[flang] CUDA Fortran - part 1/5: parsing

Begin upstreaming of CUDA Fortran support in LLVM Flang.

This first patch implements parsing for CUDA Fortran syntax,
including:
- a new LanguageFeature en

[flang] CUDA Fortran - part 1/5: parsing

Begin upstreaming of CUDA Fortran support in LLVM Flang.

This first patch implements parsing for CUDA Fortran syntax,
including:
- a new LanguageFeature enum value for CUDA Fortran
- driver change to enable that feature for *.cuf and *.CUF source files
- parse tree representation of CUDA Fortran syntax
- dumping and unparsing of the parse tree
- the actual parsers for CUDA Fortran syntax
- prescanning support for !@CUF and !$CUF
- basic sanity testing via unparsing and parse tree dumps

... along with any minimized changes elsewhere to make these
work, mostly no-op cases in common::visitors instances in
semantics and lowering to allow them to compile in the face
of new types in variant<> instances in the parse tree.

Because CUDA Fortran allows the kernel launch chevron syntax
("call foo<<<blocks, threads>>>()") only on CALL statements and
not on function references, the parse tree nodes for CallStmt,
FunctionReference, and their shared Call were rearranged a bit;
this caused a fair amount of one-line changes in many files.

More patches will follow that implement CUDA Fortran in the symbol
table and name resolution, and then semantic checking.

Differential Revision: https://reviews.llvm.org/D150159

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[Flang] Run clang-format on all flang files

This will make it easier for me to do reviews.

Differential Revision: https://reviews.llvm.org/D137291

[flang][driver] Make `flang-new -fc1` accept MLIR files

This relatively small change will allow Flang's frontend driver,
`flang-new -fc1`, to consume and parse MLIR files. Semantically (i.e.
from u

[flang][driver] Make `flang-new -fc1` accept MLIR files

This relatively small change will allow Flang's frontend driver,
`flang-new -fc1`, to consume and parse MLIR files. Semantically (i.e.
from user's perspective) this is identical to reading LLVM IR files.

Two file extensions are associated with MLIR files: .fir and .mlir. Note
that reading MLIR files makes only sense when running one of the
code-generation actions, i.e. when using one of the following action
flags: -S, -emit-obj, -emit-llvm, -emit-llvm-bc.

The majority of tests that required `tco` to run are updated to also run
with `flang-new -fc1`. A few tests are updated to use `fir-opt` instead
of `tco` (that's the preferred choice when testing a particular MLIR
pass). basic-program.fir is not updated as that test is intended to
verify the behaviour of `tco` specifically.

Differential Revision: https://reviews.llvm.org/D126890

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[flang][driver] Switch to the MLIR coding style in the driver (nfc)

This patch re-factors the driver code in LLVM Flang (frontend +
compiler) to use the MLIR style. For more context, please see:
htt

[flang][driver] Switch to the MLIR coding style in the driver (nfc)

This patch re-factors the driver code in LLVM Flang (frontend +
compiler) to use the MLIR style. For more context, please see:
https://discourse.llvm.org/t/rfc-coding-style-in-the-driver/

Most changes here are rather self-explanatory. Accessors are renamed to
be more consistent with the rest of LLVM (e.g. allSource -->
getAllSources). Additionally, MLIR clang-tidy files are added in the
affected directories.

clang-tidy and clang-format files were copied from MLIR. Small
additional changes are made to silence clang-tidy/clang-format
warnings.

[1] https://mlir.llvm.org/getting_started/DeveloperGuide/

Differential Revision: https://reviews.llvm.org/D125007

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[flang][driver] Add support for consuming LLVM IR/BC files

This change makes sure that Flang's driver recognises LLVM IR and BC as
supported file formats. To this end, `isFortran` is extended and re

[flang][driver] Add support for consuming LLVM IR/BC files

This change makes sure that Flang's driver recognises LLVM IR and BC as
supported file formats. To this end, `isFortran` is extended and renamed
as `isSupportedByFlang` (the latter better reflects the new
functionality).

New tests are added to verify that the target triple is correctly
overridden by the frontend driver's default value or the value specified
with `-triple`. Strictly speaking, this is not a functionality that's
new in this patch (it was added in D124664). This patch simply enables
us to write such tests and hence I'm including them here.

Differential Revision: https://reviews.llvm.org/D124667

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[flang] Produce proper "preprocessor output" for -E option

Rename the current -E option to "-E -Xflang -fno-reformat".

Add a new Parsing::EmitPreprocessedSource() routine to convert the
cooked char

[flang] Produce proper "preprocessor output" for -E option

Rename the current -E option to "-E -Xflang -fno-reformat".

Add a new Parsing::EmitPreprocessedSource() routine to convert the
cooked character stream output of the prescanner back to something
more closely resembling output from a traditional preprocessor;
call this new routine when -E appears.

The new -E output is suitable for use as fixed form Fortran source to
compilation by (one hopes) any Fortran compiler. If the original
top-level source file had been free form source, the output will be
suitable for use as free form source as well; otherwise there may be
diagnostics about missing spaces if they were indeed absent in the
original fixed form source.

Unless the -P option appears, #line directives are interspersed
with the output (but be advised, f18 will ignore these if presented
with them in a later compilation).

An effort has been made to preserve original alphabetic character case
and source indentation.

Add -P and -fno-reformat to the new drivers.

Tweak test options to avoid confusion with prior -E output; use
-fno-reformat where needed, but prefer to keep -E, sometimes
in concert with -P, on most, updating expected results accordingly.

Differential Revision: https://reviews.llvm.org/D106727

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[flang][driver] Add `-fno-analyzed-objects-for-unparse`

This patch adds a new option for the new Flang driver:
`-fno-analyzed-objects-for-unparse`. The semantics are similar to
`-funparse-typed-expr

[flang][driver] Add `-fno-analyzed-objects-for-unparse`

This patch adds a new option for the new Flang driver:
`-fno-analyzed-objects-for-unparse`. The semantics are similar to
`-funparse-typed-exprs-to-f18-fc` from `f18`. For consistency, the
latter is replaced with `-fno-analyzed-objects-for-unparse`.

The new option controls the behaviour of the unparser (i.e. the action
corresponding to `-fdebug-unparse`). The default behaviour is to use the
analyzed objects when unparsing. The new flag can be used to turn this
off, so that the original parse-tree objects are used. The analyzed
objects are generated during the semantic checks [1].

This patch also updates the semantics of
`-fno-analyzed-objects-for-unparse`/`-funparse-typed-exprs-to-f18-fc`
in `f18`, so that this flag is always taken into account when `Unparse`
is used (this way the semantics in `f18` and `flang-new` are identical).

The added test file is based on example from Peter Steinfeld.

[1]
https://github.com/llvm/llvm-project/blob/main/flang/docs/Semantics.md

Differential Revision: https://reviews.llvm.org/D103612

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[flang][driver] Add support for `-cpp/-nocpp`

This patch adds support for the `-cpp` and `-nocpp` flags. The
implemented semantics match f18 (i.e. the "throwaway" driver), but are
different to gfort

[flang][driver] Add support for `-cpp/-nocpp`

This patch adds support for the `-cpp` and `-nocpp` flags. The
implemented semantics match f18 (i.e. the "throwaway" driver), but are
different to gfortran. In Flang the preprocessor is always run. Instead,
`-cpp/-nocpp` are used to control whether predefined and command-line
preprocessor macro definitions are enabled or not. In practice this is
sufficient to model gfortran`s `-cpp/-nocpp`.

In the absence of `-cpp/-nocpp`, the driver will use the extension of
the input file to decide whether to include the standard macro
predefinitions. gfortran's documentation [1] was used to decide which
file extension to use for this.

The logic mentioned above was added in FrontendAction::BeginSourceFile.
That's relatively late in the driver set-up, but this roughly where the
name of the input file becomes available. The logic for deciding between
fixed and free form works in a similar way and was also moved to
FrontendAction::BeginSourceFile for consistency (and to reduce
code-duplication).

The `-cpp/-nocpp` flags are respected also when the input is read from
stdin. This is different to:
* gfortran (behaves as if `-cpp` was used)
* f18 (behaves as if `-nocpp` was used)

Starting with this patch, file extensions are significant and some test
files had to be renamed to reflect that. Where possible, preprocessor
tests were updated so that they can be shared between `f18` and
`flang-new`. This was implemented on top of adding new test for
`-cpp/-nocpp`.

[1] https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D99292

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[flang] Move .f77 to the list of fixed-form file extensions

The free form was introduced in Fortran 90, so treating .f77 as
free-form was a bug.

Differential Revision: https://reviews.llvm.org/D994

[flang] Move .f77 to the list of fixed-form file extensions

The free form was introduced in Fortran 90, so treating .f77 as
free-form was a bug.

Differential Revision: https://reviews.llvm.org/D99494

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[flang][driver] Add options for unparsing

This patch adds the following compiler frontend driver options:
* -fdebug-unparse (f18 spelling: -funparse)
* -fdebug-unparse-with-symbols (f18 spelling

[flang][driver] Add options for unparsing

This patch adds the following compiler frontend driver options:
* -fdebug-unparse (f18 spelling: -funparse)
* -fdebug-unparse-with-symbols (f18 spelling: -funparse-with-symbols)
The new driver will only accept the new spelling. `f18` will accept both
the original and the new spelling.

A new base class for frontend actions is added: `PrescanAndSemaAction`.
This is added to reduce code duplication that otherwise these new
options would lead to. Implementation from
* `ParseSyntaxOnlyAction::ExecutionAction`
is moved to:
* `PrescanAndSemaAction::BeginSourceFileAction`
This implementation is now shared between:
* PrescanAndSemaAction
* ParseSyntaxOnlyAction
* DebugUnparseAction
* DebugUnparseWithSymbolsAction

All tests that don't require other yet unimplemented options are
updated. This way `flang-new -fc1` is used instead of `f18` when
`FLANG_BUILD_NEW_DRIVER` is set to `On`. In order to facilitate this,
`%flang_fc1` is added in the LIT configuration (lit.cfg.py).

`asFortran` from f18.cpp is duplicated as `getBasicAsFortran` in
FrontendOptions.cpp. At this stage it's hard to find a good place to
share this method. I suggest that we revisit this once a switch from
`f18` to `flang-new` is complete.

Differential Revision: https://reviews.llvm.org/D96483

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[flang][driver] Move isFixedFormSuffix and isFreeFormSuffix to flangFrontend

isFixedFormSuffix and isFreeFormSuffix should be defined in
flangFrontend rather than flangFrontendTool library. That's f

[flang][driver] Move isFixedFormSuffix and isFreeFormSuffix to flangFrontend

isFixedFormSuffix and isFreeFormSuffix should be defined in
flangFrontend rather than flangFrontendTool library. That's for 2
reasons:
* these methods are used in flangFrontend rather than flangFrontendTool
* flangFrontendTool depends on flangFrontend

As mentioned in the post-commit review for D94228, without this change
shared library builds fail.

Differential Revision: https://reviews.llvm.org/D94968

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[flang][driver] Add support for fixed form detection

Currently the new flang driver always runs in free form mode. This patch
adds support for fixed form mode detection based on the file extensions.

[flang][driver] Add support for fixed form detection

Currently the new flang driver always runs in free form mode. This patch
adds support for fixed form mode detection based on the file extensions.

Like `f18`, `flang-new` will treat files ending with ".f", ".F" and
".ff" as fixed form. Additionally, ".for", ".FOR", ".fpp" and ".FPP"
file extensions are recognised as fixed form files. This is consistent
with gfortran [1]. In summary, files with the following extensions are
treated as fixed-form:
* ".f", ".F", ".ff", ".for", ".FOR", ".fpp", ".FPP"

For consistency with flang/test/lit.cfg.py and f18, this patch also adds
support for the following file extensions:
* ".ff", ".FOR", ".for", ".ff90", ".fpp", ".FPP"
This is added in flang/lib/Frontend/FrontendOptions.cpp. Additionally,
the following extensions are included:
* ".f03", ".F03", ".f08", ".F08"
This is for compatibility with gfortran [1] and other popular Fortran
compilers [2].

NOTE: internally Flang will only differentiate between fixed and free
form files. Currently Flang does not support switching between language
standards, so in this regard file extensions are irrelevant. More
specifically, both `file.f03` and `file.f18` are represented with
`Language::Fortran` (as opposed to e.g. `Language::Fortran03`).

Summary of changes:
- Set Fortran::parser::Options::sFixedForm according to the file type
- Add isFixedFormSuffix and isFreeFormSuffix helper functions to
FrontendTool/Utils.h
- Change FrontendOptions::GetInputKindForExtension to support the missing
file extensions that f18 supports and some additional ones
- FrontendActionTest.cpp is updated to make sure that the test input is
treated as free-form

[1] https://gcc.gnu.org/onlinedocs/gfortran/GNU-Fortran-and-GCC.html
[2] https://github.com/llvm/llvm-project/blob/master/flang/docs/OptionComparison.md#notes

Differential Revision: https://reviews.llvm.org/D94228

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[Flang][Driver] Add infrastructure for basic frontend actions and file I/O

This patch introduces the dependencies required to read and manage input files
provided by the command line option. It also

[Flang][Driver] Add infrastructure for basic frontend actions and file I/O

This patch introduces the dependencies required to read and manage input files
provided by the command line option. It also adds the infrastructure to create
and write to output files. The output is sent to either stdout or a file
(specified with the `-o` flag).

Separately, in order to be able to test the code for file I/O, it adds
infrastructure to create frontend actions. As a basic testable example, it adds
the `InputOutputTest` FrontendAction. The sole purpose of this action is to
read a file from the command line and print it either to stdout or the output
file. This action is run by using the `-test-io` flag also introduced in this
patch (available for `flang-new` and `flang-new -fc1`). With this patch:
```
flang-new -test-io input-file.f90
```
will read input-file.f90 and print it in the output file.

The `InputOutputTest` frontend action has been introduced primarily to
facilitate testing. It is hidden from users (i.e. it's only displayed with
`--help-hidden`). Currently Clang doesn’t have an equivalent action.

`-test-io` is used to trigger the InputOutputTest action in the Flang frontend
driver. This patch makes sure that “flang-new” forwards it to “flang-new -fc1"
by creating a preprocessor job. However, in Flang.cpp, `-test-io` is passed to
“flang-new -fc1” without `-E`. This way we make sure that the preprocessor is
_not_ run in the frontend driver. This is the desired behaviour: `-test-io`
should only read the input file and print it to the output stream.

co-authored-by: Andrzej Warzynski <andrzej.warzynski@arm.com>

Differential Revision: https://reviews.llvm.org/D87989

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[flang][driver] Add the new flang compiler and frontend drivers

Summary:

This is the first patch implementing the new Flang driver as outlined in [1],
[2] & [3]. It creates Flang driver (`flang-new

[flang][driver] Add the new flang compiler and frontend drivers

Summary:

This is the first patch implementing the new Flang driver as outlined in [1],
[2] & [3]. It creates Flang driver (`flang-new`) and Flang frontend driver
(`flang-new -fc1`). These will be renamed as `flang` and `flang -fc1` once the
current Flang throwaway driver, `flang`, can be replaced with `flang-new`.

Currently only 2 options are supported: `-help` and `--version`.

`flang-new` is implemented in terms of libclangDriver, defaulting the driver
mode to `FlangMode` (added to libclangDriver in [4]). This ensures that the
driver runs in Flang mode regardless of the name of the binary inferred from
argv[0].

The design of the new Flang compiler and frontend drivers is inspired by it
counterparts in Clang [3]. Currently, the new Flang compiler and frontend
drivers re-use Clang libraries: clangBasic, clangDriver and clangFrontend.

To identify Flang options, this patch adds FlangOption/FC1Option enums.
Driver::printHelp is updated so that `flang-new` prints only Flang options.
The new Flang driver is disabled by default. To enable it, set
`-DBUILD_FLANG_NEW_DRIVER=ON` when configuring CMake and add clang to
`LLVM_ENABLE_PROJECTS` (e.g. -DLLVM_ENABLE_PROJECTS=“clang;flang;mlir”).

[1] “RFC: new Flang driver - next steps”
http://lists.llvm.org/pipermail/flang-dev/2020-July/000470.html
[2] “RFC: Adding a fortran mode to the clang driver for flang”
http://lists.llvm.org/pipermail/cfe-dev/2019-June/062669.html
[3] “RFC: refactoring libclangDriver/libclangFrontend to share with Flang”
http://lists.llvm.org/pipermail/cfe-dev/2020-July/066393.html
[4] https://reviews.llvm.org/rG6bf55804924d5a1d902925ad080b1a2b57c5c75c

co-authored-by: Andrzej Warzynski <andrzej.warzynski@arm.com>

Reviewed By: richard.barton.arm, sameeranjoshi

Differential Revision: https://reviews.llvm.org/D86089

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