Index: ELF/InputSection.h
===================================================================
--- ELF/InputSection.h
+++ ELF/InputSection.h
@@ -314,6 +314,11 @@
   // to. The writer sets a value.
   uint64_t OutSecOff = 0;
 
+  // The order in which the section was added to its output section. This is
+  // used when ordering SHF_LINK_ORDER sections. It is not set for sections
+  // inserted late, such as thunk sections.
+  llvm::Optional<size_t> OutSecPos;
+
   static bool classof(const SectionBase *S);
 
   InputSectionBase *getRelocatedSection();
Index: ELF/OutputSections.h
===================================================================
--- ELF/OutputSections.h
+++ ELF/OutputSections.h
@@ -113,6 +113,11 @@
   void sort(std::function<int(InputSectionBase *S)> Order);
   void sortInitFini();
   void sortCtorsDtors();
+
+private:
+  // The number of input sections assigned to this section excluding
+  // late-inserted sections, such as thunk sections.
+  size_t InputSectionCount = 0;
 };
 
 int getPriority(StringRef S);
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -87,6 +87,7 @@
   Live = true;
   S->Parent = this;
   this->updateAlignment(S->Alignment);
+  S->OutSecPos = InputSectionCount++;
 
   // The actual offsets will be computed by assignAddresses. For now, use
   // crude approximation so that it is at least easy for other code to know the
@@ -427,7 +428,9 @@
   OutputSection *BOut = LB->getParent();
   if (AOut != BOut)
     return AOut->SectionIndex < BOut->SectionIndex;
-  return LA->OutSecOff < LB->OutSecOff;
+  assert(LA->OutSecPos && LB->OutSecPos &&
+         "Cannot compare late-inserted section positions.");
+  return LA->OutSecPos < LB->OutSecPos;
 }
 
 template <class ELFT>