X-Git-Url: http://git.tdb.fi/?a=blobdiff_plain;ds=sidebyside;f=source%2Fglsl%2Foptimize.cpp;h=a7786295f6e8c117e94f345c66ba615873d79e96;hb=b7702a7162bba41718dd56b875e5d911f5ab3edb;hp=3356a3c9aa6282c59dc1e0fa707f8224c44fa4f8;hpb=858d937501ef794c29fd62921e74b90580ffc965;p=libs%2Fgl.git

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index 3356a3c9..a7786295 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -23,6 +23,8 @@ void InlineableFunctionLocator::visit(FunctionCall &call)
 	{
 		unsigned &count = refcounts[def];
 		++count;
+		/* Don't inline functions which are called more than once or are called
+		recursively. */
 		if(count>1 || def==current_function)
 			inlineable.erase(def);
 	}
@@ -163,6 +165,8 @@ void InlineContentInjector::visit(Return &ret)
 
 	if(ret.expression)
 	{
+		/* Create a new variable to hold the return value of the inlined
+		function. */
 		r_result_name = create_unused_name("return", true);
 		RefPtr<VariableDeclaration> var = new VariableDeclaration;
 		var->source = ret.source;
@@ -243,7 +247,7 @@ void FunctionInliner::visit(FunctionCall &call)
 	{
 		string result_name = InlineContentInjector().apply(*stage, *current_function, *current_block, insert_point, *def);
 
-		// This will later get removed by UnusedVariableRemover
+		// This will later get removed by UnusedVariableRemover.
 		if(result_name.empty())
 			result_name = "msp_unused_from_inline";
 
@@ -419,8 +423,12 @@ bool UnusedVariableRemover::apply(Stage &stage)
 	BlockVariableMap &global_variables = variables.back();
 	for(BlockVariableMap::iterator i=global_variables.begin(); i!=global_variables.end(); ++i)
 	{
+		/* Don't remove output variables which are used by the next stage or the
+		graphics API. */
 		if(i->first->interface=="out" && (stage.type==Stage::FRAGMENT || i->first->linked_declaration || !i->first->name.compare(0, 3, "gl_")))
 			continue;
+
+		// Mark other unreferenced global variables as unused.
 		if(!i->second.referenced)
 		{
 			unused_nodes.insert(i->first);
@@ -443,6 +451,7 @@ void UnusedVariableRemover::visit(VariableReference &var)
 	if(var.declaration && !assignment_target)
 	{
 		VariableInfo &var_info = variables.back()[var.declaration];
+		// Previous assignments are used by this reference.
 		clear_assignments(var_info, false);
 		var_info.referenced = true;
 	}
@@ -495,12 +504,16 @@ void UnusedVariableRemover::visit(Assignment &assign)
 void UnusedVariableRemover::visit(FunctionCall &call)
 {
 	TraversingVisitor::visit(call);
+	/* Treat function calls as having side effects so expression statements
+	consisting of nothing but a function call won't be optimized away. */
 	r_side_effects = true;
 }
 
 void UnusedVariableRemover::record_assignment(VariableDeclaration &var, Node &node, bool chained)
 {
 	VariableInfo &var_info = variables.back()[&var];
+	/* An assignment which completely replaces the value of the variable causes
+	any previous unreferenced assignments to be unused. */
 	if(!chained)
 		clear_assignments(var_info, true);
 	var_info.assignments.push_back(&node);
@@ -566,11 +579,18 @@ void UnusedVariableRemover::visit(FunctionDeclaration &func)
 	func.body.visit(*this);
 
 	BlockVariableMap &block_variables = variables.back();
+
+	/* Mark global variables as conditionally assigned so assignments in other
+	functions won't be removed. */
 	for(BlockVariableMap::iterator i=block_variables.begin(); i!=block_variables.end(); ++i)
 		if(!i->second.local)
 			i->second.conditionally_assigned = true;
+
+	/* Always treat function parameters as referenced.  Removing unused
+	parameters is not currently supported. */
 	for(NodeArray<VariableDeclaration>::iterator i=func.parameters.begin(); i!=func.parameters.end(); ++i)
 		block_variables[i->get()].referenced = true;
+
 	merge_down_variables();
 }
 
@@ -584,6 +604,8 @@ void UnusedVariableRemover::merge_down_variables()
 		{
 			if(!i->second.referenced)
 				unused_nodes.insert(i->first);
+			/* Any unreferenced assignments when a variable runs out of scope
+			become unused. */
 			clear_assignments(i->second, true);
 			continue;
 		}
@@ -593,6 +615,7 @@ void UnusedVariableRemover::merge_down_variables()
 			parent_variables.insert(*i);
 		else
 		{
+			// Merge a non-local variable's state into the parent scope.
 			if(i->second.referenced || !i->second.conditionally_assigned)
 				clear_assignments(j->second, !i->second.referenced);
 			j->second.conditionally_assigned = i->second.conditionally_assigned;
@@ -613,20 +636,25 @@ void UnusedVariableRemover::visit(Conditional &cond)
 	swap(variables.back(), if_variables);
 	cond.else_body.visit(*this);
 
+	// Combine variables from both branches.
 	BlockVariableMap &else_variables = variables.back();
 	for(BlockVariableMap::iterator i=else_variables.begin(); i!=else_variables.end(); ++i)
 	{
 		BlockVariableMap::iterator j = if_variables.find(i->first);
 		if(j!=if_variables.end())
 		{
+			// The variable was found in both branches.
 			i->second.assignments.insert(i->second.assignments.end(), j->second.assignments.begin(), j->second.assignments.end());
 			i->second.conditionally_assigned |= j->second.conditionally_assigned;
 			if_variables.erase(j);
 		}
 		else
+			// Mark variables found in only one branch as conditionally assigned.
 			i->second.conditionally_assigned = true;
 	}
 
+	/* Move variables which were only used in the if block into the combined
+	block. */
 	for(BlockVariableMap::iterator i=if_variables.begin(); i!=if_variables.end(); ++i)
 	{
 		i->second.conditionally_assigned = true;