[openmp] Default to new rtl for amdgpu

[JonChesterfield]

Summary

Reverts D114965 as the compiler backend appears to be working again

[jhuber6]

If it works on your end it's good.

[JonChesterfield]

It's a bit hard to tell. Definitely might work. I'm hoping someone will feed this into the internal CI infra. @ronlieb any objection to making this change on trunk and reverting it internally if things break there?

The experimental builder at https://lab.llvm.org/staging/#/builders/200 is running (main one needs to be rebooted or similar), which means we can land this and revert it if that fails. Will do so.

clang/include/clang/Driver/Options.td

def fopenmp_assume_teams_oversubscription : Flag<["-"], "fopenmp-assume-teams-oversubscription">,
   Group<f_Group>, Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
 def fopenmp_assume_threads_oversubscription : Flag<["-"], "fopenmp-assume-threads-oversubscription">, 
   Group<f_Group>, Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
 def fno_openmp_assume_teams_oversubscription : Flag<["-"], "fno-openmp-assume-teams-oversubscription">, 
   Group<f_Group>, Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
 def fno_openmp_assume_threads_oversubscription : Flag<["-"], "fno-openmp-assume-threads-oversubscription">, 
   Group<f_Group>, Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
 defm openmp_target_new_runtime: BoolFOption<"openmp-target-new-runtime",
-  LangOpts<"OpenMPTargetNewRuntime">, DefaultFalse,
+  LangOpts<"OpenMPTargetNewRuntime">, DefaultTrue,
   PosFlag<SetTrue, [CC1Option], "Use the new bitcode library for OpenMP offloading">,
   NegFlag<SetFalse>>;
 defm openmp_optimistic_collapse : BoolFOption<"openmp-optimistic-collapse",
   LangOpts<"OpenMPOptimisticCollapse">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option]>, NegFlag<SetFalse>, BothFlags<[NoArgumentUnused, HelpHidden]>>;
 def static_openmp: Flag<["-"], "static-openmp">,
   HelpText<"Use the static host OpenMP runtime while linking.">;
 def fno_optimize_sibling_calls : Flag<["-"], "fno-optimize-sibling-calls">, Group<f_Group>;

clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp

void AMDGPUOpenMPToolChain::addClangTargetOptions(
   CC1Args.push_back(DriverArgs.MakeArgStringRef(GPUArch));
   CC1Args.push_back("-fcuda-is-device");
 
   if (DriverArgs.hasArg(options::OPT_nogpulib))
     return;
 
   std::string BitcodeSuffix;
   if (DriverArgs.hasFlag(options::OPT_fopenmp_target_new_runtime,
-                         options::OPT_fno_openmp_target_new_runtime, false))
+                         options::OPT_fno_openmp_target_new_runtime, true))
     BitcodeSuffix = "new-amdgpu-" + GPUArch;
   else
     BitcodeSuffix = "amdgcn-" + GPUArch;
 
   addOpenMPDeviceRTL(getDriver(), DriverArgs, CC1Args, BitcodeSuffix,
                      getTriple());
 }
 

clang/lib/Driver/ToolChains/Clang.cpp

case Driver::OMPRT_IOMP5:
       if (Args.hasFlag(options::OPT_fopenmp_cuda_mode,
                        options::OPT_fno_openmp_cuda_mode, /*Default=*/false))
         CmdArgs.push_back("-fopenmp-cuda-mode");
 
       // When in OpenMP offloading mode, enable or disable the new device
       // runtime.
       if (Args.hasFlag(options::OPT_fopenmp_target_new_runtime,
                        options::OPT_fno_openmp_target_new_runtime,
-                       /*Default=*/!getToolChain().getTriple().isAMDGCN()))
+                       /*Default=*/true))
         CmdArgs.push_back("-fopenmp-target-new-runtime");
 
       // When in OpenMP offloading mode, enable debugging on the device.
       Args.AddAllArgs(CmdArgs, options::OPT_fopenmp_target_debug_EQ);
       if (Args.hasFlag(options::OPT_fopenmp_target_debug,
                        options::OPT_fno_openmp_target_debug, /*Default=*/false))
         CmdArgs.push_back("-fopenmp-target-debug");