[llvm] [SYCL] Add platform enumeration and info query using liboffload (PR #166927)

[Kseniya Tikhomirova via llvm-commits]

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@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the declaration of the SYCL enum class backend that is
+/// implementation-defined and is populated with a unique identifier for each
+/// SYCL backend that the SYCL implementation can support.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBSYCL___IMPL_BACKEND_HPP
+#define _LIBSYCL___IMPL_BACKEND_HPP
+
+#include <sycl/__impl/detail/config.hpp>
+
+#include <string_view>
+#include <type_traits>
+
+_LIBSYCL_BEGIN_NAMESPACE_SYCL
+
+// 4.1. Backends
+enum class backend : char {
+  opencl = 1,
+  level_zero = 2,
+  cuda = 3,
+  hip = 4,
+  all = 5,
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KseniyaTikhomirova wrote:

hip, cuda & level_zero have mapping to liboffload values. opencl is not implemented in liboffload yet. but should be at later stages. I want to have it in enum from the very beginning since SYCL2020 spec mentions presence of opencl backend + we plan to enable it later.

https://github.com/llvm/llvm-project/pull/166927