[clang] Use enum for LangOptions::SYCLVersion instead of unsigned

[jansvoboda11]

Summary

LangOptions::SYCLVersion can only have two values. This patch introduces an enum that allows us to reduce the member size from 32 bits to 1 bit.

Consequently, this also makes marshalling of this option fit into our model for enums: D84674.

[dexonsmith]

I've reviewed the code and it seems to do the right thing. I'd like a SYCL maintainer to take a look too though.

(If for some reason changing the interface to an enum isn't desirable, maybe there's a compromise where there's an accessor that converts back to an integer?)

[bader]

LGTM. Thanks!

@erichkeane, @mdtoguchi, we should upstream support for SYCL-2020 version in addition to SYCL-2017.

clang/include/clang/Basic/LangOptions.h

enum MSVCMajorVersion {
     MSVC2013 = 1800,
     MSVC2015 = 1900,
     MSVC2017 = 1910,
     MSVC2017_5 = 1912,
     MSVC2017_7 = 1914,
     MSVC2019 = 1920,
   };
 
+  enum SYCLMajorVersion {
+    SYCL_None,
+    SYCL_2017,
+  };
+
   /// Clang versions with different platform ABI conformance.
   enum class ClangABI {
     /// Attempt to be ABI-compatible with code generated by Clang 3.8.x
     /// (SVN r257626). This causes <1 x long long> to be passed in an
     /// integer register instead of an SSE register on x64_64.
     Ver3_8,
 
     /// Attempt to be ABI-compatible with code generated by Clang 4.0.x

clang/include/clang/Basic/LangOptions.def

 LANGOPT(GPURelocatableDeviceCode, 1, 0, "generate relocatable device code")
 LANGOPT(GPUAllowDeviceInit, 1, 0, "allowing device side global init functions for HIP")
 LANGOPT(GPUMaxThreadsPerBlock, 32, 256, "default max threads per block for kernel launch bounds for HIP")
 LANGOPT(GPUDeferDiag, 1, 0, "defer host/device related diagnostic messages for CUDA/HIP")
 LANGOPT(GPUExcludeWrongSideOverloads, 1, 0, "always exclude wrong side overloads in overloading resolution for CUDA/HIP")
 
 LANGOPT(SYCL              , 1, 0, "SYCL")
 LANGOPT(SYCLIsDevice      , 1, 0, "Generate code for SYCL device")
-LANGOPT(SYCLVersion       , 32, 0, "Version of the SYCL standard used")
+ENUM_LANGOPT(SYCLVersion  , SYCLMajorVersion, 1, SYCL_None, "Version of the SYCL standard used")
 
 LANGOPT(HIPUseNewLaunchAPI, 1, 0, "Use new kernel launching API for HIP")
 
 LANGOPT(SizedDeallocation , 1, 0, "sized deallocation")
 LANGOPT(AlignedAllocation , 1, 0, "aligned allocation")
 LANGOPT(AlignedAllocationUnavailable, 1, 0, "aligned allocation functions are unavailable")
 LANGOPT(NewAlignOverride  , 32, 0, "maximum alignment guaranteed by '::operator new(size_t)'")
 LANGOPT(ConceptSatisfactionCaching , 1, 1, "enable satisfaction caching for C++20 Concepts")

clang/lib/Frontend/CompilerInvocation.cpp

else
       LangStd = OpenCLLangStd;
   }
 
   Opts.SYCLIsDevice = Opts.SYCL && Args.hasArg(options::OPT_fsycl_is_device);
   if (Opts.SYCL) {
     // -sycl-std applies to any SYCL source, not only those containing kernels,
     // but also those using the SYCL API
     if (const Arg *A = Args.getLastArg(OPT_sycl_std_EQ)) {
-      Opts.SYCLVersion = llvm::StringSwitch<unsigned>(A->getValue())
-                             .Cases("2017", "1.2.1", "121", "sycl-1.2.1", 2017)
-                             .Default(0U);
+      Opts.setSYCLVersion(
+          llvm::StringSwitch<LangOptions::SYCLMajorVersion>(A->getValue())
+              .Cases("2017", "1.2.1", "121", "sycl-1.2.1",
+                     LangOptions::SYCL_2017)
+              .Default(LangOptions::SYCL_None));
 
-      if (Opts.SYCLVersion == 0U) {
+      if (Opts.getSYCLVersion() == LangOptions::SYCL_None) {
         // User has passed an invalid value to the flag, this is an error
         Diags.Report(diag::err_drv_invalid_value)
             << A->getAsString(Args) << A->getValue();
       }
     }
   }
 
   llvm::Triple T(TargetOpts.Triple);

clang/lib/Frontend/InitPreprocessor.cpp

if (TI.isLittleEndian())
       Builder.defineMacro("__ENDIAN_LITTLE__");
 
     if (LangOpts.FastRelaxedMath)
       Builder.defineMacro("__FAST_RELAXED_MATH__");
   }
 
   if (LangOpts.SYCL) {
     // SYCL Version is set to a value when building SYCL applications
-    if (LangOpts.SYCLVersion == 2017)
+    if (LangOpts.getSYCLVersion() == LangOptions::SYCL_2017)
       Builder.defineMacro("CL_SYCL_LANGUAGE_VERSION", "121");
   }
 
   // Not "standard" per se, but available even with the -undef flag.
   if (LangOpts.AsmPreprocessor)
     Builder.defineMacro("__ASSEMBLER__");
   if (LangOpts.CUDA && !LangOpts.HIP)
     Builder.defineMacro("__CUDA__");