[gold] Add debug-pass-manager option, and use it to test new-pass-manager

[tejohnson]

Summary

Follow up from r314963.

[pcc]

LGTM

test/tools/gold/X86/new-pm.ll

+; Test plugin options new-pass-manager and debug-pass-manager
+; RUN: opt -module-summary %s -o %t.o
+
+; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold%shlibext \
+; RUN:     --plugin-opt=thinlto \
+; RUN:     --plugin-opt=new-pass-manager \
+; RUN:     --plugin-opt=debug-pass-manager \
+; RUN:     --plugin-opt=cache-dir=%t.cache \
+; RUN:     -o %t2.o %t.o 2>&1 | FileCheck %s
+
+; CHECK: Starting llvm::Module pass manager run
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @globalfunc() #0 {
+entry:
+  ret void
+}

tools/gold/gold-plugin.cpp

#endif
   // Additional options to pass into the code generator.
   // Note: This array will contain all plugin options which are not claimed
   // as plugin exclusive to pass to the code generator.
   static std::vector<const char *> extra;
   // Sample profile file path
   static std::string sample_profile;
   // New pass manager
   static bool new_pass_manager = false;
+  // Debug new pass manager
+  static bool debug_pass_manager = false;
 
   static void process_plugin_option(const char *opt_)
   {
     if (opt_ == nullptr)
       return;
     llvm::StringRef opt = opt_;
 
     if (opt.startswith("mcpu=")) {
if (opt.startswith("mcpu=")) {
               .getAsInteger(10, ParallelCodeGenParallelismLevel))
         message(LDPL_FATAL, "Invalid codegen partition level: %s", opt_ + 5);
     } else if (opt == "disable-verify") {
       DisableVerify = true;
     } else if (opt.startswith("sample-profile=")) {
       sample_profile= opt.substr(strlen("sample-profile="));
     } else if (opt == "new-pass-manager") {
       new_pass_manager = true;
+    } else if (opt == "debug-pass-manager") {
+      debug_pass_manager = true;
     } else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
       // add that.
       if (extra.empty())
         extra.push_back("LLVMgold");
 
       extra.push_back(opt_);
case options::OT_SAVE_TEMPS:
     break;
   }
 
   if (!options::sample_profile.empty())
     Conf.SampleProfile = options::sample_profile;
 
   // Use new pass manager if set in driver
   Conf.UseNewPM = options::new_pass_manager;
+  // Debug new pass manager if requested
+  Conf.DebugPassManager = options::debug_pass_manager;
 
   return llvm::make_unique<LTO>(std::move(Conf), Backend,
                                 options::ParallelCodeGenParallelismLevel);
 }
 
 // Write empty files that may be expected by a distributed build
 // system when invoked with thinlto_index_only. This is invoked when
 // the linker has decided not to include the given module in the