[RewriteStatepointsForGC] Use more stable ordering for statepoint arguments

[igor-laevsky]

Summary

When sorting statepoint arguments we can use more precise ordering. This will result in a more rare non-deterministic results from this pass.

[sanjoy]

Same comment as in D19421

lib/Transforms/Scalar/RewriteStatepointsForGC.cpp

static void StabilizeOrder(SmallVectorImpl<Value *> &BaseVec,
   SmallVector<BaseDerivedPair, 64> NameOrdering;
   NameOrdering.reserve(BaseVec.size());
 
   for (size_t i = 0, e = BaseVec.size(); i < e; i++)
     NameOrdering.push_back({BaseVec[i], LiveVec[i]});
 
   std::sort(NameOrdering.begin(), NameOrdering.end(),
             [](const BaseDerivedPair &L, const BaseDerivedPair &R) {
-              return L.Derived->getName() < R.Derived->getName();
+              return order_by_name(L.Derived, R.Derived);
             });
 
   for (size_t i = 0; i < BaseVec.size(); i++) {
     BaseVec[i] = NameOrdering[i].Base;
     LiveVec[i] = NameOrdering[i].Derived;
   }
 }