[mach-o] Add support for -S option

The darwin linker does not process dwarf debug info.  Instead it produces a
"debug map" in the output file which points back to the original .o files for
anything that wants debug info (e.g. debugger).

The -S option means "don't add a debug map".  lld for mach-o currently does
not generate the debug map, so there is nothing to do when this option is used.
But we need to process the option to get existing projects building.

llvm-svn: 221432

lld/include/lld/ReaderWriter/MachOLinkingContext.h

@@ -57,6 +57,11 @@ public:
     blackList   // -unexported_symbol[s_list], no listed symbol exported.
   };
 
+  enum class DebugInfoMode {
+    addDebugMap,    // Default
+    noDebugMap      // -S option
+  };
+
   /// Initializes the context to sane default values given the specified output
   /// file type, arch, os, and minimum os version.  This should be called before
   /// other setXXX() methods.
@@ -93,6 +98,11 @@ public:
   bool exportRestrictMode() const { return _exportMode != ExportMode::globals; }
   bool exportSymbolNamed(StringRef sym) const;
 
+  DebugInfoMode debugInfoMode() const { return _debugInfoMode; }
+  void setDebugInfoMode(DebugInfoMode mode) {
+    _debugInfoMode = mode;
+  }
+
   bool keepPrivateExterns() const { return _keepPrivateExterns; }
   void setKeepPrivateExterns(bool v) { _keepPrivateExterns = v; }
   bool demangleSymbols() const { return _demangle; }
@@ -322,6 +332,7 @@ private:
   mutable std::vector<std::unique_ptr<class MachOFileNode>> _indirectDylibs;
   ExportMode _exportMode;
   llvm::StringSet<> _exportedSymbols;
+  DebugInfoMode _debugInfoMode;
   std::unique_ptr<llvm::raw_fd_ostream> _dependencyInfo;
 };
 

lld/lib/Driver/DarwinLdDriver.cpp

@@ -640,6 +640,11 @@ bool DarwinLdDriver::parse(int argc, const char *argv[],
     }
   }
 
+  // Handle debug info handling options: -S
+  if (parsedArgs->hasArg(OPT_S)) {
+    ctx.setDebugInfoMode(MachOLinkingContext::DebugInfoMode::noDebugMap);
+  }
+
   // Handle input files
   for (auto &arg : *parsedArgs) {
     bool upward;

lld/lib/Driver/DarwinLdOptions.td

@@ -160,6 +160,8 @@ def demangle : Flag<["-"], "demangle">,
 def dependency_info : Separate<["-"], "dependency_info">,
      MetaVarName<"<file>">,
      HelpText<"Write binary list of files used during link">;
+def S : Flag<["-"], "S">,
+     HelpText<"Remove debug information (STABS or DWARF) from the output file">;
 
 def t : Flag<["-"], "t">,
      HelpText<"Print the names of the input files as ld processes them">;

lld/lib/ReaderWriter/MachO/MachOLinkingContext.cpp

@@ -145,7 +145,8 @@ MachOLinkingContext::MachOLinkingContext()
       _compatibilityVersion(0), _currentVersion(0), _deadStrippableDylib(false),
       _printAtoms(false), _testingFileUsage(false), _keepPrivateExterns(false),
       _demangle(false), _archHandler(nullptr),
-      _exportMode(ExportMode::globals) {}
+      _exportMode(ExportMode::globals),
+      _debugInfoMode(DebugInfoMode::addDebugMap) {}
 
 MachOLinkingContext::~MachOLinkingContext() {}