From e9d5d1945f110d5307036af0d4b3f0c3ebfe3d2a Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 16 Jun 2018 19:38:11 +0300
Subject: [PATCH] Reorder functions in dependency order

Otherwise the inliner might inline a function to a point before its
original definition.  This can break references to other functions
declared after the inlining point, causing the unused function eliminator
to eventually remove them.
---
 source/programcompiler.cpp | 68 ++++++++++++++++++++++++++++++++++++++
 source/programcompiler.h   |  8 +++--
 2 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/source/programcompiler.cpp b/source/programcompiler.cpp
index fbcc6598..0aed5936 100644
--- a/source/programcompiler.cpp
+++ b/source/programcompiler.cpp
@@ -987,13 +987,30 @@ void ProgramCompiler::InterfaceGenerator::visit(Passthrough &pass)
 
 
 ProgramCompiler::DeclarationReorderer::DeclarationReorderer():
+	scope_level(0),
 	kind(NO_DECLARATION)
 { }
 
+void ProgramCompiler::DeclarationReorderer::visit(FunctionCall &call)
+{
+	FunctionDeclaration *def = call.declaration;
+	if(def)
+		def = def->definition;
+	if(def && !ordered_funcs.count(def))
+		needed_funcs.insert(def);
+}
+
 void ProgramCompiler::DeclarationReorderer::visit(Block &block)
 {
+	SetForScope<unsigned> set(scope_level, scope_level+1);
+	if(scope_level>1)
+		return Visitor::visit(block);
+
 	list<RefPtr<Node> >::iterator struct_insert_point = block.body.end();
 	list<RefPtr<Node> >::iterator variable_insert_point = block.body.end();
+	list<RefPtr<Node> >::iterator function_insert_point = block.body.end();
+	unsigned unordered_func_count = 0;
+	bool ordered_any_funcs = false;
 
 	for(list<RefPtr<Node> >::iterator i=block.body.begin(); i!=block.body.end(); )
 	{
@@ -1017,13 +1034,64 @@ void ProgramCompiler::DeclarationReorderer::visit(Block &block)
 		else if(kind>VARIABLE && variable_insert_point==block.body.end())
 			variable_insert_point = i;
 
+		if(kind==FUNCTION)
+		{
+			if(function_insert_point==block.body.end())
+				function_insert_point = i;
+
+			if(needed_funcs.empty())
+			{
+				ordered_funcs.insert(i->get());
+				if(i!=function_insert_point)
+				{
+					block.body.insert(function_insert_point, *i);
+					moved = true;
+				}
+				else
+					++function_insert_point;
+				ordered_any_funcs = true;
+			}
+			else
+				++unordered_func_count;
+		}
+
 		if(moved)
+		{
+			if(function_insert_point==i)
+				++function_insert_point;
 			block.body.erase(i++);
+		}
 		else
 			++i;
+
+		if(i==block.body.end() && unordered_func_count)
+		{
+			if(!ordered_any_funcs)
+				// A subset of the remaining functions forms a recursive loop
+				/* TODO pick a function and move it up, adding any necessary
+				declarations */
+				break;
+
+			i = function_insert_point;
+			unordered_func_count = 0;
+		}
 	}
 }
 
+void ProgramCompiler::DeclarationReorderer::visit(ProgramSyntax::VariableDeclaration &var)
+{
+	Visitor::visit(var);
+	kind = VARIABLE;
+}
+
+void ProgramCompiler::DeclarationReorderer::visit(FunctionDeclaration &func)
+{
+	needed_funcs.clear();
+	func.body.visit(*this);
+	needed_funcs.erase(&func);
+	kind = FUNCTION;
+}
+
 
 ProgramCompiler::InlineableFunctionLocator::InlineableFunctionLocator():
 	in_function(0)
diff --git a/source/programcompiler.h b/source/programcompiler.h
index b14c03d8..7e8d3373 100644
--- a/source/programcompiler.h
+++ b/source/programcompiler.h
@@ -169,17 +169,21 @@ private:
 			FUNCTION
 		};
 
+		unsigned scope_level;
 		DeclarationKind kind;
+		std::set<ProgramSyntax::Node *> ordered_funcs;
+		std::set<ProgramSyntax::Node *> needed_funcs;
 
 		DeclarationReorderer();
 
 		using Visitor::visit;
 		virtual void visit(ProgramSyntax::Block &);
+		virtual void visit(ProgramSyntax::FunctionCall &);
 		virtual void visit(ProgramSyntax::InterfaceLayout &) { kind = LAYOUT; }
 		virtual void visit(ProgramSyntax::StructDeclaration &) { kind = STRUCT; }
-		virtual void visit(ProgramSyntax::VariableDeclaration &) { kind = VARIABLE; }
+		virtual void visit(ProgramSyntax::VariableDeclaration &);
 		virtual void visit(ProgramSyntax::InterfaceBlock &) { kind = VARIABLE; }
-		virtual void visit(ProgramSyntax::FunctionDeclaration &) { kind = FUNCTION; }
+		virtual void visit(ProgramSyntax::FunctionDeclaration &);
 	};
 
 	struct InlineableFunctionLocator: Visitor
-- 
2.45.2