ftn: internal compiler error "Should never reach this code (doehmke)" for in_reduction on target reading a character substring

Legality: independently confirmed. 2 independent readings find the program legal and the result required. How this is checked

Affected variants

Compiler	MI300A gfx942 unified memory (XNACK 1)	MI300A gfx942 copy (XNACK 0)	MI250X gfx90a copy (XNACK 0)	MI300X gfx942 copy (XNACK 0)	MI350X gfx950 copy (XNACK 0)	A100 sm_80 separate memory	A100 sm_80 managed memory
AFAR 24.3.0	correct	correct	correct	correct	correct	n/a	n/a
CCE 19.0.0	behaves incorrectly	behaves incorrectly	behaves incorrectly	unknown not run	unknown not run	n/a	n/a
CCE 20.0.2	behaves incorrectly	behaves incorrectly	behaves incorrectly	unknown not run	unknown not run	n/a	n/a
CCE 21.0.3	behaves incorrectly	behaves incorrectly	behaves incorrectly	unknown not run	unknown not run	n/a	n/a
CCE 21.0.4	behaves incorrectly	behaves incorrectly	behaves incorrectly	unknown not run	unknown not run	n/a	n/a
NVHPC 25.11	n/a	n/a	n/a	n/a	n/a	fails another way	fails another way
NVHPC 26.9	n/a	n/a	n/a	n/a	n/a	fails another way	fails another way
GCC 16.2.0	fails another way	fails another way	fails another way	fails another way	fails another way	fails another way	n/a

"behaves incorrectly" / "not supported": this issue, confirmed in up to four environments (another build directory, another node, a repeat). "fails another way": a different failure, not counted as this issue. "unknown": not run there, or the runs disagree.

Messages

Result	Compiler and GPU	Message
behaves incorrectly	CCE 19.0.0, MI300A unified CCE 19.0.0, MI300A copy CCE 19.0.0, MI250X	show Warning: Headers and libraries from cray-libsci/25.03.0 will be ignored because depends on PE_MPICH which is unavailable.. Error message :: Should never reach this code (doehmke) Error detected :: File '/workspace/crayftn/pdgcs/v_mt_util_misc.c', line 2697 Initiated from :: Line 1849 (v_main.c) Optimizer built :: 2025-02-07 (production) File :: s1-2592-cce21.f90 Function :: kp1
behaves incorrectly	CCE 20.0.2, MI300A unified CCE 20.0.2, MI300A copy CCE 20.0.2, MI250X	show Warning: Headers and libraries from cray-libsci/25.09.0 will be ignored because depends on PE_MPICH which is unavailable.. Error message :: Should never reach this code (doehmke) Error detected :: File '/workspace/crayftn/pdgcs/v_mt_util_misc.c', line 2711 Initiated from :: Line 1859 (v_main.c) Optimizer built :: 2025-11-17 (production) File :: s1-2592-cce21.f90 Function :: kp1
behaves incorrectly	CCE 21.0.3, MI300A unified CCE 21.0.3, MI300A copy CCE 21.0.3, MI250X	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. Error message :: Should never reach this code (doehmke) Error detected :: File '/workspace/crayftn/pdgcs/v_mt_util_misc.c', line 2719 Initiated from :: Line 1939 (v_main.c) Optimizer built :: 2026-07-14 (production) File :: s1-2592-cce21.f90 Function :: kp1
behaves incorrectly	CCE 21.0.4, MI300A unified CCE 21.0.4, MI300A copy CCE 21.0.4, MI250X	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. Error message :: Should never reach this code (doehmke) Error detected :: File '/workspace/crayftn/pdgcs/v_mt_util_misc.c', line 2719 Initiated from :: Line 1939 (v_main.c) Optimizer built :: 2026-09-24 (production) File :: s1-2592-cce21.f90 Function :: kp1
fails another way	NVHPC 25.11, A100 separate NVHPC 25.11, A100 managed	show NVFORTRAN-S-0034-Syntax error at or near identifier task_reduction (s1-2592-cce21.f90: 18) NVFORTRAN-S-0034-Syntax error at or near identifier in_reduction (s1-2592-cce21.f90: 19) NVFORTRAN/x86-64 Linux 25.11-0: compilation completed with severe errors
fails another way	NVHPC 26.9, A100 separate NVHPC 26.9, A100 managed	show NVFORTRAN-S-0034-Syntax error at or near identifier task_reduction (s1-2592-cce21.f90: 18) NVFORTRAN-S-0034-Syntax error at or near identifier in_reduction (s1-2592-cce21.f90: 19) NVFORTRAN/x86-64 Linux 26.9-0: compilation completed with severe errors
fails another way	GCC 16.2.0, MI300A unified GCC 16.2.0, MI300A copy GCC 16.2.0, MI250X GCC 16.2.0, MI300X GCC 16.2.0, MI350X GCC 16.2.0, A100 separate	show libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY, but device not found

Reproduce

CCE 19.0.0, MI300A unified

module load cce/19.0.0 craype-accel-amd-gfx942 rocm/6.4.3
module unload cray-mpich
ftn -fopenmp -O2 repro.f90 -o repro
HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro

CCE 20.0.2, MI300A unified

module load cce/20.0.2 craype-accel-amd-gfx942 rocm/6.4.3
module unload cray-mpich
ftn -fopenmp -O2 repro.f90 -o repro
HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro

CCE 21.0.3, MI300A unified

module load cce/21.0.3 craype-accel-amd-gfx942 rocm/7.2.0
module unload cray-mpich
ftn -fopenmp -O2 repro.f90 -o repro
HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro

CCE 21.0.4, MI300A unified

module load cce/21.0.4 craype-accel-amd-gfx942 rocm/7.2.0
module unload cray-mpich
ftn -fopenmp -O2 repro.f90 -o repro
HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro

AFAR 24.3.0, MI300A unified (runs correctly)

$AFAR/bin/amdflang -fopenmp --offload-arch=gfx942 -O2 repro.f90 -o repro
HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro

Program (51 lines)

! Finding: CCE 19, 20, 21 internal compiler error "Should never
! reach this code (doehmke)" (v_mt_util_misc.c; line 2697 in 19.0.0, 2711
! in 20.0.2, 2719 in 21.0.3) on a target region with in_reduction(*: r),
! inside taskgroup task_reduction(*: r), that reads a substring of a
! character dummy (ichar(xs(1:1))). With a constant instead of the
! substring all three compile (data/evidence/dataenv_probe/ice/e2.f90).
!
! Legal OpenMP 5.2: in_reduction on target (5.2 §5.5.10), task_reduction on
! taskgroup (§5.5.9), a character dummy referenced in the region (mapped
! implicitly). (A gfortran -fopenmp accept is no evidence: rule of 2026-10-23.) Expected: ichar('k') =
! 107 and mod(107, 13) = 3, so every factor is 1 and r stays -1: "RESULT
! check=pass".
!
! Observed (tuolumne, MI300A, -O2, HSA_XNACK=1 and 0, 2026-10-23,
! results/t28_probe/ice_inred_char_substring.f90.*.json):
! - CCE 19.0.0, 20.0.2, 21.0.3: the ICE above, both modes;
! - AFAR amdflang 24.0.0git: "RESULT check=pass" in both modes;
! - Tioga MI250X (gfx90a, HSA_XNACK=0): CCE 21 the same ICE
!   (results/t28_probe/g90/ice_inred_char_substring.cce21_g90.json).
! Fuzz campaign s1: the "Should never reach this code (doehmke)" cells of
! CCE 19/20/21. Representative s1 seed 2592 on cce21; the confirmer's
! reduction (results/confirm/drafts/fuzz_s1_2592_cce21_gfx942_unified,
! 189 -> 98 lines, ICE kept) reduced further by hand.
!
! ftn -fopenmp -O2
program p
  implicit none
  integer, parameter :: n = 16
  character(len=8) :: xs
  integer :: r
  xs = 'kPACnWLl'
  r = -1
  call kp1(xs)
  if (r == -1) then
    print '(a)', 'RESULT check=pass'
  else
    print '(a,i0)', 'RESULT check=fail r=', r
  end if
contains
  subroutine kp1(xs)
    character(len=*), intent(in) :: xs
    integer :: i
    !$omp taskgroup task_reduction(*: r)
      !$omp target defaultmap(tofrom: scalar) in_reduction(*: r)
        do i = 1, n
          r = r * merge(-1, 1, mod(ichar(xs(1:1)), 13) == 0)
        end do
      !$omp end target
    !$omp end taskgroup
  end subroutine kp1
end program p

Source in the repository

Something to add? Dispute its legality · Report it fixed in a newer release · Report a mistake on this page

Expected and observed

Expected

RESULT check=pass

Observed where it behaves incorrectly

Warning:
 Headers and libraries from cray-libsci/25.03.0 will be ignored because depends on PE_MPICH which is unavailable..
   Error message      ::  Should never reach this code (doehmke)
   Error detected     ::  File '/workspace/crayftn/pdgcs/v_mt_util_misc.c', line 2697
   Initiated from     ::  Line 1849 (v_main.c)
   Optimizer built    ::  2025-02-07 (production)
   File               ::  s1-2592-cce21.f90
   Function           ::  kp1

What the specification requires

The specification text this program relies on and the compiler is expected to support.

OpenMP 5.2 §5.5.10

OpenMP 5.2 §5.5.9

Evidence

Same compiler, one change

ichar('k') instead of ichar(xs(1:1)): AFAR 24.3.0: correct; CCE 19.0.0: correct; CCE 20.0.2: correct; CCE 21.0.3: correct; CCE 21.0.4: correct

Control program

program p
  implicit none
  integer, parameter :: n = 16
  character(len=8) :: xs
  integer :: r
  xs = 'kPACnWLl'
  r = -1
  call kp1(xs)
  if (r == -1) then
    print '(a)', 'RESULT check=pass'
  else
    print '(a,i0)', 'RESULT check=fail r=', r
  end if
contains
  subroutine kp1(xs)
    character(len=*), intent(in) :: xs
    integer :: i
    !$omp taskgroup task_reduction(*: r)
      !$omp target defaultmap(tofrom: scalar) in_reduction(*: r)
        do i = 1, n
          r = r * merge(-1, 1, mod(ichar('k'), 13) == 0)
        end do
      !$omp end target
    !$omp end taskgroup
  end subroutine kp1
end program p

Other compilers run it correctly

AFAR 24.3.0