[Bug fortran/91646] New: gfortran takes long time and consumes a lot of memory

[luomo1138 at yahoo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91646

            Bug ID: 91646
           Summary: gfortran takes long time and consumes a lot of memory
           Product: gcc
           Version: 9.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: luomo1138 at yahoo dot com
  Target Milestone: ---

Created attachment 46806
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46806&action=edit
source file demonstrating issue

Hello,

I have an issue with gfortran taking a very long time and consuming a lot of
memory to compile a file.

The attached file compiles in about one second when using either gfortran 4.9.2
or the Intel Fortran compiler (ifort).  However, when I use gfortran 9.1.0,
that file takes a very long time to compile.

When I compile the file with this command:

```
gfortran -Wall -c -pass-exit-codes -ffree-line-length-0 -g LVT_statsDataMod.F90
```

it takes 10 minutes to compile and uses approximately 20GB of memory.

Similarly for "-O0".  When I use either "-O1" or "-O2", it takes over an hour
to compile and uses at least 35GB of memory.  (I do not know exactly how long
because I killed it after one hour.)

I have seen similar behaviour with gfortran 7.3 and 8.1 as well.

I also compiled with "-Wextra" and "-fno-strict-aliasing -fwrapv
-fno-aggressive-loop-optimizations", but nothing was reported.

Do you have any suggestions?


* Exact version, system type, and GCC build options:

```
$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/gpfsm/dulocal/sles11/other/SLES11.3/gcc/9.1/libexec/gcc/x86_64-pc-linux-gnu/9.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /gpfsm/dnbsrc/other/GCC/SLES11/9.1/gcc-9.1.0/configure
--prefix=/gpfsm/dulocal/sles11/other/SLES11.3/gcc/9.1 --enable-languages=all
--enable-bootstrap
Thread model: posix
gcc version 9.1.0 (GCC)
```

* complete command line:

```
gfortran -Wall -c -pass-exit-codes -ffree-line-length-0 -g LVT_statsDataMod.F90
```

* compiler output:

None

* preprocessed file:

Attached file does not require any preprocessing.


Here is the version of gfortran that performs as I expect:

```
$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/gpfsm/dulocal/sles11/other/SLES11.3/gcc/4.9.2/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /gpfsm/dnbsrc/other/GCC/SLES11/4.9.2/gcc-4.9.2/configure
--prefix=/usr/local/other/SLES11.3/gcc/4.9.2 --enable-languages=all
--enable-bootstrap
Thread model: posix
gcc version 4.9.2 (GCC)
```


Thanks,
Jim