[OpenMP] diagnose zero-length array section in the depend clause

The OpenMP specification disallows having zero-length array
sections in the depend clause (OpenMP 5.0 2.17.11).

Differential Revision: https://reviews.llvm.org/D71969

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 23cd6f04a93..5a4254f11a8 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -15020,6 +15020,22 @@ Sema::ActOnOpenMPDependClause(OpenMPDependClauseKind DepKind,
       }
       OpsOffs.emplace_back(RHS, OOK);
     } else {
+      // OpenMP 5.0 [2.17.11, Restrictions]
+      // List items used in depend clauses cannot be zero-length array sections.
+      const auto *OASE = dyn_cast<OMPArraySectionExpr>(SimpleExpr);
+      if (OASE) {
+        const Expr *Length = OASE->getLength();
+        Expr::EvalResult Result;
+        if (Length && !Length->isValueDependent() &&
+            Length->EvaluateAsInt(Result, Context) &&
+            Result.Val.getInt().isNullValue()) {
+          Diag(ELoc,
+               diag::err_omp_depend_zero_length_array_section_not_allowed)
+              << SimpleExpr->getSourceRange();
+          continue;
+        }
+      }
+
       auto *ASE = dyn_cast<ArraySubscriptExpr>(SimpleExpr);
       if (!RefExpr->IgnoreParenImpCasts()->isLValue() ||
           (ASE &&