GLSL: Add option to disable buffer blocks regardless of version

CMakeLists.txt

@@ -267,7 +267,7 @@ endif()
 
 if (SPIRV_CROSS_SHARED)
 	set(spirv-cross-abi-major 0)
-	set(spirv-cross-abi-minor 6)
+	set(spirv-cross-abi-minor 7)
 	set(spirv-cross-abi-patch 0)
 	set(SPIRV_CROSS_VERSION ${spirv-cross-abi-major}.${spirv-cross-abi-minor}.${spirv-cross-abi-patch})
 	set(SPIRV_CROSS_INSTALL_LIB_DIR ${CMAKE_INSTALL_PREFIX}/lib)

main.cpp

@@ -511,6 +511,7 @@ struct CLIArguments
 	bool msl_argument_buffers = false;
 	bool msl_texture_buffer_native = false;
 	bool glsl_emit_push_constant_as_ubo = false;
+	bool glsl_emit_ubo_as_plain_uniforms = false;
 	SmallVector<uint32_t> msl_discrete_descriptor_sets;
 	SmallVector<PLSArg> pls_in;
 	SmallVector<PLSArg> pls_out;
@@ -563,6 +564,7 @@ static void print_help()
 	                "\t[--cpp]\n"
 	                "\t[--cpp-interface-name <name>]\n"
 	                "\t[--glsl-emit-push-constant-as-ubo]\n"
+	                "\t[--glsl-emit-ubo-as-plain-uniforms]\n"
 	                "\t[--msl]\n"
 	                "\t[--msl-version <MMmmpp>]\n"
 	                "\t[--msl-capture-output]\n"
@@ -854,6 +856,7 @@ static string compile_iteration(const CLIArguments &args, std::vector<uint32_t>
 	opts.vertex.flip_vert_y = args.yflip;
 	opts.vertex.support_nonzero_base_instance = args.support_nonzero_baseinstance;
 	opts.emit_push_constant_as_uniform_buffer = args.glsl_emit_push_constant_as_ubo;
+	opts.emit_uniform_buffer_as_plain_uniforms = args.glsl_emit_ubo_as_plain_uniforms;
 	compiler->set_common_options(opts);
 
 	// Set HLSL specific options.
@@ -1025,6 +1028,7 @@ static int main_inner(int argc, char *argv[])
 	cbs.add("--cpp-interface-name", [&args](CLIParser &parser) { args.cpp_interface_name = parser.next_string(); });
 	cbs.add("--metal", [&args](CLIParser &) { args.msl = true; }); // Legacy compatibility
 	cbs.add("--glsl-emit-push-constant-as-ubo", [&args](CLIParser &) { args.glsl_emit_push_constant_as_ubo = true; });
+	cbs.add("--glsl-emit-ubo-as-plain-uniforms", [&args](CLIParser &) { args.glsl_emit_ubo_as_plain_uniforms = true; });
 	cbs.add("--msl", [&args](CLIParser &) { args.msl = true; });
 	cbs.add("--hlsl", [&args](CLIParser &) { args.hlsl = true; });
 	cbs.add("--hlsl-enable-compat", [&args](CLIParser &) { args.hlsl_compat = true; });

spirv_cross_c.cpp

@@ -442,6 +442,9 @@ spvc_result spvc_compiler_options_set_uint(spvc_compiler_options options, spvc_c
 	case SPVC_COMPILER_OPTION_GLSL_EMIT_PUSH_CONSTANT_AS_UNIFORM_BUFFER:
 		options->glsl.emit_push_constant_as_uniform_buffer = value != 0;
 		break;
+	case SPVC_COMPILER_OPTION_GLSL_EMIT_UNIFORM_BUFFER_AS_PLAIN_UNIFORMS:
+		options->glsl.emit_uniform_buffer_as_plain_uniforms = value != 0;
+		break;
 #endif
 
 #if SPIRV_CROSS_C_API_HLSL

spirv_cross_c.h

@@ -33,7 +33,7 @@ extern "C" {
 /* Bumped if ABI or API breaks backwards compatibility. */
 #define SPVC_C_API_VERSION_MAJOR 0
 /* Bumped if APIs or enumerations are added in a backwards compatible way. */
-#define SPVC_C_API_VERSION_MINOR 6
+#define SPVC_C_API_VERSION_MINOR 7
 /* Bumped if internal implementation details change. */
 #define SPVC_C_API_VERSION_PATCH 0
 
@@ -426,6 +426,8 @@ typedef enum spvc_compiler_option
 
 	SPVC_COMPILER_OPTION_MSL_TEXTURE_BUFFER_NATIVE = 34 | SPVC_COMPILER_OPTION_MSL_BIT,
 
+	SPVC_COMPILER_OPTION_GLSL_EMIT_UNIFORM_BUFFER_AS_PLAIN_UNIFORMS = 35 | SPVC_COMPILER_OPTION_GLSL_BIT,
+
 	SPVC_COMPILER_OPTION_INT_MAX = 0x7fffffff
 } spvc_compiler_option;
 

spirv_glsl.cpp

@@ -1459,9 +1459,19 @@ string CompilerGLSL::layout_for_variable(const SPIRVariable &var)
 			attr.push_back(join("set = ", dec.set));
 	}
 
+	bool push_constant_block = options.vulkan_semantics && var.storage == StorageClassPushConstant;
+	bool ssbo_block = var.storage == StorageClassStorageBuffer ||
+	                  (var.storage == StorageClassUniform && typeflags.get(DecorationBufferBlock));
+	bool emulated_ubo = var.storage == StorageClassPushConstant && options.emit_push_constant_as_uniform_buffer;
+	bool ubo_block = var.storage == StorageClassUniform && typeflags.get(DecorationBlock);
+
 	// GL 3.0/GLSL 1.30 is not considered legacy, but it doesn't have UBOs ...
 	bool can_use_buffer_blocks = (options.es && options.version >= 300) || (!options.es && options.version >= 140);
 
+        // pretend no UBOs when options say so
+	if (ubo_block && options.emit_uniform_buffer_as_plain_uniforms)
+		can_use_buffer_blocks = false;
+
 	bool can_use_binding;
 	if (options.es)
 		can_use_binding = options.version >= 310;
@@ -1478,12 +1488,6 @@ string CompilerGLSL::layout_for_variable(const SPIRVariable &var)
 	if (flags.get(DecorationOffset))
 		attr.push_back(join("offset = ", dec.offset));
 
-	bool push_constant_block = options.vulkan_semantics && var.storage == StorageClassPushConstant;
-	bool ssbo_block = var.storage == StorageClassStorageBuffer ||
-	                  (var.storage == StorageClassUniform && typeflags.get(DecorationBufferBlock));
-	bool emulated_ubo = var.storage == StorageClassPushConstant && options.emit_push_constant_as_uniform_buffer;
-	bool ubo_block = var.storage == StorageClassUniform && typeflags.get(DecorationBlock);
-
 	// Instead of adding explicit offsets for every element here, just assume we're using std140 or std430.
 	// If SPIR-V does not comply with either layout, we cannot really work around it.
 	if (can_use_buffer_blocks && (ubo_block || emulated_ubo))
@@ -1611,9 +1615,13 @@ void CompilerGLSL::emit_push_constant_block_glsl(const SPIRVariable &var)
 
 void CompilerGLSL::emit_buffer_block(const SPIRVariable &var)
 {
+	auto &type = get<SPIRType>(var.basetype);
+	bool ubo_block = var.storage == StorageClassUniform &&
+	            ir.meta[type.self].decoration.decoration_flags.get(DecorationBlock);
+
 	if (flattened_buffer_blocks.count(var.self))
 		emit_buffer_block_flattened(var);
-	else if (is_legacy() || (!options.es && options.version == 130))
+	else if (is_legacy() || (!options.es && options.version == 130) || (ubo_block && options.emit_uniform_buffer_as_plain_uniforms))
 		emit_buffer_block_legacy(var);
 	else
 		emit_buffer_block_native(var);

spirv_glsl.hpp

@@ -99,6 +99,10 @@ public:
 		// In non-Vulkan GLSL, emit push constant blocks as UBOs rather than plain uniforms.
 		bool emit_push_constant_as_uniform_buffer = false;
 
+		// Always emit uniform blocks as plain uniforms, regardless of the GLSL version, even when UBOs are supported.
+		// Does not apply to shader storage or push constant blocks.
+		bool emit_uniform_buffer_as_plain_uniforms = false;
+
 		enum Precision
 		{
 			DontCare,