Index: ELF/InputSection.h
===================================================================
--- ELF/InputSection.h
+++ ELF/InputSection.h
@@ -319,6 +319,11 @@
   // 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
@@ -110,6 +110,10 @@
   std::vector<uint8_t> ZDebugHeader;
   llvm::SmallVector<char, 1> CompressedData;
 
+  // The number of input sections assigned to this section excluding
+  // late-inserted sections, such as thunk sections.
+  size_t InputSectionCount = 0;
+
   uint32_t getFiller();
 };
 
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -115,13 +115,7 @@
   IS->Parent = this;
   Flags |= IS->Flags;
   Alignment = std::max(Alignment, IS->Alignment);
-
-  // 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
-  // section order. It is also used to calculate the output section size early
-  // for compressed debug sections.
-  IS->OutSecOff = alignTo(Size, IS->Alignment);
-  this->Size = IS->OutSecOff + IS->getSize();
+  IS->OutSecPos = InputSectionCount++;
 
   // If this section contains a table of fixed-size entries, sh_entsize
   // holds the element size. Consequently, if this contains two or more
@@ -320,6 +314,14 @@
       !Name.startswith(".debug_"))
     return;
 
+  // Calculate the section offsets and size pre-compression.
+  for (BaseCommand * Cmd : SectionCommands)
+    if (auto *ISD = dyn_cast<InputSectionDescription>(Cmd))
+      for (InputSection *IS : ISD->Sections) {
+         IS->OutSecOff = alignTo(Size, IS->Alignment);
+         this->Size = IS->OutSecOff + IS->getSize();
+      }
+
   // Create a section header.
   ZDebugHeader.resize(sizeof(Elf_Chdr));
   auto *Hdr = reinterpret_cast<Elf_Chdr *>(ZDebugHeader.data());
@@ -412,7 +414,9 @@
   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>
Index: ELF/SyntheticSections.h
===================================================================
--- ELF/SyntheticSections.h
+++ ELF/SyntheticSections.h
@@ -170,7 +170,6 @@
   void writeTo(uint8_t *Buf) override;
   size_t getSize() const override { return Size; }
   bool updateAllocSize() override;
-  void finalizeContents() override;
   bool empty() const override;
   void addEntry(SymbolBody &Sym, int64_t Addend, RelExpr Expr);
   bool addDynTlsEntry(SymbolBody &Sym);
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -816,8 +816,6 @@
          LocalEntries32.size();
 }
 
-void MipsGotSection::finalizeContents() { updateAllocSize(); }
-
 bool MipsGotSection::updateAllocSize() {
   PageEntriesNum = 0;
   for (std::pair<const OutputSection *, size_t> &P : PageIndexMap) {
@@ -1147,7 +1145,11 @@
     add({DT_MIPS_FLAGS, RHF_NOTPOT});
     add({DT_MIPS_BASE_ADDRESS, Target->getImageBase()});
     add({DT_MIPS_SYMTABNO, InX::DynSymTab->getNumSymbols()});
-    add({DT_MIPS_LOCAL_GOTNO, InX::MipsGot->getLocalEntriesNum()});
+
+    // The number of local got entries has not yet been determined. This value
+    // will be set in writeTo().
+    add({DT_MIPS_LOCAL_GOTNO, uint64_t(0)});
+
     if (const SymbolBody *B = InX::MipsGot->getFirstGlobalEntry())
       add({DT_MIPS_GOTSYM, B->DynsymIndex});
     else
@@ -1182,7 +1184,10 @@
       P->d_un.d_ptr = E.Sym->getVA();
       break;
     case Entry::PlainInt:
-      P->d_un.d_val = E.Val;
+      if (E.Tag == DT_MIPS_LOCAL_GOTNO)
+        P->d_un.d_val = InX::MipsGot->getLocalEntriesNum();
+      else
+        P->d_un.d_val = E.Val;
       break;
     }
     ++P;
Index: test/ELF/linkerscript/unused-synthetic.s
===================================================================
--- test/ELF/linkerscript/unused-synthetic.s
+++ test/ELF/linkerscript/unused-synthetic.s
@@ -13,6 +13,16 @@
 # CHECK:      .text
 # CHECK-NEXT: .dynsym
 
+# Test that the size of a removed unused synthetic input section does not get
+# added to the output section size, if the output section has symbol
+# assignments, preventing removal of the output section.
+# RUN: echo "SECTIONS { \
+# RUN:    .got.plt : { a_sym = .; *(.got.plt) } \
+# RUN:  }" > %t2.script
+# RUN: ld.lld -shared -o %t2.so --script %t2.script %t.o
+# RUN: llvm-objdump -section-headers %t2.so | FileCheck %s --check-prefix=CHECK2
+# CHECK2: .got.plt 00000000
+
 .global _start
 _start:
   nop