+/// Returns true if Prefix is a prefix of longer. That means, Longer has a size
+/// that is greater than or equal to the size of prefix, and each of the
+/// elements in Prefix is the same as the corresponding elements in Longer.
+///
+/// This means it also returns true when Prefix and Longer are equal!
+static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
+ const ArgPromotion::IndicesVector &Longer) {
+ if (Prefix.size() > Longer.size())
+ return false;
+ for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
+ if (Prefix[i] != Longer[i])
+ return false;
+ return true;
+}
+
+
+/// Checks if Indices, or a prefix of Indices, is in Set.
+static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
+ std::set<ArgPromotion::IndicesVector> &Set) {
+ std::set<ArgPromotion::IndicesVector>::iterator Low;
+ Low = Set.upper_bound(Indices);
+ if (Low != Set.begin())
+ Low--;
+ // Low is now the last element smaller than or equal to Indices. This means
+ // it points to a prefix of Indices (possibly Indices itself), if such
+ // prefix exists.
+ //
+ // This load is safe if any prefix of its operands is safe to load.
+ return Low != Set.end() && IsPrefix(*Low, Indices);
+}
+
+/// Mark the given indices (ToMark) as safe in the given set of indices
+/// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
+/// is already a prefix of Indices in Safe, Indices are implicitely marked safe
+/// already. Furthermore, any indices that Indices is itself a prefix of, are
+/// removed from Safe (since they are implicitely safe because of Indices now).
+static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
+ std::set<ArgPromotion::IndicesVector> &Safe) {
+ std::set<ArgPromotion::IndicesVector>::iterator Low;
+ Low = Safe.upper_bound(ToMark);
+ // Guard against the case where Safe is empty
+ if (Low != Safe.begin())
+ Low--;
+ // Low is now the last element smaller than or equal to Indices. This
+ // means it points to a prefix of Indices (possibly Indices itself), if
+ // such prefix exists.
+ if (Low != Safe.end()) {
+ if (IsPrefix(*Low, ToMark))
+ // If there is already a prefix of these indices (or exactly these
+ // indices) marked a safe, don't bother adding these indices
+ return;
+
+ // Increment Low, so we can use it as a "insert before" hint
+ ++Low;
+ }
+ // Insert
+ Low = Safe.insert(Low, ToMark);
+ ++Low;
+ // If there we're a prefix of longer index list(s), remove those
+ std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
+ while (Low != End && IsPrefix(ToMark, *Low)) {
+ std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
+ ++Low;
+ Safe.erase(Remove);
+ }
+}