[flang][OpenACC] stop statement in one construct inside one acc region

[PeixinQiao]

subroutine test_stop_in_region3()
  integer :: x
  !$acc parallel
    x = 3
    if (x > 1) stop x
  !$acc end parallel
end

$ bbc -emit-fir -fopenacc test.f90 
error: loc("/home/qpx/compilers/llvm-community/example/fix-exit-region/acc/test.f90":4:5): operation with block successors must terminate its parent block
FATAL: verification of lowering to FIR failed

[llvmbot]

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[clementval]

Didn't you work on a patch for that (https://reviews.llvm.org/D129969)

[PeixinQiao]

@clementval I am rebasing it. I found they are different problems. If the stop statement is in one OpenMP/OpenACC region, D129969 will handle it by removing fir.unreachable. If the stop statement is in one if construct and if construct is in one OpenMP/OpenACC region, the fir.unreachable will not be removed. This case is OK in OpenMP, but it crash in OpenACC.

[llvmbot]

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