// note. pattern #1:
// * ref = atom
// * read(ref)
// conditions:
// 1) ref is read only once after it had been assigned
// 2) atom isn't reassigned before read(ref) takes place
// 3) if ref is CF$XXXX then atom can be of any node type (not only an atom)
// transformed into:
// * read(atom)
private static bool TryMatchPattern1(DfaHelper dfa, Expression atom)
{
var p1_ref = atom as Ref;
if (p1_ref == null) return false;
var p1_lastass = dfa.Writes(p1_ref).LastOrDefault();
if (p1_lastass == null) return false;
var p1_ref_onlyread_afterass = dfa.Reads(p1_ref).SingleOrDefault2(
r => dfa.ExecOrderOfStmt(r) >= dfa.ExecOrderOfStmt(p1_lastass));
if (p1_ref_onlyread_afterass == null) return false;
var p1_atom = p1_lastass.Rhs;
if (!p1_ref.Sym.Name.StartsWith("CF$") &&
!p1_ref.Sym.Name.StartsWith("CS$"))
{
if (!p1_atom.IsAtom()) return false;
var p1_atom_reasses = dfa.Writes(p1_atom).Where(w =>
dfa.ExecOrderOfStmt(p1_lastass) <= dfa.ExecOrderOfStmt(w) &&
dfa.ExecOrderOfStmt(w) <= dfa.ExecOrderOfStmt(p1_ref_onlyread_afterass));
if (p1_atom_reasses.IsNotEmpty()) return false;
}
dfa.Remove(p1_lastass);
var p1_ref_onlyread_stmt = p1_ref_onlyread_afterass.Stmt();
dfa.ReplaceRecursive(p1_ref_onlyread_stmt, p1_ref, p1_atom);
return true;
}
public static void DoRestoreOpAssignOperators(ControlFlowGraph cfg, Symbols symbols)
{
var dirty = true;
var dfa = new DfaHelper(cfg);
while (dirty)
{
dirty = false;
foreach (var atom in dfa.Atoms())
{
if (dirty |= TryMatchPattern1(dfa, atom)) break;
if (dirty |= TryMatchPattern2(dfa, atom)) break;
if (dirty |= TryMatchPattern3(dfa, atom)) break;
if (dirty |= TryMatchPattern4(dfa, atom)) break;
}
}
}
// note. pattern #2:
// * atom = atom op any
// transformed into:
// * atom [op=] any
private static bool TryMatchPattern2(DfaHelper dfa, Expression atom)
{
var p2_atom = atom;
foreach (var p2_ass in dfa.Writes(atom))
{
if (!(p2_ass.Rhs is BinaryOperator)) continue;
var binary = p2_ass.Rhs as BinaryOperator;
if (!p2_atom.Equiv(binary.Lhs)) continue;
var p2_opeq = p2_atom.CreateOpPreAssign(binary.OperatorType, binary.Rhs);
if (p2_opeq == null) return false;
dfa.Replace(p2_ass, p2_opeq);
return true;
}
return false;
}
// note. pattern #4
// <hoard> ref = atom
// <op> atom = ref op any
// <usage> read(ref)
// conditions:
// 1) exactly one read of ref
// 2) <hoard> comes before <op> and <usage>
// 3) <op> and <usage> may be ordered arbitrarily
// 4) op is either an increment or a decrement
// transformed into either:
// * read(atom++), if op is an increment (use IsInc() method to test)
// * read(atom--), if op is a decrement (use IsDec() method to test)
private static bool TryMatchPattern4(DfaHelper dfa, Expression atom)
{
var p4_ref = atom as Ref;
if (p4_ref == null) return false;
var p4_usages = dfa.Usages(p4_ref);
if (p4_usages.Count() != 3) return false;
var p4_op = p4_usages.Select(u => u.Stmt()).OfType<Assign>().SingleOrDefault2(ass =>
{
var bo = ass.Rhs as BinaryOperator;
if (bo == null) return false;
return bo.Lhs.Equiv(p4_ref);
});
if (p4_op == null) return false;
var p4_atom = p4_op.Lhs;
if (!p4_atom.IsAtom()) return false;
var p4_bop = p4_op.Rhs as BinaryOperator;
if (p4_bop == null) return false;
if (!p4_bop.Lhs.Equiv(p4_ref)) return false;
var p4_optype = p4_bop.OperatorType;
var p4_any = p4_bop.Rhs;
var p4_hoard = p4_usages.First().Stmt();
var p4_hoard_template = new Assign(p4_ref, p4_atom);
if (!p4_hoard.Equiv(p4_hoard_template)) return false;
var p4_usage = p4_usages.Select(u => u.Stmt()).Except(p4_op).Last();
var p4_opeq = p4_atom.CreateOpPostAssign(p4_optype, p4_any);
if (p4_opeq == null) return false;
dfa.Remove(p4_hoard, p4_op);
dfa.ReplaceRecursive(p4_usage, p4_ref, p4_opeq);
return true;
}
// note. pattern #3:
// <op> ref = atom op any
// <wb> atom = ref
// <usage> read(ref)
// conditions:
// 1) exactly one read of ref
// 2) <op> comes before <wb> and <usage>
// 3) <wb> and <usage> may be ordered arbitrarily
// transformed into either:
// * read(++atom), if op is an increment (use IsInc() method to test)
// * read(--atom), if op is a decrement (use IsDec() method to test)
// * read(atom [op=] any), otherwise
private static bool TryMatchPattern3(DfaHelper dfa, Expression atom)
{
var p3_ref = atom as Ref;
if (p3_ref == null) return false;
var p3_usages = dfa.Usages(p3_ref);
if (p3_usages.Count() != 3) return false;
var p3_op = p3_usages.First() as Assign;
if (p3_op == null) return false;
if (!p3_op.Lhs.Equiv(p3_ref)) return false;
var p3_bop = p3_op.Rhs as BinaryOperator;
if (p3_bop == null) return false;
var p3_atom = p3_bop.Lhs;
var p3_optype = p3_bop.OperatorType;
var p3_any = p3_bop.Rhs;
if (!p3_atom.IsAtom()) return false;
var p3_usage2_stmt = p3_usages.Second().Stmt();
var p3_usage3_stmt = p3_usages.Third().Stmt();
Expression p3_wb, p3_usage;
var p3_wb_template = new Assign(p3_atom, p3_ref);
if (p3_usage2_stmt.Equiv(p3_wb_template)) { p3_wb = (Expression)p3_usage2_stmt; p3_usage = (Expression)p3_usage3_stmt; }
else if (p3_usage3_stmt.Equiv(p3_wb_template)) { p3_wb = (Expression)p3_usage3_stmt; p3_usage = (Expression)p3_usage2_stmt; }
else return false;
var p3_opeq = p3_atom.CreateOpPreAssign(p3_optype, p3_any);
if (p3_opeq == null) return false;
dfa.Remove(p3_op, p3_wb);
dfa.ReplaceRecursive(p3_usage, p3_ref, p3_opeq);
return true;
}
