diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp
--- a/clang/lib/CodeGen/CGHLSLRuntime.cpp
+++ b/clang/lib/CodeGen/CGHLSLRuntime.cpp
@@ -94,4 +94,13 @@
     F->addFnAttr(ShaderAttrKindStr,
                  ShaderAttr->ConvertShaderTypeToStr(ShaderAttr->getType()));
   }
+  if (HLSLNumThreadsAttr *NumThreadsAttr = FD->getAttr<HLSLNumThreadsAttr>()) {
+    const StringRef NumThreadsKindStr = "hlsl.numthreads";
+    std::string NumThreadsStr;
+    raw_string_ostream OS(NumThreadsStr);
+    OS << NumThreadsAttr->getX() << "," << NumThreadsAttr->getY() << ","
+       << NumThreadsAttr->getZ();
+    OS.flush();
+    F->addFnAttr(NumThreadsKindStr, NumThreadsStr);
+  }
 }
diff --git a/clang/test/CodeGenHLSL/entry.hlsl b/clang/test/CodeGenHLSL/entry.hlsl
--- a/clang/test/CodeGenHLSL/entry.hlsl
+++ b/clang/test/CodeGenHLSL/entry.hlsl
@@ -3,8 +3,9 @@
 // Make sure not mangle entry.
 // CHECK:define void @foo()
 // Make sure add function attribute.
-// CHECK:"dx.shader"="compute"
-[numthreads(1,1,1)]
+// CHECK:"hlsl.numthreads"="16,8,1"
+// CHECK-SAME:"dx.shader"="compute"
+[numthreads(16,8,1)]
 void foo() {
 
 }