[NFC] Fix compiler warnings

[xiaoqing_wu]

Summary

Fix warnings caused by -Wrange-loop-analysis.

[aheejin]

Thanks!

llvm/include/llvm/CodeGen/WasmEHFuncInfo.h

struct WasmEHFuncInfo {
   const BasicBlock *getUnwindDest(const BasicBlock *BB) const {
     assert(hasUnwindDest(BB));
     return SrcToUnwindDest.lookup(BB).get<const BasicBlock *>();
   }
   SmallPtrSet<const BasicBlock *, 4> getUnwindSrcs(const BasicBlock *BB) const {
     assert(hasUnwindSrcs(BB));
     const auto &Set = UnwindDestToSrcs.lookup(BB);
     SmallPtrSet<const BasicBlock *, 4> Ret;
-    for (const auto &P : Set)
+    for (const auto P : Set)
       Ret.insert(P.get<const BasicBlock *>());
     return Ret;
   }
   void setUnwindDest(const BasicBlock *BB, const BasicBlock *Dest) {
     SrcToUnwindDest[BB] = Dest;
     if (!UnwindDestToSrcs.count(Dest))
       UnwindDestToSrcs[Dest] = SmallPtrSet<BBOrMBB, 4>();
     UnwindDestToSrcs[Dest].insert(BB);
MachineBasicBlock *getUnwindDest(MachineBasicBlock *MBB) const {
     assert(hasUnwindDest(MBB));
     return SrcToUnwindDest.lookup(MBB).get<MachineBasicBlock *>();
   }
   SmallPtrSet<MachineBasicBlock *, 4>
   getUnwindSrcs(MachineBasicBlock *MBB) const {
     assert(hasUnwindSrcs(MBB));
     const auto &Set = UnwindDestToSrcs.lookup(MBB);
     SmallPtrSet<MachineBasicBlock *, 4> Ret;
-    for (const auto &P : Set)
+    for (const auto P : Set)
       Ret.insert(P.get<MachineBasicBlock *>());
     return Ret;
   }
   void setUnwindDest(MachineBasicBlock *MBB, MachineBasicBlock *Dest) {
     SrcToUnwindDest[MBB] = Dest;
     if (!UnwindDestToSrcs.count(Dest))
       UnwindDestToSrcs[Dest] = SmallPtrSet<BBOrMBB, 4>();
     UnwindDestToSrcs[Dest].insert(MBB);

llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

for (auto &KV : EHInfo.SrcToUnwindDest) {
       const auto *Dest = KV.second.get<const BasicBlock *>();
       SrcToUnwindDest[MBBMap[Src]] = MBBMap[Dest];
     }
     EHInfo.SrcToUnwindDest = std::move(SrcToUnwindDest);
     DenseMap<BBOrMBB, SmallPtrSet<BBOrMBB, 4>> UnwindDestToSrcs;
     for (auto &KV : EHInfo.UnwindDestToSrcs) {
       const auto *Dest = KV.first.get<const BasicBlock *>();
       UnwindDestToSrcs[MBBMap[Dest]] = SmallPtrSet<BBOrMBB, 4>();
-      for (const auto &P : KV.second)
+      for (const auto P : KV.second)
         UnwindDestToSrcs[MBBMap[Dest]].insert(
             MBBMap[P.get<const BasicBlock *>()]);
     }
     EHInfo.UnwindDestToSrcs = std::move(UnwindDestToSrcs);
   }
 }
 
 /// clear - Clear out all the function-specific state. This returns this