private static void DeadCodeElimination(IRGraph graph)
{
Dictionary <Ident, IRIdent> identAnalysis = SimpleVariableAnalysis(graph);
Queue <Ident> worklist = new Queue <Ident>(identAnalysis.Keys);
while (worklist.Count > 0)
{
Ident ident = worklist.Dequeue();
IRIdent identObj = identAnalysis[ident];
if (identObj.CountUsesites() == 0)
{
IRTuple defStatement = identObj.GetDefsite();
if (!defStatement.HasSideEffects())
{
Console.WriteLine("SSA: Deleting tuple: " + defStatement.toString() + " as it is dead code");
HashSet <Ident> usedVars = defStatement.GetUsedVars();
foreach (Ident used in usedVars)
{
IRIdent usedObj = identAnalysis[used];
usedObj.DeleteUsesite(defStatement);
worklist.Enqueue(used);
}
graph.RemoveStatement(defStatement);
}
}
}
}
private static Dictionary <Ident, IRIdent> SimpleVariableAnalysis(IRGraph graph)
{
Dictionary <Ident, IRIdent> identAnalysis = new Dictionary <Ident, IRIdent>();
foreach (IRBlock block in graph.GetSetOfAllBlocks())
{
foreach (IRTuple stmt in block.GetStatements())
{
HashSet <Ident> usedVars = stmt.GetUsedVars();
foreach (Ident ident in usedVars)
{
IRIdent identObj;
if (identAnalysis.ContainsKey(ident))
{
identObj = identAnalysis[ident];
}
else
{
identObj = new IRIdent(ident, stmt);
identAnalysis[ident] = identObj;
}
identObj.AddUsesite(stmt);
}
HashSet <Ident> definedVars = stmt.GetDefinedVars();
foreach (Ident ident in definedVars)
{
if (!identAnalysis.ContainsKey(ident))
{
IRIdent identObj = new IRIdent(ident, stmt);
identAnalysis[ident] = identObj;
}
}
}
}
return(identAnalysis);
}
private static Dictionary<Ident, IRIdent> SimpleVariableAnalysis(IRGraph graph)
{
Dictionary<Ident, IRIdent> identAnalysis = new Dictionary<Ident, IRIdent>();
foreach (IRBlock block in graph.GetSetOfAllBlocks())
{
foreach (IRTuple stmt in block.GetStatements())
{
HashSet<Ident> usedVars = stmt.GetUsedVars();
foreach (Ident ident in usedVars)
{
IRIdent identObj;
if (identAnalysis.ContainsKey(ident)) {
identObj = identAnalysis[ident];
} else {
identObj = new IRIdent(ident, stmt);
identAnalysis[ident] = identObj;
}
identObj.AddUsesite(stmt);
}
HashSet<Ident> definedVars = stmt.GetDefinedVars();
foreach (Ident ident in definedVars)
{
if (!identAnalysis.ContainsKey(ident)) {
IRIdent identObj = new IRIdent(ident, stmt);
identAnalysis[ident] = identObj;
}
}
}
}
return identAnalysis;
}
