diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -593,7 +593,7 @@
   // MD_associated in a unique section.
   unsigned UniqueID = MCContext::GenericSectionID;
   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
-  if (AssociatedSymbol) {
+  if (GO->getMetadata(LLVMContext::MD_associated)) {
     UniqueID = NextUniqueID++;
     Flags |= ELF::SHF_LINK_ORDER;
   }
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1023,16 +1023,18 @@
     break;
   }
 
-  if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
+  unsigned Flags = Section.getFlags();
+  if (Flags & ELF::SHF_LINK_ORDER) {
     const MCSymbol *Sym = Section.getAssociatedSymbol();
-    const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
-    sh_link = SectionIndexMap.lookup(Sec);
+    if (Sym && Sym->isInSection()) {
+      const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
+      sh_link = SectionIndexMap.lookup(Sec);
+    }
   }
 
   WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
-                   Section.getType(), Section.getFlags(), 0, Offset, Size,
-                   sh_link, sh_info, Section.getAlignment(),
-                   Section.getEntrySize());
+                   Section.getType(), Flags, 0, Offset, Size, sh_link, sh_info,
+                   Section.getAlignment(), Section.getEntrySize());
 }
 
 void ELFWriter::writeSectionHeader(
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
--- a/llvm/lib/MC/MCSectionELF.cpp
+++ b/llvm/lib/MC/MCSectionELF.cpp
@@ -172,9 +172,11 @@
   }
 
   if (Flags & ELF::SHF_LINK_ORDER) {
-    assert(AssociatedSymbol);
     OS << ",";
-    printName(OS, AssociatedSymbol->getName());
+    if (AssociatedSymbol)
+      printName(OS, AssociatedSymbol->getName());
+    else
+      printName(OS, "");
   }
 
   if (isUnique())
diff --git a/llvm/test/CodeGen/X86/elf-associated-discarded.ll b/llvm/test/CodeGen/X86/elf-associated-discarded.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/X86/elf-associated-discarded.ll
@@ -0,0 +1,23 @@
+;; Test that we drop SHF_LINK_ORDER and reset sh_link to 0 if the associated
+;; symbol is not defined.
+; RUN: llc -mtriple=x86_64 -data-sections=1 < %s | FileCheck %s
+; RUN: llc -filetype=obj -mtriple=x86_64 -data-sections=1 < %s | llvm-readelf -S | FileCheck --check-prefix=SEC %s
+
+;; FIXME The assembly output cannot be assembled because foo is not defined.
+;; This is difficult to fix because we allow loops (see elf-associated.ll
+;; .data.c and .data.d).
+; CHECK: .section .data.a,"awo",@progbits,foo
+; CHECK: .section .data.b,"awo",@progbits,foo
+
+;; No 'L' (SHF_LINK_ORDER). sh_link=0.
+; SEC; Name    {{.*}} Flg Lk Inf
+; SEC: .data.a {{.*}} WAL  0   0
+; SEC: .data.b {{.*}} WAL  0   0
+
+;; The definition may be discarded by LTO.
+declare void @foo()
+
+@a = global i32 1, !associated !0
+@b = global i32 1, !associated !0
+
+!0 = !{void ()* @foo}
diff --git a/llvm/test/CodeGen/X86/elf-associated.ll b/llvm/test/CodeGen/X86/elf-associated.ll
--- a/llvm/test/CodeGen/X86/elf-associated.ll
+++ b/llvm/test/CodeGen/X86/elf-associated.ll
@@ -36,15 +36,15 @@
 ; Non-GlobalValue metadata.
 @l = global i32 1, section "ccc", !associated !5
 !5 = !{i32* null}
-; CHECK-DAG: .section	ccc,"aw",@progbits
+; CHECK-DAG: .section	ccc,"awo",@progbits,,unique,3
 
 ; Null metadata.
 @m = global i32 1, section "ddd", !associated !6
 !6 = distinct !{null}
-; CHECK-DAG: .section	ddd,"aw",@progbits
+; CHECK-DAG: .section	ddd,"awo",@progbits,,unique,4
 
 ; Aliases are OK.
 @n = alias i32, i32* inttoptr (i64 add (i64 ptrtoint (i32* @a to i64), i64 1297036692682702848) to i32*)
 @o = global i32 1, section "eee", !associated !7
 !7 = !{i32* @n}
-; CHECK-DAG: .section	eee,"awo",@progbits,n,unique,3
+; CHECK-DAG: .section	eee,"awo",@progbits,n,unique,5