Hoist out variable scope analysis.

Author: HansKristian-Work

spirv_common.hpp

@@ -764,7 +764,6 @@ struct SPIRFunction : IVariant
 	bool active = false;
 	bool flush_undeclared = true;
 	bool do_combined_parameters = true;
-	bool analyzed_variable_scope = false;
 };
 
 struct SPIRAccessChain : IVariant

spirv_cpp.cpp

@@ -300,7 +300,7 @@ string CompilerCPP::compile()
 	backend.explicit_struct_type = true;
 	backend.use_initializer_list = true;
 
-	build_function_control_flow_graphs();
+	build_function_control_flow_graphs_and_analyze();
 	update_active_builtins();
 
 	uint32_t pass_count = 0;

spirv_cross.cpp

@@ -3647,20 +3647,20 @@ void Compiler::analyze_parameter_preservation(
 	}
 }
 
-Compiler::AnalyzeVariableScopeAccessHandler::AnalyzeVariableScopeAccessHandler(spirv_cross::Compiler &compiler_,
-                                                                               spirv_cross::SPIRFunction &entry_)
+Compiler::AnalyzeVariableScopeAccessHandler::AnalyzeVariableScopeAccessHandler(Compiler &compiler_,
+                                                                               SPIRFunction &entry_)
     : compiler(compiler_)
     , entry(entry_)
 {
 }
 
-bool Compiler::AnalyzeVariableScopeAccessHandler::follow_function_call(const spirv_cross::SPIRFunction &)
+bool Compiler::AnalyzeVariableScopeAccessHandler::follow_function_call(const SPIRFunction &)
 {
 	// Only analyze within this function.
 	return false;
 }
 
-void Compiler::AnalyzeVariableScopeAccessHandler::set_current_block(const spirv_cross::SPIRBlock &block)
+void Compiler::AnalyzeVariableScopeAccessHandler::set_current_block(const SPIRBlock &block)
 {
 	current_block = █
 
@@ -3848,7 +3848,6 @@ bool Compiler::AnalyzeVariableScopeAccessHandler::handle(spv::Op op, const uint3
 		if (length < 3)
 			return false;
 
-		bool is_pure = compiler.function_is_pure(compiler.get<SPIRFunction>(args[2]));
 		length -= 3;
 		args += 3;
 
@@ -3858,8 +3857,8 @@ bool Compiler::AnalyzeVariableScopeAccessHandler::handle(spv::Op op, const uint3
 			if (var)
 			{
 				accessed_variables_to_block[var->self].insert(current_block->self);
-				if (!is_pure) // Assume we can get partial writes to this variable.
-					partial_write_variables_to_block[var->self].insert(current_block->self);
+				// Assume we can get partial writes to this variable.
+				partial_write_variables_to_block[var->self].insert(current_block->self);
 			}
 
 			// Cannot easily prove if argument we pass to a function is completely written.
@@ -4414,12 +4413,47 @@ bool Compiler::CombinedImageSamplerDrefHandler::handle(spv::Op opcode, const uin
 	return true;
 }
 
-void Compiler::build_function_control_flow_graphs()
+void Compiler::build_function_control_flow_graphs_and_analyze()
 {
 	CFGBuilder handler(*this);
 	handler.function_cfgs[entry_point].reset(new CFG(*this, get<SPIRFunction>(entry_point)));
 	traverse_all_reachable_opcodes(get<SPIRFunction>(entry_point), handler);
 	function_cfgs = move(handler.function_cfgs);
+
+	for (auto &f : function_cfgs)
+	{
+		auto &func = get<SPIRFunction>(f.first);
+		analyze_variable_scope(func);
+
+		// Check if we can actually use the loop variables we found in analyze_variable_scope.
+		// To use multiple initializers, we need the same type and qualifiers.
+		for (auto block : func.blocks)
+		{
+			auto &b = get<SPIRBlock>(block);
+			if (b.loop_variables.size() < 2)
+				continue;
+
+			auto &flags = get_decoration_bitset(b.loop_variables.front());
+			uint32_t type = get<SPIRVariable>(b.loop_variables.front()).basetype;
+			bool invalid_initializers = false;
+			for (auto loop_variable : b.loop_variables)
+			{
+				if (flags != get_decoration_bitset(loop_variable) ||
+				    type != get<SPIRVariable>(b.loop_variables.front()).basetype)
+				{
+					invalid_initializers = true;
+					break;
+				}
+			}
+
+			if (invalid_initializers)
+			{
+				for (auto loop_variable : b.loop_variables)
+					get<SPIRVariable>(loop_variable).loop_variable = false;
+				b.loop_variables.clear();
+			}
+		}
+	}
 }
 
 Compiler::CFGBuilder::CFGBuilder(spirv_cross::Compiler &compiler_)

spirv_cross.hpp

@@ -869,7 +869,7 @@ class Compiler
 		bool need_subpass_input = false;
 	};
 
-	void build_function_control_flow_graphs();
+	void build_function_control_flow_graphs_and_analyze();
 	std::unordered_map<uint32_t, std::unique_ptr<CFG>> function_cfgs;
 	struct CFGBuilder : OpcodeHandler
 	{

spirv_glsl.cpp

@@ -418,7 +418,7 @@ string CompilerGLSL::compile()
 	backend.supports_extensions = true;
 
 	// Scan the SPIR-V to find trivial uses of extensions.
-	build_function_control_flow_graphs();
+	build_function_control_flow_graphs_and_analyze();
 	find_static_extensions();
 	fixup_image_load_store_access();
 	update_active_builtins();
@@ -8909,41 +8909,6 @@ void CompilerGLSL::emit_function(SPIRFunction &func, const Bitset &return_flags)
 	current_function = &func;
 	auto &entry_block = get<SPIRBlock>(func.entry_block);
 
-	if (!func.analyzed_variable_scope)
-	{
-		analyze_variable_scope(func);
-
-		// Check if we can actually use the loop variables we found in analyze_variable_scope.
-		// To use multiple initializers, we need the same type and qualifiers.
-		for (auto block : func.blocks)
-		{
-			auto &b = get<SPIRBlock>(block);
-			if (b.loop_variables.size() < 2)
-				continue;
-
-			auto &flags = get_decoration_bitset(b.loop_variables.front());
-			uint32_t type = get<SPIRVariable>(b.loop_variables.front()).basetype;
-			bool invalid_initializers = false;
-			for (auto loop_variable : b.loop_variables)
-			{
-				if (flags != get_decoration_bitset(loop_variable) ||
-				    type != get<SPIRVariable>(b.loop_variables.front()).basetype)
-				{
-					invalid_initializers = true;
-					break;
-				}
-			}
-
-			if (invalid_initializers)
-			{
-				for (auto loop_variable : b.loop_variables)
-					get<SPIRVariable>(loop_variable).loop_variable = false;
-				b.loop_variables.clear();
-			}
-		}
-		func.analyzed_variable_scope = true;
-	}
-
 	for (auto &v : func.local_variables)
 	{
 		auto &var = get<SPIRVariable>(v);

spirv_hlsl.cpp

@@ -4572,7 +4572,7 @@ string CompilerHLSL::compile()
 	backend.can_declare_arrays_inline = false;
 	backend.can_return_array = false;
 
-	build_function_control_flow_graphs();
+	build_function_control_flow_graphs_and_analyze();
 	update_active_builtins();
 	analyze_image_and_sampler_usage();
 

spirv_msl.cpp

@@ -280,7 +280,7 @@ string CompilerMSL::compile()
 
 	struct_member_padding.clear();
 
-	build_function_control_flow_graphs();
+	build_function_control_flow_graphs_and_analyze();
 	update_active_builtins();
 	analyze_image_and_sampler_usage();
 	build_implicit_builtins();