Unverified Commit 5847857b authored by Krzysztof Parzyszek's avatar Krzysztof Parzyszek Committed by GitHub
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[flang][OpenMP] Detect DSA conflicts in nested loop constructs (#195323) 

Follow-up to https://github.com/llvm/llvm-project/pull/194961

The fix from PR194961 did not detect explicit/predefined DSA conflicts
on an iteration variable in a nested loop construct. For example, in a
testcase inspired by Fujitsu 0165_0035.f90:
```
  !$omp parallel do private(i) shared(j)
  do i=1,1
    do j=1,1
      !$omp parallel do default(none) shared(k)
      do k=1,1
      end do
      !$omp end parallel do
    end do
  end do
```
the "shared(k)" was not flagged as incorrect.

Adjust the fix to traverse the host-association chain until the symbol
from the DSA clause is found.
parent cafb6441

flang/lib/Semantics/check-omp-loop.cpp

+13 −5
Original line number Diff line number Diff line
@@ -484,6 +484,10 @@ void OmpStructureChecker::CheckIterationVariables( 


  std::vector<parser::Name> ivs;

  for (const parser::DoConstruct *loop : *doLoops) {

    // Skip DO CONCURRENT, since their iteration variables are local.

    if (loop->IsDoConcurrent()) {

      continue;

    }

    for (auto &control : GetLoopControls(*loop)) {

      if (control.iv.symbol) {

        ivs.push_back(control.iv);
@@ -498,15 +502,19 @@ void OmpStructureChecker::CheckIterationVariables( 
          "The DO loop iteration variable must be of integer type"_err_en_US,

          iv.ToString());

    }

    const Symbol *host{GetHostSymbol(*iv.symbol)};

    if (!host) {

      continue;

    }

    if (host->test(Symbol::Flag::OmpThreadprivate)) {

    if (iv.symbol->GetUltimate().test(Symbol::Flag::OmpThreadprivate)) {

      context_.Say(iv.source,

          "Loop iteration variable of an affected loop cannot be THREADPRIVATE"_err_en_US,

          iv.ToString());

    }

    // Get the symbol from the variable that was listed in a DSA clause.

    const Symbol *host{iv.symbol};

    while (host && !dsa.count(host)) {

      host = GetHostSymbol(*host);

    }

    if (!host) {

      continue;

    }

    // Check conflict between a predetermined DSA and explicit DSA.

    assert(iv.symbol->test(Symbol::Flag::OmpPreDetermined) &&

        "Expecting affected iteration variable to have predetermined DSA");

flang/test/Semantics/OpenMP/do01.f90

+17 −0
Original line number Diff line number Diff line
@@ -31,3 +31,20 @@ subroutine f01 
    end do

  end block

end



! Check DSA clause on a nested construct

subroutine f02

  integer :: i, j, k

  !$omp parallel do private(i) shared(j)

  do i = 1, 10

    do j = 1, 10

      !ERROR: Loop iteration variable with a predetermined data sharing attribute cannot appear in a SHARED clause

      !$omp parallel do default(none) shared(k)

      !BECAUSE: 'k' is an iteration variable of an affected loop

      do k = 1, 10

      end do

      !$omp end parallel do

    end do

  end do

  !$omp end parallel do

end