Compiler is missing self macro versioning

[dvrogozh]

With:

• e66b3c3 (top of sycl branch) or v6.3.0

Please, provide macro definitions to:

1. Differentiate intel/llvm compiler on C/C++ level from CLANG and ICX:
2. Differentiate intel/llvm own releases (such as 6.2.0 vs. 6.3.0)

At the moment when compiling user gets only original clang versioning:

$ ./build/install/bin/clang-23 -fsycl -dM -E -x c++ /dev/null | grep clang
#define __clang__ 1
#define __clang_major__ 23
#define __clang_minor__ 0
#define __clang_patchlevel__ 0
#define __clang_version__ "23.0.0git (https://github.com/intel/llvm.git e66b3c331f5f64b7a9b300578eb884a5b20ba52e)"

$ ./build/install/bin/clang-23 -fsycl -dM -E -x c++ /dev/null | grep -i version
#define SYCL_LANGUAGE_VERSION 202012L
#define __GXX_ABI_VERSION 1002
#define __VERSION__ "Clang 23.0.0git (https://github.com/intel/llvm.git e66b3c331f5f64b7a9b300578eb884a5b20ba52e)"
#define __clang_version__ "23.0.0git (https://github.com/intel/llvm.git e66b3c331f5f64b7a9b300578eb884a5b20ba52e)"

Please, consider to implement something simple and straightforward aligned with the rest of compilers such as:

#if defined(__clang__)
    /* Clang-specific code */
#elif defined(__GNUC__)
    /* GCC-specific code (Clang is already ruled out) */
#elif defined(_MSC_VER)
    /* MSVC-specific code (Note: Clang-cl also defines this) */
#endif

CC: @tahonermann @sarnex @frenchwr

[tahonermann]

In communication elsewhere, I suggested:

• Add __DPCPP__ as a predefined macro, and one of the following:
  • Define __DPCPP__ with a value indicating the version of the compiler in VVRRPP format as described here
  • Define __DPCPP__ as 1 and predefine the following macros with the intel/llvm DPC++ version (not the Clang version).
    • Define __dpcpp_major__ as V where V is the major version for the release (e.g., 6 in 6.3.0).
    • Define __dpcpp_minor__ as R where R is the minor version for the release (e.g., 3 in 6.3.0).
    • Define __dpcpp_patchlevel__ as P where P is the patch level for the release (e.g., 0 in 6.3.0).
• Continue to predefine __clang_major__, __clang_minor__, and __clang_patchlevel__ with their upstream Clang derived values.
• Change __VERSION__ and __clang_version__ to reflect the DPC++ name and version information, e.g., "DPC++ 6.3.0 git (https://github.com/intel/llvm.git 6133fe8)"