public static bool HasMoreThanOneUses(PStm statement, AALocalDecl decl, SharedData data, out ALocalLvalue lvalue)
{
GetUses uses = new GetUses(decl, data);
statement.Apply(uses);
lvalue = uses.lvalue;
return(uses.count > 1);
}
public static bool Parse(ControlFlowGraph cfg, SharedData data)
{
Dictionary <PStm, ControlFlowGraph.Node> statementNodes = new Dictionary <PStm, ControlFlowGraph.Node>();
//Dictionary<ControlFlowGraph.Node, List<AALocalDecl>> uses = new Dictionary<ControlFlowGraph.Node, List<AALocalDecl>>();
foreach (ControlFlowGraph.Node node in cfg.Nodes)
{
statementNodes[node.Statement] = node;
/*GetUses getUses = new GetUses();
* node.Statement.Apply(getUses);
* uses[node] = getUses.Uses;*/
}
foreach (ControlFlowGraph.Node node in cfg.Nodes)
{
if (node.Expression is AAssignmentExp)
{
AAssignmentExp exp = (AAssignmentExp)node.Expression;
if (exp.GetLvalue() is ALocalLvalue)
{
AALocalDecl decl = data.LocalLinks[(ALocalLvalue)exp.GetLvalue()];
bool dontMove = false;
LocalChecker.ModifyData declModData = LocalChecker.GetLocalData(node.Expression, data);
/*1: Search for unique use of decl
* Stop if you find an assignment to decl
* Stop if decl is not live
* Cancel if you find two uses of decl (also within one statement)
*/
ControlFlowGraph.Node useNode = null;
LinkedList <ControlFlowGraph.Node> nextNodes = new LinkedList <ControlFlowGraph.Node>();
LinkedList <ControlFlowGraph.Node> visitedNodes = new LinkedList <ControlFlowGraph.Node>();
foreach (var successor in node.Successors)
{
nextNodes.AddLast(successor);
}
while (nextNodes.Count > 0)
{
ControlFlowGraph.Node successor = nextNodes.First.Value;
nextNodes.RemoveFirst();
visitedNodes.AddLast(successor);
LocalChecker.ModifyData succData = LocalChecker.GetLocalData(successor.Expression, data);
//Stop if decl is not live
if (!successor.LiveVariables.Contains(decl))
{
continue;
}
//Check if this node uses it)
if (succData.Locals.ContainsKey(decl))
{
var val = succData.Locals[decl];
if (val.Reads)
{
if (useNode == null)
{
useNode = successor;
}
else
{
//Cancel if we found two uses
dontMove = true;
break;
}
}
//Stop if it writes to the variable
if (val.Writes)
{
continue;
}
}
foreach (ControlFlowGraph.Node nextSucc in successor.Successors)
{
if (visitedNodes.Contains(nextSucc))
{
continue;
}
nextNodes.AddLast(nextSucc);
}
}
ALocalLvalue usedLvalue;
if (dontMove ||
useNode == null ||
//Cancel if there are two uses of the local within same statement
GetUses.HasMoreThanOneUses(useNode.Statement, decl, data, out usedLvalue))
{
continue;
}
/*2: Search back from found statement, to ensure unique assignment
* Stop if assignment reached
* Cancel if start of method is reached
* Cancel if any statement reads/writes to a variable used in the statement (where one of them writes)
* Cancel if another assignment to x is found (including local decls)
*/
visitedNodes.Clear();
nextNodes.Clear();
foreach (ControlFlowGraph.Node predecessor in useNode.Predecessors)
{
nextNodes.AddLast(predecessor);
}
while (nextNodes.Count > 0)
{
ControlFlowGraph.Node predecessor = nextNodes.First.Value;
nextNodes.RemoveFirst();
visitedNodes.AddLast(predecessor);
LocalChecker.ModifyData predData = LocalChecker.GetLocalData(predecessor.Expression, data);
//Stop if assignment reached
if (predecessor == node)
{
continue;
}
//Cancel if this statement writes to decl
if (predData.Locals.ContainsKey(decl) &&
predData.Locals[decl].Writes ||
predecessor.Statement is ALocalDeclStm &&
((ALocalDeclStm)predecessor.Statement).GetLocalDecl() == decl)
{
dontMove = true;
break;
}
//Cancel if any statement reads/writes to a variable used in the statement (where one of them writes)
if (declModData.Conflicts(predData))
{
dontMove = true;
break;
}
//Cancel if start of method is reached
if (predecessor.Predecessors.Count == 0)
{
dontMove = true;
break;
}
foreach (ControlFlowGraph.Node nextPred in predecessor.Predecessors)
{
if (visitedNodes.Contains(nextPred))
{
continue;
}
nextNodes.AddLast(nextPred);
}
}
if (dontMove)
{
continue;
}
//Move it
cfg.Remove(node);
node.Statement.Parent().RemoveChild(node.Statement);
usedLvalue.Parent().ReplaceBy(exp.GetExp());
//We now need to redo liveness analysis
return(true);
}
}
}
return(false);
}
public static bool HasMoreThanOneUses(PStm statement, AALocalDecl decl, SharedData data, out ALocalLvalue lvalue)
{
GetUses uses = new GetUses(decl, data);
statement.Apply(uses);
lvalue = uses.lvalue;
return uses.count > 1;
}