Index: lld/trunk/ELF/InputSection.h
===================================================================
--- lld/trunk/ELF/InputSection.h
+++ lld/trunk/ELF/InputSection.h
@@ -144,9 +144,22 @@
                     typename InputSectionBase<ELFT>::Kind SectionKind);
 
   // For each piece of data, we maintain the offsets in the input section and
-  // in the output section. The latter may be -1 if it is not assigned yet.
+  // in the output section.
   std::vector<std::pair<uintX_t, uintX_t>> Offsets;
 
+  // Merge input sections may use the following special values as the output
+  // section offset:
+  enum {
+    // The piece is dead.
+    PieceDead = uintX_t(-1),
+    // The piece is live, and an offset has not yet been assigned. After offsets
+    // have been assigned, if the output section uses tail merging, the field
+    // will still have this value and the output section offset is available
+    // from MergeOutputSection<ELFT>::getOffset(). Otherwise, this value has no
+    // special significance, it just means that the offset is 0.
+    PieceLive = uintX_t(0),
+  };
+
   std::pair<std::pair<uintX_t, uintX_t> *, uintX_t>
   getRangeAndSize(uintX_t Offset);
 };
Index: lld/trunk/ELF/InputSection.cpp
===================================================================
--- lld/trunk/ELF/InputSection.cpp
+++ lld/trunk/ELF/InputSection.cpp
@@ -419,7 +419,8 @@
   StringRef Data((const char *)D.data(), D.size());
   std::vector<std::pair<uintX_t, uintX_t>> &Offsets = this->Offsets;
 
-  uintX_t V = Config->GcSections ? -1 : 0;
+  uintX_t V = Config->GcSections ? MergeInputSection<ELFT>::PieceDead
+                                 : MergeInputSection<ELFT>::PieceLive;
   if (Header->sh_flags & SHF_STRINGS) {
     uintX_t Offset = 0;
     while (!Data.empty()) {
@@ -478,15 +479,15 @@
   // Compute the Addend and if the Base is cached, return.
   uintX_t Addend = Offset - Start;
   uintX_t &Base = I->second;
-  if (Base != uintX_t(-1))
+  auto *MOS = static_cast<MergeOutputSection<ELFT> *>(this->OutSec);
+  if (!MOS->shouldTailMerge())
     return Base + Addend;
 
   // Map the base to the offset in the output section and cache it.
   ArrayRef<uint8_t> D = this->getSectionData();
   StringRef Data((const char *)D.data(), D.size());
   StringRef Entry = Data.substr(Start, End - Start);
-  Base =
-      static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Entry);
+  Base = MOS->getOffset(Entry);
   return Base + Addend;
 }
 
Index: lld/trunk/ELF/MarkLive.cpp
===================================================================
--- lld/trunk/ELF/MarkLive.cpp
+++ lld/trunk/ELF/MarkLive.cpp
@@ -143,7 +143,7 @@
     if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(R.Sec)) {
       std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
           MS->getRangeAndSize(R.Offset);
-      T.first->second = 0;
+      T.first->second = MergeInputSection<ELFT>::PieceLive;
     }
     if (R.Sec->Live)
       return;
Index: lld/trunk/ELF/OutputSections.h
===================================================================
--- lld/trunk/ELF/OutputSections.h
+++ lld/trunk/ELF/OutputSections.h
@@ -310,8 +310,6 @@
 class MergeOutputSection final : public OutputSectionBase<ELFT> {
   typedef typename ELFT::uint uintX_t;
 
-  bool shouldTailMerge() const;
-
 public:
   MergeOutputSection(StringRef Name, uint32_t Type, uintX_t Flags,
                      uintX_t Alignment);
@@ -319,6 +317,7 @@
   void writeTo(uint8_t *Buf) override;
   unsigned getOffset(StringRef Val);
   void finalize() override;
+  bool shouldTailMerge() const;
 
 private:
   llvm::StringTableBuilder Builder;
Index: lld/trunk/ELF/OutputSections.cpp
===================================================================
--- lld/trunk/ELF/OutputSections.cpp
+++ lld/trunk/ELF/OutputSections.cpp
@@ -1271,7 +1271,7 @@
   if (this->Header.sh_flags & SHF_STRINGS) {
     for (unsigned I = 0, N = Offsets.size(); I != N; ++I) {
       auto &P = Offsets[I];
-      if (P.second == (uintX_t)-1)
+      if (P.second == MergeInputSection<ELFT>::PieceDead)
         continue;
 
       uintX_t Start = P.first;
@@ -1279,7 +1279,7 @@
       StringRef Entry = Data.substr(Start, End - Start);
       uintX_t OutputOffset = Builder.add(Entry);
       if (shouldTailMerge())
-        OutputOffset = -1;
+        OutputOffset = MergeInputSection<ELFT>::PieceLive;
       P.second = OutputOffset;
     }
     return;
Index: lld/trunk/ELF/Writer.cpp
===================================================================
--- lld/trunk/ELF/Writer.cpp
+++ lld/trunk/ELF/Writer.cpp
@@ -1118,9 +1118,16 @@
     return false;
 
   if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B)) {
+    // Always include absolute symbols.
+    if (!D->Section)
+      return true;
     // Exclude symbols pointing to garbage-collected sections.
-    if (D->Section && !D->Section->Live)
+    if (!D->Section->Live)
       return false;
+    if (auto *S = dyn_cast<MergeInputSection<ELFT>>(D->Section))
+      if (S->getRangeAndSize(D->Value).first->second ==
+          MergeInputSection<ELFT>::PieceDead)
+        return false;
   }
   return true;
 }
Index: lld/trunk/test/ELF/string-gc.s
===================================================================
--- lld/trunk/test/ELF/string-gc.s
+++ lld/trunk/test/ELF/string-gc.s
@@ -0,0 +1,54 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld %t.o -o %t --gc-sections
+// RUN: llvm-readobj -symbols %t | FileCheck %s
+
+// CHECK:      Symbols [
+// CHECK-NEXT:   Symbol {
+// CHECK-NEXT:     Name:  (0)
+// CHECK-NEXT:     Value: 0x0
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Binding: Local (0x0)
+// CHECK-NEXT:     Type: None (0x0)
+// CHECK-NEXT:     Other: 0
+// CHECK-NEXT:     Section: Undefined (0x0)
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Symbol {
+// CHECK-NEXT:     Name: s1 (8)
+// CHECK-NEXT:     Value: 0x10120
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Binding: Local (0x0)
+// CHECK-NEXT:     Type: Object (0x1)
+// CHECK-NEXT:     Other [ (0x2)
+// CHECK-NEXT:       STV_HIDDEN (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Section: .rodata (0x1)
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Symbol {
+// CHECK-NEXT:     Name: _start (1)
+// CHECK-NEXT:     Value: 0x11000
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Binding: Global (0x1)
+// CHECK-NEXT:     Type: Function (0x2)
+// CHECK-NEXT:     Other: 0
+// CHECK-NEXT:     Section: .text (0x2)
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+
+.text
+.globl _start
+.type _start,@function
+_start:
+movl $s1, %eax
+
+.hidden s1
+.type s1,@object
+.section .rodata.str1.1,"aMS",@progbits,1
+.globl s1
+s1:
+.asciz "abcd"
+
+.hidden s2
+.type s2,@object
+.globl s2
+s2:
+.asciz "efgh"