Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -9132,6 +9132,10 @@
   "Only one %0 clause can appear on a requires directive in a single translation unit">;
 def note_omp_requires_previous_clause : Note <
   "%0 clause previously used here">;
+def err_omp_target_before_requires : Error <
+  "target region encountered before requires directive with '%0' clause">;
+def note_omp_requires_encountered_target : Note <
+  "target previously encountered here">;
 def err_omp_invalid_scope : Error <
   "'#pragma omp %0' directive must appear only in file scope">;
 def note_omp_invalid_length_on_this_ptr_mapping : Note <
Index: lib/Sema/SemaOpenMP.cpp
===================================================================
--- lib/Sema/SemaOpenMP.cpp
+++ lib/Sema/SemaOpenMP.cpp
@@ -193,6 +193,8 @@
   /// Expression for the predefined allocators.
   Expr *OMPPredefinedAllocators[OMPAllocateDeclAttr::OMPUserDefinedMemAlloc] = {
       nullptr};
+  /// Vector of previously encountered target directives
+  SmallVector<SourceLocation, 2> TargetLocations;
 
 public:
   explicit DSAStackTy(Sema &S) : SemaRef(S) {}
@@ -454,6 +456,16 @@
     return IsDuplicate;
   }
 
+  /// Add location of previously encountered target to internal vector
+  void addTargetDirLocation(SourceLocation LocStart) {
+    TargetLocations.push_back(LocStart);
+  }
+
+  // Return previously encountered target region locations.
+  ArrayRef<SourceLocation> getEncounteredTargetLocs() const {
+    return TargetLocations;
+  }
+
   /// Set default data sharing attribute to none.
   void setDefaultDSANone(SourceLocation Loc) {
     assert(!isStackEmpty());
@@ -2418,6 +2430,27 @@
 
 OMPRequiresDecl *Sema::CheckOMPRequiresDecl(SourceLocation Loc,
                                             ArrayRef<OMPClause *> ClauseList) {
+  /// For target specific clauses, the requires directive cannot be
+  /// specified after the handling of any of the target regions in the
+  /// current compilation unit.
+  ArrayRef<SourceLocation> TargetLocations =
+      DSAStack->getEncounteredTargetLocs();
+  if (!TargetLocations.empty()) {
+    for (const OMPClause *CNew : ClauseList) {
+      // Check if any of the requires clauses affect target regions.
+      if (isa<OMPUnifiedSharedMemoryClause>(CNew) ||
+          isa<OMPUnifiedAddressClause>(CNew) ||
+          isa<OMPReverseOffloadClause>(CNew) ||
+          isa<OMPDynamicAllocatorsClause>(CNew)) {
+        Diag(Loc, diag::err_omp_target_before_requires)
+            << getOpenMPClauseName(CNew->getClauseKind());
+        for (SourceLocation TargetLoc : TargetLocations) {
+          Diag(TargetLoc, diag::note_omp_requires_encountered_target);
+        }
+      }
+    }
+  }
+
   if (!DSAStack->hasDuplicateRequiresClause(ClauseList))
     return OMPRequiresDecl::Create(Context, getCurLexicalContext(), Loc,
                                    ClauseList);
@@ -4167,6 +4200,16 @@
         ->setIsOMPStructuredBlock(true);
   }
 
+  if (!CurContext->isDependentContext() &&
+      isOpenMPTargetExecutionDirective(Kind) &&
+      !(DSAStack->hasRequiresDeclWithClause<OMPUnifiedSharedMemoryClause>() ||
+        DSAStack->hasRequiresDeclWithClause<OMPUnifiedAddressClause>() ||
+        DSAStack->hasRequiresDeclWithClause<OMPReverseOffloadClause>() ||
+        DSAStack->hasRequiresDeclWithClause<OMPDynamicAllocatorsClause>())) {
+    // Register target to DSA Stack.
+    DSAStack->addTargetDirLocation(StartLoc);
+  }
+
   return Res;
 }
 
Index: test/OpenMP/requires_messages.cpp
===================================================================
--- test/OpenMP/requires_messages.cpp
+++ test/OpenMP/requires_messages.cpp
@@ -7,7 +7,7 @@
 
 #pragma omp requires unified_shared_memory, unified_shared_memory // expected-error {{Only one unified_shared_memory clause can appear on a requires directive in a single translation unit}} expected-error {{directive '#pragma omp requires' cannot contain more than one 'unified_shared_memory' clause}}
 
-#pragma omp requires unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}} 
+#pragma omp requires unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}}
 
 #pragma omp requires unified_address, unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}} expected-error {{directive '#pragma omp requires' cannot contain more than one 'unified_address' clause}}
 
@@ -29,13 +29,13 @@
 
 #pragma omp requires atomic_default_mem_order( // expected-error {{expected ')'}} expected-note {{to match this '('}} expected-error {{expected 'seq_cst', 'acq_rel' or 'relaxed' in OpenMP clause 'atomic_default_mem_order'}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
 
-#pragma omp requires atomic_default_mem_order(seq_cst // expected-error {{expected ')'}} expected-note {{to match this '('}} expected-error {{Only one atomic_default_mem_order clause can appear on a requires directive in a single translation unit}} 
+#pragma omp requires atomic_default_mem_order(seq_cst // expected-error {{expected ')'}} expected-note {{to match this '('}} expected-error {{Only one atomic_default_mem_order clause can appear on a requires directive in a single translation unit}}
 
-#pragma omp requires atomic_default_mem_order(invalid_modifier) // expected-error {{expected 'seq_cst', 'acq_rel' or 'relaxed' in OpenMP clause 'atomic_default_mem_order'}} expected-error {{expected at least one clause on '#pragma omp requires' directive}} 
+#pragma omp requires atomic_default_mem_order(invalid_modifier) // expected-error {{expected 'seq_cst', 'acq_rel' or 'relaxed' in OpenMP clause 'atomic_default_mem_order'}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
 
 #pragma omp requires atomic_default_mem_order(shared) // expected-error {{expected 'seq_cst', 'acq_rel' or 'relaxed' in OpenMP clause 'atomic_default_mem_order'}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
 
-#pragma omp requires atomic_default_mem_order(acq_rel), atomic_default_mem_order(relaxed) // expected-error {{directive '#pragma omp requires' cannot contain more than one 'atomic_default_mem_order' claus}} expected-error {{Only one atomic_default_mem_order clause can appear on a requires directive in a single translation unit}} 
+#pragma omp requires atomic_default_mem_order(acq_rel), atomic_default_mem_order(relaxed) // expected-error {{directive '#pragma omp requires' cannot contain more than one 'atomic_default_mem_order' claus}} expected-error {{Only one atomic_default_mem_order clause can appear on a requires directive in a single translation unit}}
 
 #pragma omp requires // expected-error {{expected at least one clause on '#pragma omp requires' directive}}
 
Index: test/OpenMP/requires_target_messages.cpp
===================================================================
--- test/OpenMP/requires_target_messages.cpp
+++ test/OpenMP/requires_target_messages.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100  %s
+
+void foo2() {
+  int a;
+  #pragma omp target // expected-note 4 {{Target previously encountered here}}
+  {
+    a = a + 1;
+  }
+}
+
+#pragma omp requires atomic_default_mem_order(seq_cst)
+#pragma omp requires unified_address //expected-error {{Target region encountered before requires directive with 'unified_address' clause}}
+#pragma omp requires unified_shared_memory //expected-error {{Target region encountered before requires directive with 'unified_shared_memory' clause}}
+#pragma omp requires reverse_offload //expected-error {{Target region encountered before requires directive with 'reverse_offload' clause}}
+#pragma omp requires dynamic_allocators //expected-error {{Target region encountered before requires directive with 'dynamic_allocators' clause}}