/// <summary>
/// Replace reads from variables which are never assigned with a constant `0` (the default value for unassigned vars)
/// </summary>
/// <param name="cfg"></param>
/// <returns></returns>
public static IControlFlowGraph ReplaceUnassignedReads(this IControlFlowGraph cfg)
{
var v = new FindAssignedVariables();
foreach (var vertex in cfg.Vertices)
{
v.Visit(vertex);
}
return(cfg.VisitBlocks(() => new ReplaceUnassignedReads(new HashSet <VariableName>(v.Names))));
}
[NotNull] public static IReadOnlyDictionary <VariableName, BaseExpression> FindConstants([NotNull] this IControlFlowGraph cfg, ISingleStaticAssignmentTable ssa)
{
var constants = new Dictionary <VariableName, BaseExpression>();
var count = -1;
// Keep finding more constants until no more are found
while (count != constants.Count)
{
count = constants.Count;
cfg.VisitBlocks(() => new FindConstantVariables(constants, ssa));
}
return(constants);
}
/// <summary>
/// Find variables which are guaranteed to be `0` or `1`
/// </summary>
/// <param name="cfg"></param>
/// <param name="ssa"></param>
/// <param name="types"></param>
/// <returns></returns>
[NotNull] public static ISet <VariableName> FindBooleanVariables([NotNull] this IControlFlowGraph cfg, ISingleStaticAssignmentTable ssa, ITypeAssignments types)
{
var booleans = new HashSet <VariableName>();
// Keep finding more constants until no more are found
var count = -1;
while (count != booleans.Count)
{
count = booleans.Count;
cfg.VisitBlocks(() => new FindBooleanVariables(booleans, ssa, types));
}
var result = new HashSet <VariableName>(booleans.Where(n => !n.IsExternal));
return(result);
}
/// <summary>
/// Replace expressions which result in a constant with the result
/// </summary>
/// <param name="cfg"></param>
/// <param name="ssa"></param>
/// <returns></returns>
[NotNull] public static IControlFlowGraph FoldConstants([NotNull] this IControlFlowGraph cfg, ISingleStaticAssignmentTable ssa)
{
// Keep finding and replacing constants until nothing is found
cfg = cfg.Fixpoint(c => {
// Find variables which are assigned a value which is not tainted by external reads
var constants = c.FindConstants(ssa);
// Replace reads of a constant variable with the expression assigned to that variable
c = c.VisitBlocks(() => new ReplaceConstantSubexpressions(constants));
return(c);
});
// Replace constant subexpressions with their value
cfg = cfg.VisitBlocks(() => new ConstantFoldingVisitor(true));
return(cfg);
}
/// <summary>
/// Replace inc/dec operations on numbers with a+=1 and a-=1
/// </summary>
/// <param name="cfg"></param>
/// <param name="types"></param>
/// <returns></returns>
public static IControlFlowGraph SimplifyModificationExpressions(this IControlFlowGraph cfg, ITypeAssignments types)
{
return(cfg.VisitBlocks(() => new SimplifyModify(types)));
}
public static IControlFlowGraph RecomposeModify(this IControlFlowGraph cfg)
{
return(cfg.VisitBlocks(() => new RecomposeModifyIR()));
}