Index: COFF/Driver.cpp
===================================================================
--- COFF/Driver.cpp
+++ COFF/Driver.cpp
@@ -131,7 +131,7 @@
   case file_magic::archive:
     if (WholeArchive) {
       std::unique_ptr<Archive> File =
-          check(Archive::create(MBRef),
+          CHECK(Archive::create(MBRef),
                 MBRef.getBufferIdentifier() + ": failed to parse archive");
 
       for (MemoryBufferRef M : getArchiveMembers(File.get()))
@@ -196,7 +196,7 @@
                                         StringRef SymName,
                                         StringRef ParentName) {
   if (!C.getParent()->isThin()) {
-    MemoryBufferRef MB = check(
+    MemoryBufferRef MB = CHECK(
         C.getMemoryBufferRef(),
         "could not get the buffer for the member defining symbol " + SymName);
     enqueueTask([=]() { Driver->addArchiveBuffer(MB, SymName, ParentName); });
@@ -204,7 +204,7 @@
   }
 
   auto Future = std::make_shared<std::future<MBErrPair>>(createFutureForFile(
-      check(C.getFullName(),
+      CHECK(C.getFullName(),
             "could not get the filename for the member defining symbol " +
                 SymName)));
   enqueueTask([=]() {
@@ -531,8 +531,8 @@
 }
 
 static void parseModuleDefs(StringRef Path) {
-  std::unique_ptr<MemoryBuffer> MB = check(
-    MemoryBuffer::getFile(Path, -1, false, true), "could not open " + Path);
+  std::unique_ptr<MemoryBuffer> MB = CHECK(
+      MemoryBuffer::getFile(Path, -1, false, true), "could not open " + Path);
   COFFModuleDefinition M = check(parseCOFFModuleDefinition(
       MB->getMemBufferRef(), Config->Machine, Config->MinGW));
 
@@ -577,7 +577,7 @@
   // The MSVC linker doesn't support thin archives, so if it's a thin
   // archive, we always need to rebuild it.
   std::unique_ptr<Archive> File =
-      check(Archive::create(MB), "Failed to read " + MB.getBufferIdentifier());
+      CHECK(Archive::create(MB), "Failed to read " + MB.getBufferIdentifier());
   if (File->isThin())
     return true;
 
@@ -598,7 +598,7 @@
 // its path is returned.
 static Optional<std::string>
 filterBitcodeFiles(StringRef Path, std::vector<std::string> &TemporaryFiles) {
-  std::unique_ptr<MemoryBuffer> MB = check(
+  std::unique_ptr<MemoryBuffer> MB = CHECK(
       MemoryBuffer::getFile(Path, -1, false, true), "could not open " + Path);
   MemoryBufferRef MBRef = MB->getMemBufferRef();
   file_magic Magic = identify_magic(MBRef.getBuffer());
@@ -611,7 +611,7 @@
     return Path.str();
 
   std::unique_ptr<Archive> File =
-      check(Archive::create(MBRef),
+      CHECK(Archive::create(MBRef),
             MBRef.getBufferIdentifier() + ": failed to parse archive");
 
   std::vector<NewArchiveMember> New;
@@ -957,7 +957,7 @@
 
   // Handle /lldsavecachepolicy
   if (auto *Arg = Args.getLastArg(OPT_lldltocachepolicy))
-    Config->LTOCachePolicy = check(
+    Config->LTOCachePolicy = CHECK(
         parseCachePruningPolicy(Arg->getValue()),
         Twine("/lldltocachepolicy: invalid cache policy: ") + Arg->getValue());
 
Index: COFF/DriverUtils.cpp
===================================================================
--- COFF/DriverUtils.cpp
+++ COFF/DriverUtils.cpp
@@ -317,7 +317,7 @@
   // is called (you cannot remove an opened file on Windows.)
   std::unique_ptr<MemoryBuffer> getMemoryBuffer() {
     // IsVolatileSize=true forces MemoryBuffer to not use mmap().
-    return check(MemoryBuffer::getFile(Path, /*FileSize=*/-1,
+    return CHECK(MemoryBuffer::getFile(Path, /*FileSize=*/-1,
                                        /*RequiresNullTerminator=*/false,
                                        /*IsVolatileSize=*/true),
                  "could not open " + Path);
@@ -402,7 +402,7 @@
   E.add("/out:" + StringRef(User.Path));
   E.run();
 
-  return check(MemoryBuffer::getFile(User.Path), "could not open " + User.Path)
+  return CHECK(MemoryBuffer::getFile(User.Path), "could not open " + User.Path)
       .get()
       ->getBuffer();
 }
Index: COFF/InputFiles.cpp
===================================================================
--- COFF/InputFiles.cpp
+++ COFF/InputFiles.cpp
@@ -63,7 +63,7 @@
 
 void ArchiveFile::parse() {
   // Parse a MemoryBufferRef as an archive file.
-  File = check(Archive::create(MB), toString(this));
+  File = CHECK(Archive::create(MB), toString(this));
 
   // Read the symbol table to construct Lazy objects.
   for (const Archive::Symbol &Sym : File->symbols())
@@ -73,7 +73,7 @@
 // Returns a buffer pointing to a member file containing a given symbol.
 void ArchiveFile::addMember(const Archive::Symbol *Sym) {
   const Archive::Child &C =
-      check(Sym->getMember(),
+      CHECK(Sym->getMember(),
             "could not get the member for symbol " + Sym->getName());
 
   // Return an empty buffer if we have already returned the same buffer.
@@ -88,10 +88,10 @@
   Error Err = Error::success();
   for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
     Archive::Child C =
-        check(COrErr,
+        CHECK(COrErr,
               File->getFileName() + ": could not get the child of the archive");
     MemoryBufferRef MBRef =
-        check(C.getMemoryBufferRef(),
+        CHECK(C.getMemoryBufferRef(),
               File->getFileName() +
                   ": could not get the buffer for a child of the archive");
     V.push_back(MBRef);
@@ -104,7 +104,7 @@
 
 void ObjFile::parse() {
   // Parse a memory buffer as a COFF file.
-  std::unique_ptr<Binary> Bin = check(createBinary(MB), toString(this));
+  std::unique_ptr<Binary> Bin = CHECK(createBinary(MB), toString(this));
 
   if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
     Bin.release();
Index: COFF/Writer.cpp
===================================================================
--- COFF/Writer.cpp
+++ COFF/Writer.cpp
@@ -784,7 +784,7 @@
 }
 
 void Writer::openFile(StringRef Path) {
-  Buffer = check(
+  Buffer = CHECK(
       FileOutputBuffer::create(Path, FileSize, FileOutputBuffer::F_executable),
       "failed to open " + Path);
 }
Index: ELF/Driver.cpp
===================================================================
--- ELF/Driver.cpp
+++ ELF/Driver.cpp
@@ -136,7 +136,7 @@
 std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
     MemoryBufferRef MB) {
   std::unique_ptr<Archive> File =
-      check(Archive::create(MB),
+      CHECK(Archive::create(MB),
             MB.getBufferIdentifier() + ": failed to parse archive");
 
   std::vector<std::pair<MemoryBufferRef, uint64_t>> V;
@@ -144,10 +144,10 @@
   bool AddToTar = File->isThin() && Tar;
   for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
     Archive::Child C =
-        check(COrErr, MB.getBufferIdentifier() +
+        CHECK(COrErr, MB.getBufferIdentifier() +
                           ": could not get the child of the archive");
     MemoryBufferRef MBRef =
-        check(C.getMemoryBufferRef(),
+        CHECK(C.getMemoryBufferRef(),
               MB.getBufferIdentifier() +
                   ": could not get the buffer for a child of the archive");
     if (AddToTar)
@@ -192,7 +192,7 @@
     }
 
     std::unique_ptr<Archive> File =
-        check(Archive::create(MBRef), Path + ": failed to parse archive");
+        CHECK(Archive::create(MBRef), Path + ": failed to parse archive");
 
     // If an archive file has no symbol table, it is likely that a user
     // is attempting LTO and using a default ar command that doesn't
@@ -651,7 +651,7 @@
   Config->Target1Rel = Args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
   Config->Target2 = getTarget2(Args);
   Config->ThinLTOCacheDir = Args.getLastArgValue(OPT_thinlto_cache_dir);
-  Config->ThinLTOCachePolicy = check(
+  Config->ThinLTOCachePolicy = CHECK(
       parseCachePruningPolicy(Args.getLastArgValue(OPT_thinlto_cache_policy)),
       "--thinlto-cache-policy: invalid cache policy");
   Config->ThinLTOJobs = args::getInteger(Args, OPT_thinlto_jobs, -1u);
Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -209,19 +209,19 @@
 
 template <class ELFT>
 uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
-  return checkLazy(getObj().getSectionIndex(&Sym, ELFSyms, SymtabSHNDX),
-                   [=]() { return toString(this); });
+  return CHECK(getObj().getSectionIndex(&Sym, ELFSyms, SymtabSHNDX),
+               toString(this));
 }
 
 template <class ELFT>
 void ELFFileBase<ELFT>::initSymtab(ArrayRef<Elf_Shdr> Sections,
                                    const Elf_Shdr *Symtab) {
   FirstNonLocal = Symtab->sh_info;
-  ELFSyms = check(getObj().symbols(Symtab), toString(this));
+  ELFSyms = CHECK(getObj().symbols(Symtab), toString(this));
   if (FirstNonLocal == 0 || FirstNonLocal > ELFSyms.size())
     fatal(toString(this) + ": invalid sh_info in symbol table");
 
-  StringTable = check(getObj().getStringTableForSymtab(*Symtab, Sections),
+  StringTable = CHECK(getObj().getStringTableForSymtab(*Symtab, Sections),
                       toString(this));
 }
 
@@ -253,15 +253,13 @@
   // Group signatures are stored as symbol names in object files.
   // sh_info contains a symbol index, so we fetch a symbol and read its name.
   if (this->ELFSyms.empty())
-    this->initSymtab(Sections,
-                     checkLazy(object::getSection<ELFT>(Sections, Sec.sh_link),
-                               [=]() { return toString(this); }));
-
-  const Elf_Sym *Sym =
-      checkLazy(object::getSymbol<ELFT>(this->ELFSyms, Sec.sh_info),
-                [=]() { return toString(this); });
-  StringRef Signature = checkLazy(Sym->getName(this->StringTable),
-                                  [=]() { return toString(this); });
+    this->initSymtab(
+        Sections,
+        CHECK(object::getSection<ELFT>(Sections, Sec.sh_link), toString(this)));
+
+  const Elf_Sym *Sym = CHECK(
+      object::getSymbol<ELFT>(this->ELFSyms, Sec.sh_info), toString(this));
+  StringRef Signature = CHECK(Sym->getName(this->StringTable), toString(this));
 
   // As a special case, if a symbol is a section symbol and has no name,
   // we use a section name as a signature.
@@ -279,9 +277,8 @@
 ArrayRef<typename ObjFile<ELFT>::Elf_Word>
 ObjFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
   const ELFFile<ELFT> &Obj = this->getObj();
-  ArrayRef<Elf_Word> Entries =
-      checkLazy(Obj.template getSectionContentsAsArray<Elf_Word>(&Sec),
-                [=]() { return toString(this); });
+  ArrayRef<Elf_Word> Entries = CHECK(
+      Obj.template getSectionContentsAsArray<Elf_Word>(&Sec), toString(this));
   if (Entries.empty() || Entries[0] != GRP_COMDAT)
     fatal(toString(this) + ": unsupported SHT_GROUP format");
   return Entries.slice(1);
@@ -327,11 +324,11 @@
   const ELFFile<ELFT> &Obj = this->getObj();
 
   ArrayRef<Elf_Shdr> ObjSections =
-      check(this->getObj().sections(), toString(this));
+      CHECK(this->getObj().sections(), toString(this));
   uint64_t Size = ObjSections.size();
   this->Sections.resize(Size);
   this->SectionStringTable =
-      check(Obj.getSectionStringTable(ObjSections), toString(this));
+      CHECK(Obj.getSectionStringTable(ObjSections), toString(this));
 
   for (size_t I = 0, E = ObjSections.size(); I < E; I++) {
     if (this->Sections[I] == &InputSection::Discarded)
@@ -378,7 +375,7 @@
       break;
     case SHT_SYMTAB_SHNDX:
       this->SymtabSHNDX =
-          check(Obj.getSHNDXTable(Sec, ObjSections), toString(this));
+          CHECK(Obj.getSHNDXTable(Sec, ObjSections), toString(this));
       break;
     case SHT_STRTAB:
     case SHT_NULL:
@@ -523,14 +520,13 @@
 
     size_t NumRelocations;
     if (Sec.sh_type == SHT_RELA) {
-      ArrayRef<Elf_Rela> Rels = checkLazy(this->getObj().relas(&Sec),
-                                          [=]() { return toString(this); });
+      ArrayRef<Elf_Rela> Rels =
+          CHECK(this->getObj().relas(&Sec), toString(this));
       Target->FirstRelocation = Rels.begin();
       NumRelocations = Rels.size();
       Target->AreRelocsRela = true;
     } else {
-      ArrayRef<Elf_Rel> Rels = checkLazy(this->getObj().rels(&Sec),
-                                         [=]() { return toString(this); });
+      ArrayRef<Elf_Rel> Rels = CHECK(this->getObj().rels(&Sec), toString(this));
       Target->FirstRelocation = Rels.begin();
       NumRelocations = Rels.size();
       Target->AreRelocsRela = false;
@@ -599,8 +595,8 @@
 
 template <class ELFT>
 StringRef ObjFile<ELFT>::getSectionName(const Elf_Shdr &Sec) {
-  return checkLazy(this->getObj().getSectionName(&Sec, SectionStringTable),
-                   [=]() { return toString(this); });
+  return CHECK(this->getObj().getSectionName(&Sec, SectionStringTable),
+               toString(this));
 }
 
 template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
@@ -632,7 +628,7 @@
 
   if (Binding == STB_LOCAL) {
     if (Sym->getType() == STT_FILE)
-      SourceFile = check(Sym->getName(this->StringTable), toString(this));
+      SourceFile = CHECK(Sym->getName(this->StringTable), toString(this));
 
     if (this->StringTable.size() <= Sym->st_name)
       fatal(toString(this) + ": invalid symbol name offset");
@@ -644,8 +640,7 @@
     return make<Defined>(this, Name, Binding, StOther, Type, Value, Size, Sec);
   }
 
-  StringRef Name = checkLazy(Sym->getName(this->StringTable),
-                             [=]() { return toString(this); });
+  StringRef Name = CHECK(Sym->getName(this->StringTable), toString(this));
 
   switch (Sym->st_shndx) {
   case SHN_UNDEF:
@@ -686,7 +681,7 @@
 std::pair<MemoryBufferRef, uint64_t>
 ArchiveFile::getMember(const Archive::Symbol *Sym) {
   Archive::Child C =
-      check(Sym->getMember(), toString(this) +
+      CHECK(Sym->getMember(), toString(this) +
                                   ": could not get the member for symbol " +
                                   Sym->getName());
 
@@ -694,13 +689,13 @@
     return {MemoryBufferRef(), 0};
 
   MemoryBufferRef Ret =
-      check(C.getMemoryBufferRef(),
+      CHECK(C.getMemoryBufferRef(),
             toString(this) +
                 ": could not get the buffer for the member defining symbol " +
                 Sym->getName());
 
   if (C.getParent()->isThin() && Tar)
-    Tar->append(relativeToRoot(check(C.getFullName(), toString(this))),
+    Tar->append(relativeToRoot(CHECK(C.getFullName(), toString(this))),
                 Ret.getBuffer());
   if (C.getParent()->isThin())
     return {Ret, 0};
@@ -717,7 +712,7 @@
 template <class ELFT> void SharedFile<ELFT>::parseSoName() {
   const Elf_Shdr *DynamicSec = nullptr;
   const ELFFile<ELFT> Obj = this->getObj();
-  ArrayRef<Elf_Shdr> Sections = check(Obj.sections(), toString(this));
+  ArrayRef<Elf_Shdr> Sections = CHECK(Obj.sections(), toString(this));
 
   // Search for .dynsym, .dynamic, .symtab, .gnu.version and .gnu.version_d.
   for (const Elf_Shdr &Sec : Sections) {
@@ -732,7 +727,7 @@
       break;
     case SHT_SYMTAB_SHNDX:
       this->SymtabSHNDX =
-          check(Obj.getSHNDXTable(Sec, Sections), toString(this));
+          CHECK(Obj.getSHNDXTable(Sec, Sections), toString(this));
       break;
     case SHT_GNU_versym:
       this->VersymSec = &Sec;
@@ -750,7 +745,7 @@
   if (!DynamicSec)
     return;
   ArrayRef<Elf_Dyn> Arr =
-      check(Obj.template getSectionContentsAsArray<Elf_Dyn>(DynamicSec),
+      CHECK(Obj.template getSectionContentsAsArray<Elf_Dyn>(DynamicSec),
             toString(this));
   for (const Elf_Dyn &Dyn : Arr) {
     if (Dyn.d_tag == DT_SONAME) {
@@ -811,7 +806,7 @@
   std::vector<const Elf_Verdef *> Verdefs = parseVerdefs(Versym);
 
   ArrayRef<Elf_Shdr> Sections =
-      check(this->getObj().sections(), toString(this));
+      CHECK(this->getObj().sections(), toString(this));
 
   // Add symbols to the symbol table.
   Elf_Sym_Range Syms = this->getGlobalELFSyms();
@@ -824,7 +819,7 @@
     bool Hidden = VersymIndex & VERSYM_HIDDEN;
     VersymIndex = VersymIndex & ~VERSYM_HIDDEN;
 
-    StringRef Name = check(Sym.getName(this->StringTable), toString(this));
+    StringRef Name = CHECK(Sym.getName(this->StringTable), toString(this));
     if (Sym.isUndefined()) {
       Undefs.push_back(Name);
       continue;
@@ -921,7 +916,7 @@
   MemoryBufferRef MBRef(MB.getBuffer(),
                         Saver.save(ArchiveName + MB.getBufferIdentifier() +
                                    utostr(OffsetInArchive)));
-  Obj = check(lto::InputFile::create(MBRef), toString(this));
+  Obj = CHECK(lto::InputFile::create(MBRef), toString(this));
 
   Triple T(Obj->getTargetTriple());
   EKind = getBitcodeELFKind(T);
@@ -1086,20 +1081,20 @@
   typedef typename ELFT::SymRange Elf_Sym_Range;
 
   ELFFile<ELFT> Obj = check(ELFFile<ELFT>::create(this->MB.getBuffer()));
-  ArrayRef<Elf_Shdr> Sections = check(Obj.sections(), toString(this));
+  ArrayRef<Elf_Shdr> Sections = CHECK(Obj.sections(), toString(this));
   for (const Elf_Shdr &Sec : Sections) {
     if (Sec.sh_type != SHT_SYMTAB)
       continue;
 
-    Elf_Sym_Range Syms = check(Obj.symbols(&Sec), toString(this));
+    Elf_Sym_Range Syms = CHECK(Obj.symbols(&Sec), toString(this));
     uint32_t FirstNonLocal = Sec.sh_info;
     StringRef StringTable =
-        check(Obj.getStringTableForSymtab(Sec, Sections), toString(this));
+        CHECK(Obj.getStringTableForSymtab(Sec, Sections), toString(this));
     std::vector<StringRef> V;
 
     for (const Elf_Sym &Sym : Syms.slice(FirstNonLocal))
       if (Sym.st_shndx != SHN_UNDEF)
-        V.push_back(check(Sym.getName(StringTable), toString(this)));
+        V.push_back(CHECK(Sym.getName(StringTable), toString(this)));
     return V;
   }
   return {};
@@ -1107,7 +1102,7 @@
 
 std::vector<StringRef> LazyObjFile::getBitcodeSymbols() {
   std::unique_ptr<lto::InputFile> Obj =
-      check(lto::InputFile::create(this->MB), toString(this));
+      CHECK(lto::InputFile::create(this->MB), toString(this));
   std::vector<StringRef> V;
   for (const lto::InputFile::Symbol &Sym : Obj->symbols())
     if (!Sym.isUndefined())
Index: include/lld/Common/ErrorHandler.h
===================================================================
--- include/lld/Common/ErrorHandler.h
+++ include/lld/Common/ErrorHandler.h
@@ -74,7 +74,7 @@
 
 LLVM_ATTRIBUTE_NORETURN void exitLld(int Val);
 
-// check() functions are convenient functions to strip errors
+// check functions are convenient functions to strip errors
 // from error-or-value objects.
 template <class T> T check(ErrorOr<T> E) {
   if (auto EC = E.getError())
@@ -88,25 +88,27 @@
   return std::move(*E);
 }
 
-template <class T> T check(ErrorOr<T> E, const Twine &Prefix) {
+template <class T>
+T check2(ErrorOr<T> E, llvm::function_ref<std::string()> Prefix) {
   if (auto EC = E.getError())
-    fatal(Prefix + ": " + EC.message());
-  return std::move(*E);
-}
-
-template <class T> T check(Expected<T> E, const Twine &Prefix) {
-  if (!E)
-    fatal(Prefix + ": " + toString(E.takeError()));
+    fatal(Prefix() + ": " + EC.message());
   return std::move(*E);
 }
 
-// A lazy variant that only allocates error messages when there is an error.
 template <class T>
-T checkLazy(Expected<T> E, llvm::function_ref<std::string()> getPrefix) {
+T check2(Expected<T> E, llvm::function_ref<std::string()> Prefix) {
   if (!E)
-    fatal(getPrefix() + ": " + toString(E.takeError()));
+    fatal(Prefix() + ": " + toString(E.takeError()));
   return std::move(*E);
 }
+
+inline std::string checkToString(const Twine &S) { return S.str(); }
+inline std::string checkToString(std::string S) { return S; }
+inline std::string checkToString(const char *S) { return S; }
+
+// To evaluate the second argument lazily, we use C macro.
+#define CHECK(E, S) check2(E, [&] { return checkToString(S); })
+
 } // namespace lld
 
 #endif
Index: wasm/InputFiles.cpp
===================================================================
--- wasm/InputFiles.cpp
+++ wasm/InputFiles.cpp
@@ -104,7 +104,7 @@
 void ObjFile::parse() {
   // Parse a memory buffer as a wasm file.
   DEBUG(dbgs() << "Parsing object: " << toString(this) << "\n");
-  std::unique_ptr<Binary> Bin = check(createBinary(MB), toString(this));
+  std::unique_ptr<Binary> Bin = CHECK(createBinary(MB), toString(this));
 
   auto *Obj = dyn_cast<WasmObjectFile>(Bin.get());
   if (!Obj)
@@ -223,7 +223,7 @@
 void ArchiveFile::parse() {
   // Parse a MemoryBufferRef as an archive file.
   DEBUG(dbgs() << "Parsing library: " << toString(this) << "\n");
-  File = check(Archive::create(MB), toString(this));
+  File = CHECK(Archive::create(MB), toString(this));
 
   // Read the symbol table to construct Lazy symbols.
   int Count = 0;
@@ -236,7 +236,7 @@
 
 void ArchiveFile::addMember(const Archive::Symbol *Sym) {
   const Archive::Child &C =
-      check(Sym->getMember(),
+      CHECK(Sym->getMember(),
             "could not get the member for symbol " + Sym->getName());
 
   // Don't try to load the same member twice (this can happen when members
@@ -248,7 +248,7 @@
   DEBUG(dbgs() << "from archive: " << toString(this) << "\n");
 
   MemoryBufferRef MB =
-      check(C.getMemoryBufferRef(),
+      CHECK(C.getMemoryBufferRef(),
             "could not get the buffer for the member defining symbol " +
                 Sym->getName());