[lld/mac] Process $ld$ os condition for all actions

[thakis]

Summary

All non-"previous" actions have the same conditional format,
so make them all share the condition logic.

That makes it easier to warn on the not-yet implemented actions,
and maybe also to actually implement them.

No behavior change.

[thakis]

Per https://bugs.llvm.org/show_bug.cgi?id=49800#c16 , not sure if we want to do this. Probably good to implement a few more actions first and see where that takes us.

lld/MachO/InputFiles.h

public:
   // file being linked, and that contains symbols referenced, but not
   // implemented in the bundle. When used like this, it is very similar
   // to a Dylib, so we re-used the same class to represent it.
   bool isBundleLoader;
 
 private:
   bool handleLDSymbol(StringRef originalName);
   void handleLDPreviousSymbol(StringRef name, StringRef originalName);
-  void handleLDInstallNameSymbol(StringRef name, StringRef originalName);
+  void handleLDActionSymbol(StringRef action, StringRef name,
+                            StringRef originalName);
 };
 
 // .a file
 class ArchiveFile : public InputFile {
 public:
   explicit ArchiveFile(std::unique_ptr<llvm::object::Archive> &&file);
   static bool classof(const InputFile *f) { return f->kind() == ArchiveKind; }
   void fetch(const llvm::object::Archive::Symbol &sym);

lld/MachO/InputFiles.cpp

bool DylibFile::handleLDSymbol(StringRef originalName) {
   if (!originalName.startswith("$ld$"))
     return false;
 
   StringRef action;
   StringRef name;
   std::tie(action, name) = originalName.drop_front(strlen("$ld$")).split('$');
   if (action == "previous")
     handleLDPreviousSymbol(name, originalName);
-  else if (action == "install_name")
-    handleLDInstallNameSymbol(name, originalName);
+  else
+    handleLDActionSymbol(action, name, originalName);
   return true;
 }
 
 void DylibFile::handleLDPreviousSymbol(StringRef name, StringRef originalName) {
   // originalName: $ld$ previous $ <installname> $ <compatversion> $
   // <platformstr> $ <startversion> $ <endversion> $ <symbol-name> $
   StringRef installName;
   StringRef compatVersion;
if (cVersion.tryParse(compatVersion)) {
       warn("failed to parse compatibility version, symbol '" + originalName +
            "' ignored");
       return;
     }
     compatibilityVersion = encodeVersion(cVersion);
   }
 }
 
-void DylibFile::handleLDInstallNameSymbol(StringRef name,
+void DylibFile::handleLDActionSymbol(StringRef action, StringRef name,
                                           StringRef originalName) {
-  // originalName: $ld$ install_name $ os<version> $ install_name
-  StringRef condition, installName;
-  std::tie(condition, installName) = name.split('$');
+  // originalName: $ld$ <action> $ os<version> $ symbol
+  StringRef condition, symbol;
+  std::tie(condition, symbol) = name.split('$');
   VersionTuple version;
   if (!condition.consume_front("os") || version.tryParse(condition))
     warn("failed to parse os version, symbol '" + originalName + "' ignored");
-  else if (version == config->platformInfo.minimum)
-    this->installName = saver.save(installName);
+  else if (version != config->platformInfo.minimum)
+    return;
+
+  if (action == "install_name")
+    installName = saver.save(symbol);
+  // FIXME: Support actions "compatibility_version", "hide", "add", "weak".
 }
 
 ArchiveFile::ArchiveFile(std::unique_ptr<object::Archive> &&f)
     : InputFile(ArchiveKind, f->getMemoryBufferRef()), file(std::move(f)) {
   for (const object::Archive::Symbol &sym : file->symbols())
     symtab->addLazy(sym.getName(), this, sym);
 }