[WebAssembly] Refactor config setting and checking. NFC.

[sbc100]

Summary

This matches the way the ELF backend does it.

[sbc100]

The diff algorithms seem to make a right mess of this, but this change basically splits out setConfigs and checkOptions and nothing more

[ruiu]

LGTM

ELF/Driver.cpp

static void initLLVM() {
   InitializeAllTargets();
   InitializeAllTargetMCs();
   InitializeAllAsmPrinters();
   InitializeAllAsmParsers();
 }
 
 // Some command line options or some combinations of them are not allowed.
 // This function checks for such errors.
-static void checkOptions(opt::InputArgList &Args) {
+static void checkOptions() {
   // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
   // table which is a relatively new feature.
   if (Config->EMachine == EM_MIPS && Config->GnuHash)
     error("the .gnu.hash section is not compatible with the MIPS target");
 
   if (Config->FixCortexA53Errata843419 && Config->EMachine != EM_AARCH64)
     error("--fix-cortex-a53-843419 is only supported on AArch64 targets");
 
void LinkerDriver::main(ArrayRef<const char *> ArgsArr) {
 
   initLLVM();
   createFiles(Args);
   if (errorCount())
     return;
 
   inferMachineType();
   setConfigs(Args);
-  checkOptions(Args);
+  checkOptions();
   if (errorCount())
     return;
 
   switch (Config->EKind) {
   case ELF32LEKind:
     link<ELF32LE>(Args);
     return;
   case ELF32BEKind:

wasm/Driver.cpp

for (Symbol *Sym : Symtab->getSymbols()) {
     Func->setTableIndex(0);
     Symtab->SyntheticFunctions.emplace_back(Func);
     // Hide our dummy to prevent export.
     uint32_t Flags = WASM_SYMBOL_VISIBILITY_HIDDEN;
     replaceSymbol<DefinedFunction>(Sym, Sym->getName(), Flags, nullptr, Func);
   }
 }
 
-// Force Sym to be entered in the output. Used for -u or equivalent.
-static Symbol *handleUndefined(StringRef Name) {
-  Symbol *Sym = Symtab->find(Name);
-  if (!Sym)
-    return nullptr;
-
-  // Since symbol S may not be used inside the program, LTO may
-  // eliminate it. Mark the symbol as "used" to prevent it.
-  Sym->IsUsedInRegularObj = true;
-
-  if (auto *LazySym = dyn_cast<LazySymbol>(Sym))
-    LazySym->fetch();
-
-  return Sym;
-}
-
-void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
-  WasmOptTable Parser;
-  opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
-
-  // Handle --help
-  if (Args.hasArg(OPT_help)) {
-    Parser.PrintHelp(outs(),
-                     (std::string(ArgsArr[0]) + " [options] file...").c_str(),
-                     "LLVM Linker", false);
-    return;
-  }
-
-  // Handle --version
-  if (Args.hasArg(OPT_version) || Args.hasArg(OPT_v)) {
-    outs() << getLLDVersion() << "\n";
-    return;
-  }
-
-  // Parse and evaluate -mllvm options.
-  std::vector<const char *> V;
-  V.push_back("wasm-ld (LLVM option parsing)");
-  for (auto *Arg : Args.filtered(OPT_mllvm))
-    V.push_back(Arg->getValue());
-  cl::ParseCommandLineOptions(V.size(), V.data());
-
-  errorHandler().ErrorLimit = args::getInteger(Args, OPT_error_limit, 20);
-
+// Some Config members do not directly correspond to any particular
+// command line options, but computed based on other Config values.
+// This function initialize such members. See Config.h for the details
+// of these values.
+static void setConfigs(opt::InputArgList &Args) {
   Config->AllowUndefined = Args.hasArg(OPT_allow_undefined);
   Config->CompressRelocations = Args.hasArg(OPT_compress_relocations);
   Config->Demangle = Args.hasFlag(OPT_demangle, OPT_no_demangle, true);
   Config->DisableVerify = Args.hasArg(OPT_disable_verify);
   Config->Entry = getEntry(Args, Args.hasArg(OPT_relocatable) ? "" : "_start");
   Config->ExportAll = Args.hasArg(OPT_export_all);
   Config->ExportDynamic = Args.hasFlag(OPT_export_dynamic,
       OPT_no_export_dynamic, false);
static void setConfigs(opt::InputArgList &Args) {
   errorHandler().Verbose = Args.hasArg(OPT_verbose);
   ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true);
 
   Config->InitialMemory = args::getInteger(Args, OPT_initial_memory, 0);
   Config->GlobalBase = args::getInteger(Args, OPT_global_base, 1024);
   Config->MaxMemory = args::getInteger(Args, OPT_max_memory, 0);
   Config->ZStackSize =
       args::getZOptionValue(Args, OPT_z, "stack-size", WasmPageSize);
+}
 
+// Some command line options or some combinations of them are not allowed.
+// This function checks for such errors.
+static void checkOptions(opt::InputArgList &Args) {
   if (!Config->StripDebug && !Config->StripAll && Config->CompressRelocations)
     error("--compress-relocations is incompatible with output debug"
           " information. Please pass --strip-debug or --strip-all");
 
   if (Config->LTOO > 3)
     error("invalid optimization level for LTO: " + Twine(Config->LTOO));
   if (Config->LTOPartitions == 0)
     error("--lto-partitions: number of threads must be > 0");
   if (Config->ThinLTOJobs == 0)
     error("--thinlto-jobs: number of threads must be > 0");
 
-  if (auto *Arg = Args.getLastArg(OPT_allow_undefined_file))
-    readImportFile(Arg->getValue());
-
-  if (!Args.hasArg(OPT_INPUT)) {
-    error("no input files");
-    return;
-  }
-
   if (Config->Pie && Config->Shared)
     error("-shared and -pie may not be used together");
 
   if (Config->OutputFile.empty())
     error("no output file specified");
 
   if (Config->ImportTable && Config->ExportTable)
     error("--import-table and --export-table may not be used together");
 
   if (Config->Relocatable) {
     if (!Config->Entry.empty())
       error("entry point specified for relocatable output file");
     if (Config->GcSections)
       error("-r and --gc-sections may not be used together");
     if (Config->CompressRelocations)
       error("-r -and --compress-relocations may not be used together");
     if (Args.hasArg(OPT_undefined))
       error("-r -and --undefined may not be used together");
     if (Config->Pie)
       error("-r and -pie may not be used together");
   }
+}
+
+// Force Sym to be entered in the output. Used for -u or equivalent.
+static Symbol *handleUndefined(StringRef Name) {
+  Symbol *Sym = Symtab->find(Name);
+  if (!Sym)
+    return nullptr;
+
+  // Since symbol S may not be used inside the program, LTO may
+  // eliminate it. Mark the symbol as "used" to prevent it.
+  Sym->IsUsedInRegularObj = true;
+
+  if (auto *LazySym = dyn_cast<LazySymbol>(Sym))
+    LazySym->fetch();
+
+  return Sym;
+}
+
+void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
+  WasmOptTable Parser;
+  opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
+
+  // Handle --help
+  if (Args.hasArg(OPT_help)) {
+    Parser.PrintHelp(outs(),
+                     (std::string(ArgsArr[0]) + " [options] file...").c_str(),
+                     "LLVM Linker", false);
+    return;
+  }
+
+  // Handle --version
+  if (Args.hasArg(OPT_version) || Args.hasArg(OPT_v)) {
+    outs() << getLLDVersion() << "\n";
+    return;
+  }
+
+  // Parse and evaluate -mllvm options.
+  std::vector<const char *> V;
+  V.push_back("wasm-ld (LLVM option parsing)");
+  for (auto *Arg : Args.filtered(OPT_mllvm))
+    V.push_back(Arg->getValue());
+  cl::ParseCommandLineOptions(V.size(), V.data());
+
+  errorHandler().ErrorLimit = args::getInteger(Args, OPT_error_limit, 20);
+
+  setConfigs(Args);
+  checkOptions(Args);
+
+  if (auto *Arg = Args.getLastArg(OPT_allow_undefined_file))
+    readImportFile(Arg->getValue());
+
+  if (!Args.hasArg(OPT_INPUT)) {
+    error("no input files");
+    return;
+  }
 
   Config->Pic = Config->Pie || Config->Shared;
 
   if (Config->Pic) {
     if (Config->ExportTable)
       error("-shared/-pie is incompatible with --export-table");
     Config->ImportTable = true;
   }