Add option to disable use of 420pack extension.

main.cpp

@@ -472,6 +472,7 @@ struct CLIArguments
 	bool hlsl_compat = false;
 	bool vulkan_semantics = false;
 	bool flatten_multidimensional_arrays = false;
+	bool use_420pack_extension = true;
 	bool remove_unused = false;
 	bool cfg_analysis = true;
 };
@@ -487,7 +488,7 @@ static void print_help()
 	                "[--separate-shader-objects]"
 	                "[--pls-in format input-name] [--pls-out format output-name] [--remap source_name target_name "
 	                "components] [--extension ext] [--entry name] [--remove-unused-variables] "
-	                "[--flatten-multidimensional-arrays] "
+	                "[--flatten-multidimensional-arrays] [--no-420pack-extension] "
 	                "[--remap-variable-type <variable_name> <new_variable_type>] "
 	                "[--rename-interface-variable <in|out> <location> <new_variable_name>] "
 	                "\n");
@@ -630,6 +631,7 @@ int main(int argc, char *argv[])
 	cbs.add("--hlsl-enable-compat", [&args](CLIParser &) { args.hlsl_compat = true; });
 	cbs.add("--vulkan-semantics", [&args](CLIParser &) { args.vulkan_semantics = true; });
 	cbs.add("--flatten-multidimensional-arrays", [&args](CLIParser &) { args.flatten_multidimensional_arrays = true; });
+	cbs.add("--no-420pack-extension", [&args](CLIParser &) { args.use_420pack_extension = false; });
 	cbs.add("--extension", [&args](CLIParser &parser) { args.extensions.push_back(parser.next_string()); });
 	cbs.add("--entry", [&args](CLIParser &parser) { args.entry = parser.next_string(); });
 	cbs.add("--separate-shader-objects", [&args](CLIParser &) { args.sso = true; });
@@ -751,6 +753,7 @@ int main(int argc, char *argv[])
 	opts.force_temporary = args.force_temporary;
 	opts.separate_shader_objects = args.sso;
 	opts.flatten_multidimensional_arrays = args.flatten_multidimensional_arrays;
+	opts.enable_420pack_extension = args.use_420pack_extension;
 	opts.vulkan_semantics = args.vulkan_semantics;
 	opts.vertex.fixup_clipspace = args.fixup;
 	opts.vertex.flip_vert_y = args.yflip;

spirv_glsl.cpp

@@ -349,7 +349,7 @@ void CompilerGLSL::emit_header()
 	statement("#version ", options.version, options.es && options.version > 100 ? " es" : "");
 
 	// Needed for binding = # on UBOs, etc.
-	if (!options.es && options.version < 420)
+	if (!options.es && options.version < 420 && options.enable_420pack_extension)
 	{
 		statement("#ifdef GL_ARB_shading_language_420pack");
 		statement("#extension GL_ARB_shading_language_420pack : require");
@@ -999,8 +999,15 @@ string CompilerGLSL::layout_for_variable(const SPIRVariable &var)
 			attr.push_back(join("set = ", dec.set));
 	}
 
-	if (flags & (1ull << DecorationBinding))
+	bool can_use_binding;
+	if (options.es)
+		can_use_binding = options.version >= 310;
+	else
+		can_use_binding = options.enable_420pack_extension || (options.version >= 420);
+
+	if (can_use_binding && (flags & (1ull << DecorationBinding)))
 		attr.push_back(join("binding = ", dec.binding));
+
 	if (flags & (1ull << DecorationOffset))
 		attr.push_back(join("offset = ", dec.offset));
 

spirv_glsl.hpp

@@ -56,8 +56,13 @@ class CompilerGLSL : public Compiler
 public:
 	struct Options
 	{
+		// The shading language version. Corresponds to #version $VALUE.
 		uint32_t version = 450;
+
+		// Emit the OpenGL ES shading language instead of desktop OpenGL.
 		bool es = false;
+
+		// Debug option to always emit temporary variables for all expressions.
 		bool force_temporary = false;
 
 		// If true, variables will be moved to their appropriate scope through CFG analysis.
@@ -79,6 +84,12 @@ public:
 		// Only the generated code, including declarations of interface variables are changed to be single array dimension.
 		bool flatten_multidimensional_arrays = false;
 
+		// For older desktop GLSL targets than version 420, the
+		// GL_ARB_shading_language_420pack extensions is used to be able to support
+		// layout(binding) on UBOs and samplers.
+		// If disabled on older targets, binding decorations will be stripped.
+		bool enable_420pack_extension = true;
+
 		enum Precision
 		{
 			DontCare,