Index: cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
===================================================================
--- cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
+++ cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
@@ -32,8 +32,7 @@
 } // namespace llvm
 
 namespace clang {
-class VarDecl;
-
+class Expr;
 class OMPExecutableDirective;
 class VarDecl;
 
@@ -93,7 +92,9 @@
     OMPRTL__kmpc_end_serialized_parallel,
     // Call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32 global_tid,
     // kmp_int32 num_threads);
-    OMPRTL__kmpc_push_num_threads
+    OMPRTL__kmpc_push_num_threads,
+    // Call to void __kmpc_flush(ident_t *loc, ...);
+    OMPRTL__kmpc_flush
   };
 
 private:
@@ -329,6 +330,11 @@
   EmitOMPThreadPrivateVarDefinition(const VarDecl *VD, llvm::Value *VDAddr,
                                     SourceLocation Loc, bool PerformInit,
                                     CodeGenFunction *CGF = nullptr);
+
+  /// \brief Emit flush of the variables specified in 'omp flush' directive.
+  /// \param Vars List of variables to flush.
+  virtual void EmitOMPFlush(CodeGenFunction &CGF, ArrayRef<const Expr *> Vars,
+                            SourceLocation Loc);
 };
 } // namespace CodeGen
 } // namespace clang
Index: cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
+++ cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -363,6 +363,14 @@
     RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_end_serialized_parallel");
     break;
   }
+  case OMPRTL__kmpc_flush: {
+    // Build void __kmpc_flush(ident_t *loc, ...);
+    llvm::Type *TypeParams[] = {getIdentTyPointerTy()};
+    llvm::FunctionType *FnTy =
+        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ true);
+    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_flush");
+    break;
+  }
   }
   return RTLFn;
 }
@@ -651,3 +659,14 @@
   CGF.EmitRuntimeCall(RTLFn, Args);
 }
 
+void CGOpenMPRuntime::EmitOMPFlush(CodeGenFunction &CGF, ArrayRef<const Expr *>,
+                                   SourceLocation Loc) {
+  // Build call void __kmpc_flush(ident_t *loc, ...)
+  // FIXME: List of variables is ignored by libiomp5 runtime, no need to
+  // generate it, just request full memory fence.
+  llvm::Value *Args[] = {EmitOpenMPUpdateLocation(CGF, Loc),
+                         llvm::ConstantInt::get(CGM.Int32Ty, 0)};
+  auto *RTLFn = CGF.CGM.getOpenMPRuntime().CreateRuntimeFunction(
+      CGOpenMPRuntime::OMPRTL__kmpc_flush);
+  CGF.EmitRuntimeCall(RTLFn, Args);
+}
Index: cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
+++ cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
@@ -543,8 +543,17 @@
   llvm_unreachable("CodeGen for 'omp taskwait' is not supported yet.");
 }
 
-void CodeGenFunction::EmitOMPFlushDirective(const OMPFlushDirective &) {
-  llvm_unreachable("CodeGen for 'omp flush' is not supported yet.");
+void CodeGenFunction::EmitOMPFlushDirective(const OMPFlushDirective &S) {
+  CGM.getOpenMPRuntime().EmitOMPFlush(
+      *this, [&]() -> ArrayRef<const Expr *> {
+               if (auto C = S.getSingleClause(/*K*/ OMPC_flush)) {
+                 auto FlushClause = cast<OMPFlushClause>(C);
+                 return llvm::makeArrayRef(FlushClause->varlist_begin(),
+                                           FlushClause->varlist_end());
+               }
+               return llvm::None;
+             }(),
+      S.getLocStart());
 }
 
 void CodeGenFunction::EmitOMPOrderedDirective(const OMPOrderedDirective &) {
Index: cfe/trunk/test/OpenMP/flush_codegen.cpp
===================================================================
--- cfe/trunk/test/OpenMP/flush_codegen.cpp
+++ cfe/trunk/test/OpenMP/flush_codegen.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -verify -fopenmp=libiomp5 -x c++ -emit-llvm %s -fexceptions -fcxx-exceptions -o - | FileCheck %s
+// RUN: %clang_cc1 -fopenmp=libiomp5 -x c++ -std=c++11 -triple x86_64-unknown-unknown -fexceptions -fcxx-exceptions -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp=libiomp5 -x c++ -triple x86_64-unknown-unknown -fexceptions -fcxx-exceptions -g -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+template <class T>
+T tmain(T argc) {
+  static T a;
+#pragma omp flush
+#pragma omp flush(a)
+  return a + argc;
+}
+
+// CHECK-LABEL: @main
+int main() {
+  static int a;
+#pragma omp flush
+#pragma omp flush(a)
+  // CHECK: call void (%{{.+}}*, ...)* @__kmpc_flush(%{{.+}}* {{(@|%).+}}, i32 0)
+  // CHECK: call void (%{{.+}}*, ...)* @__kmpc_flush(%{{.+}}* {{(@|%).+}}, i32 0)
+  return tmain(a);
+  // CHECK: call {{.*}} [[TMAIN:@.+]](
+  // CHECK: ret
+}
+
+// CHECK: [[TMAIN]]
+// CHECK: call void (%{{.+}}*, ...)* @__kmpc_flush(%{{.+}}* {{(@|%).+}}, i32 0)
+// CHECK: call void (%{{.+}}*, ...)* @__kmpc_flush(%{{.+}}* {{(@|%).+}}, i32 0)
+// CHECK: ret
+
+#endif