Cleaning up unreachable code in CodeLayout

[spupyrev]

Summary

• removing an unreachable instruction from the code (earlier code merge bug);
• silencing "unused variable" warnings.

[spupyrev]

get rid of unused variables

llvm/lib/Transforms/Utils/CodeLayout.cpp

std::sort(SortedChains.begin(), SortedChains.end(),
               [&](const ChainT *L, const ChainT *R) {
                 // Place the entry point is at the beginning of the order.
                 if (L->isEntry() != R->isEntry())
                   return L->isEntry();
 
                 const double DL = ChainDensity[L];
                 const double DR = ChainDensity[R];
                 // Compare by density and break ties by chain identifiers.
-                return (DL != DR) ? (DL > DR) : (L->Id < R->Id);
                 return std::make_tuple(-DL, L->Id) <
                        std::make_tuple(-DR, R->Id);
               });
 
     // Collect the nodes in the order specified by their chains.
     Order.reserve(NumNodes);
     for (const ChainT *Chain : SortedChains) {
       for (NodeT *Node : Chain->Nodes) {
void mergeChainPairs() {
     auto GainComparator = [](ChainEdge *L, ChainEdge *R) {
       return std::make_tuple(-L->gain(), L->srcChain()->Id, L->dstChain()->Id) <
              std::make_tuple(-R->gain(), R->srcChain()->Id, R->dstChain()->Id);
     };
     std::set<ChainEdge *, decltype(GainComparator)> Queue(GainComparator);
 
     // Insert the edges into the queue.
     for (ChainT *ChainPred : HotChains) {
-      for (const auto &[Chain, Edge] : ChainPred->Edges) {
+      for (const auto &[_, Edge] : ChainPred->Edges) {
         // Ignore self-edges.
         if (Edge->isSelfEdge())
           continue;
         // Ignore already processed edges.
         if (Edge->gain() != -1.0)
           continue;
 
         // Compute the gain of merging the two chains.
while (!Queue.empty()) {
       // Ignore edges with non-positive gains.
       if (BestEdge->gain() <= EPS)
         continue;
 
       ChainT *BestSrcChain = BestEdge->srcChain();
       ChainT *BestDstChain = BestEdge->dstChain();
 
       // Remove outdated edges from the queue.
-      for (const auto &[Chain, ChainEdge] : BestSrcChain->Edges)
+      for (const auto &[_, ChainEdge] : BestSrcChain->Edges)
         Queue.erase(ChainEdge);
-      for (const auto &[Chain, ChainEdge] : BestDstChain->Edges)
+      for (const auto &[_, ChainEdge] : BestDstChain->Edges)
         Queue.erase(ChainEdge);
 
       // Merge the best pair of chains.
       MergeGainT BestGain = BestEdge->getMergeGain();
       mergeChains(BestSrcChain, BestDstChain, BestGain.mergeOffset(),
                   BestGain.mergeType());
 
       // Insert newly created edges into the queue.
-      for (const auto &[Chain, Edge] : BestSrcChain->Edges) {
+      for (const auto &[_, Edge] : BestSrcChain->Edges) {
         // Ignore loop edges.
         if (Edge->isSelfEdge())
           continue;
 
         // Compute the gain of merging the two chains.
         MergeGainT Gain = getBestMergeGain(Edge);
         Edge->setMergeGain(Gain);