[CUDA] Added -f[no-]cuda-short-ptr option

[tra]

Summary

The option enables use of 32-bit pointers for accessing
const/local/shared memory. The feature is disabled by default.

[tra]

Removed debug printout.

[bkramer]

lgtm

[tra]

Do not use subtarget feature to control codegen of short pointers.
Instead we need to add a field to TargetOptions which is the only way to pass this info to NVPTXTargetInfo constructor where we calculate DataLayout.

clang/include/clang/Driver/Options.td

def fcuda_flush_denormals_to_zero : Flag<["-"], "fcuda-flush-denormals-to-zero">,
   Flags<[CC1Option]>, HelpText<"Flush denormal floating point values to zero in CUDA device mode.">;
 def fno_cuda_flush_denormals_to_zero : Flag<["-"], "fno-cuda-flush-denormals-to-zero">;
 def fcuda_approx_transcendentals : Flag<["-"], "fcuda-approx-transcendentals">,
   Flags<[CC1Option]>, HelpText<"Use approximate transcendental functions">;
 def fno_cuda_approx_transcendentals : Flag<["-"], "fno-cuda-approx-transcendentals">;
 def fcuda_rdc : Flag<["-"], "fcuda-rdc">, Flags<[CC1Option]>,
   HelpText<"Generate relocatable device code, also known as separate compilation mode.">;
 def fno_cuda_rdc : Flag<["-"], "fno-cuda-rdc">;
+def fcuda_short_ptr : Flag<["-"], "fcuda-short-ptr">, Flags<[CC1Option]>,
+  HelpText<"Use 32-bit pointers for accessing const/local/shared address spaces.">;
+def fno_cuda_short_ptr : Flag<["-"], "fno-cuda-short-ptr">;
 def dA : Flag<["-"], "dA">, Group<d_Group>;
 def dD : Flag<["-"], "dD">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print macro definitions in -E mode in addition to normal output">;
 def dI : Flag<["-"], "dI">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print include directives in -E mode in addition to normal output">;
 def dM : Flag<["-"], "dM">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print macro definitions in -E mode instead of normal output">;
 def dead__strip : Flag<["-"], "dead_strip">;

clang/lib/Basic/Targets/NVPTX.cpp

 NVPTXTargetInfo::NVPTXTargetInfo(const llvm::Triple &Triple,
                                  const TargetOptions &Opts,
                                  unsigned TargetPointerWidth)
     : TargetInfo(Triple) {
   assert((TargetPointerWidth == 32 || TargetPointerWidth == 64) &&
          "NVPTX only supports 32- and 64-bit modes.");
 
   PTXVersion = 32;
+  bool UseShortPtr = false;
   for (const StringRef Feature : Opts.FeaturesAsWritten) {
+    llvm::errs() << "F: " << Feature << "\n";
+    if (Feature == "+short-ptr")
+      UseShortPtr = true;
     if (!Feature.startswith("+ptx"))
       continue;
     PTXVersion = llvm::StringSwitch<unsigned>(Feature)
                      .Case("+ptx61", 61)
                      .Case("+ptx60", 60)
                      .Case("+ptx50", 50)
                      .Case("+ptx43", 43)
                      .Case("+ptx42", 42)
NVPTXTargetInfo::NVPTXTargetInfo(const llvm::Triple &Triple,
 
   // Define available target features
   // These must be defined in sorted order!
   NoAsmVariants = true;
   GPU = CudaArch::SM_20;
 
   if (TargetPointerWidth == 32)
     resetDataLayout("e-p:32:32-i64:64-i128:128-v16:16-v32:32-n16:32:64");
+  else if (UseShortPtr)
+    resetDataLayout(
+        "e-p3:32:32-p4:32:32-p5:32:32-i64:64-i128:128-v16:16-v32:32-n16:32:64");
   else
     resetDataLayout("e-i64:64-i128:128-v16:16-v32:32-n16:32:64");
 
   // If possible, get a TargetInfo for our host triple, so we can match its
   // types.
   llvm::Triple HostTriple(Opts.HostTriple);
   if (!HostTriple.isNVPTX())
     HostTarget.reset(AllocateTarget(llvm::Triple(Opts.HostTriple), Opts));

clang/lib/Driver/ToolChains/Cuda.cpp

void CudaToolChain::addClangTargetOptions(
   const char *PtxFeature = "+ptx42";
   if (CudaInstallation.version() >= CudaVersion::CUDA_91) {
     // CUDA-9.1 uses new instructions that are only available in PTX6.1+
     PtxFeature = "+ptx61";
   } else if (CudaInstallation.version() >= CudaVersion::CUDA_90) {
     // CUDA-9.0 uses new instructions that are only available in PTX6.0+
     PtxFeature = "+ptx60";
   }
-  CC1Args.push_back("-target-feature");
-  CC1Args.push_back(PtxFeature);
+  CC1Args.append({"-target-feature", PtxFeature});
+  if (DriverArgs.hasFlag(options::OPT_fcuda_short_ptr,
+                         options::OPT_fno_cuda_short_ptr, false))
+    CC1Args.append({"-target-feature", "+short-ptr"});
 
   if (DeviceOffloadingKind == Action::OFK_OpenMP) {
     SmallVector<StringRef, 8> LibraryPaths;
     // Add path to lib and/or lib64 folders.
     SmallString<256> DefaultLibPath =
       llvm::sys::path::parent_path(getDriver().Dir);
     llvm::sys::path::append(DefaultLibPath,
         Twine("lib") + CLANG_LIBDIR_SUFFIX);