Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -36,6 +36,7 @@
 #include "ScriptParser.h"
 #include "Strings.h"
 #include "SymbolTable.h"
+#include "SyntheticSections.h"
 #include "Target.h"
 #include "Threads.h"
 #include "Writer.h"
@@ -1000,15 +1001,16 @@
   for (BinaryFile *F : Symtab.getBinaryFiles())
     for (InputSectionBase *S : F->getSections())
       InputSections.push_back(cast<InputSection>(S));
+  if (!Config->Relocatable)
+    InputSections.push_back(createCommentSection<ELFT>());
 
-  // Do size optimizations: garbage collection and identical code folding.
+  // Do size optimizations: garbage collection, merging of SHF_MERGE sections
+  // and identical code folding.
   if (Config->GcSections)
     markLive<ELFT>();
-  if (Config->ICF)
-    doIcf<ELFT>();
 
-  // MergeInputSection::splitIntoPieces needs to be called before
-  // any call of MergeInputSection::getOffset. Do that.
+  // splitIntoPieces needs to be called on each MergeInputSection before calling
+  // mergeSections(). Do that first.
   parallelForEach(InputSections.begin(), InputSections.end(),
                   [](InputSectionBase *S) {
                     if (!S->Live)
@@ -1018,6 +1020,10 @@
                     if (auto *MS = dyn_cast<MergeInputSection>(S))
                       MS->splitIntoPieces();
                   });
+  mergeSections();
+
+  if (Config->ICF)
+    doIcf<ELFT>();
 
   // Write the result to the file.
   writeResult<ELFT>();
Index: lld/ELF/SyntheticSections.h
===================================================================
--- lld/ELF/SyntheticSections.h
+++ lld/ELF/SyntheticSections.h
@@ -651,7 +651,6 @@
   void finalizeTailMerge();
   void finalizeNoTailMerge();
 
-  bool Finalized = false;
   llvm::StringTableBuilder Builder;
   std::vector<MergeInputSection *> Sections;
 };
@@ -748,6 +747,7 @@
 template <class ELFT> InputSection *createCommonSection();
 InputSection *createInterpSection();
 template <class ELFT> MergeInputSection *createCommentSection();
+void mergeSections();
 
 SymbolBody *addSyntheticLocal(StringRef Name, uint8_t Type, uint64_t Value,
                               uint64_t Size, InputSectionBase *Section);
Index: lld/ELF/SyntheticSections.cpp
===================================================================
--- lld/ELF/SyntheticSections.cpp
+++ lld/ELF/SyntheticSections.cpp
@@ -2133,7 +2133,6 @@
       Builder(StringTableBuilder::RAW, Alignment) {}
 
 void MergeSyntheticSection::addSection(MergeInputSection *MS) {
-  assert(!Finalized);
   MS->Parent = this;
   Sections.push_back(MS);
 }
@@ -2178,9 +2177,6 @@
 }
 
 void MergeSyntheticSection::finalizeContents() {
-  if (Finalized)
-    return;
-  Finalized = true;
   if (shouldTailMerge())
     finalizeTailMerge();
   else
@@ -2188,11 +2184,52 @@
 }
 
 size_t MergeSyntheticSection::getSize() const {
-  // We should finalize string builder to know the size.
-  const_cast<MergeSyntheticSection *>(this)->finalizeContents();
   return Builder.getSize();
 }
 
+// This function scans over the input sections and creates mergeable synthetic
+// sections. It removes MergeInputSections from the input section array and adds
+// new synthetic sections at the location of the first input section that it
+// replaces. It then finalizes each synthetic section in order to compute an
+// output offset for each piece of each input section.
+void elf::mergeSections() {
+  std::vector<MergeSyntheticSection *> MergeSections;
+  for (InputSectionBase *&S : InputSections) {
+    MergeInputSection *MS = dyn_cast<MergeInputSection>(S);
+    if (!MS)
+      continue;
+
+    // We do not want to handle sections that are not alive, so just remove
+    // them instead of trying to merge.
+    if (!MS->Live)
+      continue;
+
+    StringRef OutsecName = getOutputSectionName(MS->Name);
+    uint64_t Flags = MS->Flags & ~(uint64_t)SHF_GROUP;
+    uint32_t Alignment = std::max<uint32_t>(MS->Alignment, MS->Entsize);
+
+    auto I = llvm::find_if(MergeSections, [=](MergeSyntheticSection *Sec) {
+      return Sec->Name == OutsecName && Sec->Flags == Flags &&
+             Sec->Alignment == Alignment;
+    });
+    if (I == MergeSections.end()) {
+      MergeSyntheticSection *Syn =
+          make<MergeSyntheticSection>(OutsecName, MS->Type, Flags, Alignment);
+      MergeSections.push_back(Syn);
+      I = std::prev(MergeSections.end());
+      S = Syn;
+    } else {
+      S = nullptr;
+    }
+    (*I)->addSection(MS);
+  }
+  for (auto *MS : MergeSections)
+    MS->finalizeContents();
+
+  std::vector<InputSectionBase *> &V = InputSections;
+  V.erase(std::remove(V.begin(), V.end(), nullptr), V.end());
+}
+
 MipsRldMapSection::MipsRldMapSection()
     : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, Config->Wordsize,
                        ".rld_map") {}
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -137,46 +137,6 @@
   Phdrs.erase(I, Phdrs.end());
 }
 
-// This function scans over the input sections and creates mergeable
-// synthetic sections. It removes MergeInputSections from array and
-// adds new synthetic ones. Each synthetic section is added to the
-// location of the first input section it replaces.
-static void combineMergableSections() {
-  std::vector<MergeSyntheticSection *> MergeSections;
-  for (InputSectionBase *&S : InputSections) {
-    MergeInputSection *MS = dyn_cast<MergeInputSection>(S);
-    if (!MS)
-      continue;
-
-    // We do not want to handle sections that are not alive, so just remove
-    // them instead of trying to merge.
-    if (!MS->Live)
-      continue;
-
-    StringRef OutsecName = getOutputSectionName(MS->Name);
-    uint64_t Flags = MS->Flags & ~(uint64_t)SHF_GROUP;
-    uint32_t Alignment = std::max<uint32_t>(MS->Alignment, MS->Entsize);
-
-    auto I = llvm::find_if(MergeSections, [=](MergeSyntheticSection *Sec) {
-      return Sec->Name == OutsecName && Sec->Flags == Flags &&
-             Sec->Alignment == Alignment;
-    });
-    if (I == MergeSections.end()) {
-      MergeSyntheticSection *Syn =
-          make<MergeSyntheticSection>(OutsecName, MS->Type, Flags, Alignment);
-      MergeSections.push_back(Syn);
-      I = std::prev(MergeSections.end());
-      S = Syn;
-    } else {
-      S = nullptr;
-    }
-    (*I)->addSection(MS);
-  }
-
-  std::vector<InputSectionBase *> &V = InputSections;
-  V.erase(std::remove(V.begin(), V.end(), nullptr), V.end());
-}
-
 template <class ELFT> static void combineEhFrameSections() {
   for (InputSectionBase *&S : InputSections) {
     EhInputSection *ES = dyn_cast<EhInputSection>(S);
@@ -205,7 +165,6 @@
   // Create linker-synthesized sections such as .got or .plt.
   // Such sections are of type input section.
   createSyntheticSections();
-  combineMergableSections();
 
   if (!Config->Relocatable)
     combineEhFrameSections<ELFT>();
@@ -340,9 +299,6 @@
     InX::Interp = nullptr;
   }
 
-  if (!Config->Relocatable)
-    Add(createCommentSection<ELFT>());
-
   if (Config->Strip != StripPolicy::All) {
     InX::StrTab = make<StringTableSection>(".strtab", false);
     InX::SymTab = make<SymbolTableSection<ELFT>>(*InX::StrTab);