private static bool SimplifyScans(AbstractSyntaxTree root)
{
if (root.Count > 1)
{
bool RetVal = false;
foreach (AbstractSyntaxTree ast in root.ChildNodes)
{
RetVal |= SimplifyScans(ast);
}
return(RetVal);
}
if (root.Count == 1)
{
if (root[0].Op == OpCode.AddPtr)
{
root.RemoveAt(0);
root.Op = OpCode.ScanRight;
return(true);
}
if (root[0].Op == OpCode.SubPtr)
{
root.RemoveAt(0);
root.Op = OpCode.ScanLeft;
return(true);
}
}
return(false);
}
private static bool EliminateUnreachableLoops(AbstractSyntaxTree root, bool trueRoot)
{
bool RetVal = false;
for (int i = 1; i < root.Count; i++)
{
RetVal |= EliminateUnreachableLoops(root[i], false);
if (root[i].Op == OpCode.Loop && (root[i - 1].Op == OpCode.Loop || root[i - 1].Op == OpCode.AssignZero))
{
root.RemoveAt(i);
RetVal = true;
i--;
}
}
if (trueRoot)
{
if (root.Count > 0 && root[0].Op == OpCode.Loop)
{
root.RemoveAt(0);
return(true);
}
if (root.Count == 0 && root.Op == OpCode.Loop)
{
root.Op = OpCode.Nop;
return(true);
}
}
return(RetVal);
}
private static bool EliminateDeadStores(AbstractSyntaxTree root, bool trueRoot)
{
bool RetVal = false;
for (int i = root.Count - 2; i >= 0; i--)
{
RetVal |= EliminateDeadStores(root[i], false);
if (root[i + 1].Op == OpCode.AssignZero || root[i + 1].Op == OpCode.AssignVal)
{
AbstractSyntaxTree ast = root[i];
if (ast.Op.AssignsValue() || ast.Op == OpCode.AssignZero || ast.Op.ModifiesValue())
{
root.Remove(ast);
}
}
}
if (root.Count > 0 && root[0].Op == OpCode.AssignZero && trueRoot)
{
root.RemoveAt(0);
return(true);
}
return(RetVal);
}
internal static bool EliminateConflictingInstructions(AbstractSyntaxTree ast)
{
bool RetVal = false;
if (ast.Count > 0)
{
RetVal |= EliminateConflictingInstructions(ast[0]);
}
for (int i = 1; i < ast.Count; i++)
{
RetVal |= EliminateConflictingInstructions(ast[i]);
if (ast[i - 1].Op.IsReversable() && ast[i - 1].Op.GetReversedOpCode() == ast[i].Op)
{
ast.RemoveAt(i);
ast.RemoveAt(i - 1);
i += 2;
RetVal = true;
}
}
return(RetVal);
}