[flang-commits] [flang] [llvm] [mlir] [flang][OpenMP] Support the FULL clause on the UNROLL construct (PR #214115)

[Sairudra More via flang-commits]

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@@ -443,6 +443,41 @@ void OmpStructureChecker::Enter(const parser::OpenMPLoopConstruct &x) {
       beginName.v == llvm::omp::Directive::OMPD_distribute_simd) {
     CheckDistLinear(x);
   }
+  if (beginName.v == llvm::omp::Directive::OMPD_unroll) {
+    CheckUnrollFullTripCount(x);
+  }
+}
+
+// A loop that is fully unrolled must have a trip count that is known at compile
+// time, so its bounds and step have to be constant expressions.
+void OmpStructureChecker::CheckUnrollFullTripCount(
+    const parser::OpenMPLoopConstruct &x) {
+  const parser::OmpDirectiveSpecification &beginSpec{x.BeginDir()};
+  const parser::OmpClause *full{
+      parser::omp::FindClause(beginSpec, llvm::omp::Clause::OMPC_full)};
+  if (!full) {
+    return;
+  }
+
+  const parser::DoConstruct *doConstruct{x.GetNestedLoop()};
+  if (!doConstruct) {
+    return;
+  }
+  const auto &control{doConstruct->GetLoopControl()};
+  if (!control) {
+    return;
+  }
+  const auto *bounds{std::get_if<parser::LoopControl::Bounds>(&control->u)};
+  if (!bounds) {
+    return;
+  }
+  bool isConstant{GetIntValue(bounds->Lower()).has_value() &&
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Saieiei wrote:

Could we check the folded trip count here instead of requiring each bound and the step to be constant? The OpenMP restriction is on the iteration count itself. For example, `do i = m, m` has a constant trip count of 1, but this check rejects it because `m` isn't constant. A positive test for that case would be useful.

https://github.com/llvm/llvm-project/pull/214115