Dispatch without hash table lookup.

[ruiu]

Summary

Cmd used to be the single central place to dispatch. It is not longer
the case because we have a logic for readProvideOrAssignment().
This patch removes the hash table so that evrything is in a single
function. This is slightly verbose but should improve readability.

[grimar]

Honestly saying I do not like both ways of dispatching. But have no any suggestions here.
I agree that it is probably slightly more readable now when we have readProvideOrAssignment, so LGTM.

lld/trunk/ELF/LinkerScript.cpp

 private:
   void addFile(StringRef Path);
 
   void readAsNeeded();
   void readEntry();
   void readExtern();
   void readGroup();
   void readInclude();
-  void readNothing() {}
   void readOutput();
   void readOutputArch();
   void readOutputFormat();
   void readPhdrs();
   void readSearchDir();
   void readSections();
   void readVersion();
   void readVersionScriptCommand();
private:
   Expr readParenExpr();
 
   // For parsing version script.
   void readExtern(std::vector<SymbolVersion> *Globals);
   void readVersionDeclaration(StringRef VerStr);
   void readGlobal(StringRef VerStr);
   void readLocal();
 
-  const static StringMap<Handler> Cmd;
   ScriptConfiguration &Opt = *ScriptConfig;
   StringSaver Saver = {ScriptConfig->Alloc};
   bool IsUnderSysroot;
 };
 
-const StringMap<elf::ScriptParser::Handler> elf::ScriptParser::Cmd = {
-    {"ENTRY", &ScriptParser::readEntry},
-    {"EXTERN", &ScriptParser::readExtern},
-    {"GROUP", &ScriptParser::readGroup},
-    {"INCLUDE", &ScriptParser::readInclude},
-    {"INPUT", &ScriptParser::readGroup},
-    {"OUTPUT", &ScriptParser::readOutput},
-    {"OUTPUT_ARCH", &ScriptParser::readOutputArch},
-    {"OUTPUT_FORMAT", &ScriptParser::readOutputFormat},
-    {"PHDRS", &ScriptParser::readPhdrs},
-    {"SEARCH_DIR", &ScriptParser::readSearchDir},
-    {"SECTIONS", &ScriptParser::readSections},
-    {"VERSION", &ScriptParser::readVersion},
-    {";", &ScriptParser::readNothing}};
-
 void ScriptParser::readVersionScript() {
   readVersionScriptCommand();
   if (!atEOF())
     setError("EOF expected, but got " + next());
 }
 
 void ScriptParser::readVersionScriptCommand() {
   if (skip("{")) {
void ScriptParser::readVersion() {
   expect("{");
   readVersionScriptCommand();
   expect("}");
 }
 
 void ScriptParser::readLinkerScript() {
   while (!atEOF()) {
     StringRef Tok = next();
-    if (Handler Fn = Cmd.lookup(Tok)) {
-      (this->*Fn)();
+    if (Tok == ";")
+      continue;
+
+    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)) {
       if (Opt.HasContents)
         Opt.Commands.emplace_back(Cmd);
       else
         Opt.Assignments.emplace_back(Cmd);
     } else {
       setError("unknown directive: " + Tok);
     }