Add compatibility option for PointSize in HLSL.

If we opt-in to it, PointSize can be ignored to avoid more annoying
workarounds.

main.cpp

@@ -435,6 +435,7 @@ struct CLIArguments
 	bool msl = false;
 	bool msl_pack_ubos = true;
 	bool hlsl = false;
+	bool hlsl_compat = false;
 	bool vulkan_semantics = false;
 	bool remove_unused = false;
 	bool cfg_analysis = true;
@@ -447,7 +448,7 @@ static void print_help()
 	                "[--vulkan-semantics] [--flatten-ubo] [--fixup-clipspace] [--iterations iter] "
 	                "[--cpp] [--cpp-interface-name <name>] "
 	                "[--msl] [--msl-no-pack-ubos] "
-	                "[--hlsl] [--shader-model] "
+	                "[--hlsl] [--shader-model] [--hlsl-enable-compat] "
 	                "[--pls-in format input-name] [--pls-out format output-name] [--remap source_name target_name "
 	                "components] [--extension ext] [--entry name] [--remove-unused-variables] "
 	                "[--remap-variable-type <variable_name> <new_variable_type>]\n");
@@ -571,6 +572,7 @@ int main(int argc, char *argv[])
 	cbs.add("--msl", [&args](CLIParser &) { args.msl = true; });
 	cbs.add("--msl-no-pack-ubos", [&args](CLIParser &) { args.msl_pack_ubos = false; });
 	cbs.add("--hlsl", [&args](CLIParser &) { args.hlsl = true; });
+	cbs.add("--hlsl-enable-compat", [&args](CLIParser &) { args.hlsl_compat = true; });
 	cbs.add("--vulkan-semantics", [&args](CLIParser &) { args.vulkan_semantics = true; });
 	cbs.add("--extension", [&args](CLIParser &parser) { args.extensions.push_back(parser.next_string()); });
 	cbs.add("--entry", [&args](CLIParser &parser) { args.entry = parser.next_string(); });
@@ -698,6 +700,12 @@ int main(int argc, char *argv[])
 
 			hlsl_opts.shader_model = args.shader_model;
 		}
+
+		if (args.hlsl_compat)
+		{
+			// Enable all compat options.
+			hlsl_opts.point_size_compat = true;
+		}
 		hlsl->set_options(hlsl_opts);
 	}
 

reference/shaders-hlsl/vert/point-size-compat.vert

@@ -0,0 +1,20 @@
+static float4 gl_Position;
+static float gl_PointSize;
+struct SPIRV_Cross_Output
+{
+    float4 gl_Position : SV_Position;
+};
+
+void vert_main()
+{
+    gl_Position = float4(1.0f, 1.0f, 1.0f, 1.0f);
+    gl_PointSize = 10.0f;
+}
+
+SPIRV_Cross_Output main()
+{
+    vert_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.gl_Position = gl_Position;
+    return stage_output;
+}

shaders-hlsl/vert/point-size-compat.vert

@@ -0,0 +1,8 @@
+#version 310 es
+
+void main()
+{
+	gl_Position = vec4(1.0);
+	gl_PointSize = 10.0;
+}
+

spirv_hlsl.cpp

@@ -270,6 +270,15 @@ void CompilerHLSL::emit_builtin_outputs_in_struct()
 			semantic = legacy ? "DEPTH" : "SV_Depth";
 			break;
 
+		case BuiltInPointSize:
+			// If point_size_compat is enabled, just ignore PointSize.
+			// PointSize does not exist in HLSL, but some code bases might want to be able to use these shaders,
+			// even if it means working around the missing feature.
+			if (options.point_size_compat)
+				break;
+			else
+				SPIRV_CROSS_THROW("Unsupported builtin in HLSL.");
+
 		default:
 			SPIRV_CROSS_THROW("Unsupported builtin in HLSL.");
 			break;
@@ -499,6 +508,16 @@ void CompilerHLSL::emit_builtin_variables()
 			type = "int";
 			break;
 
+		case BuiltInPointSize:
+			if (options.point_size_compat)
+			{
+				// Just emit the global variable, it will be ignored.
+				type = "float";
+				break;
+			}
+			else
+				SPIRV_CROSS_THROW(join("Unsupported builtin in HLSL: ", unsigned(builtin)));
+
 		default:
 			SPIRV_CROSS_THROW(join("Unsupported builtin in HLSL: ", unsigned(builtin)));
 			break;
@@ -1035,6 +1054,10 @@ void CompilerHLSL::emit_hlsl_entry_point()
 			if (!(active_output_builtins & (1ull << i)))
 				continue;
 
+			// PointSize doesn't exist in HLSL.
+			if (i == BuiltInPointSize)
+				continue;
+
 			auto builtin = builtin_to_glsl(static_cast<BuiltIn>(i));
 			statement("stage_output.", builtin, " = ", builtin, ";");
 		}

spirv_hlsl.hpp

@@ -31,6 +31,9 @@ public:
 		uint32_t shader_model = 30; // TODO: map ps_4_0_level_9_0,... somehow
 		bool fixup_clipspace = false;
 		bool flip_vert_y = false;
+
+		// Allows the PointSize builtin, and ignores it, as PointSize is not supported in HLSL.
+		bool point_size_compat = true;
 	};
 
 	CompilerHLSL(std::vector<uint32_t> spirv_)

test_shaders.py

@@ -107,7 +107,7 @@ def cross_compile_hlsl(shader):
     os.close(hlsl_f)
     subprocess.check_call(['glslangValidator', '-V', '-o', spirv_path, shader])
     spirv_cross_path = './spirv-cross'
-    subprocess.check_call([spirv_cross_path, '--entry', 'main', '--output', hlsl_path, spirv_path, '--hlsl', '--shader-model', '50'])
+    subprocess.check_call([spirv_cross_path, '--entry', 'main', '--output', hlsl_path, spirv_path, '--hlsl-enable-compat', '--hlsl', '--shader-model', '50'])
     subprocess.check_call(['spirv-val', spirv_path])
 
     validate_shader_hlsl(hlsl_path)