[Driver] Pass -plugin-opt=no-new-pass-manager to the linker

[MaskRay]

Summary

So that if -fno-new-pass-manager is requested for an
-DENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=on build, ld.bfd/gold/ld.lld can know to
use the legacy PM.

Actually we only need to pass an option when the specified option is different
from the configured default, but that is difficult to test. So we unconditionally
pass a linker option when -f[no-]new-pass-manager is specified

Depends on D92916

[MaskRay]

Improve

[MaskRay]

I just merged this into D92915

clang/lib/Driver/ToolChains/CommonArgs.cpp

if (CSPGOGenerateArg) {
     SmallString<128> Path(
         ProfileUseArg->getNumValues() == 0 ? "" : ProfileUseArg->getValue());
     if (Path.empty() || llvm::sys::fs::is_directory(Path))
       llvm::sys::path::append(Path, "default.profdata");
     CmdArgs.push_back(Args.MakeArgString(Twine("-plugin-opt=cs-profile-path=") +
                                          Path));
   }
 
-  // Need this flag to turn on new pass manager via Gold plugin.
-  if (Args.hasFlag(options::OPT_fnew_pass_manager,
-                   options::OPT_fno_new_pass_manager,
-                   /* Default */ LLVM_ENABLE_NEW_PASS_MANAGER)) {
+  // Pass an option to enable/disable the new pass manager.
+  if (auto *A = Args.getLastArg(options::OPT_fnew_pass_manager,
+                                options::OPT_fno_new_pass_manager)) {
+    if (A->getOption().matches(options::OPT_fnew_pass_manager))
       CmdArgs.push_back("-plugin-opt=new-pass-manager");
+    else
+      CmdArgs.push_back("-plugin-opt=no-new-pass-manager");
   }
 
   // Setup statistics file output.
   SmallString<128> StatsFile = getStatsFileName(Args, Output, Input, D);
   if (!StatsFile.empty())
     CmdArgs.push_back(
         Args.MakeArgString(Twine("-plugin-opt=stats-file=") + StatsFile));
 

clang/test/Driver/fnew-pass-manager.c

 // LEGACY-NOT: -fnew-pass-manager
 
 /// For full/Thin LTO, -fnew-pass-manager passes -plugin-opt=new-pass-manager to the linker (which may not be LLD).
 // RUN: %clang -### -target x86_64-linux -flto -fnew-pass-manager %s 2>&1 | FileCheck --check-prefix=LTO_NEW %s
 // RUN: %clang -### -target x86_64-linux -flto=thin -fexperimental-new-pass-manager %s 2>&1 | FileCheck --check-prefix=LTO_NEW %s
 
 // LTO_NEW:    "-plugin-opt=new-pass-manager"
 
-/// TODO Add the negative option and pass it to the linker.
 // RUN: %clang -### -target x86_64-linux -flto -fno-new-pass-manager %s 2>&1 | FileCheck --check-prefix=LTO_LEGACY %s
 // RUN: %clang -### -target x86_64-linux -flto=thin -fno-experimental-new-pass-manager %s 2>&1 | FileCheck --check-prefix=LTO_LEGACY %s
 
-// LTO_LEGACY-NOT: "-plugin-opt=new-pass-manager"
+// LTO_LEGACY: "-plugin-opt=no-new-pass-manager"
+
+// RUN: %clang -### -target x86_64-linux -flto %s 2>&1 | FileCheck --check-prefix=DEFAULT %s
+
+// DEFAULT-NOT: "-plugin-opt=new-pass-manager"
+// DEFAULT-NOT: "-plugin-opt=no-new-pass-manager"