From c8690cb4213e1a4d47406484dec260f406b69525 Mon Sep 17 00:00:00 2001
From: Fabian Knorr <fabian.knorr@dps.uibk.ac.at>
Date: Tue, 19 Dec 2023 14:44:43 +0100
Subject: [PATCH] Make sycl::half support compiler-dependent

---
 CMakeLists.txt                      |  8 ++++++++
 cmake/simsycl-config.cmake.in       |  3 +++
 include/simsycl/config.hh.in        |  2 ++
 include/simsycl/sycl/forward.hh     |  3 +++
 include/simsycl/sycl/math.hh        |  9 +++++++++
 include/simsycl/sycl/type_traits.hh | 13 ++++++++++++-
 include/simsycl/sycl/vec.hh         |  2 ++
 7 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 11c4263..1038c72 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,6 +17,14 @@ endif()
 
 find_package(Boost 1.70 COMPONENTS context REQUIRED)
 
+include(CheckTypeSize)
+check_type_size(_Float16 FLOAT16 BUILTIN_TYPES_ONLY LANGUAGE CXX)
+if (HAVE_FLOAT16)
+  set(SIMSYCL_FEATURE_HALF_TYPE 1)
+else ()
+  set(SIMSYCL_FEATURE_HALF_TYPE 0)
+endif()
+
 set(SIMSYCL_CHECK_MODE "SIMSYCL_CHECK_ABORT" CACHE STRING "Check mode to use")
 
 set(CONFIG_PATH "${CMAKE_CURRENT_BINARY_DIR}/include/simsycl/config.hh")
diff --git a/cmake/simsycl-config.cmake.in b/cmake/simsycl-config.cmake.in
index dd005fe..07e4a2b 100644
--- a/cmake/simsycl-config.cmake.in
+++ b/cmake/simsycl-config.cmake.in
@@ -19,3 +19,6 @@ find_dependency(Boost 1.70 COMPONENTS context REQUIRED)
 include("${CMAKE_CURRENT_LIST_DIR}/simsycl-targets.cmake")
 
 set(CMAKE_MODULE_PATH "${SIMSYCL_ORIGINAL_CMAKE_MODULE_PATH}")
+
+set(SIMSYCL_FEATURE_HALF_TYPE "@SIMSYCL_FEATURE_HALF_TYPE@")
+set(SIMSYCL_CHECK_MODE "@SIMSYCL_CHECK_MODE@")
diff --git a/include/simsycl/config.hh.in b/include/simsycl/config.hh.in
index 2423424..80af744 100644
--- a/include/simsycl/config.hh.in
+++ b/include/simsycl/config.hh.in
@@ -5,6 +5,8 @@
 #define SIMSYCL_VERSION_MINOR @SIMSYCL_VERSION_MINOR@
 #define SIMSYCL_VERSION_PATCH @SIMSYCL_VERSION_PATCH@
 
+#define SIMSYCL_FEATURE_HALF_TYPE @SIMSYCL_FEATURE_HALF_TYPE@
+
 #ifndef SIMSYCL_CHECK_MODE
 #define SIMSYCL_CHECK_MODE @SIMSYCL_CHECK_MODE@
 #endif
diff --git a/include/simsycl/sycl/forward.hh b/include/simsycl/sycl/forward.hh
index f61fc82..0fb9bc1 100644
--- a/include/simsycl/sycl/forward.hh
+++ b/include/simsycl/sycl/forward.hh
@@ -3,6 +3,7 @@
 #include "allocator.hh"
 #include "enums.hh"
 
+#include <simsycl/config.hh>
 #include "../detail/preprocessor.hh"
 
 #include <functional>
@@ -46,7 +47,9 @@ class exception_list;
 
 class handler;
 
+#if SIMSYCL_FEATURE_HALF_TYPE
 using half = _Float16; // currently requires a compiler that supports _Float16
+#endif
 
 template<typename DataT, int Dimensions = 1,
     access_mode AccessMode = (std::is_const_v<DataT> ? access_mode::read : access_mode::read_write)>
diff --git a/include/simsycl/sycl/math.hh b/include/simsycl/sycl/math.hh
index 0b2d7ef..10079af 100644
--- a/include/simsycl/sycl/math.hh
+++ b/include/simsycl/sycl/math.hh
@@ -21,6 +21,8 @@
         return result;                                                                                                 \
     }
 
+#if SIMSYCL_FEATURE_HALF_TYPE
+
 #define SIMSYCL_DETAIL_MATH_DERIVE_UNARY_FUNCTION_FOR_HALF(name)                                                       \
     inline half name(const half x) { return static_cast<half>(name(static_cast<float>(x))); }
 
@@ -34,6 +36,13 @@
         return static_cast<half>(name(static_cast<float>(x), static_cast<float>(y), static_cast<float>(z)));           \
     }
 
+#else
+
+#define SIMSYCL_DETAIL_MATH_DERIVE_UNARY_FUNCTION_FOR_HALF(name)
+#define SIMSYCL_DETAIL_MATH_DERIVE_BINARY_FUNCTION_FOR_HALF(name)
+#define SIMSYCL_DETAIL_MATH_DERIVE_TERNARY_FUNCTION_FOR_HALF(name)
+
+#endif
 
 namespace simsycl::sycl {
 
diff --git a/include/simsycl/sycl/type_traits.hh b/include/simsycl/sycl/type_traits.hh
index 17b43fa..79d9ee7 100644
--- a/include/simsycl/sycl/type_traits.hh
+++ b/include/simsycl/sycl/type_traits.hh
@@ -36,14 +36,25 @@ struct is_function_object : std::false_type {};
 template<class Fn>
 inline constexpr bool is_function_object_v = is_function_object<Fn>::value;
 
+#if SIMSYCL_FEATURE_HALF_TYPE
 template<typename T>
 struct is_arithmetic : std::bool_constant<std::is_arithmetic_v<T> || std::is_same_v<T, sycl::half>> {};
+#else
+using std::is_arithmetic;
+#endif
+
 template<class T>
 inline constexpr bool is_arithmetic_v = is_arithmetic<T>::value;
 
 template<typename T>
 struct is_floating_point
-    : std::bool_constant<std::is_same_v<T, sycl::half> || std::is_same_v<T, float> || std::is_same_v<T, double>> {};
+#if SIMSYCL_FEATURE_HALF_TYPE
+    : std::bool_constant<std::is_same_v<T, sycl::half> || std::is_same_v<T, float> || std::is_same_v<T, double>> {
+#else
+    : std::bool_constant<std::is_same_v<T, float> || std::is_same_v<T, double>> {
+#endif
+};
+
 template<class T>
 inline constexpr bool is_floating_point_v = is_floating_point<T>::value;
 
diff --git a/include/simsycl/sycl/vec.hh b/include/simsycl/sycl/vec.hh
index c0419ca..b3be697 100644
--- a/include/simsycl/sycl/vec.hh
+++ b/include/simsycl/sycl/vec.hh
@@ -475,11 +475,13 @@ using ulong4 = vec<uint64_t, 4>;
 using ulong8 = vec<uint64_t, 8>;
 using ulong16 = vec<uint64_t, 16>;
 
+#if SIMSYCL_FEATURE_HALF_TYPE
 using half2 = vec<half, 2>;
 using half3 = vec<half, 3>;
 using half4 = vec<half, 4>;
 using half8 = vec<half, 8>;
 using half16 = vec<half, 16>;
+#endif
 
 using float2 = vec<float, 2>;
 using float3 = vec<float, 3>;