Optimizer - DCE: find conditionals with constant inputs

TODO

@@ -14,8 +14,6 @@ Scripting:
 * Aliases
 * Display errors in UI
 * Optimizer:
-	* Constant propagation
-		* Call arguments
 	* Dead code elimination
 		* Local variables
 		* Unused arguments

c-opopt.cc

@@ -1573,5 +1573,49 @@ bool opopt::RemoveDeadCode(
 		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;
+	oData.visitor.visit( program.root , [&]( A_Node& node , const bool exit ) {
+		const auto nt{ node.type( ) };
+
+		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 } );
+				return false;
+			}
+		}
+
+		return !dynamic_cast< A_ExpressionNode* >( &node );
+	} );
+
+	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 );
+			if ( cn.hasCase( cc.value ) ) {
+				printf( "Will replace with case\n" );
+				replacement = &cn.getCase( cc.value ).instructions( );
+			} else if ( cn.hasDefaultCase( ) ) {
+				printf( "Will replace with default\n" );
+				replacement = &cn.defaultCase( ).instructions( );
+			} else {
+				printf( "DELETE! DELETE! DELETE!\n" );
+				replacement = nullptr;
+			}
+		}
+	}
+
 	return false;
 }

test/build.srd

@@ -8,6 +8,7 @@
 			(fixed-resolution on)
 		)
 		(constant-propagation on)
+		(dead-code-elimination on)
 	)
 )