X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=blobdiff_plain;f=source%2Fglsl%2Foptimize.cpp;h=7b3f8f28c8ad00007b520446ed5c2cc1180c49d0;hp=f938314814ea9cd4211279d5e94ff817c2a92fcc;hb=4fb346536bfefd612635a248f558b1f1471deae6;hpb=cb8ee1f5ea24a5f7b561fc88d4ff5af3ae364038

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index f9383148..7b3f8f28 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -34,8 +34,12 @@ void InlineableFunctionLocator::visit(FunctionCall &call)
 
 void InlineableFunctionLocator::visit(FunctionDeclaration &func)
 {
+	bool has_out_params = false;
+	for(NodeArray<VariableDeclaration>::const_iterator i=func.parameters.begin(); (!has_out_params && i!=func.parameters.end()); ++i)
+		has_out_params = ((*i)->interface=="out");
+
 	unsigned &count = refcounts[func.definition];
-	if(count<=1 && func.parameters.empty())
+	if(count<=1 && !has_out_params)
 		inlineable.insert(func.definition);
 
 	SetForScope<FunctionDeclaration *> set(current_function, &func);
@@ -66,75 +70,113 @@ void InlineableFunctionLocator::visit(Return &ret)
 
 InlineContentInjector::InlineContentInjector():
 	source_func(0),
-	remap_names(false),
-	deps_only(false)
+	pass(DEPENDS)
 { }
 
-const string &InlineContentInjector::apply(Stage &stage, FunctionDeclaration &target_func, Block &tgt_blk, const NodeList<Statement>::iterator &ins_pt, FunctionDeclaration &src)
+const string &InlineContentInjector::apply(Stage &stage, FunctionDeclaration &target_func, Block &tgt_blk, const NodeList<Statement>::iterator &ins_pt, FunctionCall &call)
 {
-	target_block = &tgt_blk;
-	source_func = &src;
-	for(NodeList<Statement>::iterator i=src.body.body.begin(); i!=src.body.body.end(); ++i)
+	source_func = call.declaration->definition;
+
+	// Collect all declarations the inlined function depends on.
+	pass = DEPENDS;
+	source_func->visit(*this);
+
+	/* Populate referenced_names from the target function so we can rename
+	variables from the inlined function that would conflict. */
+	pass = REFERENCED;
+	target_func.visit(*this);
+
+	/* Inline and rename passes must be interleaved so used variable names are
+	known when inlining the return statement. */
+	pass = INLINE;
+	staging_block.parent = &tgt_blk;
+	staging_block.variables.clear();
+
+	std::vector<RefPtr<VariableDeclaration> > params;
+	params.reserve(source_func->parameters.size());
+	for(NodeArray<VariableDeclaration>::iterator i=source_func->parameters.begin(); i!=source_func->parameters.end(); ++i)
+	{
+		RefPtr<VariableDeclaration> var = (*i)->clone();
+		var->interface.clear();
+
+		SetForScope<Pass> set_pass(pass, RENAME);
+		var->visit(*this);
+
+		staging_block.body.push_back_nocopy(var);
+		params.push_back(var);
+	}
+
+	for(NodeList<Statement>::iterator i=source_func->body.body.begin(); i!=source_func->body.body.end(); ++i)
 	{
 		r_inlined_statement = 0;
 		(*i)->visit(*this);
 		if(!r_inlined_statement)
 			r_inlined_statement = (*i)->clone();
 
-		SetFlag set_remap(remap_names);
+		SetForScope<Pass> set_pass(pass, RENAME);
 		r_inlined_statement->visit(*this);
-		tgt_blk.body.insert(ins_pt, r_inlined_statement);
+
+		staging_block.body.push_back_nocopy(r_inlined_statement);
 	}
 
+	/* Now collect names from the staging block.  Local variables that would
+	have conflicted with the target function were renamed earlier. */
+	pass = REFERENCED;
+	referenced_names.clear();
+	staging_block.variables.clear();
+	staging_block.visit(*this);
+
+	/* Rename variables in the target function so they don't interfere with
+	global identifiers used by the source function. */
+	pass = RENAME;
+	staging_block.parent = source_func->body.parent;
+	target_func.visit(*this);
+
+	// Put the argument expressions in place after all renaming has been done.
+	for(unsigned i=0; i<source_func->parameters.size(); ++i)
+		params[i]->init_expression = call.arguments[i]->clone();
+
+	tgt_blk.body.splice(ins_pt, staging_block.body);
+
 	NodeReorderer().apply(stage, target_func, dependencies);
 
 	return r_result_name;
 }
 
-string InlineContentInjector::create_unused_name(const string &base, bool always_prefix)
-{
-	string result = base;
-	if(always_prefix || target_block->variables.count(result))
-		result = format("_%s_%s", source_func->name, base);
-	unsigned initial_size = result.size();
-	for(unsigned i=1; target_block->variables.count(result); ++i)
-	{
-		result.erase(initial_size);
-		result += format("_%d", i);
-	}
-	return result;
-}
-
 void InlineContentInjector::visit(VariableReference &var)
 {
-	if(remap_names)
+	if(pass==RENAME)
 	{
-		map<string, VariableDeclaration *>::const_iterator i = variable_map.find(var.name);
-		if(i!=variable_map.end())
+		map<string, VariableDeclaration *>::const_iterator i = staging_block.variables.find(var.name);
+		if(i!=staging_block.variables.end())
 			var.name = i->second->name;
 	}
-	else if(var.declaration)
+	else if(pass==DEPENDS && var.declaration)
 	{
-		SetFlag set_deps(deps_only);
 		dependencies.insert(var.declaration);
 		var.declaration->visit(*this);
 	}
+	else if(pass==REFERENCED)
+		referenced_names.insert(var.name);
 }
 
 void InlineContentInjector::visit(InterfaceBlockReference &iface)
 {
-	if(!remap_names && iface.declaration)
+	if(pass==DEPENDS && iface.declaration)
 	{
-		SetFlag set_deps(deps_only);
 		dependencies.insert(iface.declaration);
 		iface.declaration->visit(*this);
 	}
+	else if(pass==REFERENCED)
+		referenced_names.insert(iface.name);
 }
 
 void InlineContentInjector::visit(FunctionCall &call)
 {
-	if(!remap_names && call.declaration)
+	if(pass==DEPENDS && call.declaration)
 		dependencies.insert(call.declaration);
+	else if(pass==REFERENCED)
+		referenced_names.insert(call.name);
 	TraversingVisitor::visit(call);
 }
 
@@ -142,32 +184,39 @@ void InlineContentInjector::visit(VariableDeclaration &var)
 {
 	TraversingVisitor::visit(var);
 
-	if(var.type_declaration)
+	if(pass==RENAME)
 	{
-		SetFlag set_deps(deps_only);
-		dependencies.insert(var.type_declaration);
-		var.type_declaration->visit(*this);
+		/* Check against conflicts with the other context as well as variables
+		already renamed here. */
+		bool conflict = (staging_block.variables.count(var.name) || referenced_names.count(var.name));
+		staging_block.variables[var.name] = &var;
+		if(conflict)
+		{
+			string mapped_name = get_unused_variable_name(staging_block, var.name);
+			if(mapped_name!=var.name)
+			{
+				staging_block.variables[mapped_name] = &var;
+				var.name = mapped_name;
+			}
+		}
 	}
-
-	if(!remap_names && !deps_only)
+	else if(pass==DEPENDS && var.type_declaration)
 	{
-		RefPtr<VariableDeclaration> inlined_var = var.clone();
-		inlined_var->name = create_unused_name(var.name, false);
-		r_inlined_statement = inlined_var;
-
-		variable_map[var.name] = inlined_var.get();
+		dependencies.insert(var.type_declaration);
+		var.type_declaration->visit(*this);
 	}
+	else if(pass==REFERENCED)
+		referenced_names.insert(var.type);
 }
 
 void InlineContentInjector::visit(Return &ret)
 {
 	TraversingVisitor::visit(ret);
 
-	if(ret.expression)
+	if(pass==INLINE && ret.expression)
 	{
-		/* Create a new variable to hold the return value of the inlined
-		function. */
-		r_result_name = create_unused_name("return", true);
+		// Create a new variable to hold the return value of the inlined function.
+		r_result_name = get_unused_variable_name(staging_block, "_return");
 		RefPtr<VariableDeclaration> var = new VariableDeclaration;
 		var->source = ret.source;
 		var->line = ret.line;
@@ -181,7 +230,8 @@ void InlineContentInjector::visit(Return &ret)
 
 FunctionInliner::FunctionInliner():
 	current_function(0),
-	r_any_inlined(false)
+	r_any_inlined(false),
+	r_inlined_here(false)
 { }
 
 bool FunctionInliner::apply(Stage &s)
@@ -193,7 +243,7 @@ bool FunctionInliner::apply(Stage &s)
 	return r_any_inlined;
 }
 
-void FunctionInliner::visit_and_inline(RefPtr<Expression> &ptr)
+void FunctionInliner::visit(RefPtr<Expression> &ptr)
 {
 	r_inline_result = 0;
 	ptr->visit(*this);
@@ -209,33 +259,20 @@ void FunctionInliner::visit(Block &block)
 {
 	SetForScope<Block *> set_block(current_block, &block);
 	SetForScope<NodeList<Statement>::iterator> save_insert_point(insert_point, block.body.begin());
-	for(NodeList<Statement>::iterator i=block.body.begin(); i!=block.body.end(); ++i)
+	for(NodeList<Statement>::iterator i=block.body.begin(); (!r_inlined_here && i!=block.body.end()); ++i)
 	{
 		insert_point = i;
 		(*i)->visit(*this);
 	}
 }
 
-void FunctionInliner::visit(UnaryExpression &unary)
-{
-	visit_and_inline(unary.expression);
-}
-
-void FunctionInliner::visit(BinaryExpression &binary)
-{
-	visit_and_inline(binary.left);
-	visit_and_inline(binary.right);
-}
-
-void FunctionInliner::visit(MemberAccess &memacc)
-{
-	visit_and_inline(memacc.left);
-}
-
 void FunctionInliner::visit(FunctionCall &call)
 {
-	for(NodeArray<Expression>::iterator i=call.arguments.begin(); i!=call.arguments.end(); ++i)
-		visit_and_inline(*i);
+	for(NodeArray<Expression>::iterator i=call.arguments.begin(); (!r_inlined_here && i!=call.arguments.end()); ++i)
+		visit(*i);
+
+	if(r_inlined_here)
+		return;
 
 	FunctionDeclaration *def = call.declaration;
 	if(def)
@@ -243,11 +280,11 @@ void FunctionInliner::visit(FunctionCall &call)
 
 	if(def && inlineable.count(def))
 	{
-		string result_name = InlineContentInjector().apply(*stage, *current_function, *current_block, insert_point, *def);
+		string result_name = InlineContentInjector().apply(*stage, *current_function, *current_block, insert_point, call);
 
 		// This will later get removed by UnusedVariableRemover.
 		if(result_name.empty())
-			result_name = "msp_unused_from_inline";
+			result_name = "_msp_unused_from_inline";
 
 		RefPtr<VariableReference> ref = new VariableReference;
 		ref->name = result_name;
@@ -256,30 +293,15 @@ void FunctionInliner::visit(FunctionCall &call)
 		/* Inlined variables need to be resolved before this function can be
 		inlined further. */
 		inlineable.erase(current_function);
+		r_inlined_here = true;
 	}
 }
 
-void FunctionInliner::visit(ExpressionStatement &expr)
-{
-	visit_and_inline(expr.expression);
-}
-
-void FunctionInliner::visit(VariableDeclaration &var)
-{
-	if(var.init_expression)
-		visit_and_inline(var.init_expression);
-}
-
 void FunctionInliner::visit(FunctionDeclaration &func)
 {
 	SetForScope<FunctionDeclaration *> set_func(current_function, &func);
 	TraversingVisitor::visit(func);
-}
-
-void FunctionInliner::visit(Conditional &cond)
-{
-	visit_and_inline(cond.condition);
-	cond.body.visit(*this);
+	r_inlined_here = false;
 }
 
 void FunctionInliner::visit(Iteration &iter)
@@ -296,20 +318,11 @@ void FunctionInliner::visit(Iteration &iter)
 	iter.body.visit(*this);
 }
 
-void FunctionInliner::visit(Return &ret)
-{
-	if(ret.expression)
-		visit_and_inline(ret.expression);
-}
-
 
 ExpressionInliner::ExpressionInfo::ExpressionInfo():
 	expression(0),
 	assign_scope(0),
 	inline_point(0),
-	inner_oper(0),
-	outer_oper(0),
-	inline_on_rhs(false),
 	trivial(false),
 	available(true)
 { }
@@ -331,10 +344,40 @@ bool ExpressionInliner::apply(Stage &s)
 	return r_any_inlined;
 }
 
-void ExpressionInliner::visit_and_record(RefPtr<Expression> &ptr, const Operator *outer_oper, bool on_rhs)
+void ExpressionInliner::inline_expression(Expression &expr, RefPtr<Expression> &ptr)
+{
+	ptr = expr.clone();
+	r_any_inlined = true;
+}
+
+void ExpressionInliner::visit(Block &block)
+{
+	TraversingVisitor::visit(block);
+
+	for(map<string, VariableDeclaration *>::iterator i=block.variables.begin(); i!=block.variables.end(); ++i)
+	{
+		map<Assignment::Target, ExpressionInfo>::iterator j = expressions.lower_bound(i->second);
+		for(; (j!=expressions.end() && j->first.declaration==i->second); )
+		{
+			if(j->second.expression && j->second.inline_point)
+				inline_expression(*j->second.expression, *j->second.inline_point);
+
+			expressions.erase(j++);
+		}
+	}
+
+	/* Expressions assigned in this block may depend on local variables of the
+	block.  If this is a conditionally executed block, the assignments might not
+	always happen.  Mark the expressions as not available to any outer blocks. */
+	for(map<Assignment::Target, ExpressionInfo>::iterator i=expressions.begin(); i!=expressions.end(); ++i)
+		if(i->second.assign_scope==&block)
+			i->second.available = false;
+}
+
+void ExpressionInliner::visit(RefPtr<Expression> &expr)
 {
 	r_ref_info = 0;
-	ptr->visit(*this);
+	expr->visit(*this);
 	if(r_ref_info && r_ref_info->expression && r_ref_info->available)
 	{
 		if(iteration_body && !r_ref_info->trivial)
@@ -348,75 +391,22 @@ void ExpressionInliner::visit_and_record(RefPtr<Expression> &ptr, const Operator
 				return;
 		}
 
-		r_ref_info->outer_oper = outer_oper;
 		if(r_ref_info->trivial)
-			inline_expression(*r_ref_info->expression, ptr, outer_oper, r_ref_info->inner_oper, on_rhs);
+			inline_expression(*r_ref_info->expression, expr);
 		else
-		{
 			/* Record the inline point for a non-trivial expression but don't
 			inline it yet.  It might turn out it shouldn't be inlined after all. */
-			r_ref_info->inline_point = &ptr;
-			r_ref_info->inline_on_rhs = on_rhs;
-		}
+			r_ref_info->inline_point = &expr;
 	}
+	r_oper = expr->oper;
 	r_ref_info = 0;
 }
 
-void ExpressionInliner::inline_expression(Expression &expr, RefPtr<Expression> &ptr, const Operator *outer_oper, const Operator *inner_oper, bool on_rhs)
-{
-	unsigned outer_precedence = (outer_oper ? outer_oper->precedence : 20);
-	unsigned inner_precedence = (inner_oper ? inner_oper->precedence : 0);
-
-	bool needs_parentheses = (inner_precedence>=outer_precedence);
-	if(inner_oper && inner_oper==outer_oper)
-		// Omit parentheses if the operator's natural grouping works out.
-		needs_parentheses = (inner_oper->assoc!=Operator::ASSOCIATIVE && on_rhs!=(inner_oper->assoc==Operator::RIGHT_TO_LEFT));
-
-	if(needs_parentheses)
-	{
-		RefPtr<ParenthesizedExpression> parexpr = new ParenthesizedExpression;
-		parexpr->expression = expr.clone();
-		ptr = parexpr;
-	}
-	else
-		ptr = expr.clone();
-
-	r_any_inlined = true;
-}
-
-void ExpressionInliner::visit(Block &block)
-{
-	TraversingVisitor::visit(block);
-
-	for(map<VariableDeclaration *, ExpressionInfo>::iterator i=expressions.begin(); i!=expressions.end(); )
-	{
-		map<string, VariableDeclaration *>::iterator j = block.variables.find(i->first->name);
-		if(j!=block.variables.end() && j->second==i->first)
-		{
-			if(i->second.expression && i->second.inline_point)
-				inline_expression(*i->second.expression, *i->second.inline_point, i->second.outer_oper, i->second.inner_oper, i->second.inline_on_rhs);
-
-			expressions.erase(i++);
-		}
-		else
-		{
-			/* The expression was assigned in this block and may depend on local
-			variables of the block.  If this is a conditionally executed block,
-			the assignment might not always happen.  Mark the expression as not
-			available to any outer blocks. */
-			if(i->second.assign_scope==&block)
-				i->second.available = false;
-
-			++i;
-		}
-	}
-}
-
 void ExpressionInliner::visit(VariableReference &var)
 {
 	if(var.declaration)
 	{
-		map<VariableDeclaration *, ExpressionInfo>::iterator i = expressions.find(var.declaration);
+		map<Assignment::Target, ExpressionInfo>::iterator i = expressions.find(var.declaration);
 		if(i!=expressions.end())
 		{
 			/* If a non-trivial expression is referenced multiple times, don't
@@ -434,27 +424,30 @@ void ExpressionInliner::visit(VariableReference &var)
 
 void ExpressionInliner::visit(MemberAccess &memacc)
 {
-	visit_and_record(memacc.left, memacc.oper, false);
-	r_oper = memacc.oper;
+	visit(memacc.left);
+	r_trivial = false;
+}
+
+void ExpressionInliner::visit(Swizzle &swizzle)
+{
+	visit(swizzle.left);
 	r_trivial = false;
 }
 
 void ExpressionInliner::visit(UnaryExpression &unary)
 {
 	SetFlag set_target(mutating, mutating || unary.oper->token[1]=='+' || unary.oper->token[1]=='-');
-	visit_and_record(unary.expression, unary.oper, false);
-	r_oper = unary.oper;
+	visit(unary.expression);
 	r_trivial = false;
 }
 
 void ExpressionInliner::visit(BinaryExpression &binary)
 {
-	visit_and_record(binary.left, binary.oper, false);
+	visit(binary.left);
 	{
 		SetFlag clear_target(mutating, false);
-		visit_and_record(binary.right, binary.oper, true);
+		visit(binary.right);
 	}
-	r_oper = binary.oper;
 	r_trivial = false;
 }
 
@@ -462,35 +455,36 @@ void ExpressionInliner::visit(Assignment &assign)
 {
 	{
 		SetFlag set_target(mutating);
-		visit_and_record(assign.left, assign.oper, false);
+		visit(assign.left);
 	}
 	r_oper = 0;
-	visit_and_record(assign.right, assign.oper, true);
+	visit(assign.right);
 
-	if(assign.target_declaration)
+	map<Assignment::Target, ExpressionInfo>::iterator i = expressions.find(assign.target);
+	if(i!=expressions.end())
 	{
-		map<VariableDeclaration *, ExpressionInfo>::iterator i = expressions.find(assign.target_declaration);
-		if(i!=expressions.end())
-		{
-			/* Self-referencing assignments can't be inlined without additional
-			work.  Just clear any previous expression. */
-			i->second.expression = (assign.self_referencing ? 0 : assign.right.get());
-			i->second.assign_scope = current_block;
-			i->second.inline_point = 0;
-			i->second.inner_oper = r_oper;
-			i->second.available = true;
-		}
+		/* Self-referencing assignments can't be inlined without additional
+		work.  Just clear any previous expression. */
+		i->second.expression = (assign.self_referencing ? 0 : assign.right.get());
+		i->second.assign_scope = current_block;
+		i->second.inline_point = 0;
+		i->second.available = true;
 	}
 
-	r_oper = assign.oper;
+	r_trivial = false;
+}
+
+void ExpressionInliner::visit(TernaryExpression &ternary)
+{
+	visit(ternary.condition);
+	visit(ternary.true_expr);
+	visit(ternary.false_expr);
 	r_trivial = false;
 }
 
 void ExpressionInliner::visit(FunctionCall &call)
 {
-	for(NodeArray<Expression>::iterator i=call.arguments.begin(); i!=call.arguments.end(); ++i)
-		visit_and_record(*i, 0, false);
-	r_oper = 0;
+	TraversingVisitor::visit(call);
 	r_trivial = false;
 }
 
@@ -498,8 +492,7 @@ void ExpressionInliner::visit(VariableDeclaration &var)
 {
 	r_oper = 0;
 	r_trivial = true;
-	if(var.init_expression)
-		visit_and_record(var.init_expression, 0, false);
+	TraversingVisitor::visit(var);
 
 	bool constant = var.constant;
 	if(constant && var.layout)
@@ -518,17 +511,10 @@ void ExpressionInliner::visit(VariableDeclaration &var)
 		will have their values change throughout the iteration. */
 		info.expression = (iteration_init ? 0 : var.init_expression.get());
 		info.assign_scope = current_block;
-		info.inner_oper = r_oper;
 		info.trivial = r_trivial;
 	}
 }
 
-void ExpressionInliner::visit(Conditional &cond)
-{
-	visit_and_record(cond.condition, 0, false);
-	cond.body.visit(*this);
-}
-
 void ExpressionInliner::visit(Iteration &iter)
 {
 	SetForScope<Block *> set_block(current_block, &iter.body);
@@ -540,16 +526,291 @@ void ExpressionInliner::visit(Iteration &iter)
 
 	SetForScope<Block *> set_body(iteration_body, &iter.body);
 	if(iter.condition)
-		iter.condition->visit(*this);
+		visit(iter.condition);
 	iter.body.visit(*this);
 	if(iter.loop_expression)
-		iter.loop_expression->visit(*this);
+		visit(iter.loop_expression);
+}
+
+
+BasicTypeDeclaration::Kind ConstantFolder::get_value_kind(const Variant &value)
+{
+	if(value.check_type<bool>())
+		return BasicTypeDeclaration::BOOL;
+	else if(value.check_type<int>())
+		return BasicTypeDeclaration::INT;
+	else if(value.check_type<float>())
+		return BasicTypeDeclaration::FLOAT;
+	else
+		return BasicTypeDeclaration::VOID;
+}
+
+template<typename T>
+T ConstantFolder::evaluate_logical(char oper, T left, T right)
+{
+	switch(oper)
+	{
+	case '&': return left&right;
+	case '|': return left|right;
+	case '^': return left^right;
+	default: return T();
+	}
+}
+
+template<typename T>
+bool ConstantFolder::evaluate_relation(const char *oper, T left, T right)
+{
+	switch(oper[0]|oper[1])
+	{
+	case '<': return left<right;
+	case '<'|'=': return left<=right;
+	case '>': return left>right;
+	case '>'|'=': return left>=right;
+	default: return false;
+	}
+}
+
+template<typename T>
+T ConstantFolder::evaluate_arithmetic(char oper, T left, T right)
+{
+	switch(oper)
+	{
+	case '+': return left+right;
+	case '-': return left-right;
+	case '*': return left*right;
+	case '/': return left/right;
+	default: return T();
+	}
+}
+
+void ConstantFolder::set_result(const Variant &value, bool literal)
+{
+	r_constant_value = value;
+	r_constant = true;
+	r_literal = literal;
+}
+
+void ConstantFolder::visit(RefPtr<Expression> &expr)
+{
+	r_constant_value = Variant();
+	r_constant = false;
+	r_literal = false;
+	r_uses_iter_var = false;
+	expr->visit(*this);
+	/* Don't replace literals since they'd only be replaced with an identical
+	literal.  Also skip anything that uses an iteration variable, but pass on
+	the result so the Iteration visiting function can handle it. */
+	if(!r_constant || r_literal || r_uses_iter_var)
+		return;
+
+	BasicTypeDeclaration::Kind kind = get_value_kind(r_constant_value);
+	if(kind==BasicTypeDeclaration::VOID)
+	{
+		r_constant = false;
+		return;
+	}
+
+	RefPtr<Literal> literal = new Literal;
+	if(kind==BasicTypeDeclaration::BOOL)
+		literal->token = (r_constant_value.value<bool>() ? "true" : "false");
+	else if(kind==BasicTypeDeclaration::INT)
+		literal->token = lexical_cast<string>(r_constant_value.value<int>());
+	else if(kind==BasicTypeDeclaration::FLOAT)
+		literal->token = lexical_cast<string>(r_constant_value.value<float>());
+	literal->value = r_constant_value;
+	expr = literal;
+}
+
+void ConstantFolder::visit(Literal &literal)
+{
+	set_result(literal.value, true);
+}
+
+void ConstantFolder::visit(VariableReference &var)
+{
+	/* If an iteration variable is initialized with a constant value, return
+	that value here for the purpose of evaluating the loop condition for the
+	first iteration. */
+	if(var.declaration==iteration_var)
+	{
+		set_result(iter_init_value);
+		r_uses_iter_var = true;
+	}
+}
+
+void ConstantFolder::visit(MemberAccess &memacc)
+{
+	TraversingVisitor::visit(memacc);
+	r_constant = false;
+}
+
+void ConstantFolder::visit(Swizzle &swizzle)
+{
+	TraversingVisitor::visit(swizzle);
+	r_constant = false;
+}
+
+void ConstantFolder::visit(UnaryExpression &unary)
+{
+	TraversingVisitor::visit(unary);
+	bool can_fold = r_constant;
+	r_constant = false;
+	if(!can_fold)
+		return;
+
+	BasicTypeDeclaration::Kind kind = get_value_kind(r_constant_value);
+
+	char oper = unary.oper->token[0];
+	char oper2 = unary.oper->token[1];
+	if(oper=='!')
+	{
+		if(kind==BasicTypeDeclaration::BOOL)
+			set_result(!r_constant_value.value<bool>());
+	}
+	else if(oper=='~')
+	{
+		if(kind==BasicTypeDeclaration::INT)
+			set_result(~r_constant_value.value<int>());
+	}
+	else if(oper=='-' && !oper2)
+	{
+		if(kind==BasicTypeDeclaration::INT)
+			set_result(-r_constant_value.value<int>());
+		else if(kind==BasicTypeDeclaration::FLOAT)
+			set_result(-r_constant_value.value<float>());
+	}
+}
+
+void ConstantFolder::visit(BinaryExpression &binary)
+{
+	visit(binary.left);
+	bool left_constant = r_constant;
+	bool left_iter_var = r_uses_iter_var;
+	Variant left_value = r_constant_value;
+	visit(binary.right);
+	if(left_iter_var)
+		r_uses_iter_var = true;
+
+	bool can_fold = (left_constant && r_constant);
+	r_constant = false;
+	if(!can_fold)
+		return;
+
+	BasicTypeDeclaration::Kind left_kind = get_value_kind(left_value);
+	BasicTypeDeclaration::Kind right_kind = get_value_kind(r_constant_value);
+	// Currently only expressions with both sides of equal types are handled.
+	if(left_kind!=right_kind)
+		return;
+
+	char oper = binary.oper->token[0];
+	char oper2 = binary.oper->token[1];
+	if(oper=='&' || oper=='|' || oper=='^')
+	{
+		if(oper2==oper && left_kind==BasicTypeDeclaration::BOOL)
+			set_result(evaluate_logical(oper, left_value.value<bool>(), r_constant_value.value<bool>()));
+		else if(!oper2 && left_kind==BasicTypeDeclaration::INT)
+			set_result(evaluate_logical(oper, left_value.value<int>(), r_constant_value.value<int>()));
+	}
+	else if((oper=='<' || oper=='>') && oper2!=oper)
+	{
+		if(left_kind==BasicTypeDeclaration::INT)
+			set_result(evaluate_relation(binary.oper->token, left_value.value<int>(), r_constant_value.value<int>()));
+		else if(left_kind==BasicTypeDeclaration::FLOAT)
+			set_result(evaluate_relation(binary.oper->token, left_value.value<float>(), r_constant_value.value<float>()));
+	}
+	else if((oper=='=' || oper=='!') && oper2=='=')
+	{
+		if(left_kind==BasicTypeDeclaration::INT)
+			set_result((left_value.value<int>()==r_constant_value.value<int>()) == (oper=='='));
+		if(left_kind==BasicTypeDeclaration::FLOAT)
+			set_result((left_value.value<float>()==r_constant_value.value<float>()) == (oper=='='));
+	}
+	else if(oper=='+' || oper=='-' || oper=='*' || oper=='/')
+	{
+		if(left_kind==BasicTypeDeclaration::INT)
+			set_result(evaluate_arithmetic(oper, left_value.value<int>(), r_constant_value.value<int>()));
+		else if(left_kind==BasicTypeDeclaration::FLOAT)
+			set_result(evaluate_arithmetic(oper, left_value.value<float>(), r_constant_value.value<float>()));
+	}
+	else if(oper=='%' || ((oper=='<' || oper=='>') && oper2==oper))
+	{
+		if(left_kind!=BasicTypeDeclaration::INT)
+			return;
+
+		if(oper=='%')
+			set_result(left_value.value<int>()%r_constant_value.value<int>());
+		else if(oper=='<')
+			set_result(left_value.value<int>()<<r_constant_value.value<int>());
+		else if(oper=='>')
+			set_result(left_value.value<int>()>>r_constant_value.value<int>());
+	}
+}
+
+void ConstantFolder::visit(Assignment &assign)
+{
+	TraversingVisitor::visit(assign);
+	r_constant = false;
+}
+
+void ConstantFolder::visit(TernaryExpression &ternary)
+{
+	TraversingVisitor::visit(ternary);
+	r_constant = false;
 }
 
-void ExpressionInliner::visit(Return &ret)
+void ConstantFolder::visit(FunctionCall &call)
 {
-	if(ret.expression)
-		visit_and_record(ret.expression, 0, false);
+	TraversingVisitor::visit(call);
+	r_constant = false;
+}
+
+void ConstantFolder::visit(VariableDeclaration &var)
+{
+	if(iteration_init && var.init_expression)
+	{
+		visit(var.init_expression);
+		if(r_constant)
+		{
+			/* Record the value of a constant initialization expression of an
+			iteration, so it can be used to evaluate the loop condition. */
+			iteration_var = &var;
+			iter_init_value = r_constant_value;
+		}
+	}
+	else
+		TraversingVisitor::visit(var);
+}
+
+void ConstantFolder::visit(Iteration &iter)
+{
+	SetForScope<Block *> set_block(current_block, &iter.body);
+
+	/* The iteration variable is not normally inlined into expressions, so we
+	process it specially here.  If the initial value causes the loop condition
+	to evaluate to false, then the expression can be folded. */
+	iteration_var = 0;
+	if(iter.init_statement)
+	{
+		SetFlag set_init(iteration_init);
+		iter.init_statement->visit(*this);
+	}
+
+	if(iter.condition)
+	{
+		visit(iter.condition);
+		if(r_constant && r_constant_value.check_type<bool>() && !r_constant_value.value<bool>())
+		{
+			RefPtr<Literal> literal = new Literal;
+			literal->token = "false";
+			literal->value = r_constant_value;
+			iter.condition = literal;
+		}
+	}
+	iteration_var = 0;
+
+	iter.body.visit(*this);
+	if(iter.loop_expression)
+		visit(iter.loop_expression);
 }
 
 
@@ -559,6 +820,14 @@ void ConstantConditionEliminator::apply(Stage &stage)
 	NodeRemover().apply(stage, nodes_to_remove);
 }
 
+ConstantConditionEliminator::ConstantStatus ConstantConditionEliminator::check_constant_condition(const Expression &expr)
+{
+	if(const Literal *literal = dynamic_cast<const Literal *>(&expr))
+		if(literal->value.check_type<bool>())
+			return (literal->value.value<bool>() ? CONSTANT_TRUE : CONSTANT_FALSE);
+	return NOT_CONSTANT;
+}
+
 void ConstantConditionEliminator::visit(Block &block)
 {
 	SetForScope<Block *> set_block(current_block, &block);
@@ -569,13 +838,31 @@ void ConstantConditionEliminator::visit(Block &block)
 	}
 }
 
+void ConstantConditionEliminator::visit(RefPtr<Expression> &expr)
+{
+	r_ternary_result = 0;
+	expr->visit(*this);
+	if(r_ternary_result)
+		expr = r_ternary_result;
+	r_ternary_result = 0;
+}
+
+void ConstantConditionEliminator::visit(TernaryExpression &ternary)
+{
+	ConstantStatus result = check_constant_condition(*ternary.condition);
+	if(result!=NOT_CONSTANT)
+		r_ternary_result = (result==CONSTANT_TRUE ? ternary.true_expr : ternary.false_expr);
+	else
+		r_ternary_result = 0;
+}
+
 void ConstantConditionEliminator::visit(Conditional &cond)
 {
-	ExpressionEvaluator eval;
-	cond.condition->visit(eval);
-	if(eval.is_result_valid())
+	ConstantStatus result = check_constant_condition(*cond.condition);
+	if(result!=NOT_CONSTANT)
 	{
-		Block &block = (eval.get_result() ? cond.body : cond.else_body);
+		Block &block = (result==CONSTANT_TRUE ? cond.body : cond.else_body);
+		// TODO should check variable names for conflicts.  Potentially reuse InlineContentInjector?
 		current_block->body.splice(insert_point, block.body);
 		nodes_to_remove.insert(&cond);
 		return;
@@ -588,14 +875,8 @@ void ConstantConditionEliminator::visit(Iteration &iter)
 {
 	if(iter.condition)
 	{
-		/* If the loop condition is always false on the first iteration, the
-		entire loop can be removed */
-		ExpressionEvaluator::ValueMap values;
-		if(VariableDeclaration *var = dynamic_cast<VariableDeclaration *>(iter.init_statement.get()))
-			values[var] = var->init_expression.get();
-		ExpressionEvaluator eval(values);
-		iter.condition->visit(eval);
-		if(eval.is_result_valid() && !eval.get_result())
+		ConstantStatus result = check_constant_condition(*iter.condition);
+		if(result==CONSTANT_FALSE)
 		{
 			nodes_to_remove.insert(&iter);
 			return;
@@ -606,13 +887,6 @@ void ConstantConditionEliminator::visit(Iteration &iter)
 }
 
 
-UnusedVariableRemover::VariableInfo::VariableInfo():
-	local(false),
-	conditionally_assigned(false),
-	referenced(false)
-{ }
-
-
 bool UnusedTypeRemover::apply(Stage &stage)
 {
 	stage.content.visit(*this);
@@ -637,6 +911,12 @@ void UnusedTypeRemover::visit(BinaryExpression &binary)
 	TraversingVisitor::visit(binary);
 }
 
+void UnusedTypeRemover::visit(TernaryExpression &ternary)
+{
+	unused_nodes.erase(ternary.type);
+	TraversingVisitor::visit(ternary);
+}
+
 void UnusedTypeRemover::visit(FunctionCall &call)
 {
 	unused_nodes.erase(call.type);
@@ -668,6 +948,11 @@ void UnusedTypeRemover::visit(VariableDeclaration &var)
 	unused_nodes.erase(var.type_declaration);
 }
 
+void UnusedTypeRemover::visit(InterfaceBlock &iface)
+{
+	unused_nodes.erase(iface.type_declaration);
+}
+
 void UnusedTypeRemover::visit(FunctionDeclaration &func)
 {
 	unused_nodes.erase(func.return_type_declaration);
@@ -676,65 +961,71 @@ void UnusedTypeRemover::visit(FunctionDeclaration &func)
 
 
 UnusedVariableRemover::UnusedVariableRemover():
-	aggregate(0),
+	stage(0),
+	interface_block(0),
 	r_assignment(0),
 	assignment_target(false),
-	r_assign_to_subfield(false),
 	r_side_effects(false)
 { }
 
-bool UnusedVariableRemover::apply(Stage &stage)
+bool UnusedVariableRemover::apply(Stage &s)
 {
-	variables.push_back(BlockVariableMap());
-	stage.content.visit(*this);
-	BlockVariableMap &global_variables = variables.back();
-	for(BlockVariableMap::iterator i=global_variables.begin(); i!=global_variables.end(); ++i)
+	stage = &s;
+	s.content.visit(*this);
+
+	for(list<AssignmentInfo>::const_iterator i=assignments.begin(); i!=assignments.end(); ++i)
+		if(i->used_by.empty())
+			unused_nodes.insert(i->node);
+
+	for(map<string, InterfaceBlock *>::const_iterator i=s.interface_blocks.begin(); i!=s.interface_blocks.end(); ++i)
+		if(i->second->instance_name.empty())
+			unused_nodes.insert(i->second);
+
+	for(BlockVariableMap::const_iterator i=variables.begin(); i!=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;
+		if(i->second.output)
+		{
+			/* The last visible assignments of output variables are used by the
+			next stage or the API. */
+			for(vector<AssignmentInfo *>::const_iterator j=i->second.assignments.begin(); j!=i->second.assignments.end(); ++j)
+				unused_nodes.erase((*j)->node);
+		}
 
-		// Mark other unreferenced global variables as unused.
-		if(!i->second.referenced)
+		if(!i->second.output && !i->second.referenced)
 		{
-			unused_nodes.insert(i->first);
-			clear_assignments(i->second, true);
+			// Don't remove variables from inside interface blocks.
+			if(!i->second.interface_block)
+				unused_nodes.insert(i->first);
 		}
+		else if(i->second.interface_block)
+			// Interface blocks are kept if even one member is used.
+			unused_nodes.erase(i->second.interface_block);
 	}
-	variables.pop_back();
 
-	NodeRemover().apply(stage, unused_nodes);
+	NodeRemover().apply(s, unused_nodes);
 
 	return !unused_nodes.empty();
 }
 
-void UnusedVariableRemover::visit(VariableReference &var)
+void UnusedVariableRemover::referenced(const Assignment::Target &target, Node &node)
 {
-	map<VariableDeclaration *, Node *>::iterator i = aggregates.find(var.declaration);
-	if(i!=aggregates.end())
-		unused_nodes.erase(i->second);
-
-	if(var.declaration && !assignment_target)
+	VariableInfo &var_info = variables[target.declaration];
+	var_info.referenced = true;
+	if(!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;
+		for(vector<AssignmentInfo *>::const_iterator i=var_info.assignments.begin(); i!=var_info.assignments.end(); ++i)
+			(*i)->used_by.push_back(&node);
 	}
 }
 
-void UnusedVariableRemover::visit(InterfaceBlockReference &iface)
+void UnusedVariableRemover::visit(VariableReference &var)
 {
-	unused_nodes.erase(iface.declaration);
+	referenced(var.declaration, var);
 }
 
-void UnusedVariableRemover::visit(MemberAccess &memacc)
+void UnusedVariableRemover::visit(InterfaceBlockReference &iface)
 {
-	if(assignment_target)
-		r_assign_to_subfield = true;
-	TraversingVisitor::visit(memacc);
-	unused_nodes.erase(memacc.declaration);
+	referenced(iface.declaration, iface);
 }
 
 void UnusedVariableRemover::visit(UnaryExpression &unary)
@@ -748,8 +1039,6 @@ void UnusedVariableRemover::visit(BinaryExpression &binary)
 {
 	if(binary.oper->token[0]=='[')
 	{
-		if(assignment_target)
-			r_assign_to_subfield = true;
 		binary.left->visit(*this);
 		SetFlag set(assignment_target, false);
 		binary.right->visit(*this);
@@ -761,7 +1050,7 @@ void UnusedVariableRemover::visit(BinaryExpression &binary)
 void UnusedVariableRemover::visit(Assignment &assign)
 {
 	{
-		SetFlag set(assignment_target, !assign.self_referencing);
+		SetFlag set(assignment_target, (assign.oper->token[0]=='='));
 		assign.left->visit(*this);
 	}
 	assign.right->visit(*this);
@@ -775,166 +1064,156 @@ void UnusedVariableRemover::visit(FunctionCall &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);
-	var_info.conditionally_assigned = false;
+	if(stage->type==Stage::GEOMETRY && call.name=="EmitVertex")
+	{
+		for(map<Statement *, VariableInfo>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
+			if(i->second.output)
+				referenced(i->first, call);
+	}
 }
 
-void UnusedVariableRemover::clear_assignments(VariableInfo &var_info, bool mark_unused)
+void UnusedVariableRemover::record_assignment(const Assignment::Target &target, Node &node)
 {
-	if(mark_unused)
+	assignments.push_back(AssignmentInfo());
+	AssignmentInfo &assign_info = assignments.back();
+	assign_info.node = &node;
+	assign_info.target = target;
+
+	/* An assignment to the target hides any assignments to the same target or
+	its subfields. */
+	VariableInfo &var_info = variables[target.declaration];
+	for(unsigned i=0; i<var_info.assignments.size(); ++i)
 	{
-		for(vector<Node *>::iterator i=var_info.assignments.begin(); i!=var_info.assignments.end(); ++i)
-			unused_nodes.insert(*i);
+		const Assignment::Target &t = var_info.assignments[i]->target;
+
+		bool subfield = (t.chain_len>=target.chain_len);
+		for(unsigned j=0; (subfield && j<target.chain_len); ++j)
+			subfield = (t.chain[j]==target.chain[j]);
+
+		if(subfield)
+			var_info.assignments.erase(var_info.assignments.begin()+i);
+		else
+			++i;
 	}
-	var_info.assignments.clear();
+
+	var_info.assignments.push_back(&assign_info);
 }
 
 void UnusedVariableRemover::visit(ExpressionStatement &expr)
 {
 	r_assignment = 0;
-	r_assign_to_subfield = false;
 	r_side_effects = false;
 	TraversingVisitor::visit(expr);
-	if(r_assignment && r_assignment->target_declaration)
-		record_assignment(*r_assignment->target_declaration, expr, (r_assignment->self_referencing || r_assign_to_subfield));
+	if(r_assignment && r_assignment->target.declaration)
+		record_assignment(r_assignment->target, expr);
 	if(!r_side_effects)
 		unused_nodes.insert(&expr);
 }
 
-void UnusedVariableRemover::visit(StructDeclaration &strct)
-{
-	SetForScope<Node *> set(aggregate, &strct);
-	TraversingVisitor::visit(strct);
-}
-
 void UnusedVariableRemover::visit(VariableDeclaration &var)
 {
-	if(aggregate)
-		aggregates[&var] = aggregate;
+	VariableInfo &var_info = variables[&var];
+	var_info.interface_block = interface_block;
+
+	/* Mark variables as output if they're used by the next stage or the
+	graphics API. */
+	if(interface_block)
+		var_info.output = (interface_block->interface=="out" && (interface_block->linked_block || !interface_block->block_name.compare(0, 3, "gl_")));
 	else
+		var_info.output = (var.interface=="out" && (stage->type==Stage::FRAGMENT || var.linked_declaration || !var.name.compare(0, 3, "gl_")));
+
+	if(var.init_expression)
 	{
-		variables.back()[&var].local = true;
-		if(var.init_expression)
-			record_assignment(var, *var.init_expression, false);
+		var_info.initialized = true;
+		record_assignment(&var, *var.init_expression);
 	}
 	TraversingVisitor::visit(var);
 }
 
 void UnusedVariableRemover::visit(InterfaceBlock &iface)
 {
-	SetForScope<Node *> set(aggregate, &iface);
-	unused_nodes.insert(&iface);
-	TraversingVisitor::visit(iface);
+	if(iface.instance_name.empty())
+	{
+		SetForScope<InterfaceBlock *> set_block(interface_block, &iface);
+		iface.struct_declaration->members.visit(*this);
+	}
+	else
+	{
+		VariableInfo &var_info = variables[&iface];
+		var_info.output = (iface.interface=="out" && (iface.linked_block || !iface.block_name.compare(0, 3, "gl_")));
+	}
+}
+
+void UnusedVariableRemover::merge_variables(const BlockVariableMap &other_vars)
+{
+	for(BlockVariableMap::const_iterator i=other_vars.begin(); i!=other_vars.end(); ++i)
+	{
+		BlockVariableMap::iterator j = variables.find(i->first);
+		if(j!=variables.end())
+		{
+			/* The merged blocks started as copies of each other so any common
+			assignments must be in the beginning. */
+			unsigned k = 0;
+			for(; (k<i->second.assignments.size() && k<j->second.assignments.size()); ++k)
+				if(i->second.assignments[k]!=j->second.assignments[k])
+					break;
+
+			// Remaining assignments are unique to each block; merge them.
+			j->second.assignments.insert(j->second.assignments.end(), i->second.assignments.begin()+k, i->second.assignments.end());
+			j->second.referenced |= i->second.referenced;
+		}
+		else
+			variables.insert(*i);
+	}
 }
 
 void UnusedVariableRemover::visit(FunctionDeclaration &func)
 {
-	variables.push_back(BlockVariableMap());
-
-	for(NodeArray<VariableDeclaration>::iterator i=func.parameters.begin(); i!=func.parameters.end(); ++i)
-		(*i)->visit(*this);
-	func.body.visit(*this);
-
-	BlockVariableMap &block_variables = variables.back();
+	if(func.body.body.empty())
+		return;
 
-	/* 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;
+	BlockVariableMap saved_vars = variables;
+	// Assignments from other functions should not be visible.
+	for(BlockVariableMap::iterator i=variables.begin(); i!=variables.end(); ++i)
+		i->second.assignments.resize(i->second.initialized);
+	TraversingVisitor::visit(func);
+	swap(variables, saved_vars);
+	merge_variables(saved_vars);
 
 	/* 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();
-}
-
-void UnusedVariableRemover::merge_down_variables()
-{
-	BlockVariableMap &parent_variables = variables[variables.size()-2];
-	BlockVariableMap &block_variables = variables.back();
-	for(BlockVariableMap::iterator i=block_variables.begin(); i!=block_variables.end(); ++i)
 	{
-		if(i->second.local)
-		{
-			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;
-		}
-
-		BlockVariableMap::iterator j = parent_variables.find(i->first);
-		if(j==parent_variables.end())
-			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;
-			j->second.referenced |= i->second.referenced;
-			j->second.assignments.insert(j->second.assignments.end(), i->second.assignments.begin(), i->second.assignments.end());
-		}
+		BlockVariableMap::iterator j = variables.find(i->get());
+		if(j!=variables.end())
+			j->second.referenced = true;
 	}
-	variables.pop_back();
 }
 
 void UnusedVariableRemover::visit(Conditional &cond)
 {
 	cond.condition->visit(*this);
-	variables.push_back(BlockVariableMap());
+	BlockVariableMap saved_vars = variables;
 	cond.body.visit(*this);
-
-	BlockVariableMap if_variables;
-	swap(variables.back(), if_variables);
+	swap(saved_vars, 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;
-		else_variables.insert(*i);
-	}
-
-	merge_down_variables();
+	/* Visible assignments after the conditional is the union of those visible
+	at the end of the if and else blocks.  If there was no else block, then it's
+	the union of the if block and the state before it. */
+	merge_variables(saved_vars);
 }
 
 void UnusedVariableRemover::visit(Iteration &iter)
 {
-	variables.push_back(BlockVariableMap());
+	BlockVariableMap saved_vars = variables;
 	TraversingVisitor::visit(iter);
-	merge_down_variables();
+
+	/* Merge assignments from the iteration, without clearing previous state.
+	Further analysis is needed to determine which parts of the iteration body
+	are always executed, if any. */
+	merge_variables(saved_vars);
 }