From 01d958626441dd209f3880fec49cea17ddc92761 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emmanuel=20Beno=C3=AEt?= <tseeker@nocternity.net>
Date: Sun, 17 Dec 2017 10:30:00 +0100
Subject: [PATCH] Optimizer - Remove unused globals

---
 TODO       |  1 +
 c-opopt.cc | 48 +++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/TODO b/TODO
index 8db62c2..cff506d 100644
--- a/TODO
+++ b/TODO
@@ -18,6 +18,7 @@ Scripting:
 		* Unused arguments
 		* Dead store: call arguments
 		* Unused functions
+		* Unused inputs
 	* Common subexpressions
 	* Strength reduction
 	* Loop-invariant code motion
diff --git a/c-opopt.cc b/c-opopt.cc
index 13e6b4f..9c1078c 100644
--- a/c-opopt.cc
+++ b/c-opopt.cc
@@ -1710,7 +1710,6 @@ bool RDCUnusedLocals_(
 		) noexcept
 {
 	M_LOGSTR_( "...... Removing unused locals" , 3 );
-	oData.buildUseDefineChains( program );
 
 	const auto nf{ program.root.nFunctions( ) };
 	bool changed{ false };
@@ -1734,7 +1733,7 @@ bool RDCUnusedLocals_(
 			}
 			oData.logger( [&](){
 				T_StringBuilder sb;
-				sb << "Removing used local variable "
+				sb << "Removing unused local variable "
 					<< ln << " at "
 					<< func.getLocalLocation( l );
 				return sb;
@@ -1747,6 +1746,49 @@ bool RDCUnusedLocals_(
 	return changed;
 }
 
+bool RDCUnusedGlobals_(
+		T_OpsParserOutput&	program ,
+		T_OptData&		oData
+		) noexcept
+{
+	M_LOGSTR_( "...... Removing unused globals" , 3 );
+
+	T_AutoArray< T_String , 16 > remove;
+	for ( auto const& gn : program.types.keys( ) ) {
+		const auto gt{ *program.types.get( gn ) };
+		if ( gt == E_DataType::BUILTIN || gt == E_DataType::INPUT ) {
+			continue;
+		}
+		const T_OptData::T_VarId vid{ gn };
+		if ( !oData.varUDChains.contains( vid ) ) {
+			remove.add( gn );
+		}
+	}
+
+	const auto nr{ remove.size( ) };
+	for ( auto i = 0u ; i < nr ; i ++ ) {
+		auto const& gn{ remove[ i ] };
+		oData.logger( [&](){
+			T_StringBuilder sb;
+			sb << "Removing unused global " << gn;
+			return sb;
+		} , 4 );
+		program.types.remove( gn );
+	}
+	return remove.size( );
+}
+
+bool RDCUnused_(
+		T_OpsParserOutput&	program ,
+		T_OptData&		oData
+		) noexcept
+{
+	oData.buildUseDefineChains( program );
+	const bool locals{ RDCUnusedLocals_( program , oData ) };
+	const bool globals{ RDCUnusedGlobals_( program , oData ) };
+	return locals || globals;
+}
+
 } // namespace <anon>
 
 /*----------------------------------------------------------------------------*/
@@ -1770,7 +1812,7 @@ bool opopt::RemoveDeadCode(
 
 		didStuffThisTime = RDCConditionals_( program , oData )
 			|| RDCDeadStores_( program , oData )
-			|| RDCUnusedLocals_( program , oData );
+			|| RDCUnused_( program , oData );
 		didStuff = didStuff || didStuffThisTime;
 	} while ( didStuffThisTime );