[flang][cuda] Reapply restriction on kernel subprogram but not device (#91764)

The restriction was completely removed in #89677. This was a bit too
much. Reapply the restriction on elemental, pure and recursive but only
for kernel subprogram (`grid_global` and `global` attributes).

Author: clementval

flang/lib/Semantics/check-declarations.cpp

@@ -1470,6 +1470,13 @@ void CheckHelper::CheckSubprogram(
     messages_.Say(symbol.name(),
         "A function may not have ATTRIBUTES(GLOBAL) or ATTRIBUTES(GRID_GLOBAL)"_err_en_US);
   }
+  if (cudaAttrs &&
+      (*cudaAttrs == common::CUDASubprogramAttrs::Global ||
+          *cudaAttrs == common::CUDASubprogramAttrs::Grid_Global) &&
+      symbol.attrs().HasAny({Attr::RECURSIVE, Attr::PURE, Attr::ELEMENTAL})) {
+    messages_.Say(symbol.name(),
+        "A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL"_err_en_US);
+  }
   if (cudaAttrs && *cudaAttrs != common::CUDASubprogramAttrs::Host) {
     // CUDA device subprogram checks
     if (ClassifyProcedure(symbol) == ProcedureDefinitionClass::Internal) {

flang/test/Semantics/cuf02.cuf

@@ -29,11 +29,23 @@ module m
   !ERROR: A function may not have ATTRIBUTES(GLOBAL) or ATTRIBUTES(GRID_GLOBAL)
   attributes(global) real function f1
   end
-  recursive attributes(global) subroutine s7 ! ok
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  recursive attributes(global) subroutine s7
   end
-  pure attributes(global) subroutine s8 ! ok
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  pure attributes(global) subroutine s8
   end
-  elemental attributes(global) subroutine s9 ! ok
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  elemental attributes(global) subroutine s9
+  end
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  recursive attributes(grid_global) subroutine s10
+  end
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  pure attributes(grid_global) subroutine s11
+  end
+  !ERROR: A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL
+  elemental attributes(grid_global) subroutine s12
   end
 end