Commit Graph

51 Commits

Author SHA1 Message Date
Slava Zakharin
2b86fb21f8 [flang][runtime] Avoid recursive calls in F18 runtime CUDA build. (#87428)
Recurrencies in the call graph (even if they are not executed)
prevent computing the minimal stack size required for a kernel
execution. This change disables some functionality of F18 IO
to avoid recursive calls. A couple of functions are rewritten
to work without using recursion.
2024-04-02 21:03:49 -07:00
Slava Zakharin
7860f97066 [flang][runtime] Use cuda::std::variant in the CUDA build. (#86615)
Added `FLANG_LIBCUDACXX_PATH` CMake variable to specify
installation of header-only libcudacxx library.
If it is specified, the `<cuda/std/variant>` is used to provide
implementation of `std::variant`.
2024-03-26 09:47:10 -07:00
Slava Zakharin
8ebf741136 [flang][runtime] Prepare enabling PRINT of integer32 for device. (#86247)
This commit adds required files into the offload build closure,
which means adding RT_API_ATTRS and other markers.

The implementation does not work for CUDA yet, because of
std::variant,swap,reverse usage. These issues will be resolved
separately (e.g. by using libcudacxx header files).
2024-03-25 16:01:25 -07:00
Slava Zakharin
00f3454bbe [flang][runtime] Added pseudo file unit for simplified PRINT. (#86134)
A file unit is emulated via a temporary buffer that accumulates
the output, which is printed out via std::printf at the end
of the IO statement. This implementation will be used for the offload
devices.
2024-03-21 15:12:31 -07:00
Slava Zakharin
71e0261fb0 [flang][runtime] Added Fortran::common::optional for use on device.
This is a simplified implementation of std::optional that can be used
in the offload builds for the device code. The methods are properly
marked with RT_API_ATTRS so that the device compilation succedes.

Reviewers: klausler, jeanPerier

Reviewed By: jeanPerier

Pull Request: https://github.com/llvm/llvm-project/pull/85177
2024-03-15 14:25:47 -07:00
Peter Klausler
c21ef15ec6 [flang][runtime] Allow 1023 active asynchronous IDs (#82446)
The present limit of 63 is too low for some tests; bump it up to 1023 by
using an array of bit-sets.
2024-03-01 14:28:39 -08:00
Peter Klausler
c94f780487 [flang][runtime] Support READ after WRITE w/o positioning (#74650)
Most Fortran implementations support a READ statement after a WRITE
without repositioning on a sequential unit; it implies on ENDFILE and
then hits an EOF condition.

Fixes llvm-test-suite/Fortran/gfortran/regression/backspace_2.f.
2023-12-11 12:56:34 -08:00
Peter Klausler
ccc573c6d8 [flang][runtime] When OPEN implies CLOSE, disable later extant unit c… (#69390)
…hecks

An OPEN statement on an existing unit can imply a CLOSE of that unit;
for example, OPEN(5, FILE="mydata", FORM="formatted") should implicitly
close the standard input that had been preconnected to unit 5. When this
happens, later checks in OPEN statement completion that apply only to
existing units should be disabled.
2023-10-31 10:25:29 -07:00
Peter Klausler
7cf1608b4d [flang] Rework handling of non-type-bound user-defined I/O
A fairly recent introduction of runtime I/O APIs called OutputDerivedType()
and InputDerivedType() didn't cover NAMELIST I/O's need to access
non-type-bound generic interfaces for user-defined derived type I/O
when those generic interfaces are defined in some scope other than the
one that defines the derived type.

The patch adds a new data structure shared between lowering
and the runtime that can represent all of the cases that can
arise with non-type-bound defined I/O.  It can represent
scopes in which non-type-bound defined I/O generic interfaces
are inaccessible, too, due to IMPORT statements.

The data structure is now an operand to OutputDerivedType() and
InputDerivedType() as well as a data member in the NamelistGroup
structure.

Differential Revision: https://reviews.llvm.org/D148257
2023-04-13 15:35:01 -07:00
Peter Klausler
79f6b81235 [flang][runtime] Corrections to formatted child I/O
A handful of I/O statements (OPEN, CLOSE, positioning) are not allowed
on units during child I/O; catch violations and report errors.
Also finesse error handling during FORMAT runtime parsing of DT
derived type edit descriptors, and ensure that formatted child
I/O is nonadvancing.

Differential Revision: https://reviews.llvm.org/D145751
2023-03-10 10:09:44 -08:00
Peter Klausler
00a1c6d036 [flang] Restore old unit locking behavior
Rework  the recursive I/O error check on I/O units so that
threads again hold a lock on a unit throughout an I/O statement.
Add an API to the runtime's Lock class implementation for pthreads
to allow detection of solf-deadlock without depending on EDEADLK
or recursive mutexes.

This should fix I/O from OpenMP threads.

Differential Revision: https://reviews.llvm.org/D139477
2022-12-08 08:34:46 -08:00
Peter Klausler
c7fe5e83db [flang][runtime] Handle endian-swapped record headers & footers on input
The runtime I/O library correctly handles endianness conversions on payload
data I/O and on the output of sequential record headers and footers, but
does not swap endianness when required when reading sequential record headers
and footers back in for READ and BACKSPACE statements.  Mea culpa.  Fix.

Fixes https://github.com/llvm/llvm-project/issues/57126

Differential Revision: https://reviews.llvm.org/D132168
2022-08-18 15:36:32 -07:00
Peter Klausler
341c7c05df [flang][runtime] Improve Fortran I/O behavior when main program is C/C++
Ensure that I/O buffers are flushed at the end of the program,
and properly detect ttys for predefined units so that Fortran
output is interspersed with output from non-Fortran code.

Fixes https://github.com/llvm/llvm-project/issues/56944

Differential Revision: https://reviews.llvm.org/D132152

Update: fix typo in comment
2022-08-18 14:10:45 -07:00
Peter Klausler
921316af6e [flang][runtime] Catch & report attempts at recursive I/O
When an I/O statement contains a function call that attempts
to perform I/O on the same unit, detect the recursive I/O
and terminate with a useful message rather than deadlocking in
the threading library.

Differential Revision: https://reviews.llvm.org/D131097
2022-08-07 12:52:56 -07:00
Peter Klausler
d771245a9d [flang] Fix READ/WRITE with POS= on stream units, with refactoring
First, ExternalFileUnit::SetPosition was being used both as a utility
within the class' member functions as well as an API from I/O statement
processing.  Make it private, and add APIs for SetStreamPos and SetDirectRec.

Second, ensure that SetStreamPos for POS= positioning in a stream
doesn't leave the current record number and endfile record number
in an arbitrary state.  In stream I/O they are used only to manage
end-of-file detection, and shouldn't produce false positive results
from IsAtEnd() after repositioning.

Differential Revision: https://reviews.llvm.org/D128388
2022-06-23 09:16:49 -07:00
Peter Klausler
17853928a6 [flang] Correct implementation of WAIT with no ID
Previous one was returning a bogus error status about a bad WAIT
statement ID number.

Differential Revision: https://reviews.llvm.org/D127979
2022-06-16 10:00:40 -07:00
Peter Klausler
cfbde7149d [flang][runtime] Catch more (all?) negative unit number errors
Fortran does have negative unit numbers -- they show up in child I/O
subroutines for defined I/O and for OPEN(NEWUNIT=) -- but the runtime
needs to catch the cases where a negative unit number that wasn't
generated by the runtime is passed in for OPEN or for an I/O statement
that would ordinarily create an anonymous "fort.NNN" file for a
hitherto unseen unit.

Differential Revision: https://reviews.llvm.org/D127788
2022-06-15 17:29:50 -07:00
Peter Klausler
f6253eb9ba [flang][runtime] Fix INQUIRE(POS=n) for non-advancing I/O
Position inquiries need to account for offsets in records to be
accurate in the case of non-advancing I/O.

Differential Revision: https://reviews.llvm.org/D127789
2022-06-15 14:14:06 -07:00
Peter Klausler
142db43b62 [flang][runtime] Allow recovery from BACKSPACE(badUnit)
When an unconnected unit number is used in a BACKSPACE statement
with ERR=, IOSTAT=, &/or IOMSG= control specifiers, don't crash,
but let the program deal with the error.

Differential Revision: https://reviews.llvm.org/D127782
2022-06-15 13:00:54 -07:00
Peter Klausler
166d6ed5c7 [flang][runtime] Better (but still synchronous) support for asynchronous I/O
Track pending "asynchronous" I/O operation IDs so that WAIT statements can
report errors about bad ID numbers.

Lowering will need to extended to call GetAsynchronousId() for a READ or
WRITE statement with ID=n.

Differential Revision: https://reviews.llvm.org/D127421
2022-06-13 10:43:14 -07:00
Peter Klausler
03c066ab13 [flang][runtime] Catch OPEN of connected file
Diagnose OPEN(FILE=f) when f is already connected by the same name to
a distinct external I/O unit.

Differential Revision: https://reviews.llvm.org/D127035
2022-06-04 11:06:37 -07:00
Peter Klausler
8527f9e443 [flang][runtime] Handle BACKSPACE after reading past EOF
An external READ(END=) that hits the end of the file must
also note the virtual position of the endfile record that
has just been discovered, so that a later BACKSPACE statement
won't end up at the wrong record.

Differential Revision: https://reviews.llvm.org/D126146
2022-05-24 10:27:50 -07:00
Peter Klausler
deb62f5ad6 [flang][runtime] Clean up asynchronous I/O APIs
Now that the requirements and implementation of asynchronous I/O are
better understood, adjust their I/O runtime APIs.  In particular:
1) Remove the BeginAsynchronousOutput/Input APIs; they're not needed,
   since any data transfer statement might have ASYNCHRONOUS= and
   (if ASYNCHRONOUS='YES') ID= control list specifiers that need to
   at least be checked.
2) Add implementations for BeginWait(All) to check for the error
   case of a bad unit number and nonzero ID=.
3) Rearrange and comment SetAsynchronous so that it's clear that
   it can be called for READ/WRITE as well as for OPEN.

The implementation remains completely synchronous, but should be conforming.
Where opportunities make sense for true asynchronous implementations of
some big block transfers without SIZE= in the future, we'll need to add
a GetAsynchronousId API to capture ID= on a READ or WRITE; add sourceFile
and sourceLine arguments to BeginWait(All) for good error reporting;
track pending operations in unit.h; and add code to force synchronization
to non-asynchronous I/O operations.

Lowering should call SetAsynchronous when ASYNCHRONOUS= appears as
a control list specifier.  It should also set ID=x variables to 0
until such time as we support asynchronous operations, if ever.
This patch only removes the removed APIs from lowering.

Differential Revision: https://reviews.llvm.org/D126143
2022-05-24 07:54:57 -07:00
Peter Klausler
d2b339f176 [flang] Respect left tab limit with Tn editing after ADVANCE='NO'
Correct the implementation of non-advancing I/O after some testing
to ensure that T tab edit descriptors are not allowed to back up
into positions of a record prior to where it stood at the beginning
of the I/O statement.

Differential Revision: https://reviews.llvm.org/D123709
2022-04-13 21:45:53 -07:00
Peter Klausler
bafbae238a [flang] Initial UTF-8 support in runtime I/O
Implements UTF-8 encoding and decoding for external units
with OPEN(ENCODING='UTF-8').  This encoding applies to default
CHARACTER values that are not 7-bit ASCII as well as to
the wide CHARACTER kinds 2 and 4.  Basic testing is in place
via direct calls to the runtime I/O APIs, but serious checkout
awaits lowering support of the wide CHARACTER kinds.

Differential Revision: https://reviews.llvm.org/D122038
2022-03-22 11:48:14 -07:00
Peter Klausler
507f7317a0 [flang] Catch READ/WRITE on direct-access file without REC=
A data transfer statement must have REC= in its control list
if (and only if) the unit was opened with ACCESS='DIRECT'.
The runtime wasn't catching this error, but was just silently
advancing to the next record as if the access were sequential.

Differential Revision: https://reviews.llvm.org/D120838
2022-03-02 12:38:11 -08:00
Peter Klausler
df38f35acb [flang] Allow data transfer stmt control list errors to be caught
The runtime crashes on several fundamental I/O data transfer statement
control list errors, like list I/O on a direct-access unit, or
input from a write-only unit, &c.  These errors should not be fatal
when ERR= or IOSTAT= are present.

This patch creates a new ErroneousIoStatementState class and
uses it for the state of an I/O statement that is doomed to fail
from these errors.  If there is no ERR= label or IOSTAT= variable,
the error will be raised at the end of the statement.  Data transfer
operations along the way will be no-op failures.

Differential Revision: https://reviews.llvm.org/D120745
2022-03-01 14:39:30 -08:00
Peter Klausler
991696c2eb [flang] Debugging of ACCESS='STREAM' I/O (take 2)
Corrects the runtime implementation of I/O on files with
the access mode ACCESS='STREAM'.  This is a collection
of edge-case tweaks to ensure that the distinctions between
stream and direct/sequential files, unformatted or formatted,
are respected where appropriate.

Moves NextInField() from io-stmt.h to io-stmt.cpp --
it was getting too big to keep in a header.

This patch exposed a problem with the I/O runtime
on Windows and it was reverted.  This version also
fixes that problem; files are now opened on Windows
in binary mode to prevent inadvertent insertions of
carriage returns before line feeds, and those line
endings (CR+LF) are now explicitly generated.

Differential Revision: https://reviews.llvm.org/D119015
2022-02-04 18:02:34 -08:00
Andrzej Warzynski
4e53e28374 Revert "[flang] Debugging of ACCESS='STREAM' I/O"
This reverts commit be9946b877.

This change has caused Flang's Windows buildbot to start failing:
* https://lab.llvm.org/buildbot/#/builders/172/builds/7664
2022-02-03 15:19:42 +00:00
Peter Klausler
be9946b877 [flang] Debugging of ACCESS='STREAM' I/O
Corrects the runtime implementation of I/O on files with
the access mode ACCESS='STREAM'.  This is a collection
of edge-case tweaks to ensure that the distinctions between
stream and direct/sequential files, unformatted or formatted,
are respected where appropriate.
Moves NextInField() from io-stmt.h to io-stmt.cpp --
it was getting too big to keep in a header.

Differential Revision: https://reviews.llvm.org/D118834
2022-02-02 13:09:38 -08:00
Peter Klausler
c7f4c333af [flang] Make NEWUNIT= use a range suitable for INTEGER(KIND=1) and recycle unit numbers
Use a bit-set to manage runtime-generated I/O unit numbers, recycle
them after they're closed, and use a range of values that fits in
a minimal-sized integer.

Differential Revision: https://reviews.llvm.org/D118651
2022-01-31 15:20:21 -08:00
Peter Klausler
b1856009fb [flang] Allow INQUIRE() on a child unit in user-defined I/O procedure
A procedure that implements a user-defined derived type I/O operation
is allowed to perform an INQUIRE statement on its unit.

Differential Revision: https://reviews.llvm.org/D117905https://reviews.llvm.org/D117905
2022-01-21 18:23:56 -08:00
Peter Klausler
80cdf0db67 [flang] Correct INQUIRE(POSITION= & PAD=)
INQUIRE(POSITION=)'s results need to reflect the POSITION=
specifier used for the OPEN statement until the unit has been
repositioned.  Preserve the POSITION= from OPEN and used it
for INQUIRE(POSITION=) until is becomes obsolete.

INQUIRE(PAD=) is implemented here in the case of an unconnected unit
with Fortran 2018 semantics; i.e., "UNDEFINED", rather than Fortran 90's
"YES"/"NO" (see 4.3.6 para 2).  Apparent failures with F'90-only tests
will persist with INQUIRE(PAD=); these discrepancies don't seem to warrant
an option or environment variable.

To make the implementation of INQUIRE more closely match the language
in the standard, rename IsOpen() to IsConnected(), and use it explicitly
for the various INQUIRE specifiers.

Differential Revision: https://reviews.llvm.org/D114755
2021-11-30 13:51:48 -08:00
Peter Klausler
da25f968a9 [flang] Runtime performance improvements to real formatted input
Profiling a basic internal real input read benchmark shows some
hot spots in the code used to prepare input for decimal-to-binary
conversion, which is of course where the time should be spent.
The library that implements decimal to/from binary conversions has
been optimized, but not the code in the Fortran runtime that calls it,
and there are some obvious light changes worth making here.

Move some member functions from *.cpp files into the class definitions
of Descriptor and IoStatementState to enable inlining and specialization.

Make GetNextInputBytes() the new basic input API within the
runtime, replacing GetCurrentChar() -- which is rewritten in terms of
GetNextInputBytes -- so that input routines can have the
ability to acquire more than one input character at a time
and amortize overhead.

These changes speed up the time to read 1M random reals
using internal I/O from a character array from 1.29s to 0.54s
on my machine, which on par with Intel Fortran and much faster than
GNU Fortran.

Differential Revision: https://reviews.llvm.org/D113697
2021-11-12 11:40:02 -08:00
Peter Klausler
830c0b9023 [flang] Move runtime API headers to flang/include/flang/Runtime
Move the closure of the subset of flang/runtime/*.h header files that
are referenced by source files outside flang/runtime (apart from unit tests)
into a new directory (flang/include/flang/Runtime) so that relative
include paths into ../runtime need not be used.

flang/runtime/pgmath.h.inc is moved to flang/include/flang/Evaluate;
it's not used by the runtime.

Differential Revision: https://reviews.llvm.org/D109107
2021-09-03 11:08:34 -07:00
peter klausler
cd0a1226b5 [flang] Fix "non-advancing" I/O, support $ in FORMAT
Non-advancing I/O was failing; ExternalFileUnit was losing
track of what writes had been committed to the file.  Fixed.
Also, support the common extension of $ and \ in a FORMAT
as being equivalent to ADVANCE=NO.

Differential Revision: https://reviews.llvm.org/D105046
2021-06-28 12:18:25 -07:00
peter klausler
43fadefb0e [flang] Implement user-defined derived type runtime I/O
With derived type description tables now available to the
runtime library, it is possible to implement the concept
of "child" I/O statements in the runtime and use them to
convert instances of derived type I/O data transfers into
calls to user-defined subroutines when they have been specified
for a type.  (See Fortran 2018, subclauses 12.6.4.8 & 13.7.6).

 - Support formatted, list-directed, and NAMELIST
   transfers to internal parent units; support these, and unformatted
   transfers, for external parent units.
 - Support nested child defined derived type I/O.
 - Parse DT'foo'(v-list) FORMAT data edit descriptors and passes
   their strings &/or v-list values as arguments to the defined
   formatted I/O routines.
 - Fix problems with this feature encountered in semantics and
   FORMAT valiation during development and end-to-end testing.
 - Convert typeInfo::SpecialBinding from a struct to a class
   after adding a member function.

Differential Revision: https://reviews.llvm.org/D104930
2021-06-28 11:36:19 -07:00
peter klausler
199a623ebf [flang] Runtime must defer formatted/unformatted determination
What the Fortran standard calls "preconnected" external I/O units
might not be known to be connected to unformatted or formatted files
until the first I/O data transfer statement is executed.
Support this deferred determination by representing the flag as
a tri-state Boolean and adapting its points of use.

Differential Revision: https://reviews.llvm.org/D101929
2021-05-06 11:06:43 -07:00
peter klausler
e81c96d6f8 [flang] Handle END= situations better in runtime input
Debug the input path for READ statements with END= labels;
don't emit errors when the program can handle them.
BeginReadingRecord() member functions have been made
"bool" for more convenient handling of error cases,
and some code in IoErrorHandler has been cleaned up.

Differential Revision: https://reviews.llvm.org/D100421
2021-04-14 09:34:14 -07:00
peter klausler
f4ecd5a128 [flang] More precise enforcement of runtime constraint
An OPEN statement that affects an already connected unit
without changing its external file is required to have
STATUS="OLD" or default STATUS=.  The code was eliciting
spurious runtime errors in situations where an OPEN statement
pertained to an existing unit number but did not need to have
STATUS="OLD'.

Differential Revision: https://reviews.llvm.org/D100352
2021-04-13 16:00:32 -07:00
peter klausler
e24f0ac7a3 [flang] Allow record advancement in external formatted sequential READ
The '/' control edit descriptor causes a runtime crash for an
external formatted sequential READ because the AdvanceRecord()
member function for external units implemented only the tasks
to finish reading the current record.  Split those out into
a new FinishReadingRecord() member function, call that instead
from EndIoStatement(), and change AdvanceRecord() to both
finish reading the current record and to begin reading the next
one.

Differential revision: https://reviews.llvm.org/D88607
2020-09-30 17:16:55 -07:00
peter klausler
675ad1bc6a [flang] Implement runtime support for INQUIRE statements
Differential Revision: https://reviews.llvm.org/D85166
2020-08-03 17:15:08 -07:00
peter klausler
8f2c5c4314 [flang] Implement byte-swapped external unformatted I/O in runtime
Add SetConvert() to the OPEN statement's runtime API.
Add ByteswapOption() to the main program's runtime API.
Check a $FORT_CONVERT environment variable, too, for
a swapping specifier.

Reviewed By: sscalpone

Differential Revision: https://reviews.llvm.org/D84284
2020-07-21 18:14:46 -07:00
peter klausler
ea4758a125 [flang] Rework read/write permission management for runtime file opening
Anonymous Fortran unit files (e.g., "./fort.7") need to be created
O_RDWR so that they can be written, rewound, and read.  Other
files opened with no ACTION= specifier need to set read/write
permissions based on the file, if it exists.

Reviewed By: sscalpone

Differential Revision: https://reviews.llvm.org/D84063
2020-07-17 14:44:58 -07:00
peter klausler
bd43fa29e3 [flang] Implement anonymous units in the runtime
I/O from/to an unopened unit number needs to open &/or create
a "fort.$UNIT" file.

Fixes FCVS test fm401.f.

Reviewed By: tskeith

Differential Revision: https://reviews.llvm.org/D83809
2020-07-14 16:12:06 -07:00
peter klausler
45b5c79a31 [flang] Extend & fix per-I/O-statement state (ext. I/O work part 7)
The per-I/O-statement state structures need to support missing
external I/O statements, and some bugs found in testing with
formatted input and record advancement are fixed.  The effects
of these changes will not be visible until further patches to
the I/O API handlers are pushed.

Reviewed By: tskeith

Differential Revision: https://reviews.llvm.org/D83151
2020-07-04 10:49:00 -07:00
peter klausler
0006354c3b [flang] Further implementation of external I/O unit operations (part 6)
Rework initial implementation of external I/O unit operations to
fix problems exposed in unit tests (in a later patch).  Add flushing.

Reviewed By: sscalpone

Differential Revision: https://reviews.llvm.org/D83147
2020-07-03 17:31:01 -07:00
Tim Keith
1f8790050b [flang] Reformat with latest clang-format and .clang-format
Original-commit: flang-compiler/f18@9fe84f45d7
Reviewed-on: https://github.com/flang-compiler/f18/pull/1094
2020-03-28 21:00:16 -07:00
peter klausler
3b63571425 [flang] Use hash table for UnitMap, avoid C++ STL binary dependence
Scan FORMAT strings locally to avoid C++ binary runtime dependence when computing deepest parenthesis nesting

Remove a dependency on ostream from runtime

Remove remaining direct external references from runtime to C++ library binaries

Remove runtime dependences on lib/common

SetPos() and SetRec()

Instantiate templates for input

Begin input; rearrange locking, deal with CLOSE races

View()

Update error message in test to agree with compiler change

First cut at real input

More robust I/O runtime error handling

Debugging of REAL input

Add iostat.{h,cpp}

Rename runtime/numeric-* to runtime/edit-*

Move templates around, templatize integer output editing

Move LOGICAL and CHARACTER output from io-api.cpp to edit-output.cpp

Change pointer argument to reference

More list-directed input

Complex list-directed input

Use enum class Direction rather than bool for templates

Catch up with changes to master

Undo reformatting of Lower code

Use record number instead of subscripts for internal unit

Unformatted sequential backspace

Testing and debugging

Dodge bogus GCC warning

Add <cstddef> for std::size_t to fix CI build

Address review comments

Original-commit: flang-compiler/f18@50406b3496
Reviewed-on: https://github.com/flang-compiler/f18/pull/1053
2020-03-11 13:23:39 -07:00
peter klausler
95696d563b [flang] Progress on Fortran I/O runtime
Use internal units for internal I/O state

Replace use of virtual functions

reference_wrapper

Internal formatted output to array descriptor

Delete dead code

Begin list-directed internal output

Refactorings and renamings for clarity

List-directed external I/O (character)

COMPLEX list-directed output

Control list items

First cut at unformatted I/O

More OPEN statement work; rename class to ExternalFileUnit

Complete OPEN (exc. for POSITION=), add CLOSE()

OPEN(POSITION=)

Flush buffers on crash and for terminal output; clean up

Documentation

Fix backquote in documentation

Fix typo in comment

Begin implementation of input

Refactor binary floating-point properties to a new header, simplify numeric output editing

Dodge spurious GCC 7.2 build warning

Address review comments

Original-commit: flang-compiler/f18@9c4bba11cf
Reviewed-on: https://github.com/flang-compiler/f18/pull/982
2020-02-13 10:31:26 -08:00