// Constructs a simple expression from the given Cetus expression
protected SimpleExpression(Expression e) {
this();
if (e instanceof UnaryExpression) parse((UnaryExpression) e);
else if (e instanceof BinaryExpression) parse((BinaryExpression) e);
else if (e.getChildren() != null && !e.getChildren().isEmpty()) parseTree(e);
else parseLeaf(e);
}
// Parses a generic expression and returns true if it contains side effect.
private void parseTree(Expression e) {
if (e instanceof MinMaxExpression) {
MinMaxExpression mme = (MinMaxExpression) e;
sop = (mme.isMin()) ? MIN : MAX;
} else {
sop = TREE;
expr = e;
order = TREE_ORDER;
if (e instanceof FunctionCall || e instanceof VaArgExpression) contains_side_effect = true;
}
if (e instanceof StatementExpression) // parsing stops here.
return;
for (Object o : e.getChildren()) {
if (o instanceof Expression) {
SimpleExpression child = new SimpleExpression((Expression) o);
contains_side_effect |= child.contains_side_effect;
add(child);
} else Tools.exit("[SimpleExpression] unable to parse a generic expression");
}
}
/** Normalization for points-to analysis. */
private static Expression normalize(Expression arg, Symbol param) {
Expression ret = arg.clone(); // default behavior.
// Converts array accesses to address-of expressions.
if (ret instanceof ArrayAccess) {
ArrayAccess array = (ArrayAccess) ret;
// Normalize the array name.
Expression name = normalize(array.getArrayName(), null);
Symbol base = SymbolTools.getSymbolOf(name);
if (base != null && param != null && SymbolTools.isPointerParameter(param)) {
// case 1: the base symbol has an array specifier.
// --> - keeps the array indices while adding trailing [0].
// - converts to address-of expression.
// - adds dereference operator if base is a formal parameter
if (SymbolTools.isArray(base)) {
// Adds a trailing subscript "[0]" intentionally.
array.addIndex(new IntegerLiteral(0));
ret = new UnaryExpression(UnaryOperator.ADDRESS_OF, ret);
// Formal parameter is normalized: a[10] to (*a)[10].
// This conversion is used only internally (not legal in C).
if (SymbolTools.isPointerParameter(base)) {
array
.getArrayName()
.swapWith(new UnaryExpression(UnaryOperator.DEREFERENCE, name.clone()));
}
// case 2: the base symbol does not have an array specifier.
// --> just take the base object while converting a subscript
// to a dereference.
} else {
ret = name;
for (int i = 0; i < array.getNumIndices(); i++) {
ret = new UnaryExpression(UnaryOperator.DEREFERENCE, ret.clone());
}
}
} else { // just normalizes the array name.
array.getArrayName().swapWith(name);
}
// Removes pointer access and adds trailing dummy index for pointer
// type.
} else if (ret instanceof AccessExpression) {
AccessExpression access = (AccessExpression) ret;
// POINTER_ACCESS to MEMBER_ACCESS
if (access.getOperator() == AccessOperator.POINTER_ACCESS) {
// Normalize the LHS.
Expression lhs = normalize(access.getLHS(), null);
ret =
new AccessExpression(
new UnaryExpression(UnaryOperator.DEREFERENCE, lhs.clone()),
AccessOperator.MEMBER_ACCESS,
access.getRHS().clone());
}
// Pointer type to address-of expression.
if (param != null && SymbolTools.isPointerParameter(param)) {
ret =
new UnaryExpression(
UnaryOperator.ADDRESS_OF, new ArrayAccess(ret.clone(), new IntegerLiteral(0)));
}
// Just normalize the expression child.
} else if (ret instanceof UnaryExpression) {
UnaryExpression ue = (UnaryExpression) ret;
ue.setExpression(normalize(ue.getExpression(), null));
// Tries to convert simple pointer arithmetic to array access.
} else if (ret instanceof BinaryExpression) {
BinaryExpression be = (BinaryExpression) ret;
Expression lhs = normalize(be.getLHS(), null);
Expression rhs = normalize(be.getRHS(), null);
if (param != null
&& SymbolTools.isPointerParameter(param)
&& be.getOperator() == BinaryOperator.ADD) {
if (isPointerArithmeticOperand(lhs, rhs)) {
ret =
new UnaryExpression(
UnaryOperator.ADDRESS_OF, new ArrayAccess(rhs.clone(), lhs.clone()));
} else if (isPointerArithmeticOperand(rhs, lhs)) {
ret =
new UnaryExpression(
UnaryOperator.ADDRESS_OF, new ArrayAccess(lhs.clone(), rhs.clone()));
}
} else {
ret = new BinaryExpression(lhs.clone(), be.getOperator(), rhs.clone());
}
// Type cast is discarded.
} else if (ret instanceof Typecast) {
ret = (Expression) ret.getChildren().get(0);
}
return ret;
}
