// Substitute s into all members of the set
void LocationSet::substitute(Assign& a)
{
Exp* lhs = a.getLeft();
if (lhs == NULL) return;
Exp* rhs = a.getRight();
if (rhs == NULL) return; // ? Will this ever happen?
std::set<Exp*, lessExpStar>::iterator it;
// Note: it's important not to change the pointer in the set of pointers to expressions, without removing and
// inserting again. Otherwise, the set becomes out of order, and operations such as set comparison fail!
// To avoid any funny behaviour when iterating the loop, we use the following two sets
LocationSet removeSet; // These will be removed after the loop
LocationSet removeAndDelete; // These will be removed then deleted
LocationSet insertSet; // These will be inserted after the loop
bool change;
for (it = lset.begin(); it != lset.end(); it++)
{
Exp* loc = *it;
Exp* replace;
if (loc->search(lhs, replace))
{
if (rhs->isTerminal())
{
// This is no longer a location of interest (e.g. %pc)
removeSet.insert(loc);
continue;
}
loc = loc->clone()->searchReplaceAll(lhs, rhs, change);
if (change)
{
loc = loc->simplifyArith();
loc = loc->simplify();
// If the result is no longer a register or memory (e.g.
// r[28]-4), then delete this expression and insert any
// components it uses (in the example, just r[28])
if (!loc->isRegOf() && !loc->isMemOf())
{
// Note: can't delete the expression yet, because the
// act of insertion into the remove set requires silent
// calls to the compare function
removeAndDelete.insert(*it);
loc->addUsedLocs(insertSet);
continue;
}
// Else we just want to replace it
// Regardless of whether the top level expression pointer has
// changed, remove and insert it from the set of pointers
removeSet.insert(*it); // Note: remove the unmodified ptr
insertSet.insert(loc);
}
}
}
makeDiff(removeSet); // Remove the items to be removed
makeDiff(removeAndDelete); // These are to be removed as well
makeUnion(insertSet); // Insert the items to be added
// Now delete the expressions that are no longer needed
std::set<Exp*, lessExpStar>::iterator dd;
for (dd = removeAndDelete.lset.begin(); dd != removeAndDelete.lset.end();
dd++)
delete *dd; // Plug that memory leak
}
bool StrengthReductionReversalPass::execute(UserProc *proc)
{
StatementList stmts;
proc->getStatements(stmts);
for (Statement *s : stmts) {
if (!s->isAssign()) {
continue;
}
Assign *as = static_cast<Assign *>(s);
// of the form x = x{p} + c
if ((as->getRight()->getOper() == opPlus) && as->getRight()->getSubExp1()->isSubscript() &&
(*as->getLeft() == *as->getRight()->getSubExp1()->getSubExp1()) &&
as->getRight()->getSubExp2()->isIntConst()) {
int c = as->getRight()->access<Const, 2>()->getInt();
auto r = as->getRight()->access<RefExp, 1>();
if (r->getDef() && r->getDef()->isPhi()) {
PhiAssign *p = static_cast<PhiAssign *>(r->getDef());
if (p->getNumDefs() == 2) {
Statement *first = p->begin()->getDef();
Statement *second = p->rbegin()->getDef();
if (first == as) {
// want the increment in second
std::swap(first, second);
}
// first must be of form x := 0
if (first && first->isAssign() &&
static_cast<Assign *>(first)->getRight()->isIntConst() &&
static_cast<Assign *>(first)->getRight()->access<Const>()->getInt() == 0) {
// ok, fun, now we need to find every reference to p and
// replace with x{p} * c
StatementList stmts2;
proc->getStatements(stmts2);
for (Statement *stmt2 : stmts2) {
if (stmt2 != as) {
stmt2->searchAndReplace(
*r, Binary::get(opMult, r->clone(), Const::get(c)));
}
}
// that done we can replace c with 1 in as
as->getRight()->access<Const, 2>()->setInt(1);
}
}
}
}
}
return true;
}