[Flang][OpenMP] Add semantic tests for threadprivate variables with host assoc (#134680)

flang/test/Semantics/OpenMP/default-none.f90

@@ -58,3 +58,18 @@ subroutine sub( aaa)
      ccc= aaa(ip)
   end do
 end subroutine sub
+
+! Test that threadprivate variables with host association
+! have a predetermined DSA
+subroutine host_assoc()
+  integer, save :: i
+  !$omp threadprivate(i)
+  real, save :: r
+  !$omp threadprivate(r)
+contains
+  subroutine internal()
+!$omp parallel default(none)
+    print *, i, r
+!$omp end parallel
+  end subroutine internal
+end subroutine host_assoc

flang/test/Semantics/OpenMP/threadprivate09.f90

@@ -0,0 +1,33 @@
+! RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+! OpenMP Version 5.1
+! Check OpenMP construct validity for the following directives:
+! 2.21.2 Threadprivate Directive
+
+subroutine host_assoc_fail()
+  integer :: i
+  ! ERROR: A variable that appears in a THREADPRIVATE directive must be declared in the scope of a module or have the SAVE attribute, either explicitly or implicitly
+  !$omp threadprivate(i)
+  real :: r
+  ! ERROR: A variable that appears in a THREADPRIVATE directive must be declared in the scope of a module or have the SAVE attribute, either explicitly or implicitly
+  !$omp threadprivate(r)
+contains
+  subroutine internal()
+!$omp parallel
+    print *, i, r
+!$omp end parallel
+  end subroutine internal
+end subroutine host_assoc_fail
+
+! This sub-test is not supposed to emit a compiler error.
+subroutine host_assoc()
+  integer, save :: i
+  !$omp threadprivate(i)
+  real, save :: r
+  !$omp threadprivate(r)
+contains
+  subroutine internal()
+!$omp parallel
+    print *, i, r
+!$omp end parallel
+  end subroutine internal
+end subroutine host_assoc