Re: beta gfortran 14.x.y (using -march=native and intrinsic repeat) gives a signal SIGILL

[Paul Richard Thomas <paul.richard.thomas@gmail.com>]

I wonder why the development 14.0.0 doesn't exhibit this behaviour?

Could you please rerun with the compile options -g -fdump-tree-original .

The later should generate a file *.original with the content:

void test ()
{
  character(kind=1) cc[1:32];

  __builtin_memmove ((void *) &cc, (void *) &"
       "[1]{lb: 1 sz: 1}, 32);
  {
    struct __st_parameter_dt dt_parm.0;

    dt_parm.0.common.filename = &"test_repeat.f90"[1]{lb: 1 sz: 1};
    dt_parm.0.common.line = 7;
    dt_parm.0.common.flags = 128;
    dt_parm.0.common.unit = 6;
    _gfortran_st_write (&dt_parm.0);
    {
      character(kind=1) str.1[38];
      character(kind=1) str.2[41];

      _gfortran_concat_string (38, (character(kind=1)[1:] *) &str.1,
6, &" cc : "[1]{lb: 1 sz: 1}, 32, &cc);
      _gfortran_concat_string (41, (character(kind=1)[1:] *) &str.2,
38, (character(kind=1)[1:] *) &str.1, 3, &"end"[1]{lb: 1 sz: 1});
      _gfortran_transfer_character_write (&dt_parm.0,
(character(kind=1)[1:] *) &str.2, 41);
    }
    _gfortran_st_write_done (&dt_parm.0);
  }
}

Note that repeat is reduced to the builtin memmove with 32 spaces going to cc.

Regards

Paul

On Fri, 11 Aug 2023 at 17:21, Jerry D via Fortran <fortran@gcc.gnu.org> wrote:
>
> On 8/11/23 5:34 AM, Jorge D'Elia via Fortran wrote:
> > Dear GFortran developers,
> >
> > With the beta gfortran 14.x.y versions we are noticing some runtime
> > errors in a production code.
> >
> > One type of runtime errors is related to the concurrent use of the
> > intrinsic "repeat" when the source code is compiled with the
> > flag -march=native, please, see below:
> >
> > $ cat test.f90
> > program test
> >    implicit none
> >    integer      , parameter :: iin = kind (1)
> >    integer (iin), parameter :: pp = 32
> >    character (len=pp) :: cc
> >    cc (1:pp) = repeat (" ",pp)
> >    write (*,*)" cc : " // cc
> > end program test
> >
> > $ gfortran --version
> > GNU Fortran (GCC) 14.0.0 20230808 (experimental)
> > Copyright (C) 2023 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> >
> > a) Compiling with the flag -mtune=native only, without -march=native, the test is ok:
> >
> > $ gfortran -mtune=native -fcheck=all -std=f2018 -Wall -Werror -Wextra -Og -o test.exe test.f90
> > $ test.exe
> >    cc :
> >
> > b) However, compiling with the flag -march=native:
> >
> > $ gfortran -march=native -fcheck=all -std=f2018 -Wall -Werror -Wextra -Og -o test.exe test.f90
> > $ test.exe
> >
> > Program received signal SIGILL: Illegal instruction.
> >
> > Backtrace for this error:
> > #0  0x14fae277fb1f in ???
> > #1  0x4011ad in ???
> > #2  0x401272 in ???
> > #3  0x14fae276a50f in ???
> > #4  0x14fae276a5c8 in ???
> > #5  0x4010c4 in ???
> > #6  0xffffffffffffffff in ???
> > Illegal instruction (core dumped)
> >
> > On the other hand, compiling with the system version (GNU Fortran (GCC)
> > 12.3.1 20230508 (Red Hat 12.3.1-1)) or replacing the intrinsic repeat
> > with:
> >
> > do kk = 1, pp
> >    cc (kk:kk) = " "
> > end do
> >
> > both tests are ok. The error occurs on any of Intel or AMD computers,
> > e.g. in the present case:
> >
> > $ lscpu
> > Architecture:           x86_64
> >    CPU op-mode(s):       32-bit, 64-bit
> >    Address sizes:        46 bits physical, 48 bits virtual
> >    Byte Order:           Little Endian
> > CPU(s):                 6
> >    On-line CPU(s) list:  0-5
> > Vendor ID:              GenuineIntel
> >    Model name:           Intel(R) Core(TM) i7-3930K CPU @ 3.20GHz
> >      CPU family:         6
> >      Model:              45
> >      Thread(s) per core: 1
> >      Core(s) per socket: 6
> >      Socket(s):          1
> >      Stepping:           7
> >      BogoMIPS:           6400.22
> > Caches (sum of all):
> >    L1d:                  192 KiB (6 instances)
> >    L1i:                  192 KiB (6 instances)
> >    L2:                   1.5 MiB (6 instances)
> >    L3:                   12 MiB (1 instance)
> > NUMA:
> >    NUMA node(s):         1
> >    NUMA node0 CPU(s):    0-5
> >
> >
> > By the way, I do not know if the -march=native flag or the intrinsic
> > repeat would be of deprecated use (or not)...
>
> Regardless, we should never segfault.  Thanks for the code example. We
> need to get a bug report opened on this.  I am on travel this morning,
> but if I have time i will do so this afternnon if someone else does not
> beat me to it.
>
> There were some recent patches in this area IIRC.
>
> Jerry
>