From 96881e56ececfa3f4b0707dc168c687b35d249a0 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 12 Nov 2016 02:04:14 +0200
Subject: [PATCH] Return back to first stage after some optimization happens

Unused variable removal can propagate towards earlier stages so those
have to be checked again.
---
 source/programcompiler.cpp | 27 ++++++++++++++-------------
 source/programcompiler.h   |  2 +-
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/source/programcompiler.cpp b/source/programcompiler.cpp
index 79031e41..934416c2 100644
--- a/source/programcompiler.cpp
+++ b/source/programcompiler.cpp
@@ -55,8 +55,13 @@ void ProgramCompiler::process()
 {
 	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); ++i)
 		generate(*i);
-	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); ++i)
-		optimize(*i);
+	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); )
+	{
+		if(optimize(*i))
+			i = module->stages.begin();
+		else
+			++i;
+	}
 }
 
 void ProgramCompiler::generate(Stage &stage)
@@ -69,20 +74,16 @@ void ProgramCompiler::generate(Stage &stage)
 	apply<VariableRenamer>(stage);
 }
 
-void ProgramCompiler::optimize(Stage &stage)
+bool ProgramCompiler::optimize(Stage &stage)
 {
-	while(1)
-	{
-		UnusedVariableLocator unused_locator;
-		unused_locator.apply(stage);
+	UnusedVariableLocator unused_locator;
+	unused_locator.apply(stage);
 
-		NodeRemover remover;
-		remover.to_remove = unused_locator.unused_nodes;
-		remover.apply(stage);
+	NodeRemover remover;
+	remover.to_remove = unused_locator.unused_nodes;
+	remover.apply(stage);
 
-		if(!remover.n_removed)
-			break;
-	}
+	return remover.n_removed;
 }
 
 void ProgramCompiler::inject_block(Block &target, const Block &source)
diff --git a/source/programcompiler.h b/source/programcompiler.h
index 3b63c5e9..34b64b55 100644
--- a/source/programcompiler.h
+++ b/source/programcompiler.h
@@ -139,7 +139,7 @@ public:
 private:
 	void process();
 	void generate(ProgramSyntax::Stage &);
-	void optimize(ProgramSyntax::Stage &);
+	bool optimize(ProgramSyntax::Stage &);
 	static void inject_block(ProgramSyntax::Block &, const ProgramSyntax::Block &);
 	template<typename T>
 	static void apply(ProgramSyntax::Stage &);
-- 
2.43.0