[flang] Error detection/avoidance for TRANSFER with empty MOLD= type

When MOLD= is an array and there is no SIZE= in a call to TRANSFER(),
the size of an element of the MOLD= is used as the denomina

[flang] Error detection/avoidance for TRANSFER with empty MOLD= type

When MOLD= is an array and there is no SIZE= in a call to TRANSFER(),
the size of an element of the MOLD= is used as the denominator in a
division to establish the extent of the vector result. When the
total storage size of the SOURCE= is known to be zero, the result is
empty and no division is needed.

To avoid a division by zero at runtime, we need to check for a zero-sized
MOLD= element type when the storage size of SOURCE= is nonzero and there
is no SIZE=. Further, in the compilation-time rewriting of calls to
SHAPE(TRANSFER(...)) and SIZE(TRANSFER(...)) for constant folding and
simplification purposes, we can't replace the call with an arithmetic
element count expression when the storage size of SOURCE= is not known
to be zero and the element size of MOLD= is not known to be nonzero at
compilation time.

These changes mostly affect tests using a MOLD= argument that is an
assumed-length character.

Differential Revision: https://reviews.llvm.org/D129680

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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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[flang] Fix Symbol::Rank for ProcEntityDetails

When a procedure pointer or procedure dummy argument has a
defined interface, the rank of the pointer (or dummy) is the
rank of the interface.

Also tw

[flang] Fix Symbol::Rank for ProcEntityDetails

When a procedure pointer or procedure dummy argument has a
defined interface, the rank of the pointer (or dummy) is the
rank of the interface.

Also tweak code discovered in shape analysis when investigating
this problam so that it returns a vector of emptied extents rather
than std::nullopt when the extents are not scope-invariant, so that
the rank can at least be known.

Differential Revision: https://reviews.llvm.org/D123727

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[flang] Fix shape analysis of RESHAPE result

Shape analysis of RESHAPE(..., SHAPE=s) should of course return
the SHAPE= actual argument when it is constant; but when it is
not, its length is still k

[flang] Fix shape analysis of RESHAPE result

Shape analysis of RESHAPE(..., SHAPE=s) should of course return
the SHAPE= actual argument when it is constant; but when it is
not, its length is still known, and thus so is the rank of the
result of RESHAPE(), and shape analysis should at least return
a shape vector of the right length rather than a result that
makes the result appear to be a scalar, which can lead to some
bogus error messages.

Also, while here: rename a private GetShapeHelper::AsShape()
routine so that it can't be confused with the ones in the API
of shape.h.

Differential Revision: https://reviews.llvm.org/D123712

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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] Fix LBOUND rewrite on descriptor components

GetLowerBoundHelper rewrite in https://reviews.llvm.org/D121488 was
incorrect with POINTER/ALLOCATABLE components. The rewrite created a
descripto

[flang] Fix LBOUND rewrite on descriptor components

GetLowerBoundHelper rewrite in https://reviews.llvm.org/D121488 was
incorrect with POINTER/ALLOCATABLE components. The rewrite created a
descriptor inquiry to the component symbol only instead of the whole
named entity. The base information was lost, and not retrievable.
LBOUND(a(10)%p) became LBOUND(p).

Fix this regression, and also update DescriptorInquiry unparsing to
carry the kind information. DescriptorInquiries are KIND 8 expressions,
while LBOUND/SIZE/RANK, %LEN are default kind expressions.
This caused `print *,lbound(x,kind=8)` to unparse as `print*,lbound(x)` which is not
semantically the same (this unparsing issue was not an issue for
lowering, but I noticed it while writing my regression test).

Differential Revision: https://reviews.llvm.org/D122406

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[flang] UBOUND() edge case: empty dimension

Similarly to LBOUND in https://reviews.llvm.org/D121488, UBOUND must
return zero for an empty dimension, no matter the specification
expression.

Add a Ge

[flang] UBOUND() edge case: empty dimension

Similarly to LBOUND in https://reviews.llvm.org/D121488, UBOUND must
return zero for an empty dimension, no matter the specification
expression.

Add a GetUBOUND method to be used in expression rewrite that prevents
folding UBOUND to a bound specification expression if the extent is
not a compile time constant.

Fold the case where the extents is known to be zero (and also deal with
this case in LBOUND since we can and should to comply with constant
expression requirements).

Differential Revision: https://reviews.llvm.org/D122242

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[flang] LBOUND() edge case: empty dimension

LBOUND must return 1 for an empty dimension, no matter what
explicit expression might appear in a declaration or arrive in
a descriptor.

Differential Rev

[flang] LBOUND() edge case: empty dimension

LBOUND must return 1 for an empty dimension, no matter what
explicit expression might appear in a declaration or arrive in
a descriptor.

Differential Revision: https://reviews.llvm.org/D121488

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[flang] Check constraint C711 correctly

An assumed-type actual argument that corresponds to an assumed-rank dummy
argument shall be assumed-shape or assumed-rank.

Differential Revision: https://rev

[flang] Check constraint C711 correctly

An assumed-type actual argument that corresponds to an assumed-rank dummy
argument shall be assumed-shape or assumed-rank.

Differential Revision: https://reviews.llvm.org/D120750

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[flang] Prevent any non constant result extent to be inlined on caller side

UBOUND, SIZE, and SHAPE folding was still creating expressions that are
invalid on the caller side without the call expres

[flang] Prevent any non constant result extent to be inlined on caller side

UBOUND, SIZE, and SHAPE folding was still creating expressions that are
invalid on the caller side without the call expression context.
A previous patch intended to deal with this situation (https://reviews.llvm.org/D116933)
but it assumed the return expression would be a descriptor inquiry to
the result symbol, which is not the case if the extent expression is
"scope invariant" inside the called subroutine (e.g., referring to
intent(in) dummy arguments). Simply prevent folding from inlining non
constant extent expression on the caller side.

Folding could be later improved by having ad-hoc folding for UBOUND, SIZE, and
SHAPE on function references where it could try replacing the dummy symbols
by the actual expression, but this is left as a possible later improvement.

Differential Revision: https://reviews.llvm.org/D117686

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[flang] Do not lose call in shape inquiry on function reference

Currently, something like `print *, size(foo(n,m))` was rewritten
to `print *, size(foo_result_symbol)` when foo result is a non const

[flang] Do not lose call in shape inquiry on function reference

Currently, something like `print *, size(foo(n,m))` was rewritten
to `print *, size(foo_result_symbol)` when foo result is a non constant
shape array. This cannot be processed by lowering or reprocessed by a
Fortran compiler since the syntax is wrong (`foo_result_symbol` is
unknown on the caller side) and the arguments are lost when they might
be required to compute the result shape.

It is not possible (and probably not desired) to make GetShape fail in
general in such case since returning nullopt seems only expected for
scalars or assumed rank (see GetRank usage in lib/Semantics/check-call.cpp),
and returning a vector with nullopt extent may trigger some checks to
believe they are facing an assumed size (like here in intrinsic argument
checks: https://github.com/llvm/llvm-project/blob/196204c72c68a577c72af95d70f18e3550939a5e/flang/lib/Evaluate/intrinsics.cpp#L1530).

Hence, I went for a solution that limits the rewrite change to folding
(where the original expression is returned if the shape depends on a non
constant shape from a call).

I added a non default option to GetShapeHelper that prevents the rewrite
of shape inquiry on calls to descriptor inquiries. At first I wanted to
avoid touching GetShapeHelper, but it would require to re-implement all
its logic to determine if the shape comes from a function call or not
(the expression could be `size(1+foo(n,m))`). So added an alternate
entry point to GetShapeHelper seemed the cleanest solution to me.

Differential Revision: https://reviews.llvm.org/D116933

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[flang] Adjust names in Semantics that imply too much (NFC)

Some kinds of Fortran arrays are declared with the same syntax,
and it is impossible to tell from a shape (:, :) or (*) whether
the object

[flang] Adjust names in Semantics that imply too much (NFC)

Some kinds of Fortran arrays are declared with the same syntax,
and it is impossible to tell from a shape (:, :) or (*) whether
the object is assumed shape, deferred shape, assumed size, implied
shape, or whatever without recourse to more information about the
symbol in question. This patch softens the names of some predicate
functions (IsAssumedShape to CanBeAssumedShape) and makes others
more reflective of the syntax they represent (isAssumed to isStar)
in an attempt to encourage coders to seek and find definitive
predicate functions whose names deliver what they seem to mean.

Address TODO comments in IsSimplyContiguous() by using the
updated IsAssumedShape() predicate.

Differential Revision: https://reviews.llvm.org/D114829

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[flang] Don't reference non-invariant symbols in shape expressions

When an array's shape involves references to symbols that are not
invariant in a scope -- the classic example being a dummy array
w

[flang] Don't reference non-invariant symbols in shape expressions

When an array's shape involves references to symbols that are not
invariant in a scope -- the classic example being a dummy array
with an explicit shape involving other dummy arguments -- the
compiler was creating shape expressions that referenced those
symbols. This might be valid if those symbols are somehow
captured and copied at each entry point to a subprogram, and
the copies referenced in the shapes instead, but that's not
the case.

This patch introduces a new expression predicate IsScopeInvariantExpr(),
which defines a class of expressions that contains constant expressions
(in the sense that the standard uses that term) as well as references
to items that may be safely accessed in a context-free way throughout
their scopes. This includes dummy arguments that are INTENT(IN)
and not VALUE, descriptor inquiries into descriptors that cannot
change, and bare LEN type parameters within the definitions of
derived types. The new predicate is then used in shape analysis
to winnow out results that would have otherwise been contextual.

Differential Revision: https://reviews.llvm.org/D113309

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[flang] Fold FINDLOC()

Fold the transformational intrinsic function FINDLOC() for
all combinations of optional arguments and data types.

Differential Revision: https://reviews.llvm.org/D110757

[flang] Validate SIZE(x,DIM=n) dimension for assumed-size array x

Catch invalid attempts to extract the unknowable extent of the last
dimension of an assumed-size array dummy argument, and clean up

[flang] Validate SIZE(x,DIM=n) dimension for assumed-size array x

Catch invalid attempts to extract the unknowable extent of the last
dimension of an assumed-size array dummy argument, and clean up
problems with assumed-rank arguments in similar circumstances
exposed by testing the fix.

Differential Revision: https://reviews.llvm.org/D109918

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[flang] Accept SIZE(assumed-rank, DIM=n)

Silence a bogus error message about an out-of-range DIM= argument
when the argument is assumed-rank. (More generally, don't pretend
to be able to discern a

[flang] Accept SIZE(assumed-rank, DIM=n)

Silence a bogus error message about an out-of-range DIM= argument
when the argument is assumed-rank. (More generally, don't pretend
to be able to discern a shape of known rank for an assumed-rank
object.)

Differential Revision: https://reviews.llvm.org/D109915

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[flang] Fix the extent calculation when upper bounds are less than lower bounds

When the upper bound is less than the lower bound, the extent is zero. This is
specified in section 8.5.8.2, paragrap

[flang] Fix the extent calculation when upper bounds are less than lower bounds

When the upper bound is less than the lower bound, the extent is zero. This is
specified in section 8.5.8.2, paragraph 3.

Note that similar problems exist in the lowering code. This change only fixes
the problem for the front end.

I also added a test.

Differential Revision: https://reviews.llvm.org/D107832

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[flang] Run-time derived type initialization and destruction

Use derived type information tables to drive default component
initialization (when needed), component destruction, and calls to
final su

[flang] Run-time derived type initialization and destruction

Use derived type information tables to drive default component
initialization (when needed), component destruction, and calls to
final subroutines. Perform these operations automatically for
ALLOCATE()/DEALLOCATE() APIs for allocatables, automatics, and
pointers. Add APIs for use in lowering to perform these operations
for non-allocatable/automatic non-pointer variables.
Data pointer component initialization supports arbitrary constant
designators, a F'2008 feature, which may be a first for Fortran
implementations.

Differential Revision: https://reviews.llvm.org/D106297

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[flang] preserve symbol in DescriptorInquiry

Do not use ultimate symbols in DescriptorInquiry. Using the ultimate
symbol may lead to issues later for at least two reasons:

- The original symbols ma

[flang] preserve symbol in DescriptorInquiry

Do not use ultimate symbols in DescriptorInquiry. Using the ultimate
symbol may lead to issues later for at least two reasons:

- The original symbols may have volatile/asynchronous attributes that
the ultimate may not have. Later phases working on the DescriptorInquiry
would then not apply potential care required by these attributes.
- HostAssociatedDetails symbols are used by OpenMP for symbols with
special OpenMP attributes inside OpenMP region (e.g variables with
private attribute), so it is very important to preserve this
aspect in the DescriptorInquiry, that would otherwise apply on the
symbol outside of the region.

Differential Revision: https://reviews.llvm.org/D104385

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[flang] Fold MAXVAL & MINVAL

Implement constant folding for the reduction transformational
intrinsic functions MAXVAL and MINVAL.

In anticipation of more folding work to follow, with (I hope)
some

[flang] Fold MAXVAL & MINVAL

Implement constant folding for the reduction transformational
intrinsic functions MAXVAL and MINVAL.

In anticipation of more folding work to follow, with (I hope)
some common infrastructure, these two have been implemented in a
new header file.

Differential Revision: https://reviews.llvm.org/D104337

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[flang] CheckConformance: tristate-ify result

To ensure that errors are emitted by CheckConformance and
its callers in all situations, it's necessary for the returned result
of that function to dist

[flang] CheckConformance: tristate-ify result

To ensure that errors are emitted by CheckConformance and
its callers in all situations, it's necessary for the returned result
of that function to distinguish between three possible
outcomes: the arrays are known to conform at compilation time,
the arrays are known to not conform (and a message has been
produced), and an indeterminate result in which is not possible
to determine conformance. So convert CheckConformance's
result into an optional<bool>, and convert its confusing
Boolean flag arguments into a bit-set of named flags too.

Differential Revision: https://reviews.llvm.org/D103654

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[flang] Add TypeAndShape::MeasureElementSizeInBytes()

Split up MeasureSizeInBytes() so that array element sizes can be
calculated accurately; use the new API in some places where
DynamicType::Measur

[flang] Add TypeAndShape::MeasureElementSizeInBytes()

Split up MeasureSizeInBytes() so that array element sizes can be
calculated accurately; use the new API in some places where
DynamicType::MeasureSizeInBytes() was being used but the new
API performs better due to TypeAndShape having precise CHARACTER
length information.

Differential Revision: https://reviews.llvm.org/D95897

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[flang] Improve shape & length characterization

Analyze the shape of the result of TRANSFER(ptr,array) correctly
when "ptr" is an array of deferred shape. Fixing this bug led to
some refactoring an

[flang] Improve shape & length characterization

Analyze the shape of the result of TRANSFER(ptr,array) correctly
when "ptr" is an array of deferred shape. Fixing this bug led to
some refactoring and concentration of common code in TypeAndShape
member functions with code in general shape and character length
analysis, and this led to some regression test failures that have
all been cleaned up.

Differential Revision: https://reviews.llvm.org/D95744

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[flang] Support disabled alternative PARAMETER statement

Legacy Fortran implementations support an alternative form of the
PARAMETER statement; it differs syntactically from the standard's
PARAMETER

[flang] Support disabled alternative PARAMETER statement

Legacy Fortran implementations support an alternative form of the
PARAMETER statement; it differs syntactically from the standard's
PARAMETER statement by lacking parentheses, and semantically by
using the type and shape of the initialization expression to define
the attributes of the named constant. (GNU Fortran gets that part
wrong; Intel Fortran and nvfortran have full support.)

This patch disables the old style PARAMETER statement by default, as
it is syntactically ambiguous with conforming assignment statements;
adds a new "-falternative-parameter-statement" option to enable it;
and implements it correctly when enabled.

Fixes https://bugs.llvm.org/show_bug.cgi?id=48774, in which a user
tripped over the syntactic ambiguity.

Differential Revision: https://reviews.llvm.org/D95697

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