[flang][OpenMP] Add semantic check for device clause

[shraiysh]

This patch adds the following semantic check:

The ancestor device-modifier must not appear on the device clause on any
directive other than the target construct.

[llvmbot]

@llvm/pr-subscribers-flang-openmp

@llvm/pr-subscribers-flang-semantics

Author: Shraiysh (shraiysh)

Changes

This patch adds the following semantic check:

The ancestor device-modifier must not appear on the device clause on any
directive other than the target construct.

---

Full diff: https://github.com/llvm/llvm-project/pull/72789.diff

2 Files Affected:

• (modified) flang/lib/Semantics/check-omp-structure.cpp (+12)
• (added) flang/test/Semantics/OpenMP/device-clause01.f90 (+31)

diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 0b1a581bf298196..a79ff19915476e8 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -8,8 +8,10 @@
 
 #include "check-omp-structure.h"
 #include "definable.h"
+#include "flang/Parser/characters.h"
 #include "flang/Parser/parse-tree.h"
 #include "flang/Semantics/tools.h"
+#include "llvm/Frontend/OpenMP/OMP.h.inc"
 
 namespace Fortran::semantics {
 
@@ -2748,6 +2750,16 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Device &x) {
   const auto &device{std::get<1>(deviceClause.t)};
   RequiresPositiveParameter(
       llvm::omp::Clause::OMPC_device, device, "device expression");
+  auto modifier = std::get<0>(x.v.t);
+  if (modifier.has_value() &&
+      modifier.value() == parser::OmpDeviceClause::DeviceModifier::Ancestor) {
+    if(GetContext().directive != llvm::omp::OMPD_target) {
+      context_.Say(GetContext().clauseSource,
+          "The ANCESTOR device-modifier must not appear on the DEVICE clause on"
+          " any directive other than the TARGET construct. Found on %s construct."_err_en_US,
+          parser::ToUpperCaseLetters(getDirectiveName(GetContext().directive)));
+    }
+  }
 }
 
 void OmpStructureChecker::Enter(const parser::OmpClause::Depend &x) {
diff --git a/flang/test/Semantics/OpenMP/device-clause01.f90 b/flang/test/Semantics/OpenMP/device-clause01.f90
new file mode 100644
index 000000000000000..6f95d162790d575
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/device-clause01.f90
@@ -0,0 +1,31 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.2
+! 13.2 Device clause
+
+subroutine foo
+
+  integer :: a
+
+  !$omp target device(ancestor:0)
+  !$omp end target
+  !$omp target device(device_num:0)
+  !$omp end target
+  
+  !ERROR: The ANCESTOR device-modifier must not appear on the DEVICE clause on any directive other than the TARGET construct. Found on TARGET DATA construct.
+  !$omp target data device(ancestor:0) map(tofrom:a)
+  !$omp end target data
+  !$omp target data device(device_num:0) map(tofrom:a)
+  !$omp end target data
+
+  
+  !ERROR: The ANCESTOR device-modifier must not appear on the DEVICE clause on any directive other than the TARGET construct. Found on TARGET ENTER DATA construct.
+  !$omp target enter data device(ancestor:0) map(to:a)
+  !$omp target exit data map(from:a)
+  !$omp target enter data device(device_num:0) map(to:a)
+  !$omp target exit data map(from:a)
+
+  !ERROR: The ANCESTOR device-modifier must not appear on the DEVICE clause on any directive other than the TARGET construct. Found on TARGET UPDATE construct.
+  !$omp target update device(ancestor:0) to(a)
+  !$omp target update device(device_num:0) to(a)
+
+end subroutine foo

[kiranchandramohan]

LG with Nit comments.

[kiranchandramohan]

Suggested change

	auto modifier = std::get<0>(x.v.t);
	std::optional<parser::OmpDeviceClause::DeviceModifier> modifier = std::get<0>(deviceClause.t);

[kiranchandramohan]

Suggested change

	if (modifier.has_value() &&
	modifier.value() == parser::OmpDeviceClause::DeviceModifier::Ancestor) {
	if (modifier &&
	*modifier == parser::OmpDeviceClause::DeviceModifier::Ancestor) {

[raghavendhra]

LGTM

[agozillon]

LGTM, thank you for the patch!