Enabling new pass manager in LTO (and thinLTO) link step via -fexperimental-new-pass-manager option

[gyiu]

Summary

Modifications to driver and gold plugin code to get the new pass manager path enabled in LTO (and thinLTO).

[tejohnson]

Thanks for adding this. Please add a test like the one for -ffunction-sections (tools/clang/test/Driver/gold-lto-sections.c).

[gyiu]

Add new testcase to make sure plugin-opt is passed to gold linker to enable new pass manager.

[tejohnson]

LGTM
thanks!

cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp

#endif
   if (Arg *A = getLastProfileSampleUseArg(Args)) {
     StringRef FName = A->getValue();
     if (!llvm::sys::fs::exists(FName))
       D.Diag(diag::err_drv_no_such_file) << FName;
     else
       CmdArgs.push_back(
           Args.MakeArgString(Twine("-plugin-opt=sample-profile=") + FName));
   }
+
+  // Need this flag to turn on new pass manager via Gold plugin.
+  if (Args.hasFlag(options::OPT_fexperimental_new_pass_manager,
+                   options::OPT_fno_experimental_new_pass_manager,
+                   /* Default */ false)) {
+    CmdArgs.push_back("-plugin-opt=new-pass-manager");
+  }
+
 }
 
 void tools::addArchSpecificRPath(const ToolChain &TC, const ArgList &Args,
                                  ArgStringList &CmdArgs) {
   std::string CandidateRPath = TC.getArchSpecificLibPath();
   if (TC.getVFS().exists(CandidateRPath)) {
     CmdArgs.push_back("-rpath");
     CmdArgs.push_back(Args.MakeArgString(CandidateRPath.c_str()));

cfe/trunk/test/Driver/gold-lto-new-pass-man.c

+// RUN: touch %t.o
+//
+// RUN: %clang -target ppc64le-unknown-linux -### %t.o -flto 2>&1 \
+// RUN:     -Wl,-plugin-opt=foo -O3 \
+// RUN:     -fexperimental-new-pass-manager \
+// RUN:     | FileCheck %s
+// CHECK: "-plugin-opt=new-pass-manager"