Vendor import of lld trunk r300422:vendor/lld/lld-trunk-r300422

https://llvm.org/svn/llvm-project/lld/trunk@300422

1 files changed, 466 insertions, 1453 deletions

diff --git a/ELF/LinkerScript.cpp b/ELF/LinkerScript.cpp
index 3cc235386b88..ab2ca22e9e17 100644
--- a/ELF/LinkerScript.cpp
+++ b/ELF/LinkerScript.cpp
@@ -13,27 +13,21 @@
 
 #include "LinkerScript.h"
 #include "Config.h"
-#include "Driver.h"
 #include "InputSection.h"
 #include "Memory.h"
 #include "OutputSections.h"
-#include "ScriptParser.h"
 #include "Strings.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
-#include "Target.h"
 #include "Writer.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
-#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Path.h"
 #include <algorithm>
 #include <cassert>
@@ -41,9 +35,7 @@
 #include <cstdint>
 #include <iterator>
 #include <limits>
-#include <memory>
 #include <string>
-#include <tuple>
 #include <vector>
 
 using namespace llvm;
@@ -53,77 +45,145 @@ using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::elf;
 
-LinkerScriptBase *elf::ScriptBase;
-ScriptConfiguration *elf::ScriptConfig;
+LinkerScript *elf::Script;
+
+uint64_t ExprValue::getValue() const {
+  if (Sec)
+    return Sec->getOffset(Val) + Sec->getOutputSection()->Addr;
+  return Val;
+}
+
+uint64_t ExprValue::getSecAddr() const {
+  if (Sec)
+    return Sec->getOffset(0) + Sec->getOutputSection()->Addr;
+  return 0;
+}
 
 template <class ELFT> static SymbolBody *addRegular(SymbolAssignment *Cmd) {
+  Symbol *Sym;
   uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
-  Symbol *Sym = Symtab<ELFT>::X->addUndefined(
-      Cmd->Name, /*IsLocal=*/false, STB_GLOBAL, Visibility,
-      /*Type*/ 0,
-      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
-
-  replaceBody<DefinedRegular<ELFT>>(Sym, Cmd->Name, /*IsLocal=*/false,
-                                    Visibility, STT_NOTYPE, 0, 0, nullptr,
-                                    nullptr);
+  std::tie(Sym, std::ignore) = Symtab<ELFT>::X->insert(
+      Cmd->Name, /*Type*/ 0, Visibility, /*CanOmitFromDynSym*/ false,
+      /*File*/ nullptr);
+  Sym->Binding = STB_GLOBAL;
+  ExprValue Value = Cmd->Expression();
+  SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
+
+  // We want to set symbol values early if we can. This allows us to use symbols
+  // as variables in linker scripts. Doing so allows us to write expressions
+  // like this: `alignment = 16; . = ALIGN(., alignment)`
+  uint64_t SymValue = Value.isAbsolute() ? Value.getValue() : 0;
+  replaceBody<DefinedRegular>(Sym, Cmd->Name, /*IsLocal=*/false, Visibility,
+                              STT_NOTYPE, SymValue, 0, Sec, nullptr);
   return Sym->body();
 }
 
-template <class ELFT> static SymbolBody *addSynthetic(SymbolAssignment *Cmd) {
-  uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
-  const OutputSectionBase *Sec =
-      ScriptConfig->HasSections ? nullptr : Cmd->Expression.Section();
-  Symbol *Sym = Symtab<ELFT>::X->addUndefined(
-      Cmd->Name, /*IsLocal=*/false, STB_GLOBAL, Visibility,
-      /*Type*/ 0,
-      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
-
-  replaceBody<DefinedSynthetic>(Sym, Cmd->Name, 0, Sec);
-  return Sym->body();
+OutputSection *LinkerScript::getOutputSection(const Twine &Loc,
+                                              StringRef Name) {
+  for (OutputSection *Sec : *OutputSections)
+    if (Sec->Name == Name)
+      return Sec;
+
+  static OutputSection Dummy("", 0, 0);
+  if (ErrorOnMissingSection)
+    error(Loc + ": undefined section " + Name);
+  return &Dummy;
 }
 
-static bool isUnderSysroot(StringRef Path) {
-  if (Config->Sysroot == "")
-    return false;
-  for (; !Path.empty(); Path = sys::path::parent_path(Path))
-    if (sys::fs::equivalent(Config->Sysroot, Path))
-      return true;
-  return false;
+// This function is essentially the same as getOutputSection(Name)->Size,
+// but it won't print out an error message if a given section is not found.
+//
+// Linker script does not create an output section if its content is empty.
+// We want to allow SIZEOF(.foo) where .foo is a section which happened to
+// be empty. That is why this function is different from getOutputSection().
+uint64_t LinkerScript::getOutputSectionSize(StringRef Name) {
+  for (OutputSection *Sec : *OutputSections)
+    if (Sec->Name == Name)
+      return Sec->Size;
+  return 0;
+}
+
+void LinkerScript::setDot(Expr E, const Twine &Loc, bool InSec) {
+  uint64_t Val = E().getValue();
+  if (Val < Dot) {
+    if (InSec)
+      error(Loc + ": unable to move location counter backward for: " +
+            CurOutSec->Name);
+    else
+      error(Loc + ": unable to move location counter backward");
+  }
+  Dot = Val;
+  // Update to location counter means update to section size.
+  if (InSec)
+    CurOutSec->Size = Dot - CurOutSec->Addr;
 }
 
-template <class ELFT> static void assignSymbol(SymbolAssignment *Cmd) {
-  // If there are sections, then let the value be assigned later in
-  // `assignAddresses`.
-  if (ScriptConfig->HasSections)
+// Sets value of a symbol. Two kinds of symbols are processed: synthetic
+// symbols, whose value is an offset from beginning of section and regular
+// symbols whose value is absolute.
+void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
+  if (Cmd->Name == ".") {
+    setDot(Cmd->Expression, Cmd->Location, InSec);
+    return;
+  }
+
+  if (!Cmd->Sym)
     return;
 
-  uint64_t Value = Cmd->Expression(0);
-  if (Cmd->Expression.IsAbsolute()) {
-    cast<DefinedRegular<ELFT>>(Cmd->Sym)->Value = Value;
+  auto *Sym = cast<DefinedRegular>(Cmd->Sym);
+  ExprValue V = Cmd->Expression();
+  if (V.isAbsolute()) {
+    Sym->Value = V.getValue();
   } else {
-    const OutputSectionBase *Sec = Cmd->Expression.Section();
-    if (Sec)
-      cast<DefinedSynthetic>(Cmd->Sym)->Value = Value - Sec->Addr;
+    Sym->Section = V.Sec;
+    if (Sym->Section->Flags & SHF_ALLOC)
+      Sym->Value = V.Val;
+    else
+      Sym->Value = V.getValue();
+  }
+}
+
+static SymbolBody *findSymbol(StringRef S) {
+  switch (Config->EKind) {
+  case ELF32LEKind:
+    return Symtab<ELF32LE>::X->find(S);
+  case ELF32BEKind:
+    return Symtab<ELF32BE>::X->find(S);
+  case ELF64LEKind:
+    return Symtab<ELF64LE>::X->find(S);
+  case ELF64BEKind:
+    return Symtab<ELF64BE>::X->find(S);
+  default:
+    llvm_unreachable("unknown Config->EKind");
   }
 }
 
-template <class ELFT> static void addSymbol(SymbolAssignment *Cmd) {
+static SymbolBody *addRegularSymbol(SymbolAssignment *Cmd) {
+  switch (Config->EKind) {
+  case ELF32LEKind:
+    return addRegular<ELF32LE>(Cmd);
+  case ELF32BEKind:
+    return addRegular<ELF32BE>(Cmd);
+  case ELF64LEKind:
+    return addRegular<ELF64LE>(Cmd);
+  case ELF64BEKind:
+    return addRegular<ELF64BE>(Cmd);
+  default:
+    llvm_unreachable("unknown Config->EKind");
+  }
+}
+
+void LinkerScript::addSymbol(SymbolAssignment *Cmd) {
   if (Cmd->Name == ".")
     return;
 
   // If a symbol was in PROVIDE(), we need to define it only when
   // it is a referenced undefined symbol.
-  SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
+  SymbolBody *B = findSymbol(Cmd->Name);
   if (Cmd->Provide && (!B || B->isDefined()))
     return;
 
-  // Otherwise, create a new symbol if one does not exist or an
-  // undefined one does exist.
-  if (Cmd->Expression.IsAbsolute())
-    Cmd->Sym = addRegular<ELFT>(Cmd);
-  else
-    Cmd->Sym = addSynthetic<ELFT>(Cmd);
-  assignSymbol<ELFT>(Cmd);
+  Cmd->Sym = addRegularSymbol(Cmd);
 }
 
 bool SymbolAssignment::classof(const BaseCommand *C) {
@@ -146,17 +206,13 @@ bool BytesDataCommand::classof(const BaseCommand *C) {
   return C->Kind == BytesDataKind;
 }
 
-template <class ELFT> LinkerScript<ELFT>::LinkerScript() = default;
-template <class ELFT> LinkerScript<ELFT>::~LinkerScript() = default;
-
-template <class ELFT> static StringRef basename(InputSectionBase<ELFT> *S) {
-  if (S->getFile())
-    return sys::path::filename(S->getFile()->getName());
+static StringRef basename(InputSectionBase *S) {
+  if (S->File)
+    return sys::path::filename(S->File->getName());
   return "";
 }
 
-template <class ELFT>
-bool LinkerScript<ELFT>::shouldKeep(InputSectionBase<ELFT> *S) {
+bool LinkerScript::shouldKeep(InputSectionBase *S) {
   for (InputSectionDescription *ID : Opt.KeptSections)
     if (ID->FilePat.match(basename(S)))
       for (SectionPattern &P : ID->SectionPatterns)
@@ -165,73 +221,77 @@ bool LinkerScript<ELFT>::shouldKeep(InputSectionBase<ELFT> *S) {
   return false;
 }
 
-static bool comparePriority(InputSectionData *A, InputSectionData *B) {
-  return getPriority(A->Name) < getPriority(B->Name);
-}
-
-static bool compareName(InputSectionData *A, InputSectionData *B) {
-  return A->Name < B->Name;
-}
-
-static bool compareAlignment(InputSectionData *A, InputSectionData *B) {
-  // ">" is not a mistake. Larger alignments are placed before smaller
-  // alignments in order to reduce the amount of padding necessary.
-  // This is compatible with GNU.
-  return A->Alignment > B->Alignment;
-}
-
-static std::function<bool(InputSectionData *, InputSectionData *)>
+// A helper function for the SORT() command.
+static std::function<bool(InputSectionBase *, InputSectionBase *)>
 getComparator(SortSectionPolicy K) {
   switch (K) {
   case SortSectionPolicy::Alignment:
-    return compareAlignment;
+    return [](InputSectionBase *A, InputSectionBase *B) {
+      // ">" is not a mistake. Sections with larger alignments are placed
+      // before sections with smaller alignments in order to reduce the
+      // amount of padding necessary. This is compatible with GNU.
+      return A->Alignment > B->Alignment;
+    };
   case SortSectionPolicy::Name:
-    return compareName;
+    return [](InputSectionBase *A, InputSectionBase *B) {
+      return A->Name < B->Name;
+    };
   case SortSectionPolicy::Priority:
-    return comparePriority;
+    return [](InputSectionBase *A, InputSectionBase *B) {
+      return getPriority(A->Name) < getPriority(B->Name);
+    };
   default:
     llvm_unreachable("unknown sort policy");
   }
 }
 
-template <class ELFT>
-static bool matchConstraints(ArrayRef<InputSectionBase<ELFT> *> Sections,
+// A helper function for the SORT() command.
+static bool matchConstraints(ArrayRef<InputSectionBase *> Sections,
                              ConstraintKind Kind) {
   if (Kind == ConstraintKind::NoConstraint)
     return true;
-  bool IsRW = llvm::any_of(Sections, [=](InputSectionData *Sec2) {
-    auto *Sec = static_cast<InputSectionBase<ELFT> *>(Sec2);
-    return Sec->Flags & SHF_WRITE;
+
+  bool IsRW = llvm::any_of(Sections, [](InputSectionBase *Sec) {
+    return static_cast<InputSectionBase *>(Sec)->Flags & SHF_WRITE;
   });
+
   return (IsRW && Kind == ConstraintKind::ReadWrite) ||
          (!IsRW && Kind == ConstraintKind::ReadOnly);
 }
 
-static void sortSections(InputSectionData **Begin, InputSectionData **End,
+static void sortSections(InputSectionBase **Begin, InputSectionBase **End,
                          SortSectionPolicy K) {
   if (K != SortSectionPolicy::Default && K != SortSectionPolicy::None)
     std::stable_sort(Begin, End, getComparator(K));
 }
 
 // Compute and remember which sections the InputSectionDescription matches.
-template <class ELFT>
-void LinkerScript<ELFT>::computeInputSections(InputSectionDescription *I) {
-  // Collects all sections that satisfy constraints of I
-  // and attach them to I.
-  for (SectionPattern &Pat : I->SectionPatterns) {
-    size_t SizeBefore = I->Sections.size();
-
-    for (InputSectionBase<ELFT> *S : Symtab<ELFT>::X->Sections) {
-      if (!S->Live || S->Assigned)
+std::vector<InputSectionBase *>
+LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
+  std::vector<InputSectionBase *> Ret;
+
+  // Collects all sections that satisfy constraints of Cmd.
+  for (const SectionPattern &Pat : Cmd->SectionPatterns) {
+    size_t SizeBefore = Ret.size();
+
+    for (InputSectionBase *Sec : InputSections) {
+      if (Sec->Assigned)
         continue;
 
-      StringRef Filename = basename(S);
-      if (!I->FilePat.match(Filename) || Pat.ExcludedFilePat.match(Filename))
+      // For -emit-relocs we have to ignore entries like
+      //   .rela.dyn : { *(.rela.data) }
+      // which are common because they are in the default bfd script.
+      if (Sec->Type == SHT_REL || Sec->Type == SHT_RELA)
         continue;
-      if (!Pat.SectionPat.match(S->Name))
+
+      StringRef Filename = basename(Sec);
+      if (!Cmd->FilePat.match(Filename) ||
+          Pat.ExcludedFilePat.match(Filename) ||
+          !Pat.SectionPat.match(Sec->Name))
         continue;
-      I->Sections.push_back(S);
-      S->Assigned = true;
+
+      Ret.push_back(Sec);
+      Sec->Assigned = true;
     }
 
     // Sort sections as instructed by SORT-family commands and --sort-section
@@ -245,8 +305,8 @@ void LinkerScript<ELFT>::computeInputSections(InputSectionDescription *I) {
     //    --sort-section is handled as an inner SORT command.
     // 3. If one SORT command is given, and if it is SORT_NONE, don't sort.
     // 4. If no SORT command is given, sort according to --sort-section.
-    InputSectionData **Begin = I->Sections.data() + SizeBefore;
-    InputSectionData **End = I->Sections.data() + I->Sections.size();
+    InputSectionBase **Begin = Ret.data() + SizeBefore;
+    InputSectionBase **End = Ret.data() + Ret.size();
     if (Pat.SortOuter != SortSectionPolicy::None) {
       if (Pat.SortInner == SortSectionPolicy::Default)
         sortSections(Begin, End, Config->SortSection);
@@ -255,68 +315,58 @@ void LinkerScript<ELFT>::computeInputSections(InputSectionDescription *I) {
       sortSections(Begin, End, Pat.SortOuter);
     }
   }
+  return Ret;
 }
 
-template <class ELFT>
-void LinkerScript<ELFT>::discard(ArrayRef<InputSectionBase<ELFT> *> V) {
-  for (InputSectionBase<ELFT> *S : V) {
+void LinkerScript::discard(ArrayRef<InputSectionBase *> V) {
+  for (InputSectionBase *S : V) {
     S->Live = false;
-    reportDiscarded(S);
+    if (S == InX::ShStrTab)
+      error("discarding .shstrtab section is not allowed");
+    discard(S->DependentSections);
   }
 }
 
-template <class ELFT>
-std::vector<InputSectionBase<ELFT> *>
-LinkerScript<ELFT>::createInputSectionList(OutputSectionCommand &OutCmd) {
-  std::vector<InputSectionBase<ELFT> *> Ret;
+std::vector<InputSectionBase *>
+LinkerScript::createInputSectionList(OutputSectionCommand &OutCmd) {
+  std::vector<InputSectionBase *> Ret;
 
-  for (const std::unique_ptr<BaseCommand> &Base : OutCmd.Commands) {
-    auto *Cmd = dyn_cast<InputSectionDescription>(Base.get());
+  for (BaseCommand *Base : OutCmd.Commands) {
+    auto *Cmd = dyn_cast<InputSectionDescription>(Base);
     if (!Cmd)
       continue;
-    computeInputSections(Cmd);
-    for (InputSectionData *S : Cmd->Sections)
-      Ret.push_back(static_cast<InputSectionBase<ELFT> *>(S));
+
+    Cmd->Sections = computeInputSections(Cmd);
+    Ret.insert(Ret.end(), Cmd->Sections.begin(), Cmd->Sections.end());
   }
 
   return Ret;
 }
 
-template <class ELFT>
-void LinkerScript<ELFT>::addSection(OutputSectionFactory<ELFT> &Factory,
-                                    InputSectionBase<ELFT> *Sec,
-                                    StringRef Name) {
-  OutputSectionBase *OutSec;
-  bool IsNew;
-  std::tie(OutSec, IsNew) = Factory.create(Sec, Name);
-  if (IsNew)
-    OutputSections->push_back(OutSec);
-  OutSec->addSection(Sec);
-}
-
-template <class ELFT>
-void LinkerScript<ELFT>::processCommands(OutputSectionFactory<ELFT> &Factory) {
-  for (unsigned I = 0; I < Opt.Commands.size(); ++I) {
-    auto Iter = Opt.Commands.begin() + I;
-    const std::unique_ptr<BaseCommand> &Base1 = *Iter;
+void LinkerScript::processCommands(OutputSectionFactory &Factory) {
+  // A symbol can be assigned before any section is mentioned in the linker
+  // script. In an DSO, the symbol values are addresses, so the only important
+  // section values are:
+  // * SHN_UNDEF
+  // * SHN_ABS
+  // * Any value meaning a regular section.
+  // To handle that, create a dummy aether section that fills the void before
+  // the linker scripts switches to another section. It has an index of one
+  // which will map to whatever the first actual section is.
+  Aether = make<OutputSection>("", 0, SHF_ALLOC);
+  Aether->SectionIndex = 1;
+  CurOutSec = Aether;
+  Dot = 0;
 
+  for (size_t I = 0; I < Opt.Commands.size(); ++I) {
     // Handle symbol assignments outside of any output section.
-    if (auto *Cmd = dyn_cast<SymbolAssignment>(Base1.get())) {
-      addSymbol<ELFT>(Cmd);
+    if (auto *Cmd = dyn_cast<SymbolAssignment>(Opt.Commands[I])) {
+      addSymbol(Cmd);
       continue;
     }
 
-    if (auto *Cmd = dyn_cast<AssertCommand>(Base1.get())) {
-      // If we don't have SECTIONS then output sections have already been
-      // created by Writer<ELFT>. The LinkerScript<ELFT>::assignAddresses
-      // will not be called, so ASSERT should be evaluated now.
-      if (!Opt.HasSections)
-        Cmd->Expression(0);
-      continue;
-    }
-
-    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base1.get())) {
-      std::vector<InputSectionBase<ELFT> *> V = createInputSectionList(*Cmd);
+    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I])) {
+      std::vector<InputSectionBase *> V = createInputSectionList(*Cmd);
 
       // The output section name `/DISCARD/' is special.
       // Any input section assigned to it is discarded.
@@ -332,74 +382,54 @@ void LinkerScript<ELFT>::processCommands(OutputSectionFactory<ELFT> &Factory) {
       //
       // Because we'll iterate over Commands many more times, the easiest
       // way to "make it as if it wasn't present" is to just remove it.
-      if (!matchConstraints<ELFT>(V, Cmd->Constraint)) {
-        for (InputSectionBase<ELFT> *S : V)
+      if (!matchConstraints(V, Cmd->Constraint)) {
+        for (InputSectionBase *S : V)
           S->Assigned = false;
-        Opt.Commands.erase(Iter);
+        Opt.Commands.erase(Opt.Commands.begin() + I);
         --I;
         continue;
       }
 
       // A directive may contain symbol definitions like this:
       // ".foo : { ...; bar = .; }". Handle them.
-      for (const std::unique_ptr<BaseCommand> &Base : Cmd->Commands)
-        if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base.get()))
-          addSymbol<ELFT>(OutCmd);
+      for (BaseCommand *Base : Cmd->Commands)
+        if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base))
+          addSymbol(OutCmd);
 
       // Handle subalign (e.g. ".foo : SUBALIGN(32) { ... }"). If subalign
       // is given, input sections are aligned to that value, whether the
       // given value is larger or smaller than the original section alignment.
       if (Cmd->SubalignExpr) {
-        uint32_t Subalign = Cmd->SubalignExpr(0);
-        for (InputSectionBase<ELFT> *S : V)
+        uint32_t Subalign = Cmd->SubalignExpr().getValue();
+        for (InputSectionBase *S : V)
           S->Alignment = Subalign;
       }
 
       // Add input sections to an output section.
-      for (InputSectionBase<ELFT> *S : V)
-        addSection(Factory, S, Cmd->Name);
+      for (InputSectionBase *S : V)
+        Factory.addInputSec(S, Cmd->Name);
     }
   }
+  CurOutSec = nullptr;
 }
 
 // Add sections that didn't match any sections command.
-template <class ELFT>
-void LinkerScript<ELFT>::addOrphanSections(
-    OutputSectionFactory<ELFT> &Factory) {
-  for (InputSectionBase<ELFT> *S : Symtab<ELFT>::X->Sections)
+void LinkerScript::addOrphanSections(OutputSectionFactory &Factory) {
+  for (InputSectionBase *S : InputSections)
     if (S->Live && !S->OutSec)
-      addSection(Factory, S, getOutputSectionName(S->Name));
+      Factory.addInputSec(S, getOutputSectionName(S->Name));
 }
 
-// Sets value of a section-defined symbol. Two kinds of
-// symbols are processed: synthetic symbols, whose value
-// is an offset from beginning of section and regular
-// symbols whose value is absolute.
-template <class ELFT>
-static void assignSectionSymbol(SymbolAssignment *Cmd,
-                                typename ELFT::uint Value) {
-  if (!Cmd->Sym)
-    return;
-
-  if (auto *Body = dyn_cast<DefinedSynthetic>(Cmd->Sym)) {
-    Body->Section = Cmd->Expression.Section();
-    Body->Value = Cmd->Expression(Value) - Body->Section->Addr;
-    return;
-  }
-  auto *Body = cast<DefinedRegular<ELFT>>(Cmd->Sym);
-  Body->Value = Cmd->Expression(Value);
-}
-
-template <class ELFT> static bool isTbss(OutputSectionBase *Sec) {
+static bool isTbss(OutputSection *Sec) {
   return (Sec->Flags & SHF_TLS) && Sec->Type == SHT_NOBITS;
 }
 
-template <class ELFT> void LinkerScript<ELFT>::output(InputSection<ELFT> *S) {
+void LinkerScript::output(InputSection *S) {
   if (!AlreadyOutputIS.insert(S).second)
     return;
-  bool IsTbss = isTbss<ELFT>(CurOutSec);
+  bool IsTbss = isTbss(CurOutSec);
 
-  uintX_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
+  uint64_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
   Pos = alignTo(Pos, S->Alignment);
   S->OutSecOff = Pos - CurOutSec->Addr;
   Pos += S->getSize();
@@ -409,134 +439,171 @@ template <class ELFT> void LinkerScript<ELFT>::output(InputSection<ELFT> *S) {
   // .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
   CurOutSec->Size = Pos - CurOutSec->Addr;
 
+  // If there is a memory region associated with this input section, then
+  // place the section in that region and update the region index.
+  if (CurMemRegion) {
+    CurMemRegion->Offset += CurOutSec->Size;
+    uint64_t CurSize = CurMemRegion->Offset - CurMemRegion->Origin;
+    if (CurSize > CurMemRegion->Length) {
+      uint64_t OverflowAmt = CurSize - CurMemRegion->Length;
+      error("section '" + CurOutSec->Name + "' will not fit in region '" +
+            CurMemRegion->Name + "': overflowed by " + Twine(OverflowAmt) +
+            " bytes");
+    }
+  }
+
   if (IsTbss)
     ThreadBssOffset = Pos - Dot;
   else
     Dot = Pos;
 }
 
-template <class ELFT> void LinkerScript<ELFT>::flush() {
-  if (!CurOutSec || !AlreadyOutputOS.insert(CurOutSec).second)
+void LinkerScript::flush() {
+  assert(CurOutSec);
+  if (!AlreadyOutputOS.insert(CurOutSec).second)
     return;
-  if (auto *OutSec = dyn_cast<OutputSection<ELFT>>(CurOutSec)) {
-    for (InputSection<ELFT> *I : OutSec->Sections)
-      output(I);
-  } else {
-    Dot += CurOutSec->Size;
-  }
+  for (InputSection *I : CurOutSec->Sections)
+    output(I);
 }
 
-template <class ELFT>
-void LinkerScript<ELFT>::switchTo(OutputSectionBase *Sec) {
+void LinkerScript::switchTo(OutputSection *Sec) {
   if (CurOutSec == Sec)
     return;
   if (AlreadyOutputOS.count(Sec))
     return;
 
-  flush();
   CurOutSec = Sec;
 
-  Dot = alignTo(Dot, CurOutSec->Addralign);
-  CurOutSec->Addr = isTbss<ELFT>(CurOutSec) ? Dot + ThreadBssOffset : Dot;
+  Dot = alignTo(Dot, CurOutSec->Alignment);
+  CurOutSec->Addr = isTbss(CurOutSec) ? Dot + ThreadBssOffset : Dot;
 
   // If neither AT nor AT> is specified for an allocatable section, the linker
   // will set the LMA such that the difference between VMA and LMA for the
   // section is the same as the preceding output section in the same region
   // https://sourceware.org/binutils/docs-2.20/ld/Output-Section-LMA.html
-  CurOutSec->setLMAOffset(LMAOffset);
+  if (LMAOffset)
+    CurOutSec->LMAOffset = LMAOffset();
 }
 
-template <class ELFT> void LinkerScript<ELFT>::process(BaseCommand &Base) {
-  // This handles the assignments to symbol or to a location counter (.)
-  if (auto *AssignCmd = dyn_cast<SymbolAssignment>(&Base)) {
-    if (AssignCmd->Name == ".") {
-      // Update to location counter means update to section size.
-      uintX_t Val = AssignCmd->Expression(Dot);
-      if (Val < Dot)
-        error("unable to move location counter backward for: " +
-              CurOutSec->Name);
-      Dot = Val;
-      CurOutSec->Size = Dot - CurOutSec->Addr;
-      return;
-    }
-    assignSectionSymbol<ELFT>(AssignCmd, Dot);
+void LinkerScript::process(BaseCommand &Base) {
+  // This handles the assignments to symbol or to the dot.
+  if (auto *Cmd = dyn_cast<SymbolAssignment>(&Base)) {
+    assignSymbol(Cmd, true);
     return;
   }
 
   // Handle BYTE(), SHORT(), LONG(), or QUAD().
-  if (auto *DataCmd = dyn_cast<BytesDataCommand>(&Base)) {
-    DataCmd->Offset = Dot - CurOutSec->Addr;
-    Dot += DataCmd->Size;
+  if (auto *Cmd = dyn_cast<BytesDataCommand>(&Base)) {
+    Cmd->Offset = Dot - CurOutSec->Addr;
+    Dot += Cmd->Size;
     CurOutSec->Size = Dot - CurOutSec->Addr;
     return;
   }
 
-  if (auto *AssertCmd = dyn_cast<AssertCommand>(&Base)) {
-    AssertCmd->Expression(Dot);
+  // Handle ASSERT().
+  if (auto *Cmd = dyn_cast<AssertCommand>(&Base)) {
+    Cmd->Expression();
     return;
   }
 
-  // It handles single input section description command,
-  // calculates and assigns the offsets for each section and also
+  // Handle a single input section description command.
+  // It calculates and assigns the offsets for each section and also
   // updates the output section size.
-  auto &ICmd = cast<InputSectionDescription>(Base);
-  for (InputSectionData *ID : ICmd.Sections) {
+  auto &Cmd = cast<InputSectionDescription>(Base);
+  for (InputSectionBase *Sec : Cmd.Sections) {
     // We tentatively added all synthetic sections at the beginning and removed
     // empty ones afterwards (because there is no way to know whether they were
     // going be empty or not other than actually running linker scripts.)
     // We need to ignore remains of empty sections.
-    if (auto *Sec = dyn_cast<SyntheticSection<ELFT>>(ID))
-      if (Sec->empty())
+    if (auto *S = dyn_cast<SyntheticSection>(Sec))
+      if (S->empty())
         continue;
 
-    auto *IB = static_cast<InputSectionBase<ELFT> *>(ID);
-    switchTo(IB->OutSec);
-    if (auto *I = dyn_cast<InputSection<ELFT>>(IB))
-      output(I);
-    else
-      flush();
+    if (!Sec->Live)
+      continue;
+    assert(CurOutSec == Sec->OutSec || AlreadyOutputOS.count(Sec->OutSec));
+    output(cast<InputSection>(Sec));
   }
 }
 
-template <class ELFT>
-static std::vector<OutputSectionBase *>
-findSections(StringRef Name, const std::vector<OutputSectionBase *> &Sections) {
-  std::vector<OutputSectionBase *> Ret;
-  for (OutputSectionBase *Sec : Sections)
-    if (Sec->getName() == Name)
-      Ret.push_back(Sec);
-  return Ret;
+static OutputSection *
+findSection(StringRef Name, const std::vector<OutputSection *> &Sections) {
+  for (OutputSection *Sec : Sections)
+    if (Sec->Name == Name)
+      return Sec;
+  return nullptr;
+}
+
+// This function searches for a memory region to place the given output
+// section in. If found, a pointer to the appropriate memory region is
+// returned. Otherwise, a nullptr is returned.
+MemoryRegion *LinkerScript::findMemoryRegion(OutputSectionCommand *Cmd) {
+  // If a memory region name was specified in the output section command,
+  // then try to find that region first.
+  if (!Cmd->MemoryRegionName.empty()) {
+    auto It = Opt.MemoryRegions.find(Cmd->MemoryRegionName);
+    if (It != Opt.MemoryRegions.end())
+      return &It->second;
+    error("memory region '" + Cmd->MemoryRegionName + "' not declared");
+    return nullptr;
+  }
+
+  // If at least one memory region is defined, all sections must
+  // belong to some memory region. Otherwise, we don't need to do
+  // anything for memory regions.
+  if (Opt.MemoryRegions.empty())
+    return nullptr;
+
+  OutputSection *Sec = Cmd->Sec;
+  // See if a region can be found by matching section flags.
+  for (auto &Pair : Opt.MemoryRegions) {
+    MemoryRegion &M = Pair.second;
+    if ((M.Flags & Sec->Flags) && (M.NegFlags & Sec->Flags) == 0)
+      return &M;
+  }
+
+  // Otherwise, no suitable region was found.
+  if (Sec->Flags & SHF_ALLOC)
+    error("no memory region specified for section '" + Sec->Name + "'");
+  return nullptr;
 }
 
 // This function assigns offsets to input sections and an output section
 // for a single sections command (e.g. ".text { *(.text); }").
-template <class ELFT>
-void LinkerScript<ELFT>::assignOffsets(OutputSectionCommand *Cmd) {
-  if (Cmd->LMAExpr)
-    LMAOffset = Cmd->LMAExpr(Dot) - Dot;
-  std::vector<OutputSectionBase *> Sections =
-      findSections<ELFT>(Cmd->Name, *OutputSections);
-  if (Sections.empty())
+void LinkerScript::assignOffsets(OutputSectionCommand *Cmd) {
+  OutputSection *Sec = Cmd->Sec;
+  if (!Sec)
     return;
-  switchTo(Sections[0]);
-
-  // Find the last section output location. We will output orphan sections
-  // there so that end symbols point to the correct location.
-  auto E = std::find_if(Cmd->Commands.rbegin(), Cmd->Commands.rend(),
-                        [](const std::unique_ptr<BaseCommand> &Cmd) {
-                          return !isa<SymbolAssignment>(*Cmd);
-                        })
-               .base();
-  for (auto I = Cmd->Commands.begin(); I != E; ++I)
+
+  if (Cmd->AddrExpr && (Sec->Flags & SHF_ALLOC))
+    setDot(Cmd->AddrExpr, Cmd->Location, false);
+
+  if (Cmd->LMAExpr) {
+    uint64_t D = Dot;
+    LMAOffset = [=] { return Cmd->LMAExpr().getValue() - D; };
+  }
+
+  CurMemRegion = Cmd->MemRegion;
+  if (CurMemRegion)
+    Dot = CurMemRegion->Offset;
+  switchTo(Sec);
+
+  // flush() may add orphan sections, so the order of flush() and
+  // symbol assignments is important. We want to call flush() first so
+  // that symbols pointing the end of the current section points to
+  // the location after orphan sections.
+  auto Mid =
+      std::find_if(Cmd->Commands.rbegin(), Cmd->Commands.rend(),
+                   [](BaseCommand *Cmd) { return !isa<SymbolAssignment>(Cmd); })
+          .base();
+  for (auto I = Cmd->Commands.begin(); I != Mid; ++I)
     process(**I);
-  for (OutputSectionBase *Base : Sections)
-    switchTo(Base);
   flush();
-  std::for_each(E, Cmd->Commands.end(),
-                [this](std::unique_ptr<BaseCommand> &B) { process(*B.get()); });
+  for (auto I = Mid, E = Cmd->Commands.end(); I != E; ++I)
+    process(**I);
 }
 
-template <class ELFT> void LinkerScript<ELFT>::removeEmptyCommands() {
+void LinkerScript::removeEmptyCommands() {
   // It is common practice to use very generic linker scripts. So for any
   // given run some of the output sections in the script will be empty.
   // We could create corresponding empty output sections, but that would
@@ -544,52 +611,61 @@ template <class ELFT> void LinkerScript<ELFT>::removeEmptyCommands() {
   // We instead remove trivially empty sections. The bfd linker seems even
   // more aggressive at removing them.
   auto Pos = std::remove_if(
-      Opt.Commands.begin(), Opt.Commands.end(),
-      [&](const std::unique_ptr<BaseCommand> &Base) {
-        if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
-          return findSections<ELFT>(Cmd->Name, *OutputSections).empty();
+      Opt.Commands.begin(), Opt.Commands.end(), [&](BaseCommand *Base) {
+        if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
+          return !Cmd->Sec;
         return false;
       });
   Opt.Commands.erase(Pos, Opt.Commands.end());
 }
 
 static bool isAllSectionDescription(const OutputSectionCommand &Cmd) {
-  for (const std::unique_ptr<BaseCommand> &I : Cmd.Commands)
-    if (!isa<InputSectionDescription>(*I))
+  for (BaseCommand *Base : Cmd.Commands)
+    if (!isa<InputSectionDescription>(*Base))
       return false;
   return true;
 }
 
-template <class ELFT> void LinkerScript<ELFT>::adjustSectionsBeforeSorting() {
+void LinkerScript::adjustSectionsBeforeSorting() {
   // If the output section contains only symbol assignments, create a
   // corresponding output section. The bfd linker seems to only create them if
   // '.' is assigned to, but creating these section should not have any bad
   // consequeces and gives us a section to put the symbol in.
-  uintX_t Flags = SHF_ALLOC;
-  uint32_t Type = SHT_NOBITS;
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
-    auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
+  uint64_t Flags = SHF_ALLOC;
+  uint32_t Type = SHT_PROGBITS;
+  for (BaseCommand *Base : Opt.Commands) {
+    auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
     if (!Cmd)
       continue;
-    std::vector<OutputSectionBase *> Secs =
-        findSections<ELFT>(Cmd->Name, *OutputSections);
-    if (!Secs.empty()) {
-      Flags = Secs[0]->Flags;
-      Type = Secs[0]->Type;
+    if (OutputSection *Sec = findSection(Cmd->Name, *OutputSections)) {
+      Cmd->Sec = Sec;
+      Flags = Sec->Flags;
+      Type = Sec->Type;
       continue;
     }
 
     if (isAllSectionDescription(*Cmd))
       continue;
 
-    auto *OutSec = make<OutputSection<ELFT>>(Cmd->Name, Type, Flags);
+    auto *OutSec = make<OutputSection>(Cmd->Name, Type, Flags);
     OutputSections->push_back(OutSec);
+    Cmd->Sec = OutSec;
   }
 }
 
-template <class ELFT> void LinkerScript<ELFT>::adjustSectionsAfterSorting() {
+void LinkerScript::adjustSectionsAfterSorting() {
   placeOrphanSections();
 
+  // Try and find an appropriate memory region to assign offsets in.
+  for (BaseCommand *Base : Opt.Commands) {
+    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base)) {
+      Cmd->MemRegion = findMemoryRegion(Cmd);
+      // Handle align (e.g. ".foo : ALIGN(16) { ... }").
+      if (Cmd->AlignExpr)
+	Cmd->Sec->updateAlignment(Cmd->AlignExpr().getValue());
+    }
+  }
+
   // If output section command doesn't specify any segments,
   // and we haven't previously assigned any section to segment,
   // then we simply assign section to the very first load segment.
@@ -605,10 +681,11 @@ template <class ELFT> void LinkerScript<ELFT>::adjustSectionsAfterSorting() {
 
   // Walk the commands and propagate the program headers to commands that don't
   // explicitly specify them.
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
-    auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
+  for (BaseCommand *Base : Opt.Commands) {
+    auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
     if (!Cmd)
       continue;
+
     if (Cmd->Phdrs.empty())
       Cmd->Phdrs = DefPhdrs;
     else
@@ -632,19 +709,37 @@ template <class ELFT> void LinkerScript<ELFT>::adjustSectionsAfterSorting() {
 //  /* The RW PT_LOAD starts here*/
 //  rw_sec : { *(rw_sec) }
 // would mean that the RW PT_LOAD would become unaligned.
-static bool shouldSkip(const BaseCommand &Cmd) {
+static bool shouldSkip(BaseCommand *Cmd) {
   if (isa<OutputSectionCommand>(Cmd))
     return false;
-  const auto *Assign = dyn_cast<SymbolAssignment>(&Cmd);
-  if (!Assign)
-    return true;
-  return Assign->Name != ".";
+  if (auto *Assign = dyn_cast<SymbolAssignment>(Cmd))
+    return Assign->Name != ".";
+  return true;
 }
 
-// Orphan sections are sections present in the input files which are not
-// explicitly placed into the output file by the linker script. This just
-// places them in the order already decided in OutputSections.
-template <class ELFT> void LinkerScript<ELFT>::placeOrphanSections() {
+// Orphan sections are sections present in the input files which are
+// not explicitly placed into the output file by the linker script.
+//
+// When the control reaches this function, Opt.Commands contains
+// output section commands for non-orphan sections only. This function
+// adds new elements for orphan sections so that all sections are
+// explicitly handled by Opt.Commands.
+//
+// Writer<ELFT>::sortSections has already sorted output sections.
+// What we need to do is to scan OutputSections vector and
+// Opt.Commands in parallel to find orphan sections. If there is an
+// output section that doesn't have a corresponding entry in
+// Opt.Commands, we will insert a new entry to Opt.Commands.
+//
+// There is some ambiguity as to where exactly a new entry should be
+// inserted, because Opt.Commands contains not only output section
+// commands but also other types of commands such as symbol assignment
+// expressions. There's no correct answer here due to the lack of the
+// formal specification of the linker script. We use heuristics to
+// determine whether a new output command should be added before or
+// after another commands. For the details, look at shouldSkip
+// function.
+void LinkerScript::placeOrphanSections() {
   // The OutputSections are already in the correct order.
   // This loops creates or moves commands as needed so that they are in the
   // correct order.
@@ -656,40 +751,33 @@ template <class ELFT> void LinkerScript<ELFT>::placeOrphanSections() {
   // after that.
   auto FirstSectionOrDotAssignment =
       std::find_if(Opt.Commands.begin(), Opt.Commands.end(),
-                   [](const std::unique_ptr<BaseCommand> &Cmd) {
-                     if (isa<OutputSectionCommand>(*Cmd))
-                       return true;
-                     const auto *Assign = dyn_cast<SymbolAssignment>(Cmd.get());
-                     if (!Assign)
-                       return false;
-                     return Assign->Name == ".";
-                   });
+                   [](BaseCommand *Cmd) { return !shouldSkip(Cmd); });
   if (FirstSectionOrDotAssignment != Opt.Commands.end()) {
     CmdIndex = FirstSectionOrDotAssignment - Opt.Commands.begin();
     if (isa<SymbolAssignment>(**FirstSectionOrDotAssignment))
       ++CmdIndex;
   }
 
-  for (OutputSectionBase *Sec : *OutputSections) {
-    StringRef Name = Sec->getName();
+  for (OutputSection *Sec : *OutputSections) {
+    StringRef Name = Sec->Name;
 
     // Find the last spot where we can insert a command and still get the
     // correct result.
     auto CmdIter = Opt.Commands.begin() + CmdIndex;
     auto E = Opt.Commands.end();
-    while (CmdIter != E && shouldSkip(**CmdIter)) {
+    while (CmdIter != E && shouldSkip(*CmdIter)) {
       ++CmdIter;
       ++CmdIndex;
     }
 
-    auto Pos =
-        std::find_if(CmdIter, E, [&](const std::unique_ptr<BaseCommand> &Base) {
-          auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
-          return Cmd && Cmd->Name == Name;
-        });
+    auto Pos = std::find_if(CmdIter, E, [&](BaseCommand *Base) {
+      auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
+      return Cmd && Cmd->Name == Name;
+    });
     if (Pos == E) {
-      Opt.Commands.insert(CmdIter,
-                          llvm::make_unique<OutputSectionCommand>(Name));
+      auto *Cmd = make<OutputSectionCommand>(Name);
+      Cmd->Sec = Sec;
+      Opt.Commands.insert(CmdIter, Cmd);
       ++CmdIndex;
       continue;
     }
@@ -699,55 +787,49 @@ template <class ELFT> void LinkerScript<ELFT>::placeOrphanSections() {
   }
 }
 
-template <class ELFT>
-void LinkerScript<ELFT>::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
+void LinkerScript::processNonSectionCommands() {
+  for (BaseCommand *Base : Opt.Commands) {
+    if (auto *Cmd = dyn_cast<SymbolAssignment>(Base))
+      assignSymbol(Cmd, false);
+    else if (auto *Cmd = dyn_cast<AssertCommand>(Base))
+      Cmd->Expression();
+  }
+}
+
+void LinkerScript::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
   // Assign addresses as instructed by linker script SECTIONS sub-commands.
   Dot = 0;
+  ErrorOnMissingSection = true;
+  switchTo(Aether);
 
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
-    if (auto *Cmd = dyn_cast<SymbolAssignment>(Base.get())) {
-      if (Cmd->Name == ".") {
-        Dot = Cmd->Expression(Dot);
-      } else if (Cmd->Sym) {
-        assignSectionSymbol<ELFT>(Cmd, Dot);
-      }
+  for (BaseCommand *Base : Opt.Commands) {
+    if (auto *Cmd = dyn_cast<SymbolAssignment>(Base)) {
+      assignSymbol(Cmd, false);
       continue;
     }
 
-    if (auto *Cmd = dyn_cast<AssertCommand>(Base.get())) {
-      Cmd->Expression(Dot);
+    if (auto *Cmd = dyn_cast<AssertCommand>(Base)) {
+      Cmd->Expression();
       continue;
     }
 
-    auto *Cmd = cast<OutputSectionCommand>(Base.get());
-    if (Cmd->AddrExpr)
-      Dot = Cmd->AddrExpr(Dot);
+    auto *Cmd = cast<OutputSectionCommand>(Base);
     assignOffsets(Cmd);
   }
 
-  uintX_t MinVA = std::numeric_limits<uintX_t>::max();
-  for (OutputSectionBase *Sec : *OutputSections) {
+  uint64_t MinVA = std::numeric_limits<uint64_t>::max();
+  for (OutputSection *Sec : *OutputSections) {
     if (Sec->Flags & SHF_ALLOC)
       MinVA = std::min<uint64_t>(MinVA, Sec->Addr);
     else
       Sec->Addr = 0;
   }
 
-  uintX_t HeaderSize = getHeaderSize();
-  // If the linker script doesn't have PHDRS, add ElfHeader and ProgramHeaders
-  // now that we know we have space.
-  if (HeaderSize <= MinVA && !hasPhdrsCommands())
-    allocateHeaders<ELFT>(Phdrs, *OutputSections);
-
-  // ELF and Program headers need to be right before the first section in
-  // memory. Set their addresses accordingly.
-  MinVA = alignDown(MinVA - HeaderSize, Config->MaxPageSize);
-  Out<ELFT>::ElfHeader->Addr = MinVA;
-  Out<ELFT>::ProgramHeaders->Addr = Out<ELFT>::ElfHeader->Size + MinVA;
+  allocateHeaders(Phdrs, *OutputSections, MinVA);
 }
 
 // Creates program headers as instructed by PHDRS linker script command.
-template <class ELFT> std::vector<PhdrEntry> LinkerScript<ELFT>::createPhdrs() {
+std::vector<PhdrEntry> LinkerScript::createPhdrs() {
   std::vector<PhdrEntry> Ret;
 
   // Process PHDRS and FILEHDR keywords because they are not
@@ -757,23 +839,23 @@ template <class ELFT> std::vector<PhdrEntry> LinkerScript<ELFT>::createPhdrs() {
     PhdrEntry &Phdr = Ret.back();
 
     if (Cmd.HasFilehdr)
-      Phdr.add(Out<ELFT>::ElfHeader);
+      Phdr.add(Out::ElfHeader);
     if (Cmd.HasPhdrs)
-      Phdr.add(Out<ELFT>::ProgramHeaders);
+      Phdr.add(Out::ProgramHeaders);
 
     if (Cmd.LMAExpr) {
-      Phdr.p_paddr = Cmd.LMAExpr(0);
+      Phdr.p_paddr = Cmd.LMAExpr().getValue();
       Phdr.HasLMA = true;
     }
   }
 
   // Add output sections to program headers.
-  for (OutputSectionBase *Sec : *OutputSections) {
+  for (OutputSection *Sec : *OutputSections) {
     if (!(Sec->Flags & SHF_ALLOC))
       break;
 
     // Assign headers specified by linker script
-    for (size_t Id : getPhdrIndices(Sec->getName())) {
+    for (size_t Id : getPhdrIndices(Sec->Name)) {
       Ret[Id].add(Sec);
       if (Opt.PhdrsCommands[Id].Flags == UINT_MAX)
         Ret[Id].p_flags |= Sec->getPhdrFlags();
@@ -782,60 +864,52 @@ template <class ELFT> std::vector<PhdrEntry> LinkerScript<ELFT>::createPhdrs() {
   return Ret;
 }
 
-template <class ELFT> bool LinkerScript<ELFT>::ignoreInterpSection() {
+bool LinkerScript::ignoreInterpSection() {
   // Ignore .interp section in case we have PHDRS specification
   // and PT_INTERP isn't listed.
-  return !Opt.PhdrsCommands.empty() &&
-         llvm::find_if(Opt.PhdrsCommands, [](const PhdrsCommand &Cmd) {
-           return Cmd.Type == PT_INTERP;
-         }) == Opt.PhdrsCommands.end();
+  if (Opt.PhdrsCommands.empty())
+    return false;
+  for (PhdrsCommand &Cmd : Opt.PhdrsCommands)
+    if (Cmd.Type == PT_INTERP)
+      return false;
+  return true;
 }
 
-template <class ELFT> uint32_t LinkerScript<ELFT>::getFiller(StringRef Name) {
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
-    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
+Optional<uint32_t> LinkerScript::getFiller(StringRef Name) {
+  for (BaseCommand *Base : Opt.Commands)
+    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       if (Cmd->Name == Name)
         return Cmd->Filler;
-  return 0;
+  return None;
 }
 
-template <class ELFT>
 static void writeInt(uint8_t *Buf, uint64_t Data, uint64_t Size) {
-  const endianness E = ELFT::TargetEndianness;
-
-  switch (Size) {
-  case 1:
-    *Buf = (uint8_t)Data;
-    break;
-  case 2:
-    write16<E>(Buf, Data);
-    break;
-  case 4:
-    write32<E>(Buf, Data);
-    break;
-  case 8:
-    write64<E>(Buf, Data);
-    break;
-  default:
+  if (Size == 1)
+    *Buf = Data;
+  else if (Size == 2)
+    write16(Buf, Data, Config->Endianness);
+  else if (Size == 4)
+    write32(Buf, Data, Config->Endianness);
+  else if (Size == 8)
+    write64(Buf, Data, Config->Endianness);
+  else
     llvm_unreachable("unsupported Size argument");
-  }
 }
 
-template <class ELFT>
-void LinkerScript<ELFT>::writeDataBytes(StringRef Name, uint8_t *Buf) {
+void LinkerScript::writeDataBytes(StringRef Name, uint8_t *Buf) {
   int I = getSectionIndex(Name);
   if (I == INT_MAX)
     return;
 
-  auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I].get());
-  for (const std::unique_ptr<BaseCommand> &Base : Cmd->Commands)
-    if (auto *Data = dyn_cast<BytesDataCommand>(Base.get()))
-      writeInt<ELFT>(Buf + Data->Offset, Data->Expression(0), Data->Size);
+  auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I]);
+  for (BaseCommand *Base : Cmd->Commands)
+    if (auto *Data = dyn_cast<BytesDataCommand>(Base))
+      writeInt(Buf + Data->Offset, Data->Expression().getValue(), Data->Size);
 }
 
-template <class ELFT> bool LinkerScript<ELFT>::hasLMA(StringRef Name) {
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
-    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
+bool LinkerScript::hasLMA(StringRef Name) {
+  for (BaseCommand *Base : Opt.Commands)
+    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       if (Cmd->LMAExpr && Cmd->Name == Name)
         return true;
   return false;
@@ -845,89 +919,35 @@ template <class ELFT> bool LinkerScript<ELFT>::hasLMA(StringRef Name) {
 // SECTIONS commands. Sections are laid out as the same order as they
 // were in the script. If a given name did not appear in the script,
 // it returns INT_MAX, so that it will be laid out at end of file.
-template <class ELFT> int LinkerScript<ELFT>::getSectionIndex(StringRef Name) {
+int LinkerScript::getSectionIndex(StringRef Name) {
   for (int I = 0, E = Opt.Commands.size(); I != E; ++I)
-    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I].get()))
+    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I]))
       if (Cmd->Name == Name)
         return I;
   return INT_MAX;
 }
 
-template <class ELFT> bool LinkerScript<ELFT>::hasPhdrsCommands() {
-  return !Opt.PhdrsCommands.empty();
-}
-
-template <class ELFT>
-const OutputSectionBase *LinkerScript<ELFT>::getOutputSection(const Twine &Loc,
-                                                              StringRef Name) {
-  static OutputSectionBase FakeSec("", 0, 0);
-
-  for (OutputSectionBase *Sec : *OutputSections)
-    if (Sec->getName() == Name)
-      return Sec;
-
-  error(Loc + ": undefined section " + Name);
-  return &FakeSec;
-}
-
-// This function is essentially the same as getOutputSection(Name)->Size,
-// but it won't print out an error message if a given section is not found.
-//
-// Linker script does not create an output section if its content is empty.
-// We want to allow SIZEOF(.foo) where .foo is a section which happened to
-// be empty. That is why this function is different from getOutputSection().
-template <class ELFT>
-uint64_t LinkerScript<ELFT>::getOutputSectionSize(StringRef Name) {
-  for (OutputSectionBase *Sec : *OutputSections)
-    if (Sec->getName() == Name)
-      return Sec->Size;
-  return 0;
-}
-
-template <class ELFT> uint64_t LinkerScript<ELFT>::getHeaderSize() {
-  return elf::getHeaderSize<ELFT>();
-}
-
-template <class ELFT>
-uint64_t LinkerScript<ELFT>::getSymbolValue(const Twine &Loc, StringRef S) {
-  if (SymbolBody *B = Symtab<ELFT>::X->find(S))
-    return B->getVA<ELFT>();
+ExprValue LinkerScript::getSymbolValue(const Twine &Loc, StringRef S) {
+  if (S == ".")
+    return {CurOutSec, Dot - CurOutSec->Addr};
+  if (SymbolBody *B = findSymbol(S)) {
+    if (auto *D = dyn_cast<DefinedRegular>(B))
+      return {D->Section, D->Value};
+    if (auto *C = dyn_cast<DefinedCommon>(B))
+      return {InX::Common, C->Offset};
+  }
   error(Loc + ": symbol not found: " + S);
   return 0;
 }
 
-template <class ELFT> bool LinkerScript<ELFT>::isDefined(StringRef S) {
-  return Symtab<ELFT>::X->find(S) != nullptr;
-}
-
-template <class ELFT> bool LinkerScript<ELFT>::isAbsolute(StringRef S) {
-  SymbolBody *Sym = Symtab<ELFT>::X->find(S);
-  auto *DR = dyn_cast_or_null<DefinedRegular<ELFT>>(Sym);
-  return DR && !DR->Section;
-}
-
-// Gets section symbol belongs to. Symbol "." doesn't belong to any
-// specific section but isn't absolute at the same time, so we try
-// to find suitable section for it as well.
-template <class ELFT>
-const OutputSectionBase *LinkerScript<ELFT>::getSymbolSection(StringRef S) {
-  SymbolBody *Sym = Symtab<ELFT>::X->find(S);
-  if (!Sym) {
-    if (OutputSections->empty())
-      return nullptr;
-    return CurOutSec ? CurOutSec : (*OutputSections)[0];
-  }
-
-  return SymbolTableSection<ELFT>::getOutputSection(Sym);
-}
+bool LinkerScript::isDefined(StringRef S) { return findSymbol(S) != nullptr; }
 
 // Returns indices of ELF headers containing specific section, identified
 // by Name. Each index is a zero based number of ELF header listed within
 // PHDRS {} script block.
-template <class ELFT>
-std::vector<size_t> LinkerScript<ELFT>::getPhdrIndices(StringRef SectionName) {
-  for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
-    auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
+std::vector<size_t> LinkerScript::getPhdrIndices(StringRef SectionName) {
+  for (BaseCommand *Base : Opt.Commands) {
+    auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
     if (!Cmd || Cmd->Name != SectionName)
       continue;
 
@@ -939,8 +959,7 @@ std::vector<size_t> LinkerScript<ELFT>::getPhdrIndices(StringRef SectionName) {
   return {};
 }
 
-template <class ELFT>
-size_t LinkerScript<ELFT>::getPhdrIndex(const Twine &Loc, StringRef PhdrName) {
+size_t LinkerScript::getPhdrIndex(const Twine &Loc, StringRef PhdrName) {
   size_t I = 0;
   for (PhdrsCommand &Cmd : Opt.PhdrsCommands) {
     if (Cmd.Name == PhdrName)
@@ -950,1009 +969,3 @@ size_t LinkerScript<ELFT>::getPhdrIndex(const Twine &Loc, StringRef PhdrName) {
   error(Loc + ": section header '" + PhdrName + "' is not listed in PHDRS");
   return 0;
 }
-
-class elf::ScriptParser final : public ScriptParserBase {
-  typedef void (ScriptParser::*Handler)();
-
-public:
-  ScriptParser(MemoryBufferRef MB)
-      : ScriptParserBase(MB),
-        IsUnderSysroot(isUnderSysroot(MB.getBufferIdentifier())) {}
-
-  void readLinkerScript();
-  void readVersionScript();
-  void readDynamicList();
-
-private:
-  void addFile(StringRef Path);
-
-  void readAsNeeded();
-  void readEntry();
-  void readExtern();
-  void readGroup();
-  void readInclude();
-  void readOutput();
-  void readOutputArch();
-  void readOutputFormat();
-  void readPhdrs();
-  void readSearchDir();
-  void readSections();
-  void readVersion();
-  void readVersionScriptCommand();
-
-  SymbolAssignment *readAssignment(StringRef Name);
-  BytesDataCommand *readBytesDataCommand(StringRef Tok);
-  uint32_t readFill();
-  OutputSectionCommand *readOutputSectionDescription(StringRef OutSec);
-  uint32_t readOutputSectionFiller(StringRef Tok);
-  std::vector<StringRef> readOutputSectionPhdrs();
-  InputSectionDescription *readInputSectionDescription(StringRef Tok);
-  StringMatcher readFilePatterns();
-  std::vector<SectionPattern> readInputSectionsList();
-  InputSectionDescription *readInputSectionRules(StringRef FilePattern);
-  unsigned readPhdrType();
-  SortSectionPolicy readSortKind();
-  SymbolAssignment *readProvideHidden(bool Provide, bool Hidden);
-  SymbolAssignment *readProvideOrAssignment(StringRef Tok);
-  void readSort();
-  Expr readAssert();
-
-  Expr readExpr();
-  Expr readExpr1(Expr Lhs, int MinPrec);
-  StringRef readParenLiteral();
-  Expr readPrimary();
-  Expr readTernary(Expr Cond);
-  Expr readParenExpr();
-
-  // For parsing version script.
-  std::vector<SymbolVersion> readVersionExtern();
-  void readAnonymousDeclaration();
-  void readVersionDeclaration(StringRef VerStr);
-  std::vector<SymbolVersion> readSymbols();
-  void readLocals();
-
-  ScriptConfiguration &Opt = *ScriptConfig;
-  bool IsUnderSysroot;
-};
-
-void ScriptParser::readDynamicList() {
-  expect("{");
-  readAnonymousDeclaration();
-  if (!atEOF())
-    setError("EOF expected, but got " + next());
-}
-
-void ScriptParser::readVersionScript() {
-  readVersionScriptCommand();
-  if (!atEOF())
-    setError("EOF expected, but got " + next());
-}
-
-void ScriptParser::readVersionScriptCommand() {
-  if (consume("{")) {
-    readAnonymousDeclaration();
-    return;
-  }
-
-  while (!atEOF() && !Error && peek() != "}") {
-    StringRef VerStr = next();
-    if (VerStr == "{") {
-      setError("anonymous version definition is used in "
-               "combination with other version definitions");
-      return;
-    }
-    expect("{");
-    readVersionDeclaration(VerStr);
-  }
-}
-
-void ScriptParser::readVersion() {
-  expect("{");
-  readVersionScriptCommand();
-  expect("}");
-}
-
-void ScriptParser::readLinkerScript() {
-  while (!atEOF()) {
-    StringRef Tok = next();
-    if (Tok == ";")
-      continue;
-
-    if (Tok == "ASSERT") {
-      Opt.Commands.emplace_back(new AssertCommand(readAssert()));
-    } else if (Tok == "ENTRY") {
-      readEntry();
-    } else if (Tok == "EXTERN") {
-      readExtern();
-    } else if (Tok == "GROUP" || Tok == "INPUT") {
-      readGroup();
-    } else if (Tok == "INCLUDE") {
-      readInclude();
-    } else if (Tok == "OUTPUT") {
-      readOutput();
-    } else if (Tok == "OUTPUT_ARCH") {
-      readOutputArch();
-    } else if (Tok == "OUTPUT_FORMAT") {
-      readOutputFormat();
-    } else if (Tok == "PHDRS") {
-      readPhdrs();
-    } else if (Tok == "SEARCH_DIR") {
-      readSearchDir();
-    } else if (Tok == "SECTIONS") {
-      readSections();
-    } else if (Tok == "VERSION") {
-      readVersion();
-    } else if (SymbolAssignment *Cmd = readProvideOrAssignment(Tok)) {
-      Opt.Commands.emplace_back(Cmd);
-    } else {
-      setError("unknown directive: " + Tok);
-    }
-  }
-}
-
-void ScriptParser::addFile(StringRef S) {
-  if (IsUnderSysroot && S.startswith("/")) {
-    SmallString<128> PathData;
-    StringRef Path = (Config->Sysroot + S).toStringRef(PathData);
-    if (sys::fs::exists(Path)) {
-      Driver->addFile(Saver.save(Path));
-      return;
-    }
-  }
-
-  if (sys::path::is_absolute(S)) {
-    Driver->addFile(S);
-  } else if (S.startswith("=")) {
-    if (Config->Sysroot.empty())
-      Driver->addFile(S.substr(1));
-    else
-      Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)));
-  } else if (S.startswith("-l")) {
-    Driver->addLibrary(S.substr(2));
-  } else if (sys::fs::exists(S)) {
-    Driver->addFile(S);
-  } else {
-    if (Optional<std::string> Path = findFromSearchPaths(S))
-      Driver->addFile(Saver.save(*Path));
-    else
-      setError("unable to find " + S);
-  }
-}
-
-void ScriptParser::readAsNeeded() {
-  expect("(");
-  bool Orig = Config->AsNeeded;
-  Config->AsNeeded = true;
-  while (!Error && !consume(")"))
-    addFile(unquote(next()));
-  Config->AsNeeded = Orig;
-}
-
-void ScriptParser::readEntry() {
-  // -e <symbol> takes predecence over ENTRY(<symbol>).
-  expect("(");
-  StringRef Tok = next();
-  if (Config->Entry.empty())
-    Config->Entry = Tok;
-  expect(")");
-}
-
-void ScriptParser::readExtern() {
-  expect("(");
-  while (!Error && !consume(")"))
-    Config->Undefined.push_back(next());
-}
-
-void ScriptParser::readGroup() {
-  expect("(");
-  while (!Error && !consume(")")) {
-    StringRef Tok = next();
-    if (Tok == "AS_NEEDED")
-      readAsNeeded();
-    else
-      addFile(unquote(Tok));
-  }
-}
-
-void ScriptParser::readInclude() {
-  StringRef Tok = unquote(next());
-
-  // https://sourceware.org/binutils/docs/ld/File-Commands.html:
-  // The file will be searched for in the current directory, and in any
-  // directory specified with the -L option.
-  if (sys::fs::exists(Tok)) {
-    if (Optional<MemoryBufferRef> MB = readFile(Tok))
-      tokenize(*MB);
-    return;
-  }
-  if (Optional<std::string> Path = findFromSearchPaths(Tok)) {
-    if (Optional<MemoryBufferRef> MB = readFile(*Path))
-      tokenize(*MB);
-    return;
-  }
-  setError("cannot open " + Tok);
-}
-
-void ScriptParser::readOutput() {
-  // -o <file> takes predecence over OUTPUT(<file>).
-  expect("(");
-  StringRef Tok = next();
-  if (Config->OutputFile.empty())
-    Config->OutputFile = unquote(Tok);
-  expect(")");
-}
-
-void ScriptParser::readOutputArch() {
-  // Error checking only for now.
-  expect("(");
-  skip();
-  expect(")");
-}
-
-void ScriptParser::readOutputFormat() {
-  // Error checking only for now.
-  expect("(");
-  skip();
-  StringRef Tok = next();
-  if (Tok == ")")
-    return;
-  if (Tok != ",") {
-    setError("unexpected token: " + Tok);
-    return;
-  }
-  skip();
-  expect(",");
-  skip();
-  expect(")");
-}
-
-void ScriptParser::readPhdrs() {
-  expect("{");
-  while (!Error && !consume("}")) {
-    StringRef Tok = next();
-    Opt.PhdrsCommands.push_back(
-        {Tok, PT_NULL, false, false, UINT_MAX, nullptr});
-    PhdrsCommand &PhdrCmd = Opt.PhdrsCommands.back();
-
-    PhdrCmd.Type = readPhdrType();
-    do {
-      Tok = next();
-      if (Tok == ";")
-        break;
-      if (Tok == "FILEHDR")
-        PhdrCmd.HasFilehdr = true;
-      else if (Tok == "PHDRS")
-        PhdrCmd.HasPhdrs = true;
-      else if (Tok == "AT")
-        PhdrCmd.LMAExpr = readParenExpr();
-      else if (Tok == "FLAGS") {
-        expect("(");
-        // Passing 0 for the value of dot is a bit of a hack. It means that
-        // we accept expressions like ".|1".
-        PhdrCmd.Flags = readExpr()(0);
-        expect(")");
-      } else
-        setError("unexpected header attribute: " + Tok);
-    } while (!Error);
-  }
-}
-
-void ScriptParser::readSearchDir() {
-  expect("(");
-  StringRef Tok = next();
-  if (!Config->Nostdlib)
-    Config->SearchPaths.push_back(unquote(Tok));
-  expect(")");
-}
-
-void ScriptParser::readSections() {
-  Opt.HasSections = true;
-  // -no-rosegment is used to avoid placing read only non-executable sections in
-  // their own segment. We do the same if SECTIONS command is present in linker
-  // script. See comment for computeFlags().
-  Config->SingleRoRx = true;
-
-  expect("{");
-  while (!Error && !consume("}")) {
-    StringRef Tok = next();
-    BaseCommand *Cmd = readProvideOrAssignment(Tok);
-    if (!Cmd) {
-      if (Tok == "ASSERT")
-        Cmd = new AssertCommand(readAssert());
-      else
-        Cmd = readOutputSectionDescription(Tok);
-    }
-    Opt.Commands.emplace_back(Cmd);
-  }
-}
-
-static int precedence(StringRef Op) {
-  return StringSwitch<int>(Op)
-      .Cases("*", "/", 5)
-      .Cases("+", "-", 4)
-      .Cases("<<", ">>", 3)
-      .Cases("<", "<=", ">", ">=", "==", "!=", 2)
-      .Cases("&", "|", 1)
-      .Default(-1);
-}
-
-StringMatcher ScriptParser::readFilePatterns() {
-  std::vector<StringRef> V;
-  while (!Error && !consume(")"))
-    V.push_back(next());
-  return StringMatcher(V);
-}
-
-SortSectionPolicy ScriptParser::readSortKind() {
-  if (consume("SORT") || consume("SORT_BY_NAME"))
-    return SortSectionPolicy::Name;
-  if (consume("SORT_BY_ALIGNMENT"))
-    return SortSectionPolicy::Alignment;
-  if (consume("SORT_BY_INIT_PRIORITY"))
-    return SortSectionPolicy::Priority;
-  if (consume("SORT_NONE"))
-    return SortSectionPolicy::None;
-  return SortSectionPolicy::Default;
-}
-
-// Method reads a list of sequence of excluded files and section globs given in
-// a following form: ((EXCLUDE_FILE(file_pattern+))? section_pattern+)+
-// Example: *(.foo.1 EXCLUDE_FILE (*a.o) .foo.2 EXCLUDE_FILE (*b.o) .foo.3)
-// The semantics of that is next:
-// * Include .foo.1 from every file.
-// * Include .foo.2 from every file but a.o
-// * Include .foo.3 from every file but b.o
-std::vector<SectionPattern> ScriptParser::readInputSectionsList() {
-  std::vector<SectionPattern> Ret;
-  while (!Error && peek() != ")") {
-    StringMatcher ExcludeFilePat;
-    if (consume("EXCLUDE_FILE")) {
-      expect("(");
-      ExcludeFilePat = readFilePatterns();
-    }
-
-    std::vector<StringRef> V;
-    while (!Error && peek() != ")" && peek() != "EXCLUDE_FILE")
-      V.push_back(next());
-
-    if (!V.empty())
-      Ret.push_back({std::move(ExcludeFilePat), StringMatcher(V)});
-    else
-      setError("section pattern is expected");
-  }
-  return Ret;
-}
-
-// Reads contents of "SECTIONS" directive. That directive contains a
-// list of glob patterns for input sections. The grammar is as follows.
-//
-// <patterns> ::= <section-list>
-//              | <sort> "(" <section-list> ")"
-//              | <sort> "(" <sort> "(" <section-list> ")" ")"
-//
-// <sort>     ::= "SORT" | "SORT_BY_NAME" | "SORT_BY_ALIGNMENT"
-//              | "SORT_BY_INIT_PRIORITY" | "SORT_NONE"
-//
-// <section-list> is parsed by readInputSectionsList().
-InputSectionDescription *
-ScriptParser::readInputSectionRules(StringRef FilePattern) {
-  auto *Cmd = new InputSectionDescription(FilePattern);
-  expect("(");
-  while (!Error && !consume(")")) {
-    SortSectionPolicy Outer = readSortKind();
-    SortSectionPolicy Inner = SortSectionPolicy::Default;
-    std::vector<SectionPattern> V;
-    if (Outer != SortSectionPolicy::Default) {
-      expect("(");
-      Inner = readSortKind();
-      if (Inner != SortSectionPolicy::Default) {
-        expect("(");
-        V = readInputSectionsList();
-        expect(")");
-      } else {
-        V = readInputSectionsList();
-      }
-      expect(")");
-    } else {
-      V = readInputSectionsList();
-    }
-
-    for (SectionPattern &Pat : V) {
-      Pat.SortInner = Inner;
-      Pat.SortOuter = Outer;
-    }
-
-    std::move(V.begin(), V.end(), std::back_inserter(Cmd->SectionPatterns));
-  }
-  return Cmd;
-}
-
-InputSectionDescription *
-ScriptParser::readInputSectionDescription(StringRef Tok) {
-  // Input section wildcard can be surrounded by KEEP.
-  // https://sourceware.org/binutils/docs/ld/Input-Section-Keep.html#Input-Section-Keep
-  if (Tok == "KEEP") {
-    expect("(");
-    StringRef FilePattern = next();
-    InputSectionDescription *Cmd = readInputSectionRules(FilePattern);
-    expect(")");
-    Opt.KeptSections.push_back(Cmd);
-    return Cmd;
-  }
-  return readInputSectionRules(Tok);
-}
-
-void ScriptParser::readSort() {
-  expect("(");
-  expect("CONSTRUCTORS");
-  expect(")");
-}
-
-Expr ScriptParser::readAssert() {
-  expect("(");
-  Expr E = readExpr();
-  expect(",");
-  StringRef Msg = unquote(next());
-  expect(")");
-  return [=](uint64_t Dot) {
-    uint64_t V = E(Dot);
-    if (!V)
-      error(Msg);
-    return V;
-  };
-}
-
-// Reads a FILL(expr) command. We handle the FILL command as an
-// alias for =fillexp section attribute, which is different from
-// what GNU linkers do.
-// https://sourceware.org/binutils/docs/ld/Output-Section-Data.html
-uint32_t ScriptParser::readFill() {
-  expect("(");
-  uint32_t V = readOutputSectionFiller(next());
-  expect(")");
-  expect(";");
-  return V;
-}
-
-OutputSectionCommand *
-ScriptParser::readOutputSectionDescription(StringRef OutSec) {
-  OutputSectionCommand *Cmd = new OutputSectionCommand(OutSec);
-  Cmd->Location = getCurrentLocation();
-
-  // Read an address expression.
-  // https://sourceware.org/binutils/docs/ld/Output-Section-Address.html#Output-Section-Address
-  if (peek() != ":")
-    Cmd->AddrExpr = readExpr();
-
-  expect(":");
-
-  if (consume("AT"))
-    Cmd->LMAExpr = readParenExpr();
-  if (consume("ALIGN"))
-    Cmd->AlignExpr = readParenExpr();
-  if (consume("SUBALIGN"))
-    Cmd->SubalignExpr = readParenExpr();
-
-  // Parse constraints.
-  if (consume("ONLY_IF_RO"))
-    Cmd->Constraint = ConstraintKind::ReadOnly;
-  if (consume("ONLY_IF_RW"))
-    Cmd->Constraint = ConstraintKind::ReadWrite;
-  expect("{");
-
-  while (!Error && !consume("}")) {
-    StringRef Tok = next();
-    if (SymbolAssignment *Assignment = readProvideOrAssignment(Tok)) {
-      Cmd->Commands.emplace_back(Assignment);
-    } else if (BytesDataCommand *Data = readBytesDataCommand(Tok)) {
-      Cmd->Commands.emplace_back(Data);
-    } else if (Tok == "ASSERT") {
-      Cmd->Commands.emplace_back(new AssertCommand(readAssert()));
-      expect(";");
-    } else if (Tok == "FILL") {
-      Cmd->Filler = readFill();
-    } else if (Tok == "SORT") {
-      readSort();
-    } else if (peek() == "(") {
-      Cmd->Commands.emplace_back(readInputSectionDescription(Tok));
-    } else {
-      setError("unknown command " + Tok);
-    }
-  }
-  Cmd->Phdrs = readOutputSectionPhdrs();
-
-  if (consume("="))
-    Cmd->Filler = readOutputSectionFiller(next());
-  else if (peek().startswith("="))
-    Cmd->Filler = readOutputSectionFiller(next().drop_front());
-
-  return Cmd;
-}
-
-// Read "=<number>" where <number> is an octal/decimal/hexadecimal number.
-// https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html
-//
-// ld.gold is not fully compatible with ld.bfd. ld.bfd handles
-// hexstrings as blobs of arbitrary sizes, while ld.gold handles them
-// as 32-bit big-endian values. We will do the same as ld.gold does
-// because it's simpler than what ld.bfd does.
-uint32_t ScriptParser::readOutputSectionFiller(StringRef Tok) {
-  uint32_t V;
-  if (!Tok.getAsInteger(0, V))
-    return V;
-  setError("invalid filler expression: " + Tok);
-  return 0;
-}
-
-SymbolAssignment *ScriptParser::readProvideHidden(bool Provide, bool Hidden) {
-  expect("(");
-  SymbolAssignment *Cmd = readAssignment(next());
-  Cmd->Provide = Provide;
-  Cmd->Hidden = Hidden;
-  expect(")");
-  expect(";");
-  return Cmd;
-}
-
-SymbolAssignment *ScriptParser::readProvideOrAssignment(StringRef Tok) {
-  SymbolAssignment *Cmd = nullptr;
-  if (peek() == "=" || peek() == "+=") {
-    Cmd = readAssignment(Tok);
-    expect(";");
-  } else if (Tok == "PROVIDE") {
-    Cmd = readProvideHidden(true, false);
-  } else if (Tok == "HIDDEN") {
-    Cmd = readProvideHidden(false, true);
-  } else if (Tok == "PROVIDE_HIDDEN") {
-    Cmd = readProvideHidden(true, true);
-  }
-  return Cmd;
-}
-
-static uint64_t getSymbolValue(const Twine &Loc, StringRef S, uint64_t Dot) {
-  if (S == ".")
-    return Dot;
-  return ScriptBase->getSymbolValue(Loc, S);
-}
-
-static bool isAbsolute(StringRef S) {
-  if (S == ".")
-    return false;
-  return ScriptBase->isAbsolute(S);
-}
-
-SymbolAssignment *ScriptParser::readAssignment(StringRef Name) {
-  StringRef Op = next();
-  Expr E;
-  assert(Op == "=" || Op == "+=");
-  if (consume("ABSOLUTE")) {
-    // The RHS may be something like "ABSOLUTE(.) & 0xff".
-    // Call readExpr1 to read the whole expression.
-    E = readExpr1(readParenExpr(), 0);
-    E.IsAbsolute = [] { return true; };
-  } else {
-    E = readExpr();
-  }
-  if (Op == "+=") {
-    std::string Loc = getCurrentLocation();
-    E = [=](uint64_t Dot) {
-      return getSymbolValue(Loc, Name, Dot) + E(Dot);
-    };
-  }
-  return new SymbolAssignment(Name, E);
-}
-
-// This is an operator-precedence parser to parse a linker
-// script expression.
-Expr ScriptParser::readExpr() { return readExpr1(readPrimary(), 0); }
-
-static Expr combine(StringRef Op, Expr L, Expr R) {
-  if (Op == "*")
-    return [=](uint64_t Dot) { return L(Dot) * R(Dot); };
-  if (Op == "/") {
-    return [=](uint64_t Dot) -> uint64_t {
-      uint64_t RHS = R(Dot);
-      if (RHS == 0) {
-        error("division by zero");
-        return 0;
-      }
-      return L(Dot) / RHS;
-    };
-  }
-  if (Op == "+")
-    return {[=](uint64_t Dot) { return L(Dot) + R(Dot); },
-            [=] { return L.IsAbsolute() && R.IsAbsolute(); },
-            [=] {
-              const OutputSectionBase *S = L.Section();
-              return S ? S : R.Section();
-            }};
-  if (Op == "-")
-    return [=](uint64_t Dot) { return L(Dot) - R(Dot); };
-  if (Op == "<<")
-    return [=](uint64_t Dot) { return L(Dot) << R(Dot); };
-  if (Op == ">>")
-    return [=](uint64_t Dot) { return L(Dot) >> R(Dot); };
-  if (Op == "<")
-    return [=](uint64_t Dot) { return L(Dot) < R(Dot); };
-  if (Op == ">")
-    return [=](uint64_t Dot) { return L(Dot) > R(Dot); };
-  if (Op == ">=")
-    return [=](uint64_t Dot) { return L(Dot) >= R(Dot); };
-  if (Op == "<=")
-    return [=](uint64_t Dot) { return L(Dot) <= R(Dot); };
-  if (Op == "==")
-    return [=](uint64_t Dot) { return L(Dot) == R(Dot); };
-  if (Op == "!=")
-    return [=](uint64_t Dot) { return L(Dot) != R(Dot); };
-  if (Op == "&")
-    return [=](uint64_t Dot) { return L(Dot) & R(Dot); };
-  if (Op == "|")
-    return [=](uint64_t Dot) { return L(Dot) | R(Dot); };
-  llvm_unreachable("invalid operator");
-}
-
-// This is a part of the operator-precedence parser. This function
-// assumes that the remaining token stream starts with an operator.
-Expr ScriptParser::readExpr1(Expr Lhs, int MinPrec) {
-  while (!atEOF() && !Error) {
-    // Read an operator and an expression.
-    if (consume("?"))
-      return readTernary(Lhs);
-    StringRef Op1 = peek();
-    if (precedence(Op1) < MinPrec)
-      break;
-    skip();
-    Expr Rhs = readPrimary();
-
-    // Evaluate the remaining part of the expression first if the
-    // next operator has greater precedence than the previous one.
-    // For example, if we have read "+" and "3", and if the next
-    // operator is "*", then we'll evaluate 3 * ... part first.
-    while (!atEOF()) {
-      StringRef Op2 = peek();
-      if (precedence(Op2) <= precedence(Op1))
-        break;
-      Rhs = readExpr1(Rhs, precedence(Op2));
-    }
-
-    Lhs = combine(Op1, Lhs, Rhs);
-  }
-  return Lhs;
-}
-
-uint64_t static getConstant(StringRef S) {
-  if (S == "COMMONPAGESIZE")
-    return Target->PageSize;
-  if (S == "MAXPAGESIZE")
-    return Config->MaxPageSize;
-  error("unknown constant: " + S);
-  return 0;
-}
-
-// Parses Tok as an integer. Returns true if successful.
-// It recognizes hexadecimal (prefixed with "0x" or suffixed with "H")
-// and decimal numbers. Decimal numbers may have "K" (kilo) or
-// "M" (mega) prefixes.
-static bool readInteger(StringRef Tok, uint64_t &Result) {
-  // Negative number
-  if (Tok.startswith("-")) {
-    if (!readInteger(Tok.substr(1), Result))
-      return false;
-    Result = -Result;
-    return true;
-  }
-
-  // Hexadecimal
-  if (Tok.startswith_lower("0x"))
-    return !Tok.substr(2).getAsInteger(16, Result);
-  if (Tok.endswith_lower("H"))
-    return !Tok.drop_back().getAsInteger(16, Result);
-
-  // Decimal
-  int Suffix = 1;
-  if (Tok.endswith_lower("K")) {
-    Suffix = 1024;
-    Tok = Tok.drop_back();
-  } else if (Tok.endswith_lower("M")) {
-    Suffix = 1024 * 1024;
-    Tok = Tok.drop_back();
-  }
-  if (Tok.getAsInteger(10, Result))
-    return false;
-  Result *= Suffix;
-  return true;
-}
-
-BytesDataCommand *ScriptParser::readBytesDataCommand(StringRef Tok) {
-  int Size = StringSwitch<unsigned>(Tok)
-                 .Case("BYTE", 1)
-                 .Case("SHORT", 2)
-                 .Case("LONG", 4)
-                 .Case("QUAD", 8)
-                 .Default(-1);
-  if (Size == -1)
-    return nullptr;
-
-  return new BytesDataCommand(readParenExpr(), Size);
-}
-
-StringRef ScriptParser::readParenLiteral() {
-  expect("(");
-  StringRef Tok = next();
-  expect(")");
-  return Tok;
-}
-
-Expr ScriptParser::readPrimary() {
-  if (peek() == "(")
-    return readParenExpr();
-
-  StringRef Tok = next();
-  std::string Location = getCurrentLocation();
-
-  if (Tok == "~") {
-    Expr E = readPrimary();
-    return [=](uint64_t Dot) { return ~E(Dot); };
-  }
-  if (Tok == "-") {
-    Expr E = readPrimary();
-    return [=](uint64_t Dot) { return -E(Dot); };
-  }
-
-  // Built-in functions are parsed here.
-  // https://sourceware.org/binutils/docs/ld/Builtin-Functions.html.
-  if (Tok == "ADDR") {
-    StringRef Name = readParenLiteral();
-    return {[=](uint64_t Dot) {
-              return ScriptBase->getOutputSection(Location, Name)->Addr;
-            },
-            [=] { return false; },
-            [=] { return ScriptBase->getOutputSection(Location, Name); }};
-  }
-  if (Tok == "LOADADDR") {
-    StringRef Name = readParenLiteral();
-    return [=](uint64_t Dot) {
-      return ScriptBase->getOutputSection(Location, Name)->getLMA();
-    };
-  }
-  if (Tok == "ASSERT")
-    return readAssert();
-  if (Tok == "ALIGN") {
-    expect("(");
-    Expr E = readExpr();
-    if (consume(",")) {
-      Expr E2 = readExpr();
-      expect(")");
-      return [=](uint64_t Dot) { return alignTo(E(Dot), E2(Dot)); };
-    }
-    expect(")");
-    return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
-  }
-  if (Tok == "CONSTANT") {
-    StringRef Name = readParenLiteral();
-    return [=](uint64_t Dot) { return getConstant(Name); };
-  }
-  if (Tok == "DEFINED") {
-    StringRef Name = readParenLiteral();
-    return [=](uint64_t Dot) { return ScriptBase->isDefined(Name) ? 1 : 0; };
-  }
-  if (Tok == "SEGMENT_START") {
-    expect("(");
-    skip();
-    expect(",");
-    Expr E = readExpr();
-    expect(")");
-    return [=](uint64_t Dot) { return E(Dot); };
-  }
-  if (Tok == "DATA_SEGMENT_ALIGN") {
-    expect("(");
-    Expr E = readExpr();
-    expect(",");
-    readExpr();
-    expect(")");
-    return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
-  }
-  if (Tok == "DATA_SEGMENT_END") {
-    expect("(");
-    expect(".");
-    expect(")");
-    return [](uint64_t Dot) { return Dot; };
-  }
-  // GNU linkers implements more complicated logic to handle
-  // DATA_SEGMENT_RELRO_END. We instead ignore the arguments and just align to
-  // the next page boundary for simplicity.
-  if (Tok == "DATA_SEGMENT_RELRO_END") {
-    expect("(");
-    readExpr();
-    expect(",");
-    readExpr();
-    expect(")");
-    return [](uint64_t Dot) { return alignTo(Dot, Target->PageSize); };
-  }
-  if (Tok == "SIZEOF") {
-    StringRef Name = readParenLiteral();
-    return [=](uint64_t Dot) { return ScriptBase->getOutputSectionSize(Name); };
-  }
-  if (Tok == "ALIGNOF") {
-    StringRef Name = readParenLiteral();
-    return [=](uint64_t Dot) {
-      return ScriptBase->getOutputSection(Location, Name)->Addralign;
-    };
-  }
-  if (Tok == "SIZEOF_HEADERS")
-    return [=](uint64_t Dot) { return ScriptBase->getHeaderSize(); };
-
-  // Tok is a literal number.
-  uint64_t V;
-  if (readInteger(Tok, V))
-    return [=](uint64_t Dot) { return V; };
-
-  // Tok is a symbol name.
-  if (Tok != "." && !isValidCIdentifier(Tok))
-    setError("malformed number: " + Tok);
-  return {[=](uint64_t Dot) { return getSymbolValue(Location, Tok, Dot); },
-          [=] { return isAbsolute(Tok); },
-          [=] { return ScriptBase->getSymbolSection(Tok); }};
-}
-
-Expr ScriptParser::readTernary(Expr Cond) {
-  Expr L = readExpr();
-  expect(":");
-  Expr R = readExpr();
-  return [=](uint64_t Dot) { return Cond(Dot) ? L(Dot) : R(Dot); };
-}
-
-Expr ScriptParser::readParenExpr() {
-  expect("(");
-  Expr E = readExpr();
-  expect(")");
-  return E;
-}
-
-std::vector<StringRef> ScriptParser::readOutputSectionPhdrs() {
-  std::vector<StringRef> Phdrs;
-  while (!Error && peek().startswith(":")) {
-    StringRef Tok = next();
-    Phdrs.push_back((Tok.size() == 1) ? next() : Tok.substr(1));
-  }
-  return Phdrs;
-}
-
-// Read a program header type name. The next token must be a
-// name of a program header type or a constant (e.g. "0x3").
-unsigned ScriptParser::readPhdrType() {
-  StringRef Tok = next();
-  uint64_t Val;
-  if (readInteger(Tok, Val))
-    return Val;
-
-  unsigned Ret = StringSwitch<unsigned>(Tok)
-                     .Case("PT_NULL", PT_NULL)
-                     .Case("PT_LOAD", PT_LOAD)
-                     .Case("PT_DYNAMIC", PT_DYNAMIC)
-                     .Case("PT_INTERP", PT_INTERP)
-                     .Case("PT_NOTE", PT_NOTE)
-                     .Case("PT_SHLIB", PT_SHLIB)
-                     .Case("PT_PHDR", PT_PHDR)
-                     .Case("PT_TLS", PT_TLS)
-                     .Case("PT_GNU_EH_FRAME", PT_GNU_EH_FRAME)
-                     .Case("PT_GNU_STACK", PT_GNU_STACK)
-                     .Case("PT_GNU_RELRO", PT_GNU_RELRO)
-                     .Case("PT_OPENBSD_RANDOMIZE", PT_OPENBSD_RANDOMIZE)
-                     .Case("PT_OPENBSD_WXNEEDED", PT_OPENBSD_WXNEEDED)
-                     .Case("PT_OPENBSD_BOOTDATA", PT_OPENBSD_BOOTDATA)
-                     .Default(-1);
-
-  if (Ret == (unsigned)-1) {
-    setError("invalid program header type: " + Tok);
-    return PT_NULL;
-  }
-  return Ret;
-}
-
-// Reads a list of symbols, e.g. "{ global: foo; bar; local: *; };".
-void ScriptParser::readAnonymousDeclaration() {
-  // Read global symbols first. "global:" is default, so if there's
-  // no label, we assume global symbols.
-  if (consume("global:") || peek() != "local:")
-    Config->VersionScriptGlobals = readSymbols();
-
-  readLocals();
-  expect("}");
-  expect(";");
-}
-
-void ScriptParser::readLocals() {
-  if (!consume("local:"))
-    return;
-  std::vector<SymbolVersion> Locals = readSymbols();
-  for (SymbolVersion V : Locals) {
-    if (V.Name == "*") {
-      Config->DefaultSymbolVersion = VER_NDX_LOCAL;
-      continue;
-    }
-    Config->VersionScriptLocals.push_back(V);
-  }
-}
-
-// Reads a list of symbols, e.g. "VerStr { global: foo; bar; local: *; };".
-void ScriptParser::readVersionDeclaration(StringRef VerStr) {
-  // Identifiers start at 2 because 0 and 1 are reserved
-  // for VER_NDX_LOCAL and VER_NDX_GLOBAL constants.
-  uint16_t VersionId = Config->VersionDefinitions.size() + 2;
-  Config->VersionDefinitions.push_back({VerStr, VersionId});
-
-  // Read global symbols.
-  if (consume("global:") || peek() != "local:")
-    Config->VersionDefinitions.back().Globals = readSymbols();
-
-  readLocals();
-  expect("}");
-
-  // Each version may have a parent version. For example, "Ver2"
-  // defined as "Ver2 { global: foo; local: *; } Ver1;" has "Ver1"
-  // as a parent. This version hierarchy is, probably against your
-  // instinct, purely for hint; the runtime doesn't care about it
-  // at all. In LLD, we simply ignore it.
-  if (peek() != ";")
-    skip();
-  expect(";");
-}
-
-// Reads a list of symbols for a versions cript.
-std::vector<SymbolVersion> ScriptParser::readSymbols() {
-  std::vector<SymbolVersion> Ret;
-  for (;;) {
-    if (consume("extern")) {
-      for (SymbolVersion V : readVersionExtern())
-        Ret.push_back(V);
-      continue;
-    }
-
-    if (peek() == "}" || peek() == "local:" || Error)
-      break;
-    StringRef Tok = next();
-    Ret.push_back({unquote(Tok), false, hasWildcard(Tok)});
-    expect(";");
-  }
-  return Ret;
-}
-
-// Reads an "extern C++" directive, e.g.,
-// "extern "C++" { ns::*; "f(int, double)"; };"
-std::vector<SymbolVersion> ScriptParser::readVersionExtern() {
-  StringRef Tok = next();
-  bool IsCXX = Tok == "\"C++\"";
-  if (!IsCXX && Tok != "\"C\"")
-    setError("Unknown language");
-  expect("{");
-
-  std::vector<SymbolVersion> Ret;
-  while (!Error && peek() != "}") {
-    StringRef Tok = next();
-    bool HasWildcard = !Tok.startswith("\"") && hasWildcard(Tok);
-    Ret.push_back({unquote(Tok), IsCXX, HasWildcard});
-    expect(";");
-  }
-
-  expect("}");
-  expect(";");
-  return Ret;
-}
-
-void elf::readLinkerScript(MemoryBufferRef MB) {
-  ScriptParser(MB).readLinkerScript();
-}
-
-void elf::readVersionScript(MemoryBufferRef MB) {
-  ScriptParser(MB).readVersionScript();
-}
-
-void elf::readDynamicList(MemoryBufferRef MB) {
-  ScriptParser(MB).readDynamicList();
-}
-
-template class elf::LinkerScript<ELF32LE>;
-template class elf::LinkerScript<ELF32BE>;
-template class elf::LinkerScript<ELF64LE>;
-template class elf::LinkerScript<ELF64BE>;