[flang-commits] [flang] [Flang][Openmp]Prevent TODO abort on nothing directive (PR #202679)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-openmp

Author: ShashwathiNavada

<details>
<summary>Changes</summary>

Since nothing is a no-op directive (OpenMP 5.2, 8.4), handle it during lowering instead of falling through to the generic unimplemented utility-directive path and triggering a TODO abort.

---
Full diff: https://github.com/llvm/llvm-project/pull/202679.diff


2 Files Affected:

- (modified) flang/lib/Lower/OpenMP/OpenMP.cpp (+12-3) 
- (added) flang/test/Lower/OpenMP/nothing.f90 (+8) 


``````````diff
diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index 266b06f353675..f4c46ed238dcb 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -4899,9 +4899,18 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
 static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
                    semantics::SemanticsContext &semaCtx,
                    lower::pft::Evaluation &eval,
-                   const parser::OmpUtilityDirective &) {
-  if (!semaCtx.langOptions().OpenMPSimd)
-    TODO(converter.getCurrentLocation(), "OmpUtilityDirective");
+                   const parser::OmpUtilityDirective &dir) {
+  common::visit(
+      common::visitors{
+          [&](const parser::OmpNothingDirective &) {
+            // nothing-directive is a no-op (OpenMP 5.2 [8.4])
+          },
+          [&](const parser::OmpErrorDirective &) {
+            if (!semaCtx.langOptions().OpenMPSimd)
+              TODO(converter.getCurrentLocation(), "OmpErrorDirective");
+          },
+      },
+      dir.u);
 }
 
 static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
diff --git a/flang/test/Lower/OpenMP/nothing.f90 b/flang/test/Lower/OpenMP/nothing.f90
new file mode 100644
index 0000000000000..775b6a34db45e
--- /dev/null
+++ b/flang/test/Lower/OpenMP/nothing.f90
@@ -0,0 +1,8 @@
+!RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=52 %s -o - | FileCheck %s
+!RUN: bbc -emit-hlfir -fopenmp -fopenmp-version=52 %s -o - | FileCheck %s
+
+! CHECK-LABEL: func @_QPfoo
+subroutine foo
+  ! CHECK-NOT: omp.
+  !$omp nothing
+end subroutine

``````````

</details>


https://github.com/llvm/llvm-project/pull/202679