[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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[flang] Finer control over error recovery with GetExpr()

Prior to this patch, the semantics utility GetExpr() will crash
unconditionally if it encounters a typed expression in the parse
tree that ha

[flang] Finer control over error recovery with GetExpr()

Prior to this patch, the semantics utility GetExpr() will crash
unconditionally if it encounters a typed expression in the parse
tree that has not been set by expression semantics. This is the
right behavior when called from lowering, by which time it is known
that the program had no fatal user errors, since it signifies a
fatal internal error. However, prior to lowering, in the statement
semantics checking code, a more nuanced test should be used before
crashing -- specifically, we should not crash in the face of a
missing typed expression when in error recovery mode.

Getting this right requires GetExpr() and its helper class to have
access to the semantics context, so that it can check AnyFatalErrors()
before crashing. So this patch touches nearly all of its call sites.

Differential Revision: https://reviews.llvm.org/D123873

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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] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS

The intrinsic module IEEE_ARITHMETIC must incorporate the public
names from the intrisic module IEEE_EXCEPTIONS. Rename IEEE_EXCEPTIONS
to __F

[flang] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS

The intrinsic module IEEE_ARITHMETIC must incorporate the public
names from the intrisic module IEEE_EXCEPTIONS. Rename IEEE_EXCEPTIONS
to __Fortran_ieee_exceptions so that it won't clash with the
nonintrinsic namespace, establish a new intrinic IEEE_EXCEPTIONS
module that USEs it, and add a USE to IEEE_ARITHMETIC.

Updated to use STREQUAL rather than ambiguous MATCHES in
the CMakeLists.txt file.

Differential Revision: https://reviews.llvm.org/D121490

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Revert "[flang] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS"

This reverts commit b6a7600491d755f6f700fe245b2fc7b928264c58. It caused
the following build failure:
```
ninja: error: dependency cycl

Revert "[flang] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS"

This reverts commit b6a7600491d755f6f700fe245b2fc7b928264c58. It caused
the following build failure:
```
ninja: error: dependency cycle: include/flang/__fortran_ieee_exceptions.mod -> include/flang/__fortran_ieee_exceptions.mod
```

See e.g.:
* https://lab.llvm.org/buildbot/#/builders/172/builds/9595

To reproduce:
```
cmake -G Ninja \
-DLLVM_TARGETS_TO_BUILD=host \
-DCMAKE_BUILD_TYPE=Release \
-DLLVM_ENABLE_PROJECTS="clang;flang" \
../../llvm
ninja check-flang
```

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[flang] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS

The intrinsic module IEEE_ARITHMETIC must incorporate the public
names from the intrisic module IEEE_EXCEPTIONS. Rename IEEE_EXCEPTIONS
to __F

[flang] IEEE_ARITHMETIC must imply USE IEEE_EXCEPTIONS

The intrinsic module IEEE_ARITHMETIC must incorporate the public
names from the intrisic module IEEE_EXCEPTIONS. Rename IEEE_EXCEPTIONS
to __Fortran_ieee_exceptions so that it won't clash with the
nonintrinsic namespace, establish a new intrinic IEEE_EXCEPTIONS
module that USEs it, and add a USE to IEEE_ARITHMETIC.

Differential Revision: https://reviews.llvm.org/D121490

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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] Rearrange prototype & code placement of IsCoarray()

A quick fix last week to the shared library build caused
the predicate IsCoarray(const Symbol &) to be moved from
Semantics to Evaluate.

[flang] Rearrange prototype & code placement of IsCoarray()

A quick fix last week to the shared library build caused
the predicate IsCoarray(const Symbol &) to be moved from
Semantics to Evaluate. This patch completes that move in
a way that properly combines the existing IsCoarray() tests
for expressions and other object with the test for a symbol.

Differential Revision: https://reviews.llvm.org/D114806

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[flang] Refine symbol sorting

Replace semantics::SymbolSet with alternatives that clarify
whether the set should order its contents by source position
or not. This matters because positionally-orde

[flang] Refine symbol sorting

Replace semantics::SymbolSet with alternatives that clarify
whether the set should order its contents by source position
or not. This matters because positionally-ordered sets must
not be used for Symbols that might be subjected to name
replacement during name resolution, and address-ordered
sets must not be used (without sorting) in circumstances
where the order of their contents affects the output of the
compiler.

All set<> and map<> instances in the compiler that are keyed
by Symbols now have explicit Compare types in their template
instantiations. Symbol::operator< is no more.

Differential Revision: https://reviews.llvm.org/D98878

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[flang] Fix classification of shape inquiries in specification exprs

In some contexts, including the motivating case of determining whether
the expressions that define the shape of a variable are "c

[flang] Fix classification of shape inquiries in specification exprs

In some contexts, including the motivating case of determining whether
the expressions that define the shape of a variable are "constant expressions"
in the sense of the Fortran standard, expression rewriting via Fold()
is not necessary, and should not be required. The inquiry intrinsics LBOUND,
UBOUND, and SIZE work correctly now in specification expressions and are
classified correctly as being constant expressions (or not). Getting this right
led to a fair amount of API clean-up as a consequence, including the
folding of shapes and TypeAndShape objects, and new APIs for shapes
that do not fold for those cases where folding isn't needed. Further,
the symbol-testing predicate APIs in Evaluate/tools.h now all resolve any
associations of their symbols and work transparently on use-, host-, and
construct-association symbols; the tools used to resolve those associations have
been defined and documented more precisely, and their clients adjusted as needed.

Differential Revision: https://reviews.llvm.org/D94561

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[flang] Improve initializer semantics, esp. for component default values

This patch plugs many holes in static initializer semantics, improves error
messages for default initial values and other com

[flang] Improve initializer semantics, esp. for component default values

This patch plugs many holes in static initializer semantics, improves error
messages for default initial values and other component properties in
parameterized derived type instantiations, and cleans up several small
issues noticed during development. We now do proper scalar expansion,
folding, and type, rank, and shape conformance checking for component
default initializers in derived types and PDT instantiations.
The initial values of named constants are now guaranteed to have been folded
when installed in the symbol table, and are no longer folded or
scalar-expanded at each use in expression folding. Semantics documentation
was extended with information about the various kinds of initializations
in Fortran and when each of them are processed in the compiler.

Some necessary concomitant changes have bulked this patch out a bit:
* contextual messages attachments, which are now produced for parameterized
derived type instantiations so that the user can figure out which
instance caused a problem with a component, have been added as part
of ContextualMessages, and their implementation was debugged
* several APIs in evaluate::characteristics was changed so that a FoldingContext
is passed as an argument rather than just its intrinsic procedure table;
this affected client call sites in many files
* new tools in Evaluate/check-expression.cpp to determine when an Expr
actually is a single constant value and to validate a non-pointer
variable initializer or object component default value
* shape conformance checking has additional arguments that control
whether scalar expansion is allowed
* several now-unused functions and data members noticed and removed
* several crashes and bogus errors exposed by testing this new code
were fixed
* a -fdebug-stack-trace option to enable LLVM's stack tracing on
a crash, which might be useful in the future

TL;DR: Initialization processing does more and takes place at the right
times for all of the various kinds of things that can be initialized.

Differential Review: https://reviews.llvm.org/D92783

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[Flang][OpenACC] Fix for branching out issue in OpenACC parallel construct.

From OpenACC 3.0 Standards document
840 • A program may not branch into or out of an OpenACC parallel construct.
Exits

[Flang][OpenACC] Fix for branching out issue in OpenACC parallel construct.

From OpenACC 3.0 Standards document
840 • A program may not branch into or out of an OpenACC parallel construct.
Exits are allowed provided it does not cause an exit outside the parallel region.

Test case exits out of the inner do loop, but it is still inside the parallel region.
Patch tries to extract labels from block attached to a construct,
If the exit is to a label not in the collected list then flags an error.

Reviewed By: tskeith

Differential Revision: https://reviews.llvm.org/D87906

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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] Fix crash on erroneous expressions

Summary:
If you create an expression with parse errors, the `parser::Expr.typedExpr`
will be empty, which causes a compiler crash. The crash is caused by

[flang] Fix crash on erroneous expressions

Summary:
If you create an expression with parse errors, the `parser::Expr.typedExpr`
will be empty, which causes a compiler crash. The crash is caused by the
check in check-do-forall.cpp that scans all expresssions to see if `DO`
variables are being modified.

It turned out that the problem was that I was fetching subexpressions of type
`parser::Expr`, which are not guaranteed to have a non-null `typedExpr`. I
fixed this by only grabbing the top-level expression from which to gather
arguments as part of the DO loop analysis. This, in turn, exposed a problem
where I wasn't collecting all of the actual arguments in an expression. This
was caused by the fact that I wasn't recursing through the rest of the
expression after finding an argument. I fixed this by recursing through the
argument in the member function in `CollectActualArgumentsHelper`.

Reviewers: klausler, tskeith, DavidTruby

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81101

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[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] Add explicit nullptr check in initialisation of inDoConstruct.

This explicit check is needed as we are using braced initialisation here so
implicit narrowing conversions (such as pointer to

[flang] Add explicit nullptr check in initialisation of inDoConstruct.

This explicit check is needed as we are using braced initialisation here so
implicit narrowing conversions (such as pointer to bool) are not allowed.

Original-commit: flang-compiler/f18@ff8dad10bffb70666ba3b4ff229dc4b608f9e116
Reviewed-on: https://github.com/flang-compiler/f18/pull/1083

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[flang] Remove use of std::set::merge

Some versions of clang that we are building with don't have
std::set::merge, even though it is part of C++17. Work around
that by using std::set::insert until w

[flang] Remove use of std::set::merge

Some versions of clang that we are building with don't have
std::set::merge, even though it is part of C++17. Work around
that by using std::set::insert until we can count on merge being
available everywhere.

Original-commit: flang-compiler/f18@886ccc37fbff5df00717ac728e2aba240d0a314c
Reviewed-on: https://github.com/flang-compiler/f18/pull/1014

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[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 <[email protected]>

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

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