ftn: target update from(iterator(k = 1:1): b(k:n)) fails at the host link (OmpIt$k undefined)

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	fails another way	fails another way	fails another way	fails another way	fails another way	n/a	n/a
CCE 19.0.0	not supported	not supported	not supported	unknown not run	unknown not run	n/a	n/a
CCE 20.0.2	not supported	not supported	not supported	unknown not run	unknown not run	n/a	n/a
CCE 21.0.3	not supported	not supported	not supported	unknown not run	unknown not run	n/a	n/a
CCE 21.0.4	not supported	not supported	not supported	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
not supported	CCE 19.0.0, MI300A unified CCE 19.0.0, MI300A copy	show Warning: Headers and libraries from cray-libsci/25.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/19.0.0/binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3521917/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0xa3b): undefined reference to `OmpIt$k'
not supported	CCE 19.0.0, MI250X	show Warning: Headers and libraries from cray-libsci/25.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/19.0.0/binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3604383/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0xa3b): undefined reference to `OmpIt$k'
not supported	CCE 20.0.2, MI300A unified CCE 20.0.2, MI300A copy	show Warning: Headers and libraries from cray-libsci/25.09.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/20.0.2/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3327652/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0xa44): undefined reference to `OmpIt$k'
not supported	CCE 20.0.2, MI250X	show Warning: Headers and libraries from cray-libsci/25.09.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/20.0.2/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3441927/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0xa44): undefined reference to `OmpIt$k'
not supported	CCE 21.0.3, MI300A unified CCE 21.0.3, MI300A copy	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/21.0.3/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3548529/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0x9cd): undefined reference to `OmpIt$k'
not supported	CCE 21.0.3, MI250X	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/21.0.3/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3469717/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0x9cd): undefined reference to `OmpIt$k'
not supported	CCE 21.0.4, MI300A unified CCE 21.0.4, MI300A copy	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/21.0.4/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_2877578/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0x9cd): undefined reference to `OmpIt$k'
not supported	CCE 21.0.4, MI250X	show Warning: Headers and libraries from cray-libsci/26.03.0 will be ignored because depends on PE_MPICH which is unavailable.. /opt/cray/pe/cce/21.0.4/cce/x86_64/bin/../../../binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3642988/cce-iterator-link_1.o: in function `main': The Cpu Module:(.text+0x9cd): undefined reference to `OmpIt$k'
fails another way	AFAR 24.3.0, MI300A unified AFAR 24.3.0, MI300A copy AFAR 24.3.0, MI250X AFAR 24.3.0, MI300X AFAR 24.3.0, MI350X	show error: loc("cce-iterator-link.f90":28:23): /__w/TheRock/TheRock/compiler/amd-llvm/flang/lib/Lower/OpenMP/ClauseProcessor.cpp:2112: not yet implemented: Iterator modifier is not supported yet LLVM ERROR: aborting
fails another way	NVHPC 25.11, A100 separate NVHPC 25.11, A100 managed NVHPC 26.9, A100 separate NVHPC 26.9, A100 managed	show NVFORTRAN-S-0034-Syntax error at or near = (cce-iterator-link.f90: 28) 0 inform, 0 warnings, 1 severes, 0 fatal for gen_prog
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 cce-iterator-link.f90:28:36: 28 \| !$omp target update from(iterator(k = 1:1): b(k:n)) \| 1 Error: Syntax error in OpenMP variable list at (1)

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

Program (63 lines)

! # Draft finding: omp52-clause-from-iterator on cce19
!
! - compiler: cce19
! - toolchain: cce19; arch: gfx942; machine: tuolumne; memory mode: unified; opt: -O2
! - program: catalog omp52-clause-from-iterator (f90, version 52, sha256 5869ce00261053a5)
! - expected: None (None; )
! - actual: rejected  (link_undefined_symbol: The Cpu Module:(.text+0xa3b): undefined reference to `OmpIt$k')
! - verdict: compiler_bug by rule R10b-own-link-or-hang: a link failure on symbols the compiler's own generated code needs, or a
!   compile that does not finish, on a legal program: the compiler's defect (never a rejection)
! - reason: 
! - citations: RUL-COMPILE-TIME (rulings.md)
! - legality: legal (legal by construction: offload.engine.gen / c_gen / acc_gen check every program against the catalog rules
!   and the
!   offload scope as it is built (no compiler))
! - witnesses: none
! - withdrawn: none
!
! Generated by compliance.gen (OpenMP 5.2, free-form Fortran). Do not edit.
! id: omp52-clause-from-iterator
! primary atom: omp.clause.from.iterator
! legal: yes
! observable: yes
! ran_on_host: inside the target region of interest
! evidence: copy_mode_only
! needs: none
! std: f2008
! derivation (check=pass): target enter data maps a (to) and b (alloc); the host adds 10 to a and target update to(a) copies it (5.2
! derivation: §13.9 p.289), so the device's a(i) = i + 10 and the target region writes b(i) = 2*(i + 10) + 1 on the device; target
! derivation: update from(iterator(k = 1:1): b(k:n)) expands to from(b(1:n)) (5.2 §3.2.6 p.67), so the host's b is the device's: b =
! derivation: ref = 2*(i + 10) + 1; the check accepts
program gen_prog
  use omp_lib, only: omp_is_initial_device
  implicit none
  integer, parameter :: n = 64
  integer, allocatable, target :: a(:), b(:)
  integer :: ref(n)
  integer :: i, host_flag
  logical :: ok
  integer :: k
  allocate(a(n), b(n))
  do i = 1, n
    a(i) = i
    b(i) = 0
    ref(i) = 2*(i + 10) + 1
  end do
  host_flag = 1
  !$omp target enter data map(to: a) map(alloc: b)
  do i = 1, n
    a(i) = a(i) + 10
  end do
  !$omp target update to(a)
  !$omp target map(to: a) map(from: b) map(tofrom: host_flag)
    host_flag = merge(1, 0, omp_is_initial_device())
    do i = 1, n
      b(i) = 2*a(i) + 1
    end do
  !$omp end target
  !$omp target update from(iterator(k = 1:1): b(k:n))
  !$omp target exit data map(release: a, b)
  ok = all(b == ref)
  print '(a,i0,a,a)', 'RESULT ran_on_host=', host_flag, ' check=', merge('pass', 'fail', ok)
  deallocate(a, b)
end program gen_prog

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

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..
/opt/cray/pe/cce/19.0.0/binutils/x86_64/x86_64-pc-linux-gnu/bin/ld: <dir>/pe_3521917/cce-iterator-link_1.o: in function `main':
The Cpu Module:(.text+0xa3b): undefined reference to `OmpIt$k'

What the specification requires

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

OpenMP 5.2 §13.9 p.289

OpenMP 5.2 §3.2.6 p.67

Evidence

Same compiler, one change

from(b(1:n)) without the iterator modifier: 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 gen_prog
  use omp_lib, only: omp_is_initial_device
  implicit none
  integer, parameter :: n = 64
  integer, allocatable, target :: a(:), b(:)
  integer :: ref(n)
  integer :: i, host_flag
  logical :: ok
  integer :: k
  allocate(a(n), b(n))
  do i = 1, n
    a(i) = i
    b(i) = 0
    ref(i) = 2*(i + 10) + 1
  end do
  host_flag = 1
  !$omp target enter data map(to: a) map(alloc: b)
  do i = 1, n
    a(i) = a(i) + 10
  end do
  !$omp target update to(a)
  !$omp target map(to: a) map(from: b) map(tofrom: host_flag)
    host_flag = merge(1, 0, omp_is_initial_device())
    do i = 1, n
      b(i) = 2*a(i) + 1
    end do
  !$omp end target
  !$omp target update from(b(1:n))
  !$omp target exit data map(release: a, b)
  ok = all(b == ref)
  print '(a,i0,a,a)', 'RESULT ran_on_host=', host_flag, ' check=', merge('pass', 'fail', ok)
  deallocate(a, b)
end program gen_prog