Add optimizing AT_LIGHT_PASS builtin to canvas shaders

This one allows for complex shaders paired with a simple lighting shader to skip code that would otherwise be pointlessly (and wastefully) run during the light pass.
You can use `if (AT_LIGHT_PASS) , negated or not, and that will be converted to a preprocessed #if when the shader is compiled.
Depending on your game (number of items and lights), this can be a *significant* performance gain, or at least avoids relying on the driver's optimizing abilities.

drivers/gles2/shader_compiler_gles2.cpp

@@ -502,16 +502,31 @@ String ShaderCompilerGLES2::dump_node_code(SL::Node *p_node, int p_level, bool p
 			SL::ControlFlowNode *cfnode = (SL::ControlFlowNode *)p_node;
 			if (cfnode->flow_op == SL::FLOW_OP_IF) {
 
-				code += "if (" + dump_node_code(cfnode->statements[0], p_level) + ") {" ENDL;
+				// Help lazy drivers
-				code += dump_node_code(cfnode->statements[1], p_level + 1);
+				if (!_is_condition_preprocessable(cfnode->statements[0])) {
-				if (cfnode->statements.size() == 3) {
 
-					code += "} else {" ENDL;
+					code += "if (" + dump_node_code(cfnode->statements[0], p_level) + ") {" ENDL;
-					code += dump_node_code(cfnode->statements[2], p_level + 1);
+					code += dump_node_code(cfnode->statements[1], p_level + 1);
+					if (cfnode->statements.size() == 3) {
+
+						code += "} else {" ENDL;
+						code += dump_node_code(cfnode->statements[2], p_level + 1);
+					}
+
+					code += "}" ENDL;
+				} else {
+
+					code += "#if (" + dump_node_code(cfnode->statements[0], p_level) + ")" ENDL;
+					code += dump_node_code(cfnode->statements[1], p_level);
+					if (cfnode->statements.size() == 3) {
+
+						code += "#else" ENDL;
+						code += dump_node_code(cfnode->statements[2], p_level);
+					}
+
+					code += "#endif" ENDL;
 				}
 
-				code += "}" ENDL;
-
 			} else if (cfnode->flow_op == SL::FLOW_OP_RETURN) {
 
 				if (cfnode->statements.size()) {
@@ -649,6 +664,33 @@ String ShaderCompilerGLES2::replace_string(const StringName &p_string) {
 	return "_" + p_string.operator String();
 }
 
+bool ShaderCompilerGLES2::_is_condition_preprocessable(ShaderLanguage::Node *p_condition) const {
+
+	// Check if this is a "(!)variable" expression
+
+	SL::Node *maybe_variable;
+	if (p_condition->type == SL::Node::TYPE_OPERATOR) {
+		SL::OperatorNode *op = (SL::OperatorNode *)p_condition;
+		if (op->op != SL::OP_NOT)
+			return false;
+		maybe_variable = op->arguments[0];
+	} else {
+		maybe_variable = p_condition;
+	}
+
+	if (maybe_variable->type != SL::Node::TYPE_VARIABLE)
+		return false;
+
+	SL::VariableNode *variable = (SL::VariableNode *)maybe_variable;
+	// Hardcoding since it's currently the only;
+	// if more were added, they would be better characterized
+	// in the various ShaderLanguage::BuiltinsDef
+	if (variable->name != String("AT_LIGHT_PASS"))
+		return false;
+
+	return true;
+}
+
 Error ShaderCompilerGLES2::compile(const String &p_code, ShaderLanguage::ShaderType p_type, String &r_code_line, String &r_globals_line, Flags &r_flags, Map<StringName, ShaderLanguage::Uniform> *r_uniforms) {
 
 	uses_texscreen = false;
@@ -873,6 +915,7 @@ ShaderCompilerGLES2::ShaderCompilerGLES2() {
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_VERTEX]["PROJECTION_MATRIX"] = "projection_matrix";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_VERTEX]["EXTRA_MATRIX"] = "extra_matrix";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_VERTEX]["TIME"] = "time";
+	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_VERTEX]["AT_LIGHT_PASS"] = "at_light_pass";
 
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["POSITION"] = "(gl_FragCoord.xy)";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["NORMAL"] = "normal";
@@ -888,6 +931,7 @@ ShaderCompilerGLES2::ShaderCompilerGLES2() {
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["SCREEN_UV"] = "screen_uv";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["POINT_COORD"] = "gl_PointCoord";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["TIME"] = "time";
+	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_FRAGMENT]["AT_LIGHT_PASS"] = "at_light_pass";
 
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_LIGHT]["POSITION"] = "(gl_FragCoord.xy)";
 	mode_replace_table[ShaderLanguage::SHADER_CANVAS_ITEM_LIGHT]["NORMAL"] = "normal";

drivers/gles2/shader_compiler_gles2.h

@@ -44,6 +44,8 @@ private:
 	Error compile_node(ShaderLanguage::ProgramNode *p_program);
 	static Error create_glsl_120_code(void *p_str, ShaderLanguage::ProgramNode *p_program);
 
+	bool _is_condition_preprocessable(ShaderLanguage::Node *p_condition) const;
+
 	bool uses_light;
 	bool uses_texscreen;
 	bool uses_texpos;

drivers/gles2/shaders/canvas.glsl

@@ -39,6 +39,9 @@ uniform vec2 normal_flip;
 varying highp vec2 pos;
 #endif
 
+#define at_light_pass 1
+#else
+#define at_light_pass 0
 #endif
 
 #if defined(ENABLE_VAR1_INTERP)
@@ -176,6 +179,9 @@ uniform float shadow_esm_multiplier;
 
 #endif
 
+#define at_light_pass 1
+#else
+#define at_light_pass 0
 #endif
 
 #if defined(USE_TEXPIXEL_SIZE)

servers/visual/shader_language.cpp

@@ -1124,6 +1124,7 @@ const ShaderLanguage::BuiltinsDef ShaderLanguage::ci_vertex_builtins_defs[] = {
 	{ "PROJECTION_MATRIX", TYPE_MAT4 },
 	{ "EXTRA_MATRIX", TYPE_MAT4 },
 	{ "TIME", TYPE_FLOAT },
+	{ "AT_LIGHT_PASS", TYPE_BOOL },
 	{ NULL, TYPE_VOID },
 };
 const ShaderLanguage::BuiltinsDef ShaderLanguage::ci_fragment_builtins_defs[] = {
@@ -1145,6 +1146,7 @@ const ShaderLanguage::BuiltinsDef ShaderLanguage::ci_fragment_builtins_defs[] =
 	//	{ "SCREEN_POS", TYPE_VEC2},
 	//	{ "SCREEN_TEXEL_SIZE", TYPE_VEC2},
 	{ "TIME", TYPE_FLOAT },
+	{ "AT_LIGHT_PASS", TYPE_BOOL },
 	{ NULL, TYPE_VOID }
 
 };