[Flang][OpenMP] crashes with OpenMP 'parallel do collapse' and 'do concurrent' nested loops

[k-arrows]

Reproducer:
https://godbolt.org/z/v9zsvvr7G

integer :: i, j
!$omp parallel do collapse(2)
do i = 1, 1
  do concurrent (j = 1:2)
    print *, j
  end do
end do
end

Backtrace:

flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang -fc1 -triple x86_64-unknown-linux-gnu -S -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -mllvm -x86-asm-syntax=intel -fopenmp -resource-dir /opt/compiler-explorer/clang-llvmflang-trunk-20250613/lib/clang/21 -mframe-pointer=all -o /app/output.s -x f95 /app/example.f90
 #0 0x0000000003eb5b48 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3eb5b48)
 #1 0x0000000003eb3704 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #2 0x0000739460842520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #3 0x0000000002085f69 Fortran::lower::omp::collectLoopRelatedInfo(Fortran::lower::AbstractConverter&, mlir::Location, Fortran::lower::pft::Evaluation&, llvm::SmallVector<Fortran::lower::omp::Clause, 0u> const&, mlir::omp::LoopRelatedClauseOps&, llvm::SmallVectorImpl<Fortran::semantics::Symbol const*>&) (.cold) Utils.cpp:0:0
 #4 0x00000000046a51da genLoopNestClauses(Fortran::lower::AbstractConverter&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, llvm::SmallVector<Fortran::lower::omp::Clause, 0u> const&, mlir::Location, mlir::omp::detail::Clauses<mlir::omp::LoopRelatedClauseOps>&, llvm::SmallVectorImpl<Fortran::semantics::Symbol const*>&) (.constprop.0) OpenMP.cpp:0:0
 #5 0x00000000046b9389 genStandaloneDo(Fortran::lower::AbstractConverter&, Fortran::lower::SymMap&, Fortran::lower::StatementContext&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, mlir::Location, llvm::SmallVector<tomp::DirectiveWithClauses<Fortran::lower::omp::Clause>, 0u> const&, tomp::DirectiveWithClauses<Fortran::lower::omp::Clause> const*) OpenMP.cpp:0:0
 #6 0x00000000046bf438 genOMPDispatch(Fortran::lower::AbstractConverter&, Fortran::lower::SymMap&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, mlir::Location, llvm::SmallVector<tomp::DirectiveWithClauses<Fortran::lower::omp::Clause>, 0u> const&, tomp::DirectiveWithClauses<Fortran::lower::omp::Clause> const*) OpenMP.cpp:0:0
 #7 0x00000000046b523b createBodyOfOp(mlir::Operation&, OpWithBodyGenInfo const&, llvm::SmallVector<tomp::DirectiveWithClauses<Fortran::lower::omp::Clause>, 0u> const&, tomp::DirectiveWithClauses<Fortran::lower::omp::Clause> const*) OpenMP.cpp:0:0
 #8 0x00000000046b6666 genParallelOp(Fortran::lower::AbstractConverter&, Fortran::lower::SymMap&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, mlir::Location, llvm::SmallVector<tomp::DirectiveWithClauses<Fortran::lower::omp::Clause>, 0u> const&, tomp::DirectiveWithClauses<Fortran::lower::omp::Clause> const*, mlir::omp::detail::Clauses<mlir::omp::AllocateClauseOps, mlir::omp::IfClauseOps, mlir::omp::NumThreadsClauseOps, mlir::omp::PrivateClauseOps, mlir::omp::ProcBindClauseOps, mlir::omp::ReductionClauseOps>&, Fortran::common::openmp::EntryBlockArgs const&, Fortran::lower::omp::DataSharingProcessor*, bool) OpenMP.cpp:0:0
 #9 0x00000000046bea15 genOMPDispatch(Fortran::lower::AbstractConverter&, Fortran::lower::SymMap&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, mlir::Location, llvm::SmallVector<tomp::DirectiveWithClauses<Fortran::lower::omp::Clause>, 0u> const&, tomp::DirectiveWithClauses<Fortran::lower::omp::Clause> const*) OpenMP.cpp:0:0
#10 0x00000000046c4a99 Fortran::lower::genOpenMPConstruct(Fortran::lower::AbstractConverter&, Fortran::lower::SymMap&, Fortran::semantics::SemanticsContext&, Fortran::lower::pft::Evaluation&, Fortran::parser::OpenMPConstruct const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x46c4a99)
#11 0x000000000433e280 void Fortran::common::log2visit::Log2VisitHelper<47ul, 93ul, void, Fortran::common::visitors<auto Fortran::lower::pft::ReferenceVariantBase<true, Fortran::parser::AllocateStmt, Fortran::parser::AssignmentStmt, Fortran::parser::BackspaceStmt, Fortran::parser::CallStmt, Fortran::parser::CloseStmt, Fortran::parser::ContinueStmt, Fortran::parser::CycleStmt, Fortran::parser::DeallocateStmt, Fortran::parser::EndfileStmt, Fortran::parser::EventPostStmt, Fortran::parser::EventWaitStmt, Fortran::parser::ExitStmt, Fortran::parser::FailImageStmt, Fortran::parser::FlushStmt, Fortran::parser::FormTeamStmt, Fortran::parser::GotoStmt, Fortran::parser::IfStmt, Fortran::parser::InquireStmt, Fortran::parser::LockStmt, Fortran::parser::NotifyWaitStmt, Fortran::parser::NullifyStmt, Fortran::parser::OpenStmt, Fortran::parser::PointerAssignmentStmt, Fortran::parser::PrintStmt, Fortran::parser::ReadStmt, Fortran::parser::ReturnStmt, Fortran::parser::RewindStmt, Fortran::parser::StopStmt, Fortran::parser::SyncAllStmt, Fortran::parser::SyncImagesStmt, Fortran::parser::SyncMemoryStmt, Fortran::parser::SyncTeamStmt, Fortran::parser::UnlockStmt, Fortran::parser::WaitStmt, Fortran::parser::WhereStmt, Fortran::parser::WriteStmt, Fortran::parser::ComputedGotoStmt, Fortran::parser::ForallStmt, Fortran::parser::ArithmeticIfStmt, Fortran::parser::AssignStmt, Fortran::parser::AssignedGotoStmt, Fortran::parser::PauseStmt, Fortran::parser::EntryStmt, Fortran::parser::FormatStmt, Fortran::parser::AssociateStmt, Fortran::parser::EndAssociateStmt, Fortran::parser::BlockStmt, Fortran::parser::EndBlockStmt, Fortran::parser::SelectCaseStmt, Fortran::parser::CaseStmt, Fortran::parser::EndSelectStmt, Fortran::parser::ChangeTeamStmt, Fortran::parser::EndChangeTeamStmt, Fortran::parser::CriticalStmt, Fortran::parser::EndCriticalStmt, Fortran::parser::NonLabelDoStmt, Fortran::parser::EndDoStmt, Fortran::parser::IfThenStmt, Fortran::parser::ElseIfStmt, Fortran::parser::ElseStmt, Fortran::parser::EndIfStmt, Fortran::parser::SelectRankStmt, Fortran::parser::SelectRankCaseStmt, Fortran::parser::SelectTypeStmt, Fortran::parser::TypeGuardStmt, Fortran::parser::WhereConstructStmt, Fortran::parser::MaskedElsewhereStmt, Fortran::parser::ElsewhereStmt, Fortran::parser::EndWhereStmt, Fortran::parser::ForallConstructStmt, Fortran::parser::EndForallStmt, Fortran::parser::EndProgramStmt, Fortran::parser::EndFunctionStmt, Fortran::parser::EndSubroutineStmt, Fortran::parser::EndMpSubprogramStmt, Fortran::parser::AssociateConstruct, Fortran::parser::BlockConstruct, Fortran::parser::CaseConstruct, Fortran::parser::ChangeTeamConstruct, Fortran::parser::CriticalConstruct, Fortran::parser::DoConstruct, Fortran::parser::IfConstruct, Fortran::parser::SelectRankConstruct, Fortran::parser::SelectTypeConstruct, Fortran::parser::WhereConstruct, Fortran::parser::ForallConstruct, Fortran::parser::CompilerDirective, Fortran::parser::OpenACCConstruct, Fortran::parser::OpenACCRoutineConstruct, Fortran::parser::OpenACCDeclarativeConstruct, Fortran::parser::OpenMPConstruct, Fortran::parser::OpenMPDeclarativeConstruct, Fortran::parser::OmpEndLoopDirective, Fortran::parser::CUFKernelDoConstruct>::visit<(anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&, bool)::'lambda'(auto const&)>(auto&&) const::'lambda'(auto)>, std::variant<Fortran::common::Reference<Fortran::parser::AllocateStmt const>, Fortran::common::Reference<Fortran::parser::AssignmentStmt const>, Fortran::common::Reference<Fortran::parser::BackspaceStmt const>, Fortran::common::Reference<Fortran::parser::CallStmt const>, Fortran::common::Reference<Fortran::parser::CloseStmt const>, Fortran::common::Reference<Fortran::parser::ContinueStmt const>, Fortran::common::Reference<Fortran::parser::CycleStmt const>, Fortran::common::Reference<Fortran::parser::DeallocateStmt const>, Fortran::common::Reference<Fortran::parser::EndfileStmt const>, Fortran::common::Reference<Fortran::parser::EventPostStmt const>, Fortran::common::Reference<Fortran::parser::EventWaitStmt const>, Fortran::common::Reference<Fortran::parser::ExitStmt const>, Fortran::common::Reference<Fortran::parser::FailImageStmt const>, Fortran::common::Reference<Fortran::parser::FlushStmt const>, Fortran::common::Reference<Fortran::parser::FormTeamStmt const>, Fortran::common::Reference<Fortran::parser::GotoStmt const>, Fortran::common::Reference<Fortran::parser::IfStmt const>, Fortran::common::Reference<Fortran::parser::InquireStmt const>, Fortran::common::Reference<Fortran::parser::LockStmt const>, Fortran::common::Reference<Fortran::parser::NotifyWaitStmt const>, Fortran::common::Reference<Fortran::parser::NullifyStmt const>, Fortran::common::Reference<Fortran::parser::OpenStmt const>, Fortran::common::Reference<Fortran::parser::PointerAssignmentStmt const>, Fortran::common::Reference<Fortran::parser::PrintStmt const>, Fortran::common::Reference<Fortran::parser::ReadStmt const>, Fortran::common::Reference<Fortran::parser::ReturnStmt const>, Fortran::common::Reference<Fortran::parser::RewindStmt const>, Fortran::common::Reference<Fortran::parser::StopStmt const>, Fortran::common::Reference<Fortran::parser::SyncAllStmt const>, Fortran::common::Reference<Fortran::parser::SyncImagesStmt const>, Fortran::common::Reference<Fortran::parser::SyncMemoryStmt const>, Fortran::common::Reference<Fortran::parser::SyncTeamStmt const>, Fortran::common::Reference<Fortran::parser::UnlockStmt const>, Fortran::common::Reference<Fortran::parser::WaitStmt const>, Fortran::common::Reference<Fortran::parser::WhereStmt const>, Fortran::common::Reference<Fortran::parser::WriteStmt const>, Fortran::common::Reference<Fortran::parser::ComputedGotoStmt const>, Fortran::common::Reference<Fortran::parser::ForallStmt const>, Fortran::common::Reference<Fortran::parser::ArithmeticIfStmt const>, Fortran::common::Reference<Fortran::parser::AssignStmt const>, Fortran::common::Reference<Fortran::parser::AssignedGotoStmt const>, Fortran::common::Reference<Fortran::parser::PauseStmt const>, Fortran::common::Reference<Fortran::parser::EntryStmt const>, Fortran::common::Reference<Fortran::parser::FormatStmt const>, Fortran::common::Reference<Fortran::parser::AssociateStmt const>, Fortran::common::Reference<Fortran::parser::EndAssociateStmt const>, Fortran::common::Reference<Fortran::parser::BlockStmt const>, Fortran::common::Reference<Fortran::parser::EndBlockStmt const>, Fortran::common::Reference<Fortran::parser::SelectCaseStmt const>, Fortran::common::Reference<Fortran::parser::CaseStmt const>, Fortran::common::Reference<Fortran::parser::EndSelectStmt const>, Fortran::common::Reference<Fortran::parser::ChangeTeamStmt const>, Fortran::common::Reference<Fortran::parser::EndChangeTeamStmt const>, Fortran::common::Reference<Fortran::parser::CriticalStmt const>, Fortran::common::Reference<Fortran::parser::EndCriticalStmt const>, Fortran::common::Reference<Fortran::parser::NonLabelDoStmt const>, Fortran::common::Reference<Fortran::parser::EndDoStmt const>, Fortran::common::Reference<Fortran::parser::IfThenStmt const>, Fortran::common::Reference<Fortran::parser::ElseIfStmt const>, Fortran::common::Reference<Fortran::parser::ElseStmt const>, Fortran::common::Reference<Fortran::parser::EndIfStmt const>, Fortran::common::Reference<Fortran::parser::SelectRankStmt const>, Fortran::common::Reference<Fortran::parser::SelectRankCaseStmt const>, Fortran::common::Reference<Fortran::parser::SelectTypeStmt const>, Fortran::common::Reference<Fortran::parser::TypeGuardStmt const>, Fortran::common::Reference<Fortran::parser::WhereConstructStmt const>, Fortran::common::Reference<Fortran::parser::MaskedElsewhereStmt const>, Fortran::common::Reference<Fortran::parser::ElsewhereStmt const>, Fortran::common::Reference<Fortran::parser::EndWhereStmt const>, Fortran::common::Reference<Fortran::parser::ForallConstructStmt const>, Fortran::common::Reference<Fortran::parser::EndForallStmt const>, Fortran::common::Reference<Fortran::parser::EndProgramStmt const>, Fortran::common::Reference<Fortran::parser::EndFunctionStmt const>, Fortran::common::Reference<Fortran::parser::EndSubroutineStmt const>, Fortran::common::Reference<Fortran::parser::EndMpSubprogramStmt const>, Fortran::common::Reference<Fortran::parser::AssociateConstruct const>, Fortran::common::Reference<Fortran::parser::BlockConstruct const>, Fortran::common::Reference<Fortran::parser::CaseConstruct const>, Fortran::common::Reference<Fortran::parser::ChangeTeamConstruct const>, Fortran::common::Reference<Fortran::parser::CriticalConstruct const>, Fortran::common::Reference<Fortran::parser::DoConstruct const>, Fortran::common::Reference<Fortran::parser::IfConstruct const>, Fortran::common::Reference<Fortran::parser::SelectRankConstruct const>, Fortran::common::Reference<Fortran::parser::SelectTypeConstruct const>, Fortran::common::Reference<Fortran::parser::WhereConstruct const>, Fortran::common::Reference<Fortran::parser::ForallConstruct const>, Fortran::common::Reference<Fortran::parser::CompilerDirective const>, Fortran::common::Reference<Fortran::parser::OpenACCConstruct const>, Fortran::common::Reference<Fortran::parser::OpenACCRoutineConstruct const>, Fortran::common::Reference<Fortran::parser::OpenACCDeclarativeConstruct const>, Fortran::common::Reference<Fortran::parser::OpenMPConstruct const>, Fortran::common::Reference<Fortran::parser::OpenMPDeclarativeConstruct const>, Fortran::common::Reference<Fortran::parser::OmpEndLoopDirective const>, Fortran::common::Reference<Fortran::parser::CUFKernelDoConstruct const>> const&>(Fortran::common::visitors<auto Fortran::lower::pft::ReferenceVariantBase<true, Fortran::parser::AllocateStmt, Fortran::parser::AssignmentStmt, Fortran::parser::BackspaceStmt, Fortran::parser::CallStmt, Fortran::parser::CloseStmt, Fortran::parser::ContinueStmt, Fortran::parser::CycleStmt, Fortran::parser::DeallocateStmt, Fortran::parser::EndfileStmt, Fortran::parser::EventPostStmt, Fortran::parser::EventWaitStmt, Fortran::parser::ExitStmt, Fortran::parser::FailImageStmt, Fortran::parser::FlushStmt, Fortran::parser::FormTeamStmt, Fortran::parser::GotoStmt, Fortran::parser::IfStmt, Fortran::parser::InquireStmt, Fortran::parser::LockStmt, Fortran::parser::NotifyWaitStmt, Fortran::parser::NullifyStmt, Fortran::parser::OpenStmt, Fortran::parser::PointerAssignmentStmt, Fortran::parser::PrintStmt, Fortran::parser::ReadStmt, Fortran::parser::ReturnStmt, Fortran::parser::RewindStmt, Fortran::parser::StopStmt, Fortran::parser::SyncAllStmt, Fortran::parser::SyncImagesStmt, Fortran::parser::SyncMemoryStmt, Fortran::parser::SyncTeamStmt, Fortran::parser::UnlockStmt, Fortran::parser::WaitStmt, Fortran::parser::WhereStmt, Fortran::parser::WriteStmt, Fortran::parser::ComputedGotoStmt, Fortran::parser::ForallStmt, Fortran::parser::ArithmeticIfStmt, Fortran::parser::AssignStmt, Fortran::parser::AssignedGotoStmt, Fortran::parser::PauseStmt, Fortran::parser::EntryStmt, Fortran::parser::FormatStmt, Fortran::parser::AssociateStmt, Fortran::parser::EndAssociateStmt, Fortran::parser::BlockStmt, Fortran::parser::EndBlockStmt, Fortran::parser::SelectCaseStmt, Fortran::parser::CaseStmt, Fortran::parser::EndSelectStmt, Fortran::parser::ChangeTeamStmt, Fortran::parser::EndChangeTeamStmt, Fortran::parser::CriticalStmt, Fortran::parser::EndCriticalStmt, Fortran::parser::NonLabelDoStmt, Fortran::parser::EndDoStmt, Fortran::parser::IfThenStmt, Fortran::parser::ElseIfStmt, Fortran::parser::ElseStmt, Fortran::parser::EndIfStmt, Fortran::parser::SelectRankStmt, Fortran::parser::SelectRankCaseStmt, Fortran::parser::SelectTypeStmt, Fortran::parser::TypeGuardStmt, Fortran::parser::WhereConstructStmt, Fortran::parser::MaskedElsewhereStmt, Fortran::parser::ElsewhereStmt, Fortran::parser::EndWhereStmt, Fortran::parser::ForallConstructStmt, Fortran::parser::EndForallStmt, Fortran::parser::EndProgramStmt, Fortran::parser::EndFunctionStmt, Fortran::parser::EndSubroutineStmt, Fortran::parser::EndMpSubprogramStmt, Fortran::parser::AssociateConstruct, Fortran::parser::BlockConstruct, Fortran::parser::CaseConstruct, Fortran::parser::ChangeTeamConstruct, Fortran::parser::CriticalConstruct, Fortran::parser::DoConstruct, Fortran::parser::IfConstruct, Fortran::parser::SelectRankConstruct, Fortran::parser::SelectTypeConstruct, Fortran::parser::WhereConstruct, Fortran::parser::ForallConstruct, Fortran::parser::CompilerDirective, Fortran::parser::OpenACCConstruct, Fortran::parser::OpenACCRoutineConstruct, Fortran::parser::OpenACCDeclarativeConstruct, Fortran::parser::OpenMPConstruct, Fortran::parser::OpenMPDeclarativeConstruct, Fortran::parser::OmpEndLoopDirective, Fortran::parser::CUFKernelDoConstruct>::visit<(anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&, bool)::'lambda'(auto const&)>(auto&&) const::'lambda'(auto)>&&, unsigned long, std::variant<Fortran::common::Reference<Fortran::parser::AllocateStmt const>, Fortran::common::Reference<Fortran::parser::AssignmentStmt const>, Fortran::common::Reference<Fortran::parser::BackspaceStmt const>, Fortran::common::Reference<Fortran::parser::CallStmt const>, Fortran::common::Reference<Fortran::parser::CloseStmt const>, Fortran::common::Reference<Fortran::parser::ContinueStmt const>, Fortran::common::Reference<Fortran::parser::CycleStmt const>, Fortran::common::Reference<Fortran::parser::DeallocateStmt const>, Fortran::common::Reference<Fortran::parser::EndfileStmt const>, Fortran::common::Reference<Fortran::parser::EventPostStmt const>, Fortran::common::Reference<Fortran::parser::EventWaitStmt const>, Fortran::common::Reference<Fortran::parser::ExitStmt const>, Fortran::common::Reference<Fortran::parser::FailImageStmt const>, Fortran::common::Reference<Fortran::parser::FlushStmt const>, Fortran::common::Reference<Fortran::parser::FormTeamStmt const>, Fortran::common::Reference<Fortran::parser::GotoStmt const>, Fortran::common::Reference<Fortran::parser::IfStmt const>, Fortran::common::Reference<Fortran::parser::InquireStmt const>, Fortran::common::Reference<Fortran::parser::LockStmt const>, Fortran::common::Reference<Fortran::parser::NotifyWaitStmt const>, Fortran::common::Reference<Fortran::parser::NullifyStmt const>, Fortran::common::Reference<Fortran::parser::OpenStmt const>, Fortran::common::Reference<Fortran::parser::PointerAssignmentStmt const>, Fortran::common::Reference<Fortran::parser::PrintStmt const>, Fortran::common::Reference<Fortran::parser::ReadStmt const>, Fortran::common::Reference<Fortran::parser::ReturnStmt const>, Fortran::common::Reference<Fortran::parser::RewindStmt const>, Fortran::common::Reference<Fortran::parser::StopStmt const>, Fortran::common::Reference<Fortran::parser::SyncAllStmt const>, Fortran::common::Reference<Fortran::parser::SyncImagesStmt const>, Fortran::common::Reference<Fortran::parser::SyncMemoryStmt const>, Fortran::common::Reference<Fortran::parser::SyncTeamStmt const>, Fortran::common::Reference<Fortran::parser::UnlockStmt const>, Fortran::common::Reference<Fortran::parser::WaitStmt const>, Fortran::common::Reference<Fortran::parser::WhereStmt const>, Fortran::common::Reference<Fortran::parser::WriteStmt const>, Fortran::common::Reference<Fortran::parser::ComputedGotoStmt const>, Fortran::common::Reference<Fortran::parser::ForallStmt const>, Fortran::common::Reference<Fortran::parser::ArithmeticIfStmt const>, Fortran::common::Reference<Fortran::parser::AssignStmt const>, Fortran::common::Reference<Fortran::parser::AssignedGotoStmt const>, Fortran::common::Reference<Fortran::parser::PauseStmt const>, Fortran::common::Reference<Fortran::parser::EntryStmt const>, Fortran::common::Reference<Fortran::parser::FormatStmt const>, Fortran::common::Reference<Fortran::parser::AssociateStmt const>, Fortran::common::Reference<Fortran::parser::EndAssociateStmt const>, Fortran::common::Reference<Fortran::parser::BlockStmt const>, Fortran::common::Reference<Fortran::parser::EndBlockStmt const>, Fortran::common::Reference<Fortran::parser::SelectCaseStmt const>, Fortran::common::Reference<Fortran::parser::CaseStmt const>, Fortran::common::Reference<Fortran::parser::EndSelectStmt const>, Fortran::common::Reference<Fortran::parser::ChangeTeamStmt const>, Fortran::common::Reference<Fortran::parser::EndChangeTeamStmt const>, Fortran::common::Reference<Fortran::parser::CriticalStmt const>, Fortran::common::Reference<Fortran::parser::EndCriticalStmt const>, Fortran::common::Reference<Fortran::parser::NonLabelDoStmt const>, Fortran::common::Reference<Fortran::parser::EndDoStmt const>, Fortran::common::Reference<Fortran::parser::IfThenStmt const>, Fortran::common::Reference<Fortran::parser::ElseIfStmt const>, Fortran::common::Reference<Fortran::parser::ElseStmt const>, Fortran::common::Reference<Fortran::parser::EndIfStmt const>, Fortran::common::Reference<Fortran::parser::SelectRankStmt const>, Fortran::common::Reference<Fortran::parser::SelectRankCaseStmt const>, Fortran::common::Reference<Fortran::parser::SelectTypeStmt const>, Fortran::common::Reference<Fortran::parser::TypeGuardStmt const>, Fortran::common::Reference<Fortran::parser::WhereConstructStmt const>, Fortran::common::Reference<Fortran::parser::MaskedElsewhereStmt const>, Fortran::common::Reference<Fortran::parser::ElsewhereStmt const>, Fortran::common::Reference<Fortran::parser::EndWhereStmt const>, Fortran::common::Reference<Fortran::parser::ForallConstructStmt const>, Fortran::common::Reference<Fortran::parser::EndForallStmt const>, Fortran::common::Reference<Fortran::parser::EndProgramStmt const>, Fortran::common::Reference<Fortran::parser::EndFunctionStmt const>, Fortran::common::Reference<Fortran::parser::EndSubroutineStmt const>, Fortran::common::Reference<Fortran::parser::EndMpSubprogramStmt const>, Fortran::common::Reference<Fortran::parser::AssociateConstruct const>, Fortran::common::Reference<Fortran::parser::BlockConstruct const>, Fortran::common::Reference<Fortran::parser::CaseConstruct const>, Fortran::common::Reference<Fortran::parser::ChangeTeamConstruct const>, Fortran::common::Reference<Fortran::parser::CriticalConstruct const>, Fortran::common::Reference<Fortran::parser::DoConstruct const>, Fortran::common::Reference<Fortran::parser::IfConstruct const>, Fortran::common::Reference<Fortran::parser::SelectRankConstruct const>, Fortran::common::Reference<Fortran::parser::SelectTypeConstruct const>, Fortran::common::Reference<Fortran::parser::WhereConstruct const>, Fortran::common::Reference<Fortran::parser::ForallConstruct const>, Fortran::common::Reference<Fortran::parser::CompilerDirective const>, Fortran::common::Reference<Fortran::parser::OpenACCConstruct const>, Fortran::common::Reference<Fortran::parser::OpenACCRoutineConstruct const>, Fortran::common::Reference<Fortran::parser::OpenACCDeclarativeConstruct const>, Fortran::common::Reference<Fortran::parser::OpenMPConstruct const>, Fortran::common::Reference<Fortran::parser::OpenMPDeclarativeConstruct const>, Fortran::common::Reference<Fortran::parser::OmpEndLoopDirective const>, Fortran::common::Reference<Fortran::parser::CUFKernelDoConstruct const>> const&) Bridge.cpp:0:0
#12 0x000000000433e64c (anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&, bool) (.constprop.0) Bridge.cpp:0:0
#13 0x0000000004342c7c (anonymous namespace)::FirConverter::lowerFunc(Fortran::lower::pft::FunctionLikeUnit&) Bridge.cpp:0:0
#14 0x0000000004344df4 Fortran::lower::LoweringBridge::lower(Fortran::parser::Program const&, Fortran::semantics::SemanticsContext const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x4344df4)
#15 0x00000000041c1906 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x41c1906)
#16 0x0000000003f0c9b5 Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&, Fortran::frontend::FrontendInputFile const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3f0c9b5)
#17 0x0000000003efb547 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3efb547)
#18 0x0000000003f16b13 Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3f16b13)
#19 0x000000000220a47a fc1_main(llvm::ArrayRef<char const*>, char const*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x220a47a)
#20 0x00000000020bf8f6 main (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x20bf8f6)
#21 0x0000739460829d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#22 0x0000739460829e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#23 0x0000000002208e45 _start (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x2208e45)
flang-21: error: unable to execute command: Segmentation fault (core dumped)
flang-21: error: flang frontend command failed due to signal (use -v to see invocation)
flang version 21.0.0git (https://github.com/llvm/llvm-project.git 22f9b4aa1dad597d908be77be1e10ba4c77330ce)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
flang-21: note: diagnostic msg: 

With assertion-enabled flang, the above reproducer hits the following assertion failure:

llvm-project/flang/lib/Lower/OpenMP/Utils.cpp:652: bool Fortran::lower::omp::collectLoopRelatedInfo(lower::AbstractConverter &, mlir::Location, lower::pft::Evaluation &, const omp::List<omp::Clause> &, mlir::omp::LoopRelatedClauseOps &, llvm::SmallVectorImpl<const semantics::Symbol *> &): Assertion `bounds && "Expected bounds for worksharing do loop"' failed.

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: None (k-arrows)

Reproducer: https://godbolt.org/z/v9zsvvr7G ```f90 integer :: i, j !$omp parallel do collapse(2) do i = 1, 1 do concurrent (j = 1:2) print *, j end do end do end ```

Backtrace:

flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang -fc1 -triple x86_64-unknown-linux-gnu -S -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -mllvm -x86-asm-syntax=intel -fopenmp -resource-dir /opt/compiler-explorer/clang-llvmflang-trunk-20250613/lib/clang/21 -mframe-pointer=all -o /app/output.s -x f95 /app/example.f90
 #<!-- -->0 0x0000000003eb5b48 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3eb5b48)
 #<!-- -->1 0x0000000003eb3704 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #<!-- -->2 0x0000739460842520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->3 0x0000000002085f69 Fortran::lower::omp::collectLoopRelatedInfo(Fortran::lower::AbstractConverter&amp;, mlir::Location, Fortran::lower::pft::Evaluation&amp;, llvm::SmallVector&lt;Fortran::lower::omp::Clause, 0u&gt; const&amp;, mlir::omp::LoopRelatedClauseOps&amp;, llvm::SmallVectorImpl&lt;Fortran::semantics::Symbol const*&gt;&amp;) (.cold) Utils.cpp:0:0
 #<!-- -->4 0x00000000046a51da genLoopNestClauses(Fortran::lower::AbstractConverter&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, llvm::SmallVector&lt;Fortran::lower::omp::Clause, 0u&gt; const&amp;, mlir::Location, mlir::omp::detail::Clauses&lt;mlir::omp::LoopRelatedClauseOps&gt;&amp;, llvm::SmallVectorImpl&lt;Fortran::semantics::Symbol const*&gt;&amp;) (.constprop.0) OpenMP.cpp:0:0
 #<!-- -->5 0x00000000046b9389 genStandaloneDo(Fortran::lower::AbstractConverter&amp;, Fortran::lower::SymMap&amp;, Fortran::lower::StatementContext&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, mlir::Location, llvm::SmallVector&lt;tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt;, 0u&gt; const&amp;, tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt; const*) OpenMP.cpp:0:0
 #<!-- -->6 0x00000000046bf438 genOMPDispatch(Fortran::lower::AbstractConverter&amp;, Fortran::lower::SymMap&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, mlir::Location, llvm::SmallVector&lt;tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt;, 0u&gt; const&amp;, tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt; const*) OpenMP.cpp:0:0
 #<!-- -->7 0x00000000046b523b createBodyOfOp(mlir::Operation&amp;, OpWithBodyGenInfo const&amp;, llvm::SmallVector&lt;tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt;, 0u&gt; const&amp;, tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt; const*) OpenMP.cpp:0:0
 #<!-- -->8 0x00000000046b6666 genParallelOp(Fortran::lower::AbstractConverter&amp;, Fortran::lower::SymMap&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, mlir::Location, llvm::SmallVector&lt;tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt;, 0u&gt; const&amp;, tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt; const*, mlir::omp::detail::Clauses&lt;mlir::omp::AllocateClauseOps, mlir::omp::IfClauseOps, mlir::omp::NumThreadsClauseOps, mlir::omp::PrivateClauseOps, mlir::omp::ProcBindClauseOps, mlir::omp::ReductionClauseOps&gt;&amp;, Fortran::common::openmp::EntryBlockArgs const&amp;, Fortran::lower::omp::DataSharingProcessor*, bool) OpenMP.cpp:0:0
 #<!-- -->9 0x00000000046bea15 genOMPDispatch(Fortran::lower::AbstractConverter&amp;, Fortran::lower::SymMap&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, mlir::Location, llvm::SmallVector&lt;tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt;, 0u&gt; const&amp;, tomp::DirectiveWithClauses&lt;Fortran::lower::omp::Clause&gt; const*) OpenMP.cpp:0:0
#<!-- -->10 0x00000000046c4a99 Fortran::lower::genOpenMPConstruct(Fortran::lower::AbstractConverter&amp;, Fortran::lower::SymMap&amp;, Fortran::semantics::SemanticsContext&amp;, Fortran::lower::pft::Evaluation&amp;, Fortran::parser::OpenMPConstruct const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x46c4a99)
#<!-- -->11 0x000000000433e280 void Fortran::common::log2visit::Log2VisitHelper&lt;47ul, 93ul, void, Fortran::common::visitors&lt;auto Fortran::lower::pft::ReferenceVariantBase&lt;true, Fortran::parser::AllocateStmt, Fortran::parser::AssignmentStmt, Fortran::parser::BackspaceStmt, Fortran::parser::CallStmt, Fortran::parser::CloseStmt, Fortran::parser::ContinueStmt, Fortran::parser::CycleStmt, Fortran::parser::DeallocateStmt, Fortran::parser::EndfileStmt, Fortran::parser::EventPostStmt, Fortran::parser::EventWaitStmt, Fortran::parser::ExitStmt, Fortran::parser::FailImageStmt, Fortran::parser::FlushStmt, Fortran::parser::FormTeamStmt, Fortran::parser::GotoStmt, Fortran::parser::IfStmt, Fortran::parser::InquireStmt, Fortran::parser::LockStmt, Fortran::parser::NotifyWaitStmt, Fortran::parser::NullifyStmt, Fortran::parser::OpenStmt, Fortran::parser::PointerAssignmentStmt, Fortran::parser::PrintStmt, Fortran::parser::ReadStmt, Fortran::parser::ReturnStmt, Fortran::parser::RewindStmt, Fortran::parser::StopStmt, Fortran::parser::SyncAllStmt, Fortran::parser::SyncImagesStmt, Fortran::parser::SyncMemoryStmt, Fortran::parser::SyncTeamStmt, Fortran::parser::UnlockStmt, Fortran::parser::WaitStmt, Fortran::parser::WhereStmt, Fortran::parser::WriteStmt, Fortran::parser::ComputedGotoStmt, Fortran::parser::ForallStmt, Fortran::parser::ArithmeticIfStmt, Fortran::parser::AssignStmt, Fortran::parser::AssignedGotoStmt, Fortran::parser::PauseStmt, Fortran::parser::EntryStmt, Fortran::parser::FormatStmt, Fortran::parser::AssociateStmt, Fortran::parser::EndAssociateStmt, Fortran::parser::BlockStmt, Fortran::parser::EndBlockStmt, Fortran::parser::SelectCaseStmt, Fortran::parser::CaseStmt, Fortran::parser::EndSelectStmt, Fortran::parser::ChangeTeamStmt, Fortran::parser::EndChangeTeamStmt, Fortran::parser::CriticalStmt, Fortran::parser::EndCriticalStmt, Fortran::parser::NonLabelDoStmt, Fortran::parser::EndDoStmt, Fortran::parser::IfThenStmt, Fortran::parser::ElseIfStmt, Fortran::parser::ElseStmt, Fortran::parser::EndIfStmt, Fortran::parser::SelectRankStmt, Fortran::parser::SelectRankCaseStmt, Fortran::parser::SelectTypeStmt, Fortran::parser::TypeGuardStmt, Fortran::parser::WhereConstructStmt, Fortran::parser::MaskedElsewhereStmt, Fortran::parser::ElsewhereStmt, Fortran::parser::EndWhereStmt, Fortran::parser::ForallConstructStmt, Fortran::parser::EndForallStmt, Fortran::parser::EndProgramStmt, Fortran::parser::EndFunctionStmt, Fortran::parser::EndSubroutineStmt, Fortran::parser::EndMpSubprogramStmt, Fortran::parser::AssociateConstruct, Fortran::parser::BlockConstruct, Fortran::parser::CaseConstruct, Fortran::parser::ChangeTeamConstruct, Fortran::parser::CriticalConstruct, Fortran::parser::DoConstruct, Fortran::parser::IfConstruct, Fortran::parser::SelectRankConstruct, Fortran::parser::SelectTypeConstruct, Fortran::parser::WhereConstruct, Fortran::parser::ForallConstruct, Fortran::parser::CompilerDirective, Fortran::parser::OpenACCConstruct, Fortran::parser::OpenACCRoutineConstruct, Fortran::parser::OpenACCDeclarativeConstruct, Fortran::parser::OpenMPConstruct, Fortran::parser::OpenMPDeclarativeConstruct, Fortran::parser::OmpEndLoopDirective, Fortran::parser::CUFKernelDoConstruct&gt;::visit&lt;(anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&amp;, bool)::'lambda'(auto const&amp;)&gt;(auto&amp;&amp;) const::'lambda'(auto)&gt;, std::variant&lt;Fortran::common::Reference&lt;Fortran::parser::AllocateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignmentStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::BackspaceStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CloseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ContinueStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CycleStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::DeallocateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndfileStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EventPostStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EventWaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ExitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FailImageStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FlushStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FormTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::GotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::InquireStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::LockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NotifyWaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NullifyStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PointerAssignmentStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PrintStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ReadStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ReturnStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::RewindStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::StopStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncAllStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncImagesStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncMemoryStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::UnlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WriteStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ComputedGotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ArithmeticIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignedGotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PauseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EntryStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FormatStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssociateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndAssociateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::BlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndBlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectCaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndSelectStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ChangeTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndChangeTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CriticalStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndCriticalStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NonLabelDoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndDoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfThenStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElseIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankCaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectTypeStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::TypeGuardStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereConstructStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::MaskedElsewhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElsewhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndWhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallConstructStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndForallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndProgramStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndFunctionStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndSubroutineStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndMpSubprogramStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssociateConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::BlockConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CaseConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::ChangeTeamConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CriticalConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::DoConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectTypeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CompilerDirective const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCRoutineConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCDeclarativeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenMPConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenMPDeclarativeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OmpEndLoopDirective const&gt;, Fortran::common::Reference&lt;Fortran::parser::CUFKernelDoConstruct const&gt;&gt; const&amp;&gt;(Fortran::common::visitors&lt;auto Fortran::lower::pft::ReferenceVariantBase&lt;true, Fortran::parser::AllocateStmt, Fortran::parser::AssignmentStmt, Fortran::parser::BackspaceStmt, Fortran::parser::CallStmt, Fortran::parser::CloseStmt, Fortran::parser::ContinueStmt, Fortran::parser::CycleStmt, Fortran::parser::DeallocateStmt, Fortran::parser::EndfileStmt, Fortran::parser::EventPostStmt, Fortran::parser::EventWaitStmt, Fortran::parser::ExitStmt, Fortran::parser::FailImageStmt, Fortran::parser::FlushStmt, Fortran::parser::FormTeamStmt, Fortran::parser::GotoStmt, Fortran::parser::IfStmt, Fortran::parser::InquireStmt, Fortran::parser::LockStmt, Fortran::parser::NotifyWaitStmt, Fortran::parser::NullifyStmt, Fortran::parser::OpenStmt, Fortran::parser::PointerAssignmentStmt, Fortran::parser::PrintStmt, Fortran::parser::ReadStmt, Fortran::parser::ReturnStmt, Fortran::parser::RewindStmt, Fortran::parser::StopStmt, Fortran::parser::SyncAllStmt, Fortran::parser::SyncImagesStmt, Fortran::parser::SyncMemoryStmt, Fortran::parser::SyncTeamStmt, Fortran::parser::UnlockStmt, Fortran::parser::WaitStmt, Fortran::parser::WhereStmt, Fortran::parser::WriteStmt, Fortran::parser::ComputedGotoStmt, Fortran::parser::ForallStmt, Fortran::parser::ArithmeticIfStmt, Fortran::parser::AssignStmt, Fortran::parser::AssignedGotoStmt, Fortran::parser::PauseStmt, Fortran::parser::EntryStmt, Fortran::parser::FormatStmt, Fortran::parser::AssociateStmt, Fortran::parser::EndAssociateStmt, Fortran::parser::BlockStmt, Fortran::parser::EndBlockStmt, Fortran::parser::SelectCaseStmt, Fortran::parser::CaseStmt, Fortran::parser::EndSelectStmt, Fortran::parser::ChangeTeamStmt, Fortran::parser::EndChangeTeamStmt, Fortran::parser::CriticalStmt, Fortran::parser::EndCriticalStmt, Fortran::parser::NonLabelDoStmt, Fortran::parser::EndDoStmt, Fortran::parser::IfThenStmt, Fortran::parser::ElseIfStmt, Fortran::parser::ElseStmt, Fortran::parser::EndIfStmt, Fortran::parser::SelectRankStmt, Fortran::parser::SelectRankCaseStmt, Fortran::parser::SelectTypeStmt, Fortran::parser::TypeGuardStmt, Fortran::parser::WhereConstructStmt, Fortran::parser::MaskedElsewhereStmt, Fortran::parser::ElsewhereStmt, Fortran::parser::EndWhereStmt, Fortran::parser::ForallConstructStmt, Fortran::parser::EndForallStmt, Fortran::parser::EndProgramStmt, Fortran::parser::EndFunctionStmt, Fortran::parser::EndSubroutineStmt, Fortran::parser::EndMpSubprogramStmt, Fortran::parser::AssociateConstruct, Fortran::parser::BlockConstruct, Fortran::parser::CaseConstruct, Fortran::parser::ChangeTeamConstruct, Fortran::parser::CriticalConstruct, Fortran::parser::DoConstruct, Fortran::parser::IfConstruct, Fortran::parser::SelectRankConstruct, Fortran::parser::SelectTypeConstruct, Fortran::parser::WhereConstruct, Fortran::parser::ForallConstruct, Fortran::parser::CompilerDirective, Fortran::parser::OpenACCConstruct, Fortran::parser::OpenACCRoutineConstruct, Fortran::parser::OpenACCDeclarativeConstruct, Fortran::parser::OpenMPConstruct, Fortran::parser::OpenMPDeclarativeConstruct, Fortran::parser::OmpEndLoopDirective, Fortran::parser::CUFKernelDoConstruct&gt;::visit&lt;(anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&amp;, bool)::'lambda'(auto const&amp;)&gt;(auto&amp;&amp;) const::'lambda'(auto)&gt;&amp;&amp;, unsigned long, std::variant&lt;Fortran::common::Reference&lt;Fortran::parser::AllocateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignmentStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::BackspaceStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CloseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ContinueStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CycleStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::DeallocateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndfileStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EventPostStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EventWaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ExitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FailImageStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FlushStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FormTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::GotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::InquireStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::LockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NotifyWaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NullifyStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PointerAssignmentStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PrintStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ReadStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ReturnStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::RewindStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::StopStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncAllStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncImagesStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncMemoryStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SyncTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::UnlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WaitStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WriteStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ComputedGotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ArithmeticIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssignedGotoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::PauseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EntryStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::FormatStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssociateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndAssociateStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::BlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndBlockStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectCaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndSelectStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ChangeTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndChangeTeamStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::CriticalStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndCriticalStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::NonLabelDoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndDoStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfThenStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElseIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndIfStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankCaseStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectTypeStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::TypeGuardStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereConstructStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::MaskedElsewhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ElsewhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndWhereStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallConstructStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndForallStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndProgramStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndFunctionStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndSubroutineStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::EndMpSubprogramStmt const&gt;, Fortran::common::Reference&lt;Fortran::parser::AssociateConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::BlockConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CaseConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::ChangeTeamConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CriticalConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::DoConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::IfConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectRankConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::SelectTypeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::WhereConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::ForallConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::CompilerDirective const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCRoutineConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenACCDeclarativeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenMPConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OpenMPDeclarativeConstruct const&gt;, Fortran::common::Reference&lt;Fortran::parser::OmpEndLoopDirective const&gt;, Fortran::common::Reference&lt;Fortran::parser::CUFKernelDoConstruct const&gt;&gt; const&amp;) Bridge.cpp:0:0
#<!-- -->12 0x000000000433e64c (anonymous namespace)::FirConverter::genFIR(Fortran::lower::pft::Evaluation&amp;, bool) (.constprop.0) Bridge.cpp:0:0
#<!-- -->13 0x0000000004342c7c (anonymous namespace)::FirConverter::lowerFunc(Fortran::lower::pft::FunctionLikeUnit&amp;) Bridge.cpp:0:0
#<!-- -->14 0x0000000004344df4 Fortran::lower::LoweringBridge::lower(Fortran::parser::Program const&amp;, Fortran::semantics::SemanticsContext const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x4344df4)
#<!-- -->15 0x00000000041c1906 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x41c1906)
#<!-- -->16 0x0000000003f0c9b5 Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&amp;, Fortran::frontend::FrontendInputFile const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3f0c9b5)
#<!-- -->17 0x0000000003efb547 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3efb547)
#<!-- -->18 0x0000000003f16b13 Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x3f16b13)
#<!-- -->19 0x000000000220a47a fc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x220a47a)
#<!-- -->20 0x00000000020bf8f6 main (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x20bf8f6)
#<!-- -->21 0x0000739460829d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->22 0x0000739460829e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->23 0x0000000002208e45 _start (/opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin/flang+0x2208e45)
flang-21: error: unable to execute command: Segmentation fault (core dumped)
flang-21: error: flang frontend command failed due to signal (use -v to see invocation)
flang version 21.0.0git (https://github.com/llvm/llvm-project.git 22f9b4aa1dad597d908be77be1e10ba4c77330ce)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-llvmflang-trunk-20250613/bin
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
flang-21: note: diagnostic msg: 

With assertion-enabled flang, the above reproducer hits the following assertion failure:

llvm-project/flang/lib/Lower/OpenMP/Utils.cpp:652: bool Fortran::lower::omp::collectLoopRelatedInfo(lower::AbstractConverter &, mlir::Location, lower::pft::Evaluation &, const omp::List<omp::Clause> &, mlir::omp::LoopRelatedClauseOps &, llvm::SmallVectorImpl<const semantics::Symbol *> &): Assertion `bounds && "Expected bounds for worksharing do loop"' failed.