diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -6810,5 +6810,5 @@
 def hlsl_entrypoint : Option<["--", "/", "-"], "E", KIND_JOINED_OR_SEPARATE>,
                       Group<dxc_Group>,
                       Flags<[DXCOption, CC1Option, NoXarchOption]>,
-                      MarshallingInfoString<TargetOpts<"HLSLEntry">>,
+                      MarshallingInfoString<TargetOpts<"HLSLEntry">, "\"main\"">,
                       HelpText<"Entry point name">;
diff --git a/clang/test/CodeGenHLSL/entry_default.hlsl b/clang/test/CodeGenHLSL/entry_default.hlsl
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGenHLSL/entry_default.hlsl
@@ -0,0 +1,29 @@
+// RUN: %clang --driver-mode=dxc -Tcs_6_1 -fcgl -Fo - %s | FileCheck %s
+// RUN: %clang --driver-mode=dxc -Efoo -Tcs_6_1 -fcgl -Fo - %s | FileCheck %s --check-prefix=NOTMAIN
+
+// Make sure main is default entry.
+// Make sure not mangle entry.
+// CHECK: define void @main() [[MAIN_ATTR:#[0-9]]]
+// CHECK: define void @_Z3foov() [[FOO_ATTR:#[0-9]]]
+// Make sure only main has dx.shader attribute.
+// CHECK: [[MAIN_ATTR]]
+// CHECK-SAME: "dx.shader"="compute"
+// CHECK-SAME: }
+// CHECK: [[FOO_ATTR]]
+// CHECK-NOT: "dx.shader"="compute"
+// CHECK-SAME: }
+[numthreads(1, 1, 1)] void main() {
+
+}
+
+// NOTMAIN: define void @main() [[MAIN_ATTR:#[0-9]]]
+// NOTMAIN: define void @foo() [[FOO_ATTR:#[0-9]]]
+// Make sure only foo has dx.shader attribute.
+// NOTMAIN: [[MAIN_ATTR]]
+// NOTMAIN-NOT:"dx.shader"="compute"
+// NOTMAIN-SAME:}
+// NOTMAIN: [[FOO_ATTR]]
+// NOTMAIN-SAME: "dx.shader"="compute"
+[numthreads(1, 1, 1)] void foo() {
+
+}