[ELF] - Minor refactor of LinkerScript file.

[grimar]

Summary

Removes lots of else-ifs from ScriptParser::run();

[grimar]

Removed all changes except one because:

• Moving allocator inside ScriptParser was not good idea. Its much more clear to know it's lifetime is attached to LinkerScript class and not to parser. It did not work correctly I think.
• Restored checks of Error flag where removed. That also was incorrect change, thanks to Rui Ueyama for noticing that during review of another patch.

[• rafael]

This is similar to how MC parser is done, so it is fine with me.

Rui, what do you think?

ELF/LinkerScript.cpp

122 ↗

(On Diff #48291)

Any particular reason for this order?

143 ↗

(On Diff #48291)

C is only used inside the if. Move the find call there?

[• rafael]

ELF/LinkerScript.cpp

143 ↗

(On Diff #48291)

Actually. The if is on a repeated call to find. So just use

auto C = Cmd.find(Tok);
if (C != Cmd.end())

C->second(*this);

[grimar]

ELF/LinkerScript.cpp

122 ↗

(On Diff #48291)

I think we do that in other places. Flags with flags etc.

143 ↗

(On Diff #48291)

Yep, that what I wanted initially.

[ruiu]

LGTM with a few nits.

ELF/LinkerScript.cpp

92 ↗

(On Diff #48291)

Remove this function and move the code inside the constructor.

143 ↗

(On Diff #48291)

Please rename C -> It (because it is not a command but an iterator.)

144–145 ↗

(On Diff #48291)

Please assign to a local variable to make the actual type explicit.

if (It != Cmd.end()) {
  std::function<void(ScriptParser &)> &Handler = It->second;
  Handler();
} else {
  setError(...);
}

lld/trunk/ELF/LinkerScript.cpp

 
 template <class ELFT> bool SectionRule::match(InputSectionBase<ELFT> *S) {
   return matchStr(SectionPattern, S->getSectionName());
 }
 
 class elf2::ScriptParser {
 public:
   ScriptParser(BumpPtrAllocator *A, StringRef S, bool B)
-      : Saver(*A), Tokens(tokenize(S)), IsUnderSysroot(B) {}
+      : Saver(*A), Tokens(tokenize(S)), IsUnderSysroot(B) {
+    Cmd["ENTRY"] = &ScriptParser::readEntry;
+    Cmd["EXTERN"] = &ScriptParser::readExtern;
+    Cmd["GROUP"] = &ScriptParser::readGroup;
+    Cmd["INCLUDE"] = &ScriptParser::readInclude;
+    Cmd["INPUT"] = &ScriptParser::readGroup;
+    Cmd["OUTPUT"] = &ScriptParser::readOutput;
+    Cmd["OUTPUT_ARCH"] = &ScriptParser::readOutputArch;
+    Cmd["OUTPUT_FORMAT"] = &ScriptParser::readOutputFormat;
+    Cmd["SEARCH_DIR"] = &ScriptParser::readSearchDir;
+    Cmd["SECTIONS"] = &ScriptParser::readSections;
+    Cmd[";"] = [](ScriptParser &) {};
+  }
+
   void run();
 
 private:
   void setError(const Twine &Msg);
   static std::vector<StringRef> tokenize(StringRef S);
   static StringRef skipSpace(StringRef S);
   bool atEOF();
   StringRef next();
private:
   void readOutputFormat();
   void readSearchDir();
   void readSections();
 
   void readOutputSectionDescription();
 
   StringSaver Saver;
   std::vector<StringRef> Tokens;
-  bool Error = false;
+  llvm::StringMap<std::function<void(ScriptParser &)>> Cmd;
   size_t Pos = 0;
   bool IsUnderSysroot;
+  bool Error = false;
 };
 
 void ScriptParser::run() {
   while (!atEOF()) {
     StringRef Tok = next();
-    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 == "SEARCH_DIR") {
-      readSearchDir();
-    } else if (Tok == "SECTIONS") {
-      readSections();
+    auto It = Cmd.find(Tok);
+    if (It != Cmd.end()) {
+      std::function<void(ScriptParser &)> &Handler = It->second;
+      Handler(*this);
     } else {
       setError("unknown directive: " + Tok);
-      return;
     }
   }
 }
 
 // We don't want to record cascading errors. Keep only the first one.
 void ScriptParser::setError(const Twine &Msg) {
   if (Error)
     return;