3 files changed, 54 insertions, 7 deletions
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index 53d4b6cb404..1a50c94bc7d 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -296,6 +296,16 @@ CGOpenMPRuntime::CreateRuntimeFunction(OpenMPRTLFunction Function) {
     RTLFn = CGM.CreateRuntimeFunction(FnTy, /*Name*/ "__kmpc_barrier");
     break;
   }
+  case OMPRTL__kmpc_push_num_threads: {
+    // Build void __kmpc_push_num_threads(ident_t *loc, kmp_int32 global_tid,
+    // kmp_int32 num_threads)
+    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty,
+                                CGM.Int32Ty};
+    llvm::FunctionType *FnTy =
+        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
+    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_push_num_threads");
+    break;
+  }
   case OMPRTL__kmpc_serialized_parallel: {
     // Build void __kmpc_serialized_parallel(ident_t *loc, kmp_int32
     // global_tid);
@@ -431,3 +441,15 @@ void CGOpenMPRuntime::EmitOMPBarrierCall(CodeGenFunction &CGF,
   CGF.EmitRuntimeCall(RTLFn, Args);
 }
 
+void CGOpenMPRuntime::EmitOMPNumThreadsClause(CodeGenFunction &CGF,
+                                              llvm::Value *NumThreads,
+                                              SourceLocation Loc) {
+  // Build call __kmpc_push_num_threads(&loc, global_tid, num_threads)
+  llvm::Value *Args[] = {
+      EmitOpenMPUpdateLocation(CGF, Loc), GetOpenMPThreadID(CGF, Loc),
+      CGF.Builder.CreateIntCast(NumThreads, CGF.Int32Ty, /*isSigned*/ true)};
+  llvm::Constant *RTLFn = CGF.CGM.getOpenMPRuntime().CreateRuntimeFunction(
+      CGOpenMPRuntime::OMPRTL__kmpc_push_num_threads);
+  CGF.EmitRuntimeCall(RTLFn, Args);
+}
+
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.h b/clang/lib/CodeGen/CGOpenMPRuntime.h
index 04378821d7a..c4da375acf5 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.h
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.h
@@ -80,7 +80,10 @@ public:
     OMPRTL__kmpc_serialized_parallel,
     // Call to void __kmpc_end_serialized_parallel(ident_t *loc, kmp_int32
     // global_tid);
-    OMPRTL__kmpc_end_serialized_parallel
+    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
   };
 
 private:
@@ -250,6 +253,14 @@ public:
   ///
   virtual void EmitOMPBarrierCall(CodeGenFunction &CGF, SourceLocation Loc,
                                   OpenMPLocationFlags Flags);
+
+  /// \brief Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
+  /// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
+  /// clause.
+  /// \param NumThreads An integer value of threads.
+  virtual void EmitOMPNumThreadsClause(CodeGenFunction &CGF,
+                                       llvm::Value *NumThreads,
+                                       SourceLocation Loc);
 };
 } // namespace CodeGen
 } // namespace clang
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index a459d07a723..2b0fb043be0 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -183,6 +183,23 @@ void CodeGenFunction::EmitOMPFirstprivateClause(
   }
 }
 
+/// \brief Emits code for OpenMP parallel directive in the parallel region.
+static void EmitOMPParallelCall(CodeGenFunction &CGF,
+                                const OMPParallelDirective &S,
+                                llvm::Value *OutlinedFn,
+                                llvm::Value *CapturedStruct) {
+  if (auto C = S.getSingleClause(/*K*/ OMPC_num_threads)) {
+    CodeGenFunction::RunCleanupsScope NumThreadsScope(CGF);
+    auto NumThreadsClause = cast<OMPNumThreadsClause>(C);
+    auto NumThreads = CGF.EmitScalarExpr(NumThreadsClause->getNumThreads(),
+                                         /*IgnoreResultAssign*/ true);
+    CGF.CGM.getOpenMPRuntime().EmitOMPNumThreadsClause(
+        CGF, NumThreads, NumThreadsClause->getLocStart());
+  }
+  CGF.CGM.getOpenMPRuntime().EmitOMPParallelCall(CGF, S.getLocStart(),
+                                                 OutlinedFn, CapturedStruct);
+}
+
 void CodeGenFunction::EmitOMPParallelDirective(const OMPParallelDirective &S) {
   auto CS = cast<CapturedStmt>(S.getAssociatedStmt());
   auto CapturedStruct = GenerateCapturedStmtArgument(*CS);
@@ -192,16 +209,13 @@ void CodeGenFunction::EmitOMPParallelDirective(const OMPParallelDirective &S) {
     auto Cond = cast<OMPIfClause>(C)->getCondition();
     EmitOMPIfClause(*this, Cond, [&](bool ThenBlock) {
       if (ThenBlock)
-        CGM.getOpenMPRuntime().EmitOMPParallelCall(*this, S.getLocStart(),
-                                                   OutlinedFn, CapturedStruct);
+        EmitOMPParallelCall(*this, S, OutlinedFn, CapturedStruct);
       else
         CGM.getOpenMPRuntime().EmitOMPSerialCall(*this, S.getLocStart(),
                                                  OutlinedFn, CapturedStruct);
     });
-  } else {
-    CGM.getOpenMPRuntime().EmitOMPParallelCall(*this, S.getLocStart(),
-                                               OutlinedFn, CapturedStruct);
-  }
+  } else
+    EmitOMPParallelCall(*this, S, OutlinedFn, CapturedStruct);
 }
 
 void CodeGenFunction::EmitOMPLoopBody(const OMPLoopDirective &S,