3 files changed, 67 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index abc609aebb2..b7242d8979b 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -484,6 +484,22 @@ CGOpenMPRuntime::CreateRuntimeFunction(OpenMPRTLFunction Function) {
     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 @@ void CGOpenMPRuntime::EmitOMPTaskyieldCall(CodeGenFunction &CGF,
   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);
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.h b/clang/lib/CodeGen/CGOpenMPRuntime.h
index 5ff8dd654ef..76d4f2a6239 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.h
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.h
@@ -91,6 +91,10 @@ private:
     // 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 @@ public:
   /// \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.
   ///
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 2518e55d4b3..b4dcadc5fdc 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -707,8 +707,13 @@ void CodeGenFunction::EmitOMPSectionDirective(const OMPSectionDirective &) {
   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) {