[flang] Run algebraic simplification optimization pass.

Try 2 to merge 4fbd1d6c872e8228f23a6e13914222af40ca6461.

Flang algebraic simplification pass will run algebraic simplification
rewrite patter

[flang] Run algebraic simplification optimization pass.

Try 2 to merge 4fbd1d6c872e8228f23a6e13914222af40ca6461.

Flang algebraic simplification pass will run algebraic simplification
rewrite patterns for Math/Complex/etc. dialects. It is enabled
under opt-for-speed optimization levels (i.e. for O1/O2/O3; Os/Oz will not
enable it).

With this change the FIR/MLIR optimization pipeline becomes affected
by the -O* optimization level switches. Until now these switches
only affected the middle-end and back-end.

Differential Revision: https://reviews.llvm.org/D130035

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Revert "[flang] Run algebraic simplification optimization pass."

This reverts commit 4fbd1d6c872e8228f23a6e13914222af40ca6461.

[flang] Run algebraic simplification optimization pass.

Flang algebraic simplification pass will run algebraic simplification
rewrite patterns for Math/Complex/etc. dialects. It is enabled
under opt

[flang] Run algebraic simplification optimization pass.

Flang algebraic simplification pass will run algebraic simplification
rewrite patterns for Math/Complex/etc. dialects. It is enabled
under opt-for-speed optimization levels (i.e. for O1/O2/O3; Os/Oz will not
enable it).

With this change the FIR/MLIR optimization pipeline becomes affected
by the -O* optimization level switches. Until now these switches
only affected the middle-end and back-end.

Differential Revision: https://reviews.llvm.org/D130035

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[flang] Establish a single source of target information for semantics

Create a TargetCharacteristics class to centralize the few items of
target specific information that are relevant to semantics.

[flang] Establish a single source of target information for semantics

Create a TargetCharacteristics class to centralize the few items of
target specific information that are relevant to semantics. Use the
new class for all target queries, including derived type component layout
modeling.

Future work will initialize this class with target information
provided or forwarded by the drivers, and use it to fold layout-dependent
intrinsic functions like TRANSFER().

Differential Revision: https://reviews.llvm.org/D129018

Updates: Attempts to work around build issues on Windows.

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[flang][driver] Use `-O{0|1|2|3}` to define LLVM backend pass pipeline

Support for optimisation flags in LLVM Flang was originally added in
https://reviews.llvm.org/D128043. That patch focused on LL

[flang][driver] Use `-O{0|1|2|3}` to define LLVM backend pass pipeline

Support for optimisation flags in LLVM Flang was originally added in
https://reviews.llvm.org/D128043. That patch focused on LLVM
middle-end/optimisation pipelines. With this patch, Flang will
additionally configure LLVM backend pass pipelines accordingly. This
behavior is consistent with Clang.

New hook is added to translate compiler optimisation flags (e.g. `-O3`)
into backend optimisation level: `getCGOptLevel`. Identical hooks are
available in Clang and LLVM. In other words, the meaning of these
optimisation flags remains consistent with other sub-projects that use
LLVM backends.

Differential Revision: https://reviews.llvm.org/D128050

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[flang][driver] Add support for `-O{0|1|2|3}`

This patch adds support for most common optimisation compiler flags:
`-O{0|1|2|3}`. This is implemented in both the compiler and frontend
drivers. At th

[flang][driver] Add support for `-O{0|1|2|3}`

This patch adds support for most common optimisation compiler flags:
`-O{0|1|2|3}`. This is implemented in both the compiler and frontend
drivers. At this point, these options are only used to configure the
LLVM optimisation pipelines (aka middle-end). LLVM backend or MLIR/FIR
optimisations are not supported yet.

Previously, the middle-end pass manager was only required when
generating LLVM bitcode (i.e. for `flang-new -c -emit-llvm <file>` or
`flang-new -fc1 -emit-llvm-bc <file>`). With this change, it becomes
required for all frontend actions that are represented as
`CodeGenAction` and `CodeGenAction::executeAction` is refactored
accordingly (in the spirit of better code re-use).

Additionally, the `-fdebug-pass-manager` option is enabled to facilitate
testing. This flag can be used to configure the pass manager to print
the middle-end passes that are being run. Similar option exists in Clang
and the semantics in Flang are identical. This option translates to
extra configuration when setting up the pass manager. This is
implemented in `CodeGenAction::runOptimizationPipeline`.

This patch also adds some bolier plate code to manage code-gen options
("code-gen" refers to generating machine code in LLVM in this context).
This was extracted from Clang. In Clang, it simplifies defining code-gen
options and enables option marshalling. In Flang, option marshalling is
not yet supported (we might do at some point), but being able to
auto-generate some code with macros is beneficial. This will become
particularly apparent when we start adding more options (at least in
Clang, the list of code-gen options is rather long).

Differential Revision: https://reviews.llvm.org/D128043

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[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] Fix support for `-x`

Until now, `-x` wasn't really taken into account in Flang's compiler and
frontend drivers. `flang-new` and `flang-new -fc1` only recently gained
powers to consum

[flang][driver] Fix support for `-x`

Until now, `-x` wasn't really taken into account in Flang's compiler and
frontend drivers. `flang-new` and `flang-new -fc1` only recently gained
powers to consume inputs other than Fortran files and that's probably
why this hasn't been noticed yet.

This patch makes sure that `-x` is supported correctly and consistently
with Clang. To this end, verification is added when reading LLVM IR
files (i.e. IR modules are verified with `llvm::verifyModule`). This
way, LLVM IR parsing errors are correctly reported to Flang users. This
also aids testing.

With the new functionality, we can verify that `-x ir` breaks
compilation for e.g. Fortran files and vice-versa. Tests are updated
accordingly.

Differential Revision: https://reviews.llvm.org/D127207

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[flang][driver] Generate run-time type info

This is a small follow-up for https://reviews.llvm.org/D120051. It makes
sure that tables with "run-time type information for derived types" are
generated

[flang][driver] Generate run-time type info

This is a small follow-up for https://reviews.llvm.org/D120051. It makes
sure that tables with "run-time type information for derived types" are
generated for code-gen actions. Originally, only non-code-gen actions
were updated (i.e. actions that were fully supported at that time).

Differential Revision: https://reviews.llvm.org/D127307

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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 missing parentheses in an assert

The assert in https://reviews.llvm.org/D124665 was missing parentheses,
which triggered a warning in GCC (verified with GCC 11). As `-Werror` is

[flang][driver] Add missing parentheses in an assert

The assert in https://reviews.llvm.org/D124665 was missing parentheses,
which triggered a warning in GCC (verified with GCC 11). As `-Werror` is
on by default in FLang, that triggered build errors, see e.g. [1].

The fix is rather straightforward, so I am sending this without a
review.

[1] https://lab.llvm.org/buildbot/#/builders/160/builds/7016

Differential Revision: https://reviews.llvm.org/D125027

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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][driver] Re-organise the code-gen actions (nfc)

All frontend actions that generate code (MLIR, LLVM IR/BC,
Assembly/Object Code) are re-factored as essentially one action,
`CodeGenAction`, w

[flang][driver] Re-organise the code-gen actions (nfc)

All frontend actions that generate code (MLIR, LLVM IR/BC,
Assembly/Object Code) are re-factored as essentially one action,
`CodeGenAction`, with minor specialisations. To facilate all this,
`CodeGenAction` is extended to hold `TargetMachine` and backend action
type (MLIR vs LLVM IR vs LLVM BC vs Assembly vs Object Code).

`CodeGenAction` is no longer a pure abstract class and the
corresponding `ExecuteAction` is implemented so that it covers all use
cases. All this allows a much better code re-use.

Key functionality is extracted into some helpful hooks:
* `SetUpTargetMachine`
* `GetOutputStream`
* `EmitObjectCodeHelper`
* `EmitBCHelper`
I hope that this clarifies the overall structure. I suspect that we may
need to revisit this again as the functionality grows in complexity.

Differential Revision: https://reviews.llvm.org/D124665

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[flang][driver] Define the default frontend driver triple

*SUMMARY*
Currently, the frontend driver assumes that a target triple is either:
* provided by the frontend itself (e.g. when lowering and

[flang][driver] Define the default frontend driver triple

*SUMMARY*
Currently, the frontend driver assumes that a target triple is either:
* provided by the frontend itself (e.g. when lowering and generating
code),
* specified through the `-triple/-target` command line flags.

If `-triple/-target` is not used, the frontend will simply use the host
triple.

This is going to be insufficient when e.g. consuming an LLVM IR file
that has no triple specified (reading LLVM files is WIP, see D124667).
We shouldn't require the triple to be specified via the command line in
such situation. Instead, the frontend driver should contain a good
default, e.g. the host triple.

This patch updates Flang's `CompilerInvocation` to do just that, i.e.
defines its default target triple. Similarly to Clang:
* the default `CompilerInvocation` triple is set as the host triple,
* the value specified with `-triple` takes precedence over the frontend
driver default and the current module triple,
* the frontend driver default takes precedence over the module triple.

*TESTS*
This change requires 2 unit tests to be updated. That's because relevant
frontend actions are updated to assume that there's always a valid
triple available in the current `CompilerInvocation`. This update is
required because the unit tests bypass the regular `CompilerInvocation`
set-up (in particular, they don't call
`CompilerInvocation::CreateFromArgs`). I've also taken the liberty to
disable the pre-precossor formatting in the affected unit tests as well
(it is not required).

No new tests are added. As `flang-new -fc1` does not support consuming
LLVM IR files just yet, it is not possible to compile an LLVM IR file
without a triple. More specifically, atm all LLVM IR files are generated
and stored internally and the driver makes sure that these contain a
valid target triple. This is about to change in D124667 (which adds
support for reading LLVM IR/BC files) and that's where tests for
exercising the default frontend driver triple will be added.

*WHAT DOES CLANG DO?*
For reference, the default target triple for Clang's
`CompilerInvocation` is set through option marshalling infra [1] in
Options.td. Please check the definition of the `-triple` flag:
```
def triple : Separate<["-"], "triple">,
HelpText<"Specify target triple (e.g. i686-apple-darwin9)">,
MarshallingInfoString<TargetOpts<"Triple">, "llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple())">,
AlwaysEmit, Normalizer<"normalizeTriple">;
```
Ideally, we should re-use the marshalling infra in Flang.

[1] https://clang.llvm.org/docs/InternalsManual.html#option-marshalling-infrastructure

Differential Revision: https://reviews.llvm.org/D124664

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[flang] Make the plugin API independent of the driver internals

This patch adds a few new member methods in the `PluginParseTreeAction`
frontend action base class. With these new methods, the plugin

[flang] Make the plugin API independent of the driver internals

This patch adds a few new member methods in the `PluginParseTreeAction`
frontend action base class. With these new methods, the plugin API
becomes independent of the driver internals. In particular, plugin
writers no longer require the `CompilerInstance.h` header file to access
various driver data structures (instead, they can use newly added
hooks).

This change is desirable as `CompilerInstance.h` includes various
headers from Clang (both explicitly and implicitly). Some of these
header files are generated at build time (through TableGen) and
including them creates a dependency on some of Clang's build targets.
However, plugins in Flang should not depend on Clang build targets.

Note that plugins might still work fine most of the time, even without
this change and without adding Clang build targets as dependency in
plugin's CMake definition. Indeed, these Clang build targets are often
generated early in the build process. However, that's not guaranteed and
we did notice that on occasions plugins would fail to build.

Differential Revision: https://reviews.llvm.org/D120999

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[flang][driver] Add support for `-mmlir`

The semantics of `-mmlir` are identical to `-mllvm`. The only notable
difference is that `-mmlir` options should be forwarded to MLIR rather
than LLVM.

Note

[flang][driver] Add support for `-mmlir`

The semantics of `-mmlir` are identical to `-mllvm`. The only notable
difference is that `-mmlir` options should be forwarded to MLIR rather
than LLVM.

Note that MLIR llvm::cl options are lazily constructed on demand (see
the definition of options in PassManagerOptions.cpp). This means that:
* MLIR global options are only visible when explicitly initialised and
displayed only when using `-mmlir --help`,
* Flang and LLVM global options are always visible and displayed when
using either `-mllvm -help` or `-mmlir --help`.

In other words, `-mmlir --help` is a superset of `-mllvm --help`. This is not
ideal, but we'd need to refactor all option definitions in Flang and
LLVM to improve this. I suggesting leaving this for later.

Differential Revision: https://reviews.llvm.org/D123297

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[flang][nfc] Simplify TargetMachine initialisation

[flang][driver] Add support for generating LLVM bytecode files

Support for generating LLVM BC files is added in Flang's compiler and
frontend drivers. This requires the `BitcodeWriterPass` pass to b

[flang][driver] Add support for generating LLVM bytecode files

Support for generating LLVM BC files is added in Flang's compiler and
frontend drivers. This requires the `BitcodeWriterPass` pass to be run
on the input LLVM IR module and is implemented as a dedicated frontend
aciton. The new functionality as seen by the user (compiler driver):
```
flang-new -c -emit-llvm file.90
```
or (frontend driver):
```
flang-new -fc1 -emit-llvm-bc file.f90
```

The new behaviour is consistent with `clang` and `clang -cc1`.

Differential Revision: https://reviews.llvm.org/D123211

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[flang][driver] Add support for -S and implement -c/-emit-obj

This patch adds support for:
* `-S` in Flang's compiler and frontend drivers,
and implements:
* `-emit-obj` in Flang's frontend driv

[flang][driver] Add support for -S and implement -c/-emit-obj

This patch adds support for:
* `-S` in Flang's compiler and frontend drivers,
and implements:
* `-emit-obj` in Flang's frontend driver and `-c` in Flang's compiler
driver (this is consistent with Clang).
(these options were already available before, but only as placeholders).
The semantics of these options in Clang and Flang are identical.

The `EmitObjAction` frontend action is renamed as `BackendAction`. This
new name more accurately reflects the fact that this action will
primarily run the code-gen/backend pipeline in LLVM. It also makes more
sense as an action implementing both `-emit-obj` and `-S` (originally,
it was just `-emit-obj`).

`tripleName` from FirContext.cpp is deleted and, when a target triple is
required, `mlir::LLVM::LLVMDialect::getTargetTripleAttrName()` is used
instead. In practice, this means that `fir.triple` is replaced with
`llvm.target_triple`. The former was effectively ignored. The latter is
used when lowering from the LLVM dialect in MLIR to LLVM IR (i.e. it's
embedded in the generated LLVM IR module). The driver can then re-use
it when configuring the backend. With this change, the LLVM IR files
generated by e.g. `tco` will from now on contain the correct target
triple.

The code-gen.f90 test is replaced with code-gen-x86.f90 and
code-gen-aarch64.f90. With 2 seperate files we can verify that
`--target` is correctly taken into account. LIT configuration is updated
to enable e.g.:
```
! REQUIRES: aarch64-registered-target
```

Differential Revision: https://reviews.llvm.org/D120568

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[flang][driver] Add support for `-debug-dump-pft`

This patch adds support for dumping the pre-FIR tree in `flang-new
-fc1`, i.e. Flang's frontend driver. This flag is functionally identical
to `-pft

[flang][driver] Add support for `-debug-dump-pft`

This patch adds support for dumping the pre-FIR tree in `flang-new
-fc1`, i.e. Flang's frontend driver. This flag is functionally identical
to `-pft-test` in `bbc` and semantically similar to
`-fdebug-dump-parse-tree` from `flang-new -fc1`.

Differential Revision: https://reviews.llvm.org/D121198

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[flang][driver] Add support for `--target`/`--triple`

This patch adds support for:
* `--target` in the compiler driver (`flang-new`)
* `--triple` in the frontend driver (`flang-new -fc1`)
The se

[flang][driver] Add support for `--target`/`--triple`

This patch adds support for:
* `--target` in the compiler driver (`flang-new`)
* `--triple` in the frontend driver (`flang-new -fc1`)
The semantics of these flags are inherited from `clangDriver`, i.e.
consistent with `clang --target` and `clang -cc1 --triple`,
respectively.

A new structure is defined, `TargetOptions`, that will hold various
Frontend options related to the target. Currently, this is mostly a
placeholder that contains the target triple. In the future, it will be
used for storing e.g. the CPU to tune for or the target features to
enable.

Additionally, the following target/triple related options are enabled
[*]: `-print-effective-triple`, `-print-target-triple`. Definitions in
Options.td are updated accordingly and, to facilated testing,
`-emit-llvm` is added to the list of options available in `flang-new`
(previously it was only enabled in `flang-new -fc1`).

[*] These options were actually available before (like all other options
defined in `clangDriver`), but not included in `flang-new --help`.
Before this change, `flang-new` would just use `native` for defining the
target, so these options were of little value.

Differential Revision: https://reviews.llvm.org/D120246

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[flang][driver] Make `flang-new` always generate run-time type info

Currently, the driver generates the tables with "run-time type
information for derived types" only when specific actions are run.

[flang][driver] Make `flang-new` always generate run-time type info

Currently, the driver generates the tables with "run-time type
information for derived types" only when specific actions are run.
However, the corresponding data might be required by the subsequent
compilation stages (e.g. lowering, code-gen) and should be generated
unconditionally. Note that this is only possible once the semantic
checks have been run.

Note that when generating these tables, extra semantic errors might be
generated. The driver will always report these and in most cases such
semantic errors will cause the driver to exit immediately. The only
exception are actions inheriting from `PrescanAndSemaDebugAction`.
Currently, there's only one such action: `DebugDumpAllAction`
(corresponds to `-fdebug-dump-all` command-line flag). I've updated the
comments for this action to clarify this.

This change will mostly affect lowering, which currently is only
available for most basic examples (e.g. empty programs). I wasn't able
to find a working case that would demonstrate the new behaviour. I
hope that this change is straightforward enough and am submitting it
without a test.

Differential Revision: https://reviews.llvm.org/D120051

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[flang][driver] Add support for `-emit-llvm`

This patch adds support for the `-emit-llvm` option in the frontend
driver (i.e. `flang-new -fc1`). Similarly to Clang, `flang-new -fc1
-emit-llvm file.f

[flang][driver] Add support for `-emit-llvm`

This patch adds support for the `-emit-llvm` option in the frontend
driver (i.e. `flang-new -fc1`). Similarly to Clang, `flang-new -fc1
-emit-llvm file.f` will generate a textual LLVM IR file.

Depends on D118985

Differential Revision: https://reviews.llvm.org/D119012

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[flang][driver] Add support for `-emit-mlir`

This patch adds support for generating MLIR files in Flang's frontend
driver (i.e. `flang-new -fc1`). `-emit-fir` is added as an alias for
`-emit-mlir`.

[flang][driver] Add support for `-emit-mlir`

This patch adds support for generating MLIR files in Flang's frontend
driver (i.e. `flang-new -fc1`). `-emit-fir` is added as an alias for
`-emit-mlir`. We may want to decide to split the two in the future.

A new parent class for code-gen frontend actions is introduced:
`CodeGenAction`. We will be using this class to encapsulate logic shared
between all code-generation actions, but not required otherwise. For
now, it will:
* run prescanning, parsing and semantic checks,
* lower the input to MLIR.
`EmitObjAction` is updated to inherit from this class. This means that
the behaviour of `flang-new -fc1 -emit-obj` is also updated (previously,
it would just exit immediately). This change required
`flang/test/Driver/syntax-only.f90` to be updated.

For `-emit-fir`, a specialisation of `CodeGenAction` is introduced:
`EmitMLIRAction`. The key logic for this class is implemented in
`EmitMLIRAction::ExecuteAction`.

Differential Revision: https://reviews.llvm.org/D118985

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[flang][driver] Add actions that execute despite semantic errors

This patch adds a new abstract class for frontend actions:
`PrescanAndSemaDebugAction`. It's almost identical to
`PrescanAndSemaActio

[flang][driver] Add actions that execute despite semantic errors

This patch adds a new abstract class for frontend actions:
`PrescanAndSemaDebugAction`. It's almost identical to
`PrescanAndSemaAction`, but in the presence of semantic errors it does
not skip the corresponding `ExecuteAction` specialisation. Instead, it
runs it as if there were no semantic errors. This class is for developer
actions only (i.e. front-end driver options).

The new behaviour does not affect the return code from `flang-new -fc1`
when the input file is semantically incorrect. The return code is
inferred from the number of driver diagnostics generated in
`CompilerInstance::ExecuteAction` and this patch does not change that.
More specifically, the semantic errors are still reported and hence the
driver is able to correctly report that the compilation has failed (with
a non-zero return code).

This new base class is meant for debug actions only and
`DebugDumpAllAction` is updated to demonstrate the new behaviour. With
this change, `flang-new -fc1 -fdebug-dump-all` dumps the parse tree and
symbols for all input files, regardless of whether any semantic errors
were found.

This patch addresses https://bugs.llvm.org/show_bug.cgi?id=52097.

Differential Revision: https://reviews.llvm.org/D111308

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