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[flang][OpenMP] Fix unstrucuted control flow inside a collapsed wsloop #77329

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[flang][OpenMP] Fix unstrucuted control flow inside a collapsed wsloop #77329

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6 changes: 6 additions & 0 deletions flang/lib/Lower/Bridge.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4159,6 +4159,12 @@ class FirConverter : public Fortran::lower::AbstractConverter {
successor == eval.controlSuccessor)
// Exit from a degenerate, empty construct block.
genBranch(eval.parentConstruct->constructExit->block);
else if (successor->block)
// Catch case with omp collapse(n) when dealing with an end-do statement
// which has been collapsed into an outer loop and unstructured control
// flow is used. Create a fall through branch to the successor (the
// outer loop). This is not known to affect other cases.
genBranch(successor->block);
}
}

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63 changes: 63 additions & 0 deletions flang/test/Lower/OpenMP/wsloop-unstructured.f90
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@@ -0,0 +1,63 @@
! RUN: bbc -emit-hlfir -fopenmp -o - %s | FileCheck %s

subroutine sub(imax, jmax, x, y)
integer, intent(in) :: imax, jmax
real, intent(in), dimension(1:imax, 1:jmax) :: x, y

integer :: i, j, ii

! collapse(2) is needed to reproduce the issue
!$omp parallel do collapse(2)
do j = 1, jmax
do i = 1, imax
do ii = 1, imax ! note that this loop is not collapsed
if (x(i,j) < y(ii,j)) then
! exit needed to force unstructured control flow
exit
endif
enddo
enddo
enddo
end subroutine sub

! this is testing that we don't crash generating code for this: in particular
! that all blocks are terminated

! CHECK-LABEL: func.func @_QPsub(
! CHECK-SAME: %[[VAL_0:.*]]: !fir.ref<i32> {fir.bindc_name = "imax"},
! CHECK-SAME: %[[VAL_1:.*]]: !fir.ref<i32> {fir.bindc_name = "jmax"},
! CHECK-SAME: %[[VAL_2:.*]]: !fir.ref<!fir.array<?x?xf32>> {fir.bindc_name = "x"},
! CHECK-SAME: %[[VAL_3:.*]]: !fir.ref<!fir.array<?x?xf32>> {fir.bindc_name = "y"}) {
! [...]
! CHECK: omp.wsloop for (%[[VAL_53:.*]], %[[VAL_54:.*]]) : i32 = ({{.*}}) to ({{.*}}) inclusive step ({{.*}}) {
! [...]
! CHECK: cf.br ^bb1
! CHECK: ^bb1:
! CHECK: cf.br ^bb2
! CHECK: ^bb2:
! [...]
! CHECK: cf.br ^bb3
! CHECK: ^bb3:
! [...]
! CHECK: %[[VAL_63:.*]] = arith.cmpi sgt, %{{.*}}, %{{.*}} : i32
! CHECK: cf.cond_br %[[VAL_63]], ^bb4, ^bb7
! CHECK: ^bb4:
! [...]
! CHECK: %[[VAL_76:.*]] = arith.cmpf olt, %{{.*}}, %{{.*}} fastmath<contract> : f32
! CHECK: cf.cond_br %[[VAL_76]], ^bb5, ^bb6
! CHECK: ^bb5:
! CHECK: cf.br ^bb7
! CHECK: ^bb6:
! [...]
! CHECK: cf.br ^bb3
! CHECK: ^bb7:
! CHECK: cf.br ^bb8
! CHECK: ^bb8:
! CHECK: omp.yield
! CHECK: }
! CHECK: omp.terminator
! CHECK: }
! CHECK: cf.br ^bb1
! CHECK: ^bb1:
! CHECK: return
! CHECK: }