``` | ||
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| This document summarizes Fortran standards support in Flang. The information is only provided as a guideline. The | ||
| TODOs/Not Yet Implemented messages emitted by the compiler for unimplemented features should be treated as authoritative. | ||
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| The standards support information is provided as a table with three columns that are self explanatory. The Status column uses | ||
| the letters **P**, **Y**, **N** for the implementation status: | ||
| - **P** : When the implementation is incomplete for a few cases | ||
| - **Y** : When the implementation is complete | ||
| - **N** : When the implementation is absent | ||
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| Note : No distinction is made between the support in the Parser/Semantics and MLIR or Lowering support. | ||
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| ## Fortran 2023 | ||
| See [document](F202X.md) for a brief discussion about the new features in Fortran 2023. The following table summarizes the | ||
| status of all important Fortran 2023 features. | ||
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| | Feature | Status | Comments | | ||
| |------------------------------------------------------------|--------|---------------------------------------------------------| | ||
| | Allow longer statement lines and overall statement length | Y | | | ||
| | Automatic allocation of lengths of character variables | N | | | ||
| | The specifiers typeof and classof | N | | | ||
| | Conditional expressions and arguments | N | | | ||
| | More use of boz constants | P | All usages other than enum are supported | | ||
| | Intrinsics for extracting tokens from a string | N | | | ||
| | Intrinsics for Trig functions that work in degrees | N | | | ||
| | Intrinsics for Trig functions that work in half revolutions| N | | | ||
| | Changes to system_clock | N | | | ||
| | Changes for conformance with the new IEEE standard | Y | | | ||
| | Additional named constants to specify kinds | Y | | | ||
| | Extensions for c_f_pointer intrinsic | N | | | ||
| | Procedures for converting between fortran and c strings | N | | | ||
| | The at edit descriptor | N | | | ||
| | Control over leading zeros in output of real values | N | | | ||
| | Extensions for Namelist | N | | | ||
| | Allow an object of a type with a coarray ultimate component to be an array or allocatable | N | | | ||
| | Put with Notify | N | | | ||
| | Error conditions in collectives | N | | | ||
| | Simple procedures | N | | | ||
| | Using integer arrays to specify subscripts | N | | | ||
| | Using integer arrays to specify rank and bound of an array | N | | | ||
| | Using an integer constant to specify rank | N | | | ||
| | Reduction specifier for do concurrent | P | Syntax is accepted | | ||
| | Enumerations | N | | | ||
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| ## Fortran 2018 | ||
| All features except those listed in the following table are supported. Almost all of the unsupported features are related to | ||
| the multi-image execution. | ||
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| | Feature | Status | Comments | | ||
| |------------------------------------------------------------|--------|---------------------------------------------------------| | ||
| | Asynchronous communication | P | Syntax is accepted | | ||
| | Teams | N | | | ||
| | Image failure | P | stat_failed_image is added | | ||
| | Form team statement | N | | | ||
| | Change team construct | N | | | ||
| | Coarrays allocated in teams | N | | | ||
| | Critical construct | N | | | ||
| | Lock and unlock statements | N | | | ||
| | Events | N | | | ||
| | Sync team construct | N | | | ||
| | Image selectors | N | | | ||
| | Intrinsic functions get_team and team_number | N | | | ||
| | Intrinsic function image_index | N | | | ||
| | Intrinsic function num_images | N | | | ||
| | Intrinsic function this_image | N | | | ||
| | Intrinsic move_alloc extensions | P | | | ||
| | Detecting failed and stopped images | N | | | ||
| | Collective subroutines | N | | | ||
| | New and enhanced atomic subroutines | N | | | ||
| | Failed images and stat= specifiers | N | | | ||
| | Intrinsic function coshape | N | | | ||
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| ## Fortran 2008 | ||
| All features except those listed in the following table are supported. | ||
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| | Feature | Status | Comments | | ||
| |------------------------------------------------------------|--------|---------------------------------------------------------| | ||
| | Coarrays | N | Lowering and runtime support is not implemented | | ||
| | do concurrent | P | Sequential execution works. Parallel support in progress| | ||
| | Internal procedure as an actual argument or pointer target | Y | Current implementation requires stack to be executable. See [Proposal](InternalProcedureTrampolines.md) | | ||
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| ## Fortran 2003 | ||
| All features except those listed in the following table are supported. | ||
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| | Feature | Status | Comments | | ||
| |------------------------------------------------------------|--------|---------------------------------------------------------| | ||
| | Parameterized Derived Types | P | PDT with length type parameters is not supported. See [Proposal](ParameterizedDerivedTypes.md) | | ||
| | Assignment to allocatable | P | Assignment to whole allocatable in FORALL is not implemented | | ||
| | The VOLATILE attribute | P | VOLATILE in procedure interfaces is not implemented | | ||
| | Asynchronous input/output | P | IO will happen synchronously | | ||
| | MIN/MAX extensions for CHARACTER | P | Some variants are not supported | | ||
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| ## Fortran 95 | ||
| All features are supported. | ||
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| ## Fortran 90 | ||
| All features are supported. | ||
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| ## FORTRAN 77 | ||
| All features are supported. | ||
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I still think we should make this easier for readers (explain the letters, order them by degree of completion)
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Done. The following format was used.