Optimizer - Remove dead branches

c-opast.cc

@@ -447,6 +447,50 @@ uint32_t T_FuncNode::arguments( ) const noexcept
 	return na;
 }
 
+/*= T_InstrListNode ==========================================================*/
+
+void T_InstrListNode::replaceMultiple(
+		A_InstructionNode&	instruction ,
+		T_InstrListNode*	replacement
+		) noexcept
+{
+	T_OwnPtr< A_InstructionNode > oldInstr;
+	uint32_t index{ 0xffffffff };
+	for ( auto i = 0u ; i < children_.size( ) ; i ++ ) {
+		if ( children_[ i ].get( ) == &instruction ) {
+			oldInstr = std::move( children_[ i ] );
+			index = i;
+			break;
+		}
+	}
+	assert( oldInstr );
+
+	if ( replacement ) {
+		auto& rep{ *replacement };
+
+		// Move existing children to the end of the list
+		const auto oldSize{ children_.size( ) };
+		for ( auto i = 1u ; i < rep.size( ) ; i ++ ) {
+			children_.addNew( );
+		}
+		const auto newSize{ children_.size( ) };
+		const auto nMove{ oldSize + 1 - index };
+		for ( auto i = 1u ; i < nMove ; i ++ ) {
+			children_[ newSize - i ] = std::move(
+					children_[ oldSize - i ] );
+		}
+
+		// Move replacement instructions
+		for ( auto i = 0u ; i < rep.size( ) ; i ++ ) {
+			children_[ index + i ] = std::move(
+					rep.children_[ i ] );
+			children_[ index + i ]->setParent( *this );
+		}
+	} else {
+		children_.remove( index );
+	}
+}
+
 
 /*= T_PipelineInstrNode ======================================================*/
 

c-opast.hh

@@ -72,7 +72,7 @@ class A_Node
 
     private:
 	const E_Type type_;
-	A_Node* const parent_;
+	A_Node* parent_;
 	ebcl::T_SRDLocation location_;
 
     protected:
@@ -109,6 +109,9 @@ class A_Node
 
 	bool replace( A_Node const& node ,
 			T_OwnPtr< A_Node >& replacement ) noexcept;
+
+	void setParent( A_Node& newParent ) noexcept
+		{ parent_ = &newParent; }
 };
 
 // Browser function to be used with T_Visitor
@@ -178,6 +181,10 @@ class T_InstrListNode : public A_Node
 
 	A_InstructionNode& node( const uint32_t index ) const noexcept
 		{ return dynamic_cast< A_InstructionNode& >( *children_[ index ] ); }
+
+	void replaceMultiple(
+			A_InstructionNode& instruction ,
+			T_InstrListNode* replacement ) noexcept;
 };
 
 template<

c-opopt.cc

@@ -497,10 +497,12 @@ void T_OptData::buildControlFlowGraph(
 		return;
 	}
 	numberInstructions( program );
+	M_LOGSTR_( "Building control flow graph" , 4 );
 
 	// Keep the old array, we'll reuse its contents
 	T_Array< P_CtrlFlowNode > old{ std::move( ctrlFlowGraph ) };
-	M_LOGSTR_( "Building control flow graph" , 4 );
+	callSites.clear( );
+	cfgFunctions.clear( );
 
 	// Create special nodes
 	M_ADDNEW_( );
@@ -512,7 +514,6 @@ void T_OptData::buildControlFlowGraph(
 	// Generate control flow graph for each function
 	T_BCFGStack_ stack;
 	T_Optional< uint32_t > cNode{ };
-	callSites.clear( );
 	visitor.visit( program.root , [&]( A_Node& node , const bool exit ) {
 		return BCFGVisitor_( node , exit , *this ,
 				stack , cNode , old );
@@ -1568,54 +1569,112 @@ bool opopt::PropagateConstants(
 
 
 /*= DEAD CODE REMOVAL ========================================================*/
+namespace {
 
-bool opopt::RemoveDeadCode(
+struct T_RDCConstCond_
-		T_OpsParserOutput& program ,
-		T_OptData& oData ) noexcept
 {
-	oData.buildUseDefineChains( program );
-	M_LOGSTR_( "... Eliminating dead code" , 2 );
-
-	struct T_ConstCond_ {
 	T_CondInstrNode* node;
 	int64_t value;
 };
-	T_AutoArray< T_ConstCond_ , 16 > constConds;
+using T_RDCConstCondList_ = T_AutoArray< T_RDCConstCond_ , 16 >;
-	oData.visitor.visit( program.root , [&]( A_Node& node , const bool exit ) {
+
-		const auto nt{ node.type( ) };
+bool RDCFindConditionals_(
+		A_Node&			node ,
+		const bool		exit ,
+		T_RDCConstCondList_&	constConds
+		) noexcept
+{
+	if ( exit || node.type( ) != A_Node::OP_COND ) {
+		return !dynamic_cast< A_ExpressionNode* >( &node );
+	}
 
-		if ( !exit && nt == A_Node::OP_COND ) {
 	auto& cn{ dynamic_cast< T_CondInstrNode& >( node ) };
 	auto const& ce{ cn.expression( ).expression( ) };
 	if ( ce.type( ) == A_Node::EXPR_CONST ) {
 		const int64_t ccv{ ( (T_ConstantExprNode const&) ce ).intValue( ) };
-				constConds.add( T_ConstCond_{ &cn , ccv } );
+		constConds.add( T_RDCConstCond_{ &cn , ccv } );
 		return false;
 	}
+	return true;
 }
 
-		return !dynamic_cast< A_ExpressionNode* >( &node );
+bool RDCConditionals_(
-	} );
+		T_OpsParserOutput&	program ,
+		T_OptData&		oData
+		) noexcept
+{
+	M_LOGSTR_( "...... Checking conditional instructions" , 3 );
+
+	T_RDCConstCondList_ constConds;
+	oData.visitor.visit( program.root , [&]( A_Node& node , const bool exit ) {
+		return RDCFindConditionals_( node , exit , constConds );
+	} );
+	if ( !constConds.size( ) ) {
+		return false;
+	}
 
-	if ( constConds.size( ) ) {
 	const auto ncc{ constConds.size( ) };
 	for ( auto i = 0u ; i < ncc ; i ++ ) {
 		auto const& cc{ constConds[ i ] };
 		auto& cn{ *cc.node };
 		T_InstrListNode* replacement;
-			printf( "IF (CNST: %ld)!!!\n" , cc.value );
+		oData.logger( [&](){
+			T_StringBuilder sb;
+			sb << "......... Conditional with constant argument at "
+				<< cn.location( );
+			return sb;
+		} , 4 );
 		if ( cn.hasCase( cc.value ) ) {
-				printf( "Will replace with case\n" );
 			replacement = &cn.getCase( cc.value ).instructions( );
+			oData.logger( [&](){
+				T_StringBuilder sb;
+				sb << "Will replace with case for value "
+					<< cc.value << " ("
+					<< replacement->location( ) << ")";
+				return sb;
+			} , 5 );
 		} else if ( cn.hasDefaultCase( ) ) {
-				printf( "Will replace with default\n" );
 			replacement = &cn.defaultCase( ).instructions( );
+			oData.logger( [&](){
+				T_StringBuilder sb;
+				sb << "Will replace with default case ("
+					<< replacement->location( ) << ")";
+				return sb;
+			} , 5 );
 		} else {
-				printf( "DELETE! DELETE! DELETE!\n" );
+			M_LOGSTR_( "Will delete whole instruction" , 5 );
 			replacement = nullptr;
 		}
-		}
+		( (T_InstrListNode&) cn.parent( ) ).replaceMultiple( cn , replacement );
 	}
 
-	return false;
+	oData.state = {};
+	return true;
+}
+
+} // namespace <anon>
+
+/*----------------------------------------------------------------------------*/
+
+bool opopt::RemoveDeadCode(
+		T_OpsParserOutput& program ,
+		T_OptData& oData ) noexcept
+{
+//	oData.buildUseDefineChains( program );
+	M_LOGSTR_( "... Eliminating dead code" , 2 );
+
+	bool didStuff{ false };
+//	bool tryDeadStoresFirst{ oData.state & T_OptData::E_StateItem::UDCHAINS };
+	bool didStuffThisTime;
+	do {
+		didStuffThisTime = RDCConditionals_( program , oData );
+		didStuff = didStuff || didStuffThisTime;
+	} while ( didStuffThisTime );
+
+	if ( didStuff ) {
+		M_LOGSTR_( "...... Dead code removed" , 3 );
+	} else {
+		M_LOGSTR_( "...... No dead code found" , 3 );
+	}
+	return didStuff;
 }