NFC: Use range-based for loops and more consistent naming.

[djasper]

Summary

No functional changes intended.

(I plan on doing some modifications to this function and would like to have as few unrelated changes as possible in the patch)

[chandlerc]

Nice cleanup. Feel free to submit similar no-op cleanups to this file, I'll post-commit review them.

[djasper]

Submitted as r229649.

lib/CodeGen/MachineBlockPlacement.cpp

MachineBasicBlock *MachineBlockPlacement::selectBestSuccessor(
   // weights. This is suboptimal as it means that the somewhat subtle
   // definition of edge weight semantics is encoded here as well. We should
   // improve the MBPI interface to efficiently support query patterns such as
   // this.
   uint32_t BestWeight = 0;
   uint32_t WeightScale = 0;
   uint32_t SumWeight = MBPI->getSumForBlock(BB, WeightScale);
   DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n");
-  for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
-                                        SE = BB->succ_end();
-       SI != SE; ++SI) {
-    if (BlockFilter && !BlockFilter->count(*SI))
+  for (MachineBasicBlock *Succ : BB->successors()) {
+    if (BlockFilter && !BlockFilter->count(Succ))
       continue;
-    BlockChain &SuccChain = *BlockToChain[*SI];
+    BlockChain &SuccChain = *BlockToChain[Succ];
     if (&SuccChain == &Chain) {
-      DEBUG(dbgs() << "    " << getBlockName(*SI) << " -> Already merged!\n");
+      DEBUG(dbgs() << "    " << getBlockName(Succ) << " -> Already merged!\n");
       continue;
     }
-    if (*SI != *SuccChain.begin()) {
-      DEBUG(dbgs() << "    " << getBlockName(*SI) << " -> Mid chain!\n");
+    if (Succ != *SuccChain.begin()) {
+      DEBUG(dbgs() << "    " << getBlockName(Succ) << " -> Mid chain!\n");
       continue;
     }
 
-    uint32_t SuccWeight = MBPI->getEdgeWeight(BB, *SI);
+    uint32_t SuccWeight = MBPI->getEdgeWeight(BB, Succ);
     BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight);
 
     // Only consider successors which are either "hot", or wouldn't violate
     // any CFG constraints.
     if (SuccChain.LoopPredecessors != 0) {
       if (SuccProb < HotProb) {
-        DEBUG(dbgs() << "    " << getBlockName(*SI) << " -> " << SuccProb
+        DEBUG(dbgs() << "    " << getBlockName(Succ) << " -> " << SuccProb
                      << " (prob) (CFG conflict)\n");
         continue;
       }
 
       // Make sure that a hot successor doesn't have a globally more
       // important predecessor.
       BlockFrequency CandidateEdgeFreq =
           MBFI->getBlockFreq(BB) * SuccProb * HotProb.getCompl();
       bool BadCFGConflict = false;
-      for (MachineBasicBlock::pred_iterator PI = (*SI)->pred_begin(),
-                                            PE = (*SI)->pred_end();
-           PI != PE; ++PI) {
-        if (*PI == *SI || (BlockFilter && !BlockFilter->count(*PI)) ||
-            BlockToChain[*PI] == &Chain)
+      for (MachineBasicBlock *Pred : Succ->predecessors()) {
+        if (Pred == Succ || (BlockFilter && !BlockFilter->count(Pred)) ||
+            BlockToChain[Pred] == &Chain)
           continue;
         BlockFrequency PredEdgeFreq =
-            MBFI->getBlockFreq(*PI) * MBPI->getEdgeProbability(*PI, *SI);
+            MBFI->getBlockFreq(Pred) * MBPI->getEdgeProbability(Pred, Succ);
         if (PredEdgeFreq >= CandidateEdgeFreq) {
           BadCFGConflict = true;
           break;
         }
       }
       if (BadCFGConflict) {
-        DEBUG(dbgs() << "    " << getBlockName(*SI) << " -> " << SuccProb
+        DEBUG(dbgs() << "    " << getBlockName(Succ) << " -> " << SuccProb
                      << " (prob) (non-cold CFG conflict)\n");
         continue;
       }
     }
 
-    DEBUG(dbgs() << "    " << getBlockName(*SI) << " -> " << SuccProb
+    DEBUG(dbgs() << "    " << getBlockName(Succ) << " -> " << SuccProb
                  << " (prob)"
                  << (SuccChain.LoopPredecessors != 0 ? " (CFG break)" : "")
                  << "\n");
     if (BestSucc && BestWeight >= SuccWeight)
       continue;
-    BestSucc = *SI;
+    BestSucc = Succ;
     BestWeight = SuccWeight;
   }
   return BestSucc;
 }
 
 /// \brief Select the best block from a worklist.
 ///
 /// This looks through the provided worklist as a list of candidate basic