Fix HLSL regression with struct declaration.

It actually worked surprisingly. Fix it properly.

reference/opt/shaders-hlsl/vert/struct-composite-decl.vert

@@ -0,0 +1,44 @@
+struct VOut
+{
+    float4 a;
+    float4 b;
+    float4 c;
+    float4 d;
+};
+
+static VOut vout;
+static float4 a;
+static float4 b;
+static float4 c;
+static float4 d;
+
+struct SPIRV_Cross_Input
+{
+    float4 a : TEXCOORD0;
+    float4 b : TEXCOORD1;
+    float4 c : TEXCOORD2;
+    float4 d : TEXCOORD3;
+};
+
+struct SPIRV_Cross_Output
+{
+    VOut vout : TEXCOORD0;
+};
+
+void vert_main()
+{
+    VOut _26 = { a, b, c, d };
+    vout = _26;
+}
+
+SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
+{
+    a = stage_input.a;
+    b = stage_input.b;
+    c = stage_input.c;
+    d = stage_input.d;
+    vert_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.vout = vout;
+    return stage_output;
+}

reference/shaders-hlsl/vert/struct-composite-decl.vert

@@ -0,0 +1,50 @@
+struct VOut
+{
+    float4 a;
+    float4 b;
+    float4 c;
+    float4 d;
+};
+
+static VOut vout;
+static float4 a;
+static float4 b;
+static float4 c;
+static float4 d;
+
+struct SPIRV_Cross_Input
+{
+    float4 a : TEXCOORD0;
+    float4 b : TEXCOORD1;
+    float4 c : TEXCOORD2;
+    float4 d : TEXCOORD3;
+};
+
+struct SPIRV_Cross_Output
+{
+    VOut vout : TEXCOORD0;
+};
+
+void emit_result(VOut v)
+{
+    vout = v;
+}
+
+void vert_main()
+{
+    VOut _26 = { a, b, c, d };
+    VOut param = _26;
+    emit_result(param);
+}
+
+SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
+{
+    a = stage_input.a;
+    b = stage_input.b;
+    c = stage_input.c;
+    d = stage_input.d;
+    vert_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.vout = vout;
+    return stage_output;
+}

shaders-hlsl/vert/struct-composite-decl.vert

@@ -0,0 +1,26 @@
+#version 310 es
+
+layout(location = 0) in vec4 a;
+layout(location = 1) in vec4 b;
+layout(location = 2) in vec4 c;
+layout(location = 3) in vec4 d;
+
+struct VOut
+{
+	vec4 a;
+	vec4 b;
+	vec4 c;
+	vec4 d;
+};
+
+layout(location = 0) out VOut vout;
+
+void emit_result(VOut v)
+{
+	vout = v;
+}
+
+void main()
+{
+	emit_result(VOut(a, b, c, d));
+}

spirv_glsl.cpp

@@ -5481,12 +5481,16 @@ void CompilerGLSL::emit_instruction(const Instruction &instruction)
 			}
 		}
 
+		if (out_type.basetype == SPIRType::Struct && !backend.can_declare_struct_inline)
+			forward = false;
+
 		string constructor_op;
 		if (backend.use_initializer_list && composite)
 		{
 			// Only use this path if we are building composites.
 			// This path cannot be used for arithmetic.
-			constructor_op += type_to_glsl_constructor(get<SPIRType>(result_type));
+			if (backend.use_typed_initializer_list)
+				constructor_op += type_to_glsl_constructor(get<SPIRType>(result_type));
 			constructor_op += "{ ";
 			if (splat)
 				constructor_op += to_expression(elems[0]);

spirv_glsl.hpp

@@ -313,6 +313,8 @@ protected:
 		bool flexible_member_array_supported = true;
 		bool explicit_struct_type = false;
 		bool use_initializer_list = false;
+		bool use_typed_initializer_list = false;
+		bool can_declare_struct_inline = true;
 		bool native_row_major_matrix = true;
 		bool use_constructor_splatting = true;
 		bool boolean_mix_support = true;

spirv_hlsl.cpp

@@ -3644,6 +3644,7 @@ string CompilerHLSL::compile()
 	backend.use_constructor_splatting = false;
 	backend.boolean_mix_support = false;
 	backend.can_swizzle_scalar = true;
+	backend.can_declare_struct_inline = false;
 
 	update_active_builtins();
 	analyze_sampler_comparison_states();

spirv_msl.cpp

@@ -69,6 +69,7 @@ string CompilerMSL::compile()
 	backend.swizzle_is_function = false;
 	backend.shared_is_implied = false;
 	backend.use_initializer_list = true;
+	backend.use_typed_initializer_list = true;
 	backend.native_row_major_matrix = false;
 	backend.flexible_member_array_supported = false;
 	backend.force_temp_use_for_two_vector_shuffles = true;