/// <summary>
/// Constructs a new instance
/// </summary>
/// <param name="instructions">instruction list</param>
/// <param name="dflowAnalyzer">dataflow analyzer which serves as analysis back-end</param>
public LocalVariableOptimizer(IList <XILSInstr> instructions,
DataflowAnalyzer <XILSInstr> dflowAnalyzer) :
base(instructions)
{
DflowAnalyzer = dflowAnalyzer;
SetHandler(InstructionCodes.StoreVar, HandleStoreVar);
SetHandler(InstructionCodes.LoadVar, HandleLoadVar);
}
/// <summary>
/// Constructs a new instance
/// </summary>
/// <param name="instructions">instruction list</param>
/// <param name="dflowAnalyzer">dataflow analyzer which serves as analysis back-end</param>
public LocalVariableOptimizer(IList<XILSInstr> instructions,
DataflowAnalyzer<XILSInstr> dflowAnalyzer) :
base(instructions)
{
DflowAnalyzer = dflowAnalyzer;
SetHandler(InstructionCodes.StoreVar, HandleStoreVar);
SetHandler(InstructionCodes.LoadVar, HandleLoadVar);
}
/// <summary>
/// Tries to reduce the number of local variables by replacing them with their right-hand side expressions where possible
/// </summary>
/// <param name="cfg">XIL-S control-flow graph</param>
/// <returns>resulting instruction list</returns>
public static List <XILSInstr> OptimizeLocals(ControlFlowGraph <XILSInstr> cfg)
{
var locals = cfg.Instructions.RenumerateLocalVariables();
int numLocals = locals.Any() ? locals.Max(l => ((Variable)l).LocalIndex) + 1 : 0;
var dfa = new DataflowAnalyzer <XILSInstr>(cfg, numLocals)
{
DoNotOptimizeAcrossBasicBlocks = true
};
dfa.Run();
var lva = new LocalVariableOptimizer(cfg.Instructions, dfa);
lva.Rewrite();
var newLocals = locals.Where(v => !dfa.IsEliminable(((Variable)v).LocalIndex)).ToList();
return(lva.OutInstructions);
}
