[SYCL] Add sycl cpp header for imf libdevice API

sycl/include/sycl/ext/intel/math.hpp

@@ -0,0 +1,68 @@
+//==------------- math.hpp - Intel specific math API -----------------------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// The main header of Intel specific math API
+//===----------------------------------------------------------------------===//
+
+#pragma once
+#include <sycl/half_type.hpp>
+#include <type_traits>
+
+// _iml_half_internal is internal representation for fp16 type used in intel
+// math device library. The definition here should align with definition in
+// https://github.com/intel/llvm/blob/sycl/libdevice/imf_half.hpp
+#if defined(__SPIR__)
+using _iml_half_internal = _Float16;
+#else
+using _iml_half_internal = uint16_t;
+#endif
+
+extern "C" {
+float __imf_saturatef(float);
+float __imf_copysignf(float, float);
+double __imf_copysign(double, double);
+_iml_half_internal __imf_copysignf16(_iml_half_internal, _iml_half_internal);
+};
+
+namespace sycl {
+__SYCL_INLINE_VER_NAMESPACE(_V1) {
+namespace ext {
+namespace intel {
+namespace math {
+
+#if __cplusplus >= 201703L
+template <typename Tp>
+std::enable_if_t<std::is_same_v<Tp, float>, float> saturate(Tp x) {
+  return __imf_saturatef(x);
+}
+
+template <typename Tp>
+std::enable_if_t<std::is_same_v<Tp, float>, float> copysign(Tp x, Tp y) {
+  return __imf_copysignf(x, y);
+}
+
+template <typename Tp>
+std::enable_if_t<std::is_same_v<Tp, double>, double> copysign(Tp x, Tp y) {
+  return __imf_copysign(x, y);
+}
+
+template <typename Tp>
+std::enable_if_t<std::is_same_v<Tp, sycl::half>, sycl::half> copysign(Tp x,
+                                                                      Tp y) {
+  static_assert(sizeof(sycl::half) == sizeof(_iml_half_internal),
+                "sycl::half is not compatible with _iml_half_internal.");
+  _iml_half_internal xi = __builtin_bit_cast(_iml_half_internal, x);
+  _iml_half_internal yi = __builtin_bit_cast(_iml_half_internal, y);
+  return __builtin_bit_cast(sycl::half, __imf_copysignf16(xi, yi));
+}
+
+#endif
+} // namespace math
+} // namespace intel
+} // namespace ext
+} // __SYCL_INLINE_VER_NAMESPACE(_V1)
+} // namespace sycl