[OpenMP] Don't include the device wrappers if -nostdinc is used

[jhuber6]

Summary

OpenMP uses several wrapper hearders to provide the definitions of
needed symbols contained in the host. However, some users may use the
-nostdinc option to override these definitions themselves. The OpenMP
wrapper headers are stored in the same location as the clang install. If
the user passes -nostdinc then this include directory is never looked
at by default which means that including these wrappers will always
fail. These headers should instead be included manually if they are
needed with a -nostdinc build.

[tra]

clang/lib/Driver/ToolChains/Clang.cpp

1311

Did you mean nostdinc ?

[jhuber6]

clang/lib/Driver/ToolChains/Clang.cpp

1311

Yes, thank you for catching that. That was an autocomplete mishap that I accidentally reintroduced from undoing too many times. I'll fix it.

[jhuber6]

Fix using nostdlib instead of nostdinc

[tra]

LGTM in general.

clang/lib/Driver/ToolChains/Clang.cpp

1311

A test would be useful.

clang/lib/Driver/ToolChains/Clang.cpp

void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,
   if (JA.isOffloading(Action::OFK_Cuda))
     getToolChain().AddCudaIncludeArgs(Args, CmdArgs);
   if (JA.isOffloading(Action::OFK_HIP))
     getToolChain().AddHIPIncludeArgs(Args, CmdArgs);
 
   // If we are offloading to a target via OpenMP we need to include the
   // openmp_wrappers folder which contains alternative system headers.
   if (JA.isDeviceOffloading(Action::OFK_OpenMP) &&
+      !Args.hasArg(options::OPT_nostdinc) &&
       (getToolChain().getTriple().isNVPTX() ||
        getToolChain().getTriple().isAMDGCN())) {
     if (!Args.hasArg(options::OPT_nobuiltininc)) {
       // Add openmp_wrappers/* to our system include path.  This lets us wrap
       // standard library headers.
       SmallString<128> P(D.ResourceDir);
       llvm::sys::path::append(P, "include");
       llvm::sys::path::append(P, "openmp_wrappers");