Index: ELF/InputSection.h
===================================================================
--- ELF/InputSection.h
+++ ELF/InputSection.h
@@ -314,6 +314,10 @@
   // 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.
+  size_t OutSecPos = 0;
+
   static bool classof(const SectionBase *S);
 
   InputSectionBase *getRelocatedSection();
Index: ELF/OutputSections.h
===================================================================
--- ELF/OutputSections.h
+++ ELF/OutputSections.h
@@ -113,6 +113,10 @@
   void sort(std::function<int(InputSectionBase *S)> Order);
   void sortInitFini();
   void sortCtorsDtors();
+
+private:
+  // The number of input sections assigned to this section.
+  size_t InputSectionCount = 0;
 };
 
 int getPriority(StringRef S);
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -82,17 +82,23 @@
   return Off + S->getSize();
 }
 
+static bool shouldCompress(uint64_t Flags, StringRef SectionName) {
+  return Config->CompressDebugSections && !(Flags & SHF_ALLOC) &&
+         SectionName.startswith(".debug_");
+}
+
 void OutputSection::addSection(InputSection *S) {
   assert(S->Live);
   Live = true;
   S->Parent = this;
   this->updateAlignment(S->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.
-  this->Size = updateOffset(Size, S);
+  S->OutSecPos = InputSectionCount++;
+
+  // The offset and size needs to be calculated early for compressed debug
+  // sections.
+  if (shouldCompress(Flags, Name))
+    Size = updateOffset(Size, S);
 
   // If this section contains a table of fixed-size entries, sh_entsize
   // holds the element size. Consequently, if this contains two or more
@@ -331,8 +337,7 @@
   typedef typename ELFT::Chdr Elf_Chdr;
 
   // Compress only DWARF debug sections.
-  if (!Config->CompressDebugSections || (Flags & SHF_ALLOC) ||
-      !Name.startswith(".debug_"))
+  if (!shouldCompress(Flags, Name))
     return;
 
   // Create a section header.
@@ -427,7 +432,7 @@
   OutputSection *BOut = LB->getParent();
   if (AOut != BOut)
     return AOut->SectionIndex < BOut->SectionIndex;
-  return LA->OutSecOff < LB->OutSecOff;
+  return LA->OutSecPos < LB->OutSecPos;
 }
 
 template <class ELFT>
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -819,6 +819,18 @@
 
 void MipsGotSection::finalizeContents() { updateAllocSize(); }
 
+static uint64_t estimateOutputSectionSize(const OutputSection *OS) {
+  uint64_t Size = 0;
+  for (BaseCommand *Cmd : OS->Commands) {
+    if (auto *ISD = cast<InputSectionDescription>(Cmd)) {
+      for (InputSection *IS : ISD->Sections) {
+        Size = alignTo(Size, IS->Alignment) + IS->getSize();
+      }
+    }
+  }
+  return Size;
+}
+
 void MipsGotSection::updateAllocSize() {
   PageEntriesNum = 0;
   for (std::pair<const OutputSection *, size_t> &P : PageIndexMap) {
@@ -829,7 +841,11 @@
     // against it. And take in account the case when the section intersects
     // page boundaries.
     P.second = PageEntriesNum;
-    PageEntriesNum += getMipsPageCount(P.first->Size);
+    // The OutputSection Size is not set until after assignAddresses has been
+    // called, so we cannot use it. Instead we make a rough estimate of the
+    // section size, which should be sufficient as long as users don't start
+    // modifying the section size via the linker script.
+    PageEntriesNum += getMipsPageCount(estimateOutputSectionSize(P.first));
   }
   Size = (getLocalEntriesNum() + GlobalEntries.size() + TlsEntries.size()) *
          Config->Wordsize;
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