Index: ELF/InputSection.h
===================================================================
--- ELF/InputSection.h
+++ ELF/InputSection.h
@@ -72,6 +72,7 @@
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
 
 public:
+  std::unique_ptr<uintX_t> Offsets;
   MergeInputSection(ObjectFile<ELFT> *F, const Elf_Shdr *Header);
   static bool classof(const InputSectionBase<ELFT> *S);
   uintX_t getOffset(uintX_t Offset) const;
Index: ELF/InputSection.cpp
===================================================================
--- ELF/InputSection.cpp
+++ ELF/InputSection.cpp
@@ -128,7 +128,6 @@
   return S->SectionKind == Base::Merge;
 }
 
-// FIXME: Optimize this by keeping an offset for each element.
 template <class ELFT>
 typename MergeInputSection<ELFT>::uintX_t
 MergeInputSection<ELFT>::getOffset(uintX_t Offset) const {
@@ -136,8 +135,9 @@
   uintX_t EntSize = this->Header->sh_entsize;
   if (Offset + EntSize > Data.size())
     error("Entry is past the end of the section");
-  Data = Data.slice(Offset, EntSize);
-  return static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Data);
+  assert(Offset % EntSize == 0);
+  uintX_t Index = Offset / EntSize;
+  return Offsets.get()[Index];
 }
 
 namespace lld {
Index: ELF/OutputSections.h
===================================================================
--- ELF/OutputSections.h
+++ ELF/OutputSections.h
@@ -214,8 +214,6 @@
   void addSection(MergeInputSection<ELFT> *S);
   void writeTo(uint8_t *Buf) override;
 
-  unsigned getOffset(ArrayRef<uint8_t> Val);
-
 private:
   // This map is used to find if we already have an entry for a given value and,
   // if so, at what offset it is.
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -535,8 +535,10 @@
   uintX_t EntSize = S->getSectionHdr()->sh_entsize;
   if (Data.size() % EntSize)
     error("SHF_MERGE section size must be a multiple of sh_entsize");
-  for (unsigned I = 0, N = Data.size(); I != N; I += EntSize) {
+  S->Offsets.reset(new uintX_t[Data.size() / EntSize]);
+  for (unsigned I = 0, N = Data.size(), J = 0; I != N; I += EntSize, ++J) {
     auto P = Offsets.insert(std::make_pair(Data.slice(I, EntSize), Off));
+    S->Offsets.get()[J] = P.first->second;
     if (P.second)
       Off += EntSize;
   }
@@ -544,11 +546,6 @@
 }
 
 template <class ELFT>
-unsigned MergeOutputSection<ELFT>::getOffset(ArrayRef<uint8_t> Val) {
-  return Offsets.find(Val)->second;
-}
-
-template <class ELFT>
 StringTableSection<ELFT>::StringTableSection(bool Dynamic)
     : OutputSectionBase<ELFT>(Dynamic ? ".dynstr" : ".strtab",
                               llvm::ELF::SHT_STRTAB,