lld-link: Simplify LinkerDriver::findDefaultEntry()

[thakis]

Summary

No behavior change. Not repeating the CRTStartup names makes fixing PR36523 simpler.

[ruiu]

LGTM

[thakis]

r338911, thanks!

COFF/Driver.cpp

 }
 
 // Windows specific -- find default entry point name.
 //
 // There are four different entry point functions for Windows executables,
 // each of which corresponds to a user-defined "main" function. This function
 // infers an entry point from a user-defined "main" function.
 StringRef LinkerDriver::findDefaultEntry() {
-  // As a special case, if /nodefaultlib is given, we directly look for an
-  // entry point. This is because, if no default library is linked, users
-  // need to define an entry point instead of a "main".
-  if (Config->NoDefaultLibAll) {
-    for (StringRef S : {"mainCRTStartup", "wmainCRTStartup",
-                        "WinMainCRTStartup", "wWinMainCRTStartup"}) {
-      if (findUnderscoreMangle(S))
-        return mangle(S);
-    }
-    return "";
-  }
-
   // User-defined main functions and their corresponding entry points.
   static const char *Entries[][2] = {
       {"main", "mainCRTStartup"},
       {"wmain", "wmainCRTStartup"},
       {"WinMain", "WinMainCRTStartup"},
       {"wWinMain", "wWinMainCRTStartup"},
   };
   for (auto E : Entries) {
-    if (findUnderscoreMangle(E[0]))
+    // As a special case, if /nodefaultlib is given, we directly look for an
+    // entry point. This is because, if no default library is linked, users
+    // need to define an entry point instead of a "main".
+    if (findUnderscoreMangle(E[Config->NoDefaultLibAll]))
       return mangle(E[1]);
   }
   return "";
 }
 
 WindowsSubsystem LinkerDriver::inferSubsystem() {
   if (Config->DLL)
     return IMAGE_SUBSYSTEM_WINDOWS_GUI;