[flang] Tag warnings with LanguageFeature or UsageWarning (#110304)

(This is a big patch, but it's nearly an NFC. No test results have
changed and all Fortran tests in the LLVM test suites work as

[flang] Tag warnings with LanguageFeature or UsageWarning (#110304)

(This is a big patch, but it's nearly an NFC. No test results have
changed and all Fortran tests in the LLVM test suites work as expected.)

Allow a parser::Message for a warning to be marked with the
common::LanguageFeature or common::UsageWarning that controls it. This
will allow a later patch to add hooks whereby a driver will be able to
decorate warning messages with the names of its options that enable each
particular warning, and to add hooks whereby a driver can map those
enumerators by name to command-line options that enable/disable the
language feature and enable/disable the messages.

The default settings in the constructor for LanguageFeatureControl were
moved from its header file into its C++ source file.

Hooks for a driver to use to map the name of a feature or warning to its
enumerator were also added.

To simplify the tagging of warnings with their corresponding language
feature or usage warning, to ensure that they are properly controlled by
ShouldWarn(), and to ensure that warnings never issue at code sites in
module files, two new Warn() member function templates were added to
SemanticsContext and other contextual frameworks. Warn() can't be used
before source locations can be mapped to scopes, but the bulk of
existing code blocks testing ShouldWarn() and FindModuleFile() before
calling Say() were convertible into calls to Warn(). The ones that were
not convertible were extended with explicit calls to
Message::set_languageFeature() and set_usageWarning().

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[flang] Ensure that portability warnings are conditional (#71857)

Before emitting a warning message, code should check that the usage in
question should be diagnosed by calling ShouldWarn(). A fair

[flang] Ensure that portability warnings are conditional (#71857)

Before emitting a warning message, code should check that the usage in
question should be diagnosed by calling ShouldWarn(). A fair number of
sites in the code do not, and can emit portability warnings
unconditionally, which can confuse a user that hasn't asked for them
(-pedantic) and isn't terribly concerned about portability *to* other
compilers.

Add calls to ShouldWarn() or IsEnabled() around messages that need them,
and add -pedantic to tests that now require it to test their portability
messages, and add more expected message lines to those tests when
-pedantic causes other diagnostics to fire.

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[flang] Prioritize DATA object error messages a little better (#66258)

When a DATA statement object is not valid, there's a number of possible
reasons. Emit an error message for the most egregious

[flang] Prioritize DATA object error messages a little better (#66258)

When a DATA statement object is not valid, there's a number of possible
reasons. Emit an error message for the most egregious violation, so that
an unlucky user doesn't fix something easy (due to a less-severe error
message masking one that is worse) and then run into something that
might be more serious.

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[flang] Accept intrinsic functions in DATA statement variables (#66229)

Pure intrinsic functions are acceptable in constant expressions so long
as their arguments are constant expressions. Allow th

[flang] Accept intrinsic functions in DATA statement variables (#66229)

Pure intrinsic functions are acceptable in constant expressions so long
as their arguments are constant expressions. Allow them to appear in
subscripts in DATA statement variables.

Fixes https://github.com/llvm/llvm-project/issues/65046.

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[flang][runtime] Initialize uninitialized pointer components

Pointer components without default initialization pose some
difficult (or impossible) problems when they appear as right-hand
side target

[flang][runtime] Initialize uninitialized pointer components

Pointer components without default initialization pose some
difficult (or impossible) problems when they appear as right-hand
side targets in pointer assignment statements; they may contain
garbage or stale data that looks enough like a valid descriptor
to cause a crash. Solve the problem by avoiding it -- ensure
that pointers' descriptors are at least minimally established.

Differential Revision: https://reviews.llvm.org/D149979

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[flang] Catch more bad DATA statement objects

The data statement variable checker is missing some cases, like expressions
that are not variables. Run the checker first to enjoy its very specific
er

[flang] Catch more bad DATA statement objects

The data statement variable checker is missing some cases, like expressions
that are not variables. Run the checker first to enjoy its very specific
error messages, but when it finds no problems, still apply a general
check that an expression is a "variable" and also not a constant expression
at the top level as a backstop.

Differential Revision: https://reviews.llvm.org/D146580

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[flang] Add & use a better visit() (take 2)

Adds flang/include/flang/Common/log2-visit.h, which defines
a Fortran::common::visit() template function that is a drop-in
replacement for std::visit().

[flang] Add & use a better visit() (take 2)

Adds flang/include/flang/Common/log2-visit.h, which defines
a Fortran::common::visit() template function that is a drop-in
replacement for std::visit(). Modifies most use sites in
the front-end and runtime to use common::visit().

The C++ standard mandates that std::visit() have O(1) execution
time, which forces implementations to build dispatch tables.
This new common::visit() is O(log2 N) in the number of alternatives
in a variant<>, but that N tends to be small and so this change
produces a fairly significant improvement in compiler build
memory requirements, a 5-10% improvement in compiler build time,
and a small improvement in compiler execution time.

Building with -DFLANG_USE_STD_VISIT causes common::visit()
to be an alias for std::visit().

Calls to common::visit() with multiple variant arguments
are referred to std::visit(), pending further work.

This change is enabled only for GCC builds with GCC >= 9;
an earlier attempt (D122441) ran into bugs in some versions of
clang and was reverted rather than simply disabled; and it is
not well tested with MSVC. In non-GCC and older GCC builds,
common::visit() is simply an alias for std::visit().

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Revert "[flang] Add & use a better visit()"

This reverts commit 2ab9990c9eb79682a4d4b183dfbc7612d3e55328. It has
caused multiple build failures:
* https://lab.llvm.org/buildbot/#/builders/177/build

Revert "[flang] Add & use a better visit()"

This reverts commit 2ab9990c9eb79682a4d4b183dfbc7612d3e55328. It has
caused multiple build failures:
* https://lab.llvm.org/buildbot/#/builders/177/builds/4346
* https://lab.llvm.org/buildbot/#/builders/180/builds/3803
* https://lab.llvm.org/buildbot/#/builders/175/builds/10419
* https://lab.llvm.org/buildbot/#/builders/191/builds/4318
* https://lab.llvm.org/buildbot/#/builders/173/builds/4274
* https://lab.llvm.org/buildbot/#/builders/181/builds/4297

All these bots failed with a time-out:
```
command timed out: 1200 seconds without output running [b'ninja', b'-j', b'32'], attempting to kill
```
I'm guessing that that's due to template instantiations failing at some
point (https://reviews.llvm.org/D122441 introduced a custom
implementation of std::visit). Everything seems fine when either:
* building on X86 with GCC or Clang (tested with GCC 9.3 and Clang 12)
* building on AArch64 with GCC (tested with GCC 11)

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[flang] Add & use a better visit()

Adds flang/include/flang/Common/visit.h, which defines
a Fortran::common::visit() template function that is a drop-in
replacement for std::visit(). Modifies most

[flang] Add & use a better visit()

Adds flang/include/flang/Common/visit.h, which defines
a Fortran::common::visit() template function that is a drop-in
replacement for std::visit(). Modifies most use sites in
the front-end and runtime to use common::visit().

The C++ standard mandates that std::visit() have O(1) execution
time, which forces implementations to build dispatch tables.
This new common::visit() is O(log2 N) in the number of alternatives
in a variant<>, but that N tends to be small and so this change
produces a fairly significant improvement in compiler build
memory requirements, a 5-10% improvement in compiler build time,
and a small improvement in compiler execution time.

Building with -DFLANG_USE_STD_VISIT causes common::visit()
to be an alias for std::visit().

Calls to common::visit() with multiple variant arguments
are referred to std::visit(), pending further work.

Differential Revision: https://reviews.llvm.org/D122441

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[flang] Distinguish usage and portability warning messages

Using recently established message severity codes, upgrade
non-fatal messages to usage and portability warnings as
appropriate.

Differenti

[flang] Distinguish usage and portability warning messages

Using recently established message severity codes, upgrade
non-fatal messages to usage and portability warnings as
appropriate.

Differential Revision: https://reviews.llvm.org/D121246

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[flang] Allow DATA initialization of derived types w/ allocatable components

While one cannot of course statically initialize an allocatable component
of an instance of a derived type, its mere pres

[flang] Allow DATA initialization of derived types w/ allocatable components

While one cannot of course statically initialize an allocatable component
of an instance of a derived type, its mere presence should not prevent
DATA initialization of the other nonallocatable components. Semantics
was treating the existence of an allocatable component as a case of
"default initialization", which it is, but not one that should run
afoul of C877. Add another Boolean argument to IsInitialized() to allow
for a more nuanced test.

Differential Revision: https://reviews.llvm.org/D119449

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[flang] Allow initialization in blank COMMON

This is nonconformant usage, but widely accepted as an extension.
Downgrade the error message to a warning.

Differential Revision: https://reviews.llvm.

[flang] Allow initialization in blank COMMON

This is nonconformant usage, but widely accepted as an extension.
Downgrade the error message to a warning.

Differential Revision: https://reviews.llvm.org/D117152

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[flang] Implement semantics for DEC STRUCTURE/RECORD

Implements part of the legacy "DEC structures" feature from
VMS Fortran. STRUCTUREs are processed as if they were derived
types with SEQUENCE.

[flang] Implement semantics for DEC STRUCTURE/RECORD

Implements part of the legacy "DEC structures" feature from
VMS Fortran. STRUCTUREs are processed as if they were derived
types with SEQUENCE. DATA-like object entity initialization
is supported as well (e.g., INTEGER FOO/666/) since it was used
for default component initialization in structures. Anonymous
components (named %FILL) are also supported.

These features, and UNION/MAP, were already being parsed.
An omission in the collection of structure field names in the
case of nested structures with entity declarations was fixed
in the parser.

Structures are supported in modules, but this is mostly for
testing purposes. The names of fields in structures accessed
via USE association cannot appear with dot notation in client
code (at least not yet). DEC structures antedate Fortran 90,
so their actual use in applications should not involve modules.

This patch does not implement UNION/MAP, since that feature
would impose difficulties later in lowering them to MLIR types.
In the meantime, if they appear, semantics will issue a
"not yet implemented" error message.

Differential Revision: https://reviews.llvm.org/D117151

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[flang] Catch error: base of DATA statement object can't be a pointer

A pointer with subscripts, substring indices, or components cannot
be initialized by a DATA statement (although of course a whol

[flang] Catch error: base of DATA statement object can't be a pointer

A pointer with subscripts, substring indices, or components cannot
be initialized by a DATA statement (although of course a whole pointer
can be so). Catch the missing cases.

Differential Revision: https://reviews.llvm.org/D109931

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[flang] Refine checks for pointer initialization targets

f18 was emitting a bogus error message about the lack of a TARGET
attribute when a pointer was initialized with a component of a
variable tha

[flang] Refine checks for pointer initialization targets

f18 was emitting a bogus error message about the lack of a TARGET
attribute when a pointer was initialized with a component of a
variable that was a legitimate TARGET.

Differential Revision: https://reviews.llvm.org/D99665

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[flang] Handle DATA initialization of EQUIVALENCE'd objects

Objects that are storage associated by EQUIVALENCE and
initialized with DATA are initialized by creating a
compiler temporary data object

[flang] Handle DATA initialization of EQUIVALENCE'd objects

Objects that are storage associated by EQUIVALENCE and
initialized with DATA are initialized by creating a
compiler temporary data object in the same scope,
assigning it an offset, type, and size that covers the
transitive closure of the associated initialized original
symbols, and combining their initializers into one common
initializer for the temporary.

Some problems with offset assignment of EQUIVALENCE'd objects
in COMMON were exposed and corrected, and some more error
cases are checked.

Remove obsolete function.
Small bugfix (nested implied dos).
Add a test.
Fix struct/class warning.

Differential Revision: https://reviews.llvm.org/D85560

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[flang] Support DATA statement initialization of numeric with Hollerith/CHARACTER

This is a common Fortran language extension.

Differential Revision: https://reviews.llvm.org/D85492

[flang][NFC] Get formatting in sync with latest clang-format

flang/module only contains Fortran files and one is a .h so disable
formatting on that directory.

Differential Revision: https://reviews

[flang][NFC] Get formatting in sync with latest clang-format

flang/module only contains Fortran files and one is a .h so disable
formatting on that directory.

Differential Revision: https://reviews.llvm.org/D82989

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[flang] DATA stmt processing (part 4/4): Check & convert DATA

Implement rest of DATA statement semantics and conversion of
DATA statement initializations into static initializers of
objects in their

[flang] DATA stmt processing (part 4/4): Check & convert DATA

Implement rest of DATA statement semantics and conversion of
DATA statement initializations into static initializers of
objects in their symbol table entries.

Reviewed By: tskeith, PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D82207

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[flang] DATA stmt processing (part 3/4): Remaining prep work

Rolls up small changes across the frontend to prepare for the large
forthcoming patch (part 4/4) that completes DATA statement processing

[flang] DATA stmt processing (part 3/4): Remaining prep work

Rolls up small changes across the frontend to prepare for the large
forthcoming patch (part 4/4) that completes DATA statement processing
via conversion to initializers.

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D82137

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[flang] Implemented 2 Semantic checks for DATA statement and fixed a few bugs

Summary
- Implemented C876, C877
- Fixed IsConstantExpr to check C879
- Fixed bugs in few test cases - data01.f90,

[flang] Implemented 2 Semantic checks for DATA statement and fixed a few bugs

Summary
- Implemented C876, C877
- Fixed IsConstantExpr to check C879
- Fixed bugs in few test cases - data01.f90, block-data01.f90,
pre-fir-tree02.f90
- Modified implementation of C8106 to identify all automatic objects
and modified equivalence01.f90 to reflect the changes

Differential Revision: https://reviews.llvm.org/D78424

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Rework DATA statement semantics to use typed expressions

Summary:
Updates recent work on DATA statement semantic checking in
flang/lib/Semantics/check-data.{h,cpp} to use the compiler's
internal rep

Rework DATA statement semantics to use typed expressions

Summary:
Updates recent work on DATA statement semantic checking in
flang/lib/Semantics/check-data.{h,cpp} to use the compiler's
internal representation for typed expressions rather than working
on the raw parse tree. Saves the analyzed expressions for DATA
statement values as parse tree decorations because they'll soon be
needed in lowering. Corrects wording of some error messages.

Fixes a bug in constant expression checking: structure constructors
are not constant expressions if they set an allocatable component
to anything other than NULL.

Includes infrastructure changes to make this work, some renaming
to reflect the fact that the implied DO loop indices tracked by
expression analysis are not (just) from array constructors, remove
some dead code, and improve some comments.

Reviewers: tskeith, sscalpone, jdoerfert, DavidTruby, anchu-rajendran, schweitz

Reviewed By: tskeith, anchu-rajendran, schweitz

Subscribers: llvm-commits, flang-commits

Tags: #flang, #llvm

Differential Revision: https://reviews.llvm.org/D78834

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[flang]Implemented Semantic Checkes for 5 data constraints

Summary:
C874, C875, C878, C880 and C881 checks are implemented.

Differential Revision: https://reviews.llvm.org/D78008

[flang] Reformat with latest clang-format and .clang-format

Original-commit: flang-compiler/f18@9fe84f45d7fd685051004678d6b5775dcc4c6f8f
Reviewed-on: https://github.com/flang-compiler/f18/pull/1094

[flang] [LLVMify F18] Compiler module folders should have capitalised names (flang-compiler/f18#980)

This patch renames the modules in f18 to use a capital letter in the
module name

Signed-off-b

[flang] [LLVMify F18] Compiler module folders should have capitalised names (flang-compiler/f18#980)

This patch renames the modules in f18 to use a capital letter in the
module name

Signed-off-by: Caroline Concatto <caroline.concatto@arm.com>

Original-commit: flang-compiler/f18@d2eb7a1c443d1539ef12b6f027074a0eb15b1ea0
Reviewed-on: https://github.com/flang-compiler/f18/pull/980

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