[llvm] Fix bug in DemoteRegToStack where DenseMap is not used

[ri-char]

Summary

Loads is used to keep track of and reuse load instructions we insert, but these value are inserted into Loads.

[Qfrost911]

LGTM.

llvm/lib/Transforms/Utils/DemoteRegToStack.cpp

if (PHINode *PN = dyn_cast<PHINode>(U)) {
       for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
         if (PN->getIncomingValue(i) == &I) {
           Value *&V = Loads[PN->getIncomingBlock(i)];
           if (!V) {
             // Insert the load into the predecessor block
             V = new LoadInst(I.getType(), Slot, I.getName() + ".reload",
                              VolatileLoads,
                              PN->getIncomingBlock(i)->getTerminator());
+            Loads[PN->getIncomingBlock(i)] = V;
           }
           PN->setIncomingValue(i, V);
         }
 
     } else {
       // If this is a normal instruction, just insert a load.
       Value *V = new LoadInst(I.getType(), Slot, I.getName() + ".reload",
                               VolatileLoads, U);