CodeGen: MachineBlockPlacement: Rename member to more general name. NFC.

[iteratee]

Summary

Rename ComputedTrellisEdges to ComputedEdges to allow for other methods of
pre-computing edges.

[davidxl]

lgtm

llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp

struct WeightedEdge {
     MachineBasicBlock *Src;
     MachineBasicBlock *Dest;
   };
 
   /// \brief work lists of blocks that are ready to be laid out
   SmallVector<MachineBasicBlock *, 16> BlockWorkList;
   SmallVector<MachineBasicBlock *, 16> EHPadWorkList;
 
-  /// Edges that have already been computed as optimal by the trellis code.
-  DenseMap<const MachineBasicBlock *, MachineBasicBlock *> ComputedTrellisEdges;
+  /// Edges that have already been computed as optimal.
+  DenseMap<const MachineBasicBlock *, BlockAndTailDupResult> ComputedEdges;
 
   /// \brief Machine Function
   MachineFunction *F;
 
   /// \brief A handle to the branch probability pass.
   const MachineBranchProbabilityInfo *MBPI;
 
   /// \brief A handle to the function-wide block frequency pass.
if (TailDupPlacement && shouldTailDuplicate(Succ2) &&
                    << ", probability: " << Succ2Prob << " (Tail Duplicate)\n");
       Result.BB = Succ2;
       Result.ShouldTailDup = true;
       return Result;
     }
   }
   // We have already computed the optimal edge for the other side of the
   // trellis.
-  ComputedTrellisEdges[BestB.Src] = BestB.Dest;
+  ComputedEdges[BestB.Src] = { BestB.Dest, false };
 
   auto TrellisSucc = BestA.Dest;
   DEBUG(BranchProbability SuccProb = getAdjustedProbability(
             MBPI->getEdgeProbability(BB, TrellisSucc), AdjustedSumProb);
         dbgs() << "    Selected: " << getBlockName(TrellisSucc)
                << ", probability: " << SuccProb << " (Trellis)\n");
   Result.BB = TrellisSucc;
   return Result;
MachineBlockPlacement::selectBestSuccessor(
   auto BestProb = BranchProbability::getZero();
 
   SmallVector<MachineBasicBlock *, 4> Successors;
   auto AdjustedSumProb =
       collectViableSuccessors(BB, Chain, BlockFilter, Successors);
 
   DEBUG(dbgs() << "Selecting best successor for: " << getBlockName(BB) << "\n");
 
-  // if we already precomputed the best successor for BB as part of a trellis we
-  // saw earlier, return that if still applicable.
-  auto FoundEdge = ComputedTrellisEdges.find(BB);
-  if (FoundEdge != ComputedTrellisEdges.end()) {
-    MachineBasicBlock *Succ = FoundEdge->second;
-    ComputedTrellisEdges.erase(FoundEdge);
+  // if we already precomputed the best successor for BB, return that if still
+  // applicable.
+  auto FoundEdge = ComputedEdges.find(BB);
+  if (FoundEdge != ComputedEdges.end()) {
+    MachineBasicBlock *Succ = FoundEdge->second.BB;
+    ComputedEdges.erase(FoundEdge);
     BlockChain *SuccChain = BlockToChain[Succ];
     if (BB->isSuccessor(Succ) && (!BlockFilter || BlockFilter->count(Succ)) &&
-        SuccChain != &Chain && Succ == *SuccChain->begin()) {
-      BestSucc.BB = Succ;
-      return BestSucc;
-    }
+        SuccChain != &Chain && Succ == *SuccChain->begin())
+      return FoundEdge->second;
   }
 
   // if BB is part of a trellis, Use the trellis to determine the optimal
   // fallthrough edges
   if (isTrellis(BB, Successors, Chain, BlockFilter))
     return getBestTrellisSuccessor(BB, Successors, AdjustedSumProb, Chain,
                                    BlockFilter);