Fix DEBUG logs in MachineLICM.

[jlebar]

Summary

MBBs don't necessarily have a name (in my experience, they almost never
do), in which case this logging is quite unhelpful. The number seems to
work well.

llvm/trunk/lib/CodeGen/MachineLICM.cpp

for (MachineBasicBlock *CurrentLoopExitingBlock : CurrentLoopExitingBlocks)
       }
   }
 
   SpeculationState = SpeculateFalse;
   return true;
 }
 
 void MachineLICM::EnterScope(MachineBasicBlock *MBB) {
-  DEBUG(dbgs() << "Entering: " << MBB->getName() << '\n');
+  DEBUG(dbgs() << "Entering BB#" << MBB->getNumber() << '\n');
 
   // Remember livein register pressure.
   BackTrace.push_back(RegPressure);
 }
 
 void MachineLICM::ExitScope(MachineBasicBlock *MBB) {
-  DEBUG(dbgs() << "Exiting: " << MBB->getName() << '\n');
+  DEBUG(dbgs() << "Exiting BB#" << MBB->getNumber() << '\n');
   BackTrace.pop_back();
 }
 
 /// Destroy scope for the MBB that corresponds to the given dominator tree node
 /// if its a leaf or all of its children are done. Walk up the dominator tree to
 /// destroy ancestors which are now done.
 void MachineLICM::ExitScopeIfDone(MachineDomTreeNode *Node,
                 DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
if (!IsLoopInvariantInst(*MI) || !IsProfitableToHoist(*MI)) {
     MI = ExtractHoistableLoad(MI);
     if (!MI) return false;
   }
 
   // Now move the instructions to the predecessor, inserting it before any
   // terminator instructions.
   DEBUG({
       dbgs() << "Hoisting " << *MI;
-      if (Preheader->getBasicBlock())
-        dbgs() << " to MachineBasicBlock "
-               << Preheader->getName();
       if (MI->getParent()->getBasicBlock())
-        dbgs() << " from MachineBasicBlock "
-               << MI->getParent()->getName();
+        dbgs() << " from BB#" << MI->getParent()->getNumber();
+      if (Preheader->getBasicBlock())
+        dbgs() << " to BB#" << Preheader->getNumber();
       dbgs() << "\n";
     });
 
   // If this is the first instruction being hoisted to the preheader,
   // initialize the CSE map with potential common expressions.
   if (FirstInLoop) {
     InitCSEMap(Preheader);
     FirstInLoop = false;