Index: lld/COFF/Chunks.h
===================================================================
--- lld/COFF/Chunks.h
+++ lld/COFF/Chunks.h
@@ -16,6 +16,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Object/COFF.h"
 #include <utility>
 #include <vector>
@@ -60,6 +61,10 @@
   // before calling this function.
   virtual void writeTo(uint8_t *Buf) const {}
 
+  // Called by the writer after an RVA is assigned, but before calling
+  // getSize().
+  virtual void finalizeContents() {}
+
   // The writer sets and uses the addresses.
   uint64_t getRVA() const { return RVA; }
   void setRVA(uint64_t V) { RVA = V; }
@@ -222,6 +227,22 @@
   uint32_t Class[2] = {0, 0};
 };
 
+struct MergeChunk : public Chunk {
+  static std::map<uint32_t, MergeChunk *> Instances;
+
+  std::vector<SectionChunk *> Sections;
+  llvm::StringTableBuilder Builder;
+
+  MergeChunk(uint32_t Alignment);
+  static void addSection(SectionChunk *C);
+  void finalizeContents() override;
+
+  uint32_t getPermissions() const override;
+  StringRef getSectionName() const override { return ".rdata"; }
+  size_t getSize() const override;
+  void writeTo(uint8_t *Buf) const override;
+};
+
 // A chunk for common symbols. Common chunks don't have actual data.
 class CommonChunk : public Chunk {
 public:
Index: lld/COFF/Chunks.cpp
===================================================================
--- lld/COFF/Chunks.cpp
+++ lld/COFF/Chunks.cpp
@@ -571,5 +571,51 @@
   }
 }
 
+std::map<uint32_t, MergeChunk *> MergeChunk::Instances;
+
+MergeChunk::MergeChunk(uint32_t Alignment)
+    : Builder(StringTableBuilder::RAW, Alignment) {}
+
+void MergeChunk::addSection(SectionChunk *C) {
+  auto *&MC = Instances[C->Alignment];
+  if (!MC)
+    MC = make<MergeChunk>(C->Alignment);
+  MC->Sections.push_back(C);
+}
+
+void MergeChunk::finalizeContents() {
+  auto Str = [](SectionChunk *C) {
+    ArrayRef<uint8_t> Contents = C->getContents();
+    return StringRef{reinterpret_cast<const char *>(Contents.data()),
+                     Contents.size()};
+  };
+
+  for (SectionChunk *C : Sections)
+    if (C->isLive())
+      Builder.add(Str(C));
+  Builder.finalize();
+
+  for (SectionChunk *C : Sections) {
+    if (C->isLive()) {
+      size_t Off = Builder.getOffset(Str(C));
+      C->setOutputSection(Out);
+      C->setRVA(RVA + Off);
+      C->OutputSectionOff = OutputSectionOff + Off;
+    }
+  }
+}
+
+uint32_t MergeChunk::getPermissions() const {
+  return IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_INITIALIZED_DATA;
+}
+
+size_t MergeChunk::getSize() const {
+  return Builder.getSize();
+}
+
+void MergeChunk::writeTo(uint8_t *Buf) const {
+  Builder.write(Buf + OutputSectionOff);
+}
+
 } // namespace coff
 } // namespace lld
Index: lld/COFF/ICF.cpp
===================================================================
--- lld/COFF/ICF.cpp
+++ lld/COFF/ICF.cpp
@@ -224,6 +224,12 @@
     }
   }
 
+  // Make sure that ICF doesn't merge sections that are being handled by string
+  // tail merging.
+  for (auto &P : MergeChunk::Instances)
+    for (auto *SC : P.second->Sections)
+      SC->Class[0] = NextId++;
+
   // Initially, we use hash values to partition sections.
   for_each(parallel::par, Chunks.begin(), Chunks.end(), [&](SectionChunk *SC) {
     // Set MSB to 1 to avoid collisions with non-hash classs.
Index: lld/COFF/InputFiles.h
===================================================================
--- lld/COFF/InputFiles.h
+++ lld/COFF/InputFiles.h
@@ -150,7 +150,8 @@
 
   SectionChunk *
   readSection(uint32_t SectionNumber,
-              const llvm::object::coff_aux_section_definition *Def);
+              const llvm::object::coff_aux_section_definition *Def,
+              StringRef LeaderName);
 
   void readAssociativeDefinition(
       COFFSymbolRef COFFSym,
Index: lld/COFF/InputFiles.cpp
===================================================================
--- lld/COFF/InputFiles.cpp
+++ lld/COFF/InputFiles.cpp
@@ -138,12 +138,13 @@
     if (Sec->Characteristics & IMAGE_SCN_LNK_COMDAT)
       SparseChunks[I] = PendingComdat;
     else
-      SparseChunks[I] = readSection(I, nullptr);
+      SparseChunks[I] = readSection(I, nullptr, "");
   }
 }
 
 SectionChunk *ObjFile::readSection(uint32_t SectionNumber,
-                                   const coff_aux_section_definition *Def) {
+                                   const coff_aux_section_definition *Def,
+                                   StringRef LeaderName) {
   const coff_section *Sec;
   StringRef Name;
   if (auto EC = COFFObj->getSection(SectionNumber, Sec))
@@ -189,6 +190,12 @@
     GuardLJmpChunks.push_back(C);
   else if (Name == ".sxdata")
     SXDataChunks.push_back(C);
+  else if (Config->DoICF && Sec->NumberOfRelocations == 0 && Name == ".rdata" &&
+           LeaderName.startswith("??_C@"))
+    // COFF sections that look like string literal sections (i.e. no
+    // relocations, in .rdata, leader symbol name matches the MSVC name mangling
+    // for string literals) are subject to string tail merging.
+    MergeChunk::addSection(C);
   else
     Chunks.push_back(C);
 
@@ -209,7 +216,7 @@
   // the section; otherwise mark it as discarded.
   int32_t SectionNumber = Sym.getSectionNumber();
   if (Parent) {
-    SparseChunks[SectionNumber] = readSection(SectionNumber, Def);
+    SparseChunks[SectionNumber] = readSection(SectionNumber, Def, "");
     if (SparseChunks[SectionNumber])
       Parent->addAssociative(SparseChunks[SectionNumber]);
   } else {
@@ -343,7 +350,7 @@
       Prevailing = true;
     }
     if (Prevailing) {
-      SectionChunk *C = readSection(SectionNumber, Def);
+      SectionChunk *C = readSection(SectionNumber, Def, Name);
       SparseChunks[SectionNumber] = C;
       C->Sym = cast<DefinedRegular>(Leader);
       cast<DefinedRegular>(Leader)->Data = &C->Repl;
Index: lld/COFF/Writer.cpp
===================================================================
--- lld/COFF/Writer.cpp
+++ lld/COFF/Writer.cpp
@@ -426,6 +426,9 @@
 void Writer::createMiscChunks() {
   OutputSection *RData = createSection(".rdata");
 
+  for (auto &P : MergeChunk::Instances)
+    RData->addChunk(P.second);
+
   // Create thunks for locally-dllimported symbols.
   if (!Symtab->LocalImportChunks.empty()) {
     for (Chunk *C : Symtab->LocalImportChunks)
@@ -665,6 +668,7 @@
       VirtualSize = alignTo(VirtualSize, C->Alignment);
       C->setRVA(RVA + VirtualSize);
       C->OutputSectionOff = VirtualSize;
+      C->finalizeContents();
       VirtualSize += C->getSize();
       if (C->hasData())
         RawSize = alignTo(VirtualSize, SectorSize);
Index: lld/test/COFF/string-tail-merge.s
===================================================================
--- /dev/null
+++ lld/test/COFF/string-tail-merge.s
@@ -0,0 +1,72 @@
+# REQUIRES: x86
+# RUN: llvm-mc -triple=x86_64-windows-msvc -filetype=obj -o %t.obj %s
+# RUN: lld-link %t.obj /out:%t.exe /entry:main /subsystem:console
+# RUN: llvm-objdump -s -j .text %t.exe | FileCheck %s
+
+.globl main
+main:
+# CHECK: 140003000 12200040 01000000 18200040 01000000
+.8byte "??_C@_0M@LACCCNMM@hello?5world?$AA@"
+.8byte "??_C@_05MCBCHHEJ@world?$AA@"
+# CHECK: 140003010 1e200040 01000000 2a200040 01000000
+.8byte "??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+.8byte "??_C@_1M@NBBDDHIO@?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+# CHECK: 140003020 00200040 01000000 0c200040 01000000
+.8byte "??_D@not_a_string_literal"
+.8byte "??_C@string_literal_with_relocs"
+# CHECK: 140003030 00100040 01000000
+.8byte "??_C@string_literal_in_wrong_section"
+
+.section .rdata,"dr",discard,"??_C@_0M@LACCCNMM@hello?5world?$AA@"
+.globl "??_C@_0M@LACCCNMM@hello?5world?$AA@"
+"??_C@_0M@LACCCNMM@hello?5world?$AA@":
+.asciz "hello world"
+
+.section .rdata,"dr",discard,"??_C@_05MCBCHHEJ@world?$AA@"
+.globl "??_C@_05MCBCHHEJ@world?$AA@"
+"??_C@_05MCBCHHEJ@world?$AA@":
+.asciz "world"
+
+.section .rdata,"dr",discard,"??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+.globl "??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+.p2align 1
+"??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@":
+.short 104
+.short 101
+.short 108
+.short 108
+.short 111
+.short 32
+.short 119
+.short 111
+.short 114
+.short 108
+.short 100
+.short 0
+
+.section .rdata,"dr",discard,"??_C@_1M@NBBDDHIO@?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+.globl "??_C@_1M@NBBDDHIO@?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"
+.p2align 1
+"??_C@_1M@NBBDDHIO@?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@":
+.short 119
+.short 111
+.short 114
+.short 108
+.short 100
+.short 0
+
+.section .data,"drw",discard,"??_C@string_literal_in_wrong_section"
+.globl "??_C@string_literal_in_wrong_section"
+"??_C@string_literal_in_wrong_section":
+.asciz "hello world"
+
+.section .rdata,"dr",discard,"??_D@not_a_string_literal"
+.globl "??_D@not_a_string_literal"
+"??_D@not_a_string_literal":
+.asciz "hello world"
+
+.section .rdata,"dr",discard,"??_C@string_literal_with_relocs"
+.globl "??_C@string_literal_with_relocs"
+"??_C@string_literal_with_relocs":
+.4byte main + 119 + (111 << 8) + (114 << 16) + (108 << 24) # main + "worl"
+.asciz "d"