Index: cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
===================================================================
--- cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
+++ cfe/trunk/lib/CodeGen/CGOpenMPRuntime.h
@@ -91,6 +91,10 @@
     // Call to kmp_int32 __kmpc_omp_taskyield(ident_t *, kmp_int32 global_tid,
     // int end_part);
     OMPRTL__kmpc_omp_taskyield,
+    // Call to kmp_int32 __kmpc_single(ident_t *, kmp_int32 global_tid);
+    OMPRTL__kmpc_single,
+    // Call to void __kmpc_end_single(ident_t *, kmp_int32 global_tid);
+    OMPRTL__kmpc_end_single,
   };
 
   /// \brief Values for bit flags used in the ident_t to describe the fields.
@@ -312,6 +316,13 @@
   /// \brief Emits code for a taskyield directive.
   virtual void EmitOMPTaskyieldCall(CodeGenFunction &CGF, SourceLocation Loc);
 
+  /// \brief Emits a single region.
+  /// \param SingleOpGen Generator for the statement associated with the given
+  /// single region.
+  virtual void EmitOMPSingleRegion(CodeGenFunction &CGF,
+                                   const std::function<void()> &SingleOpGen,
+                                   SourceLocation Loc);
+
   /// \brief Emits explicit barrier for OpenMP threads.
   /// \param IsExplicit true, if it is explicitly specified barrier.
   ///
Index: cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
+++ cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -484,6 +484,22 @@
     RTLFn = CGM.CreateRuntimeFunction(FnTy, /*Name=*/"__kmpc_omp_taskyield");
     break;
   }
+  case OMPRTL__kmpc_single: {
+    // Build kmp_int32 __kmpc_single(ident_t *loc, kmp_int32 global_tid);
+    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty};
+    llvm::FunctionType *FnTy =
+        llvm::FunctionType::get(CGM.Int32Ty, TypeParams, /*isVarArg=*/false);
+    RTLFn = CGM.CreateRuntimeFunction(FnTy, /*Name=*/"__kmpc_single");
+    break;
+  }
+  case OMPRTL__kmpc_end_single: {
+    // Build void __kmpc_end_single(ident_t *loc, kmp_int32 global_tid);
+    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty};
+    llvm::FunctionType *FnTy =
+        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg=*/false);
+    RTLFn = CGM.CreateRuntimeFunction(FnTy, /*Name=*/"__kmpc_end_single");
+    break;
+  }
   }
   return RTLFn;
 }
@@ -805,6 +821,39 @@
   CGF.EmitRuntimeCall(RTLFn, Args);
 }
 
+void CGOpenMPRuntime::EmitOMPSingleRegion(
+    CodeGenFunction &CGF, const std::function<void()> &SingleOpGen,
+    SourceLocation Loc) {
+  // if(__kmpc_single(ident_t *, gtid)) {
+  //   SingleOpGen();
+  //   __kmpc_end_single(ident_t *, gtid);
+  // }
+  // Prepare arguments and build a call to __kmpc_single
+  llvm::Value *Args[] = {EmitOpenMPUpdateLocation(CGF, Loc),
+                         GetOpenMPThreadID(CGF, Loc)};
+  auto RTLFn = CreateRuntimeFunction(OMPRTL__kmpc_single);
+  auto *IsSingle = CGF.EmitRuntimeCall(RTLFn, Args);
+  EmitOMPIfStmt(CGF, IsSingle, [&]() -> void {
+    SingleOpGen();
+    // Build a call to __kmpc_end_single.
+    // OpenMP [1.2.2 OpenMP Language Terminology]
+    // For C/C++, an executable statement, possibly compound, with a single
+    // entry at the top and a single exit at the bottom, or an OpenMP construct.
+    // * Access to the structured block must not be the result of a branch.
+    // * The point of exit cannot be a branch out of the structured block.
+    // * The point of entry must not be a call to setjmp().
+    // * longjmp() and throw() must not violate the entry/exit criteria.
+    // * An expression statement, iteration statement, selection statement, or
+    // try block is considered to be a structured block if the corresponding
+    // compound statement obtained by enclosing it in { and } would be a
+    // structured block.
+    // It is analyzed in Sema, so we can just call __kmpc_end_single() on
+    // fallthrough rather than pushing a normal cleanup for it.
+    RTLFn = CreateRuntimeFunction(OMPRTL__kmpc_end_single);
+    CGF.EmitRuntimeCall(RTLFn, Args);
+  });
+}
+
 void CGOpenMPRuntime::EmitOMPBarrierCall(CodeGenFunction &CGF,
                                          SourceLocation Loc, bool IsExplicit) {
   // Build call __kmpc_cancel_barrier(loc, thread_id);
Index: cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
+++ cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp
@@ -707,8 +707,13 @@
   llvm_unreachable("CodeGen for 'omp section' is not supported yet.");
 }
 
-void CodeGenFunction::EmitOMPSingleDirective(const OMPSingleDirective &) {
-  llvm_unreachable("CodeGen for 'omp single' is not supported yet.");
+void CodeGenFunction::EmitOMPSingleDirective(const OMPSingleDirective &S) {
+  CGM.getOpenMPRuntime().EmitOMPSingleRegion(*this, [&]() -> void {
+    InlinedOpenMPRegion Region(*this, S.getAssociatedStmt());
+    RunCleanupsScope Scope(*this);
+    EmitStmt(cast<CapturedStmt>(S.getAssociatedStmt())->getCapturedStmt());
+    EnsureInsertPoint();
+  }, S.getLocStart());
 }
 
 void CodeGenFunction::EmitOMPMasterDirective(const OMPMasterDirective &S) {
Index: cfe/trunk/test/OpenMP/single_codegen.cpp
===================================================================
--- cfe/trunk/test/OpenMP/single_codegen.cpp
+++ cfe/trunk/test/OpenMP/single_codegen.cpp
@@ -0,0 +1,46 @@
+// 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 -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+// CHECK:       [[IDENT_T_TY:%.+]] = type { i32, i32, i32, i32, i8* }
+
+// CHECK:       define void [[FOO:@.+]]()
+
+void foo() {}
+
+// CHECK-LABEL: @main
+int main() {
+  // CHECK:       [[A_ADDR:%.+]] = alloca i8
+  char a;
+
+// CHECK:       [[GTID:%.+]] = call i32 @__kmpc_global_thread_num([[IDENT_T_TY]]* [[DEFAULT_LOC:@.+]])
+// CHECK:       [[RES:%.+]] = call i32 @__kmpc_single([[IDENT_T_TY]]* [[DEFAULT_LOC]], i32 [[GTID]])
+// CHECK-NEXT:  [[IS_SINGLE:%.+]] = icmp ne i32 [[RES]], 0
+// CHECK-NEXT:  br i1 [[IS_SINGLE]], label {{%?}}[[THEN:.+]], label {{%?}}[[EXIT:.+]]
+// CHECK:       [[THEN]]
+// CHECK-NEXT:  store i8 2, i8* [[A_ADDR]]
+// CHECK-NEXT:  call void @__kmpc_end_single([[IDENT_T_TY]]* [[DEFAULT_LOC]], i32 [[GTID]])
+// CHECK-NEXT:  br label {{%?}}[[EXIT]]
+// CHECK:       [[EXIT]]
+#pragma omp single
+  a = 2;
+// CHECK:       [[RES:%.+]] = call i32 @__kmpc_single([[IDENT_T_TY]]* [[DEFAULT_LOC]], i32 [[GTID]])
+// CHECK-NEXT:  [[IS_SINGLE:%.+]] = icmp ne i32 [[RES]], 0
+// CHECK-NEXT:  br i1 [[IS_SINGLE]], label {{%?}}[[THEN:.+]], label {{%?}}[[EXIT:.+]]
+// CHECK:       [[THEN]]
+// CHECK-NEXT:  call void [[FOO]]()
+// CHECK-NEXT:  call void @__kmpc_end_single([[IDENT_T_TY]]* [[DEFAULT_LOC]], i32 [[GTID]])
+// CHECK-NEXT:  br label {{%?}}[[EXIT]]
+// CHECK:       [[EXIT]]
+#pragma omp single
+  foo();
+// CHECK-NOT:   call i32 @__kmpc_single
+// CHECK-NOT:   call void @__kmpc_end_single
+  return a;
+}
+
+#endif