diff --git a/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag b/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
index f42aeb876..29ff2dd7c 100644
--- a/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
+++ b/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
@@ -1,3 +1,5 @@
+#pragma clang diagnostic ignored "-Wmissing-prototypes"
+
 #include <metal_stdlib>
 #include <simd/simd.h>
 
@@ -8,18 +10,24 @@ struct main0_out
     float FragColor [[color(0)]];
 };
 
+static inline __attribute__((always_inline))
+void func(thread float& FragColor, thread bool& gl_HelperInvocation)
+{
+    bool _14 = gl_HelperInvocation;
+    float _17 = float(_14);
+    FragColor = _17;
+    gl_HelperInvocation = true, discard_fragment();
+    bool _18 = gl_HelperInvocation;
+    float _19 = float(_18);
+    FragColor = _19;
+}
+
 fragment main0_out main0()
 {
     main0_out out = {};
     bool gl_HelperInvocation = {};
     gl_HelperInvocation = simd_is_helper_thread();
-    bool _12 = gl_HelperInvocation;
-    float _15 = float(_12);
-    out.FragColor = _15;
-    gl_HelperInvocation = true, discard_fragment();
-    bool _16 = gl_HelperInvocation;
-    float _17 = float(_16);
-    out.FragColor = _17;
+    func(out.FragColor, gl_HelperInvocation);
     return out;
 }
 
diff --git a/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag b/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
index 9a8d9d20b..44cd4f117 100644
--- a/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
+++ b/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
@@ -3,9 +3,14 @@
 
 layout(location = 0) out float FragColor;
 
-void main()
+void func()
 {
 	FragColor = float(gl_HelperInvocation);
 	demote;
 	FragColor = float(gl_HelperInvocation);
 }
+
+void main()
+{
+	func();
+}
diff --git a/spirv_msl.cpp b/spirv_msl.cpp
index 383ce688e..38cfedb75 100644
--- a/spirv_msl.cpp
+++ b/spirv_msl.cpp
@@ -1576,8 +1576,7 @@ string CompilerMSL::compile()
 	preprocess_op_codes();
 	build_implicit_builtins();
 
-	if (needs_manual_helper_invocation_updates() &&
-	    (active_input_builtins.get(BuiltInHelperInvocation) || needs_helper_invocation))
+	if (needs_manual_helper_invocation_updates() && needs_helper_invocation)
 	{
 		string builtin_helper_invocation = builtin_to_glsl(BuiltInHelperInvocation, StorageClassInput);
 		string discard_expr = join(builtin_helper_invocation, " = true, discard_fragment()");
@@ -1721,7 +1720,7 @@ void CompilerMSL::preprocess_op_codes()
 	    (is_sample_rate() && (active_input_builtins.get(BuiltInFragCoord) ||
 	                          (need_subpass_input_ms && !msl_options.use_framebuffer_fetch_subpasses))))
 		needs_sample_id = true;
-	if (preproc.needs_helper_invocation)
+	if (preproc.needs_helper_invocation || active_input_builtins.get(BuiltInHelperInvocation))
 		needs_helper_invocation = true;
 
 	// OpKill is removed by the parser, so we need to identify those by inspecting
@@ -2058,8 +2057,7 @@ void CompilerMSL::extract_global_variables_from_function(uint32_t func_id, std::
 			}
 
 			case OpDemoteToHelperInvocation:
-				if (needs_manual_helper_invocation_updates() &&
-				    (active_input_builtins.get(BuiltInHelperInvocation) || needs_helper_invocation))
+				if (needs_manual_helper_invocation_updates() && needs_helper_invocation)
 					added_arg_ids.insert(builtin_helper_invocation_id);
 				break;
 
@@ -2112,7 +2110,7 @@ void CompilerMSL::extract_global_variables_from_function(uint32_t func_id, std::
 			}
 
 			if (needs_manual_helper_invocation_updates() && b.terminator == SPIRBlock::Kill &&
-			    (active_input_builtins.get(BuiltInHelperInvocation) || needs_helper_invocation))
+			    needs_helper_invocation)
 				added_arg_ids.insert(builtin_helper_invocation_id);
 
 			// TODO: Add all other operations which can affect memory.
@@ -13215,7 +13213,10 @@ string CompilerMSL::get_type_address_space(const SPIRType &type, uint32_t id, bo
 		addr_space = type.pointer || (argument && type.basetype == SPIRType::ControlPointArray) ? "thread" : "";
 	}
 
-	return join(decoration_flags_signal_volatile(flags) ? "volatile " : "", addr_space);
+	if (decoration_flags_signal_volatile(flags) && 0 != strcmp(addr_space, "thread"))
+		return join("volatile ", addr_space);
+	else
+		return addr_space;
 }
 
 const char *CompilerMSL::to_restrict(uint32_t id, bool space)