[SYCL] Refactor builtins implementation (#11956)

See `builtins_preview.hpp` for the outline of the new design. This PR
changes the implementation under `-fpreview-breaking-changes` and
removes reliance on a python builtins generator script.

Suggested reading/review order: `builtins_preview.hpp`,
`helper_macros.hpp`,
`host_helper_macros.hpp`, then headers implementing user-visible side
with
the library implementation `sycl/source/builtins/*_functions.cpp` last.

sycl/include/sycl/builtins.hpp

@@ -12,10 +12,7 @@
 
 #ifdef __INTEL_PREVIEW_BREAKING_CHANGES
 
-// Include the generated builtins.
-#include <sycl/builtins_marray_gen.hpp>
-#include <sycl/builtins_scalar_gen.hpp>
-#include <sycl/builtins_vector_gen.hpp>
+#include <sycl/builtins_preview.hpp>
 
 #else // __INTEL_PREVIEW_BREAKING_CHANGES
 

sycl/include/sycl/builtins_preview.hpp

@@ -0,0 +1,270 @@
+//==------------------- builtins_preview.hpp -------------------------------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Implement SYCL builtin functions. This implementation is mainly driven by the
+// requirement of not including <cmath> anywhere in the SYCL headers (i.e. from
+// within <sycl/sycl.hpp>), because it pollutes global namespace. Note that we
+// can avoid that using MSVC's STL as the pollution happens even from
+// <vector>/<string> and other headers that have to be included per the SYCL
+// specification. As such, an alternative approach might be to use math
+// intrinsics with GCC/clang-based compilers and use <cmath> when using MSVC as
+// a host compiler. That hasn't been tried/investigated.
+//
+// Current implementation splits builtins into several files following the SYCL
+// 2020 (revision 8) split into common/math/geometric/relational/etc. functions.
+// For each set, the implementation is split into a user-visible
+// include/sycl/detail/builtins/*_functions.hpp providing full device-side
+// implementation as well as defining user-visible APIs and defining ABI
+// implemented under source/builtins/*_functions.cpp for the host side. We
+// provide both scalar/vector overloads through symbols in the SYCL runtime
+// library due to the <cmath> limitation above (for scalars) and due to
+// performance reasons for vector overloads (to be able to benefit from
+// vectorization).
+//
+// Providing declaration for the host side symbols contained in the library
+// comes with its own challenges. One is compilation time - blindly providing
+// all those declarations takes significant time (about 10% slowdown for
+// "clang++ -fsycl" when compiling just "#include <sycl/sycl.hpp>"). Another
+// issue is that return type for templates is part of the mangling (and as such
+// SFINAE requirements too). To overcome that we structure host side
+// implementation roughly like this (in most cases):
+//
+// math_function.cpp exports:
+//   float sycl::__sin_impl(float);
+//   float1 sycl::__sin_impl(float1);
+//   float2 sycl::__sin_impl(float2);
+//   ...
+//   /* same for other types */
+//
+// math_functions.hpp provide an implementation based on the following idea (in
+// ::sycl namespace):
+//   float sin(float x) {
+//     extern __sin_impl(float);
+//     return __sin_impl(x);
+//   }
+//   template <typename T>
+//   enable_if_valid_type<T> sin(T x) {
+//     if constexpr (marray_or_swizzle) {
+//       ...
+//       call sycl::sin(vector_or_scalar)
+//     } else {
+//       extern T __sin_impl(T);
+//       return __sin_impl(x);
+//     }
+//   }
+// That way we avoid having the full set of explicit declaration for the symbols
+// in the library and instead only pay with compile time when those template
+// instantiations actually happen.
+
+#pragma once
+
+#include <sycl/builtins_utils_vec.hpp>
+
+namespace sycl {
+inline namespace _V1 {
+namespace detail {
+template <typename... Ts>
+inline constexpr bool builtin_same_shape_v =
+    ((... && is_scalar_arithmetic_v<Ts>) || (... && is_marray_v<Ts>) ||
+     (... && is_vec_or_swizzle_v<Ts>)) &&
+    (... && (num_elements<Ts>::value ==
+             num_elements<typename first_type<Ts...>::type>::value));
+
+template <typename... Ts>
+inline constexpr bool builtin_same_or_swizzle_v =
+    // Use builtin_same_shape_v to filter out types unrelated to builtins.
+    builtin_same_shape_v<Ts...> && all_same_v<simplify_if_swizzle_t<Ts>...>;
+
+namespace builtins {
+#ifdef __SYCL_DEVICE_ONLY__
+template <typename T> auto convert_arg(T &&x) {
+  using no_cv_ref = std::remove_cv_t<std::remove_reference_t<T>>;
+  if constexpr (is_vec_v<no_cv_ref>) {
+    using elem_type = get_elem_type_t<no_cv_ref>;
+    using converted_elem_type =
+        decltype(convert_arg(std::declval<elem_type>()));
+
+    constexpr auto N = no_cv_ref::size();
+    using result_type = std::conditional_t<N == 1, converted_elem_type,
+                                           converted_elem_type
+                                           __attribute__((ext_vector_type(N)))>;
+    // TODO: We should have this bit_cast impl inside vec::convert.
+    return bit_cast<result_type>(static_cast<typename no_cv_ref::vector_t>(x));
+  } else if constexpr (std::is_same_v<no_cv_ref, half>)
+    return static_cast<half_impl::BIsRepresentationT>(x);
+  else if constexpr (is_multi_ptr_v<no_cv_ref>) {
+    return convert_arg(x.get_decorated());
+  } else if constexpr (is_scalar_arithmetic_v<no_cv_ref>) {
+    // E.g. on linux: long long -> int64_t (long), or char -> int8_t (signed
+    // char) and same for unsigned; Windows has long/long long reversed.
+    // TODO: Inline this scalar impl.
+    return static_cast<ConvertToOpenCLType_t<no_cv_ref>>(x);
+  } else if constexpr (std::is_pointer_v<no_cv_ref>) {
+    using elem_type = remove_decoration_t<std::remove_pointer_t<no_cv_ref>>;
+    using converted_elem_type =
+        decltype(convert_arg(std::declval<elem_type>()));
+    using result_type =
+        typename DecoratedType<converted_elem_type,
+                               deduce_AS<no_cv_ref>::value>::type *;
+    return reinterpret_cast<result_type>(x);
+  } else if constexpr (is_swizzle_v<no_cv_ref>) {
+    return convert_arg(simplify_if_swizzle_t<no_cv_ref>{x});
+  } else {
+    // TODO: should it be unreachable? What can it be?
+    return std::forward<T>(x);
+  }
+}
+
+template <typename RetTy, typename T> auto convert_result(T &&x) {
+  if constexpr (is_vec_v<RetTy>) {
+    return bit_cast<typename RetTy::vector_t>(x);
+  } else {
+    return std::forward<T>(x);
+  }
+}
+#endif
+} // namespace builtins
+
+template <typename FuncTy, typename... Ts>
+auto builtin_marray_impl(FuncTy F, const Ts &...x) {
+  using ret_elem_type = decltype(F(x[0]...));
+  using T = typename first_type<Ts...>::type;
+  marray<ret_elem_type, T::size()> Res;
+  constexpr auto N = T::size();
+  for (size_t I = 0; I < N / 2; ++I) {
+    auto PartialRes = F(to_vec2(x, I * 2)...);
+    std::memcpy(&Res[I * 2], &PartialRes, sizeof(decltype(PartialRes)));
+  }
+  if (N % 2)
+    Res[N - 1] = F(x[N - 1]...);
+  return Res;
+}
+
+template <typename FuncTy, typename... Ts>
+auto builtin_default_host_impl(FuncTy F, const Ts &...x) {
+  // We implement support for marray/swizzle in the headers and export symbols
+  // for scalars/vector from the library binary. The reason is that scalar
+  // implementations mostly depend on <cmath> which pollutes global namespace,
+  // so we can't unconditionally include it from the SYCL headers. Vector
+  // overloads have to be implemented in the library next to scalar overloads in
+  // order to be vectorizable.
+  if constexpr ((... || is_marray_v<Ts>)) {
+    return builtin_marray_impl(F, x...);
+  } else {
+    return F(simplify_if_swizzle_t<Ts>{x}...);
+  }
+}
+
+template <typename FuncTy, typename... Ts>
+auto builtin_delegate_to_scalar(FuncTy F, const Ts &...x) {
+  using T = typename first_type<Ts...>::type;
+  if constexpr (is_vec_or_swizzle_v<T>) {
+    using ret_elem_type = decltype(F(x[0]...));
+    // TODO: using r{} to avoid Werror. Not sure if ok.
+    vec<ret_elem_type, T::size()> r{};
+    loop<T::size()>([&](auto idx) { r[idx] = F(x[idx]...); });
+    return r;
+  } else {
+    static_assert(is_marray_v<T>);
+    return builtin_marray_impl(F, x...);
+  }
+}
+
+template <typename T>
+struct any_elem_type
+    : std::bool_constant<check_type_in_v<
+          get_elem_type_t<T>, float, double, half, char, signed char, short,
+          int, long, long long, unsigned char, unsigned short, unsigned int,
+          unsigned long, unsigned long long>> {};
+template <typename T>
+struct fp_elem_type
+    : std::bool_constant<
+          check_type_in_v<get_elem_type_t<T>, float, double, half>> {};
+template <typename T>
+struct float_elem_type
+    : std::bool_constant<check_type_in_v<get_elem_type_t<T>, float>> {};
+template <typename T>
+struct integer_elem_type
+    : std::bool_constant<
+          check_type_in_v<get_elem_type_t<T>, char, signed char, short, int,
+                          long, long long, unsigned char, unsigned short,
+                          unsigned int, unsigned long, unsigned long long>> {};
+template <typename T>
+struct suint32_elem_type
+    : std::bool_constant<
+          check_type_in_v<get_elem_type_t<T>, int32_t, uint32_t>> {};
+
+template <typename... Ts>
+struct same_basic_shape : std::bool_constant<builtin_same_shape_v<Ts...>> {};
+
+template <typename... Ts>
+struct same_elem_type : std::bool_constant<same_basic_shape<Ts...>::value &&
+                                           all_same_v<get_elem_type_t<Ts>...>> {
+};
+
+template <typename> struct any_shape : std::true_type {};
+
+template <typename T>
+struct scalar_only : std::bool_constant<is_scalar_arithmetic_v<T>> {};
+
+template <typename T>
+struct non_scalar_only : std::bool_constant<!is_scalar_arithmetic_v<T>> {};
+
+template <typename T> struct default_ret_type {
+  using type = T;
+};
+
+template <typename T> struct scalar_ret_type {
+  using type = get_elem_type_t<T>;
+};
+
+template <template <typename> typename RetTypeTrait,
+          template <typename> typename ElemTypeChecker,
+          template <typename> typename ShapeChecker,
+          template <typename...> typename ExtraConditions, typename... Ts>
+struct builtin_enable
+    : std::enable_if<
+          ElemTypeChecker<typename first_type<Ts...>::type>::value &&
+              ShapeChecker<typename first_type<Ts...>::type>::value &&
+              ExtraConditions<Ts...>::value,
+          typename RetTypeTrait<
+              simplify_if_swizzle_t<typename first_type<Ts...>::type>>::type> {
+};
+#define BUILTIN_CREATE_ENABLER(NAME, RET_TYPE_TRAIT, ELEM_TYPE_CHECKER,        \
+                               SHAPE_CHECKER, EXTRA_CONDITIONS)                \
+  namespace detail {                                                           \
+  template <typename... Ts>                                                    \
+  using NAME##_t =                                                             \
+      typename builtin_enable<RET_TYPE_TRAIT, ELEM_TYPE_CHECKER,               \
+                              SHAPE_CHECKER, EXTRA_CONDITIONS, Ts...>::type;   \
+  }
+} // namespace detail
+
+BUILTIN_CREATE_ENABLER(builtin_enable_generic, default_ret_type, any_elem_type,
+                       any_shape, same_elem_type)
+BUILTIN_CREATE_ENABLER(builtin_enable_generic_scalar, default_ret_type,
+                       any_elem_type, scalar_only, same_elem_type)
+BUILTIN_CREATE_ENABLER(builtin_enable_generic_non_scalar, default_ret_type,
+                       any_elem_type, non_scalar_only, same_elem_type)
+} // namespace _V1
+} // namespace sycl
+
+// The headers below are specifically implemented without including all the
+// necessary headers to allow preprocessing them on their own and providing
+// human-friendly result. One can use a command like this to achieve that:
+// clang++ -[DU]__SYCL_DEVICE_ONLY__ -x c++ math_functions.inc  \
+//         -I <..>/llvm/sycl/include -E -o - \
+//     | grep -v '^#' | clang-format > math_functions.{host|device}.ii
+
+#include <sycl/detail/builtins/common_functions.inc>
+#include <sycl/detail/builtins/geometric_functions.inc>
+#include <sycl/detail/builtins/half_precision_math_functions.inc>
+#include <sycl/detail/builtins/integer_functions.inc>
+#include <sycl/detail/builtins/math_functions.inc>
+#include <sycl/detail/builtins/native_math_functions.inc>
+#include <sycl/detail/builtins/relational_functions.inc>

sycl/include/sycl/detail/builtins/common_functions.inc

@@ -0,0 +1,103 @@
+//==------------------- common_functions.hpp -------------------------------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Intentionally insufficient set of includes and no "#pragma once".
+
+#include <sycl/detail/builtins/helper_macros.hpp>
+
+namespace sycl {
+inline namespace _V1 {
+BUILTIN_CREATE_ENABLER(builtin_enable_common, default_ret_type, fp_elem_type,
+                       any_shape, same_elem_type)
+BUILTIN_CREATE_ENABLER(builtin_enable_common_non_scalar, default_ret_type,
+                       fp_elem_type, non_scalar_only, same_elem_type)
+
+#ifdef __SYCL_DEVICE_ONLY__
+#define BUILTIN_COMMON(NUM_ARGS, NAME, SPIRV_IMPL)                             \
+  DEVICE_IMPL_TEMPLATE(NUM_ARGS, NAME, builtin_enable_common_t, SPIRV_IMPL)
+#else
+#define BUILTIN_COMMON(NUM_ARGS, NAME, SPIRV_IMPL)                             \
+  HOST_IMPL_TEMPLATE(NUM_ARGS, NAME, builtin_enable_common_t, common,          \
+                     default_ret_type)
+#endif
+
+BUILTIN_COMMON(ONE_ARG, degrees, __spirv_ocl_degrees)
+BUILTIN_COMMON(ONE_ARG, radians, __spirv_ocl_radians)
+BUILTIN_COMMON(ONE_ARG, sign, __spirv_ocl_sign)
+
+BUILTIN_COMMON(THREE_ARGS, mix, __spirv_ocl_mix)
+template <typename T0, typename T1>
+detail::builtin_enable_common_non_scalar_t<T0, T1>
+mix(T0 x, T1 y, detail::get_elem_type_t<T0> z) {
+  return mix(detail::simplify_if_swizzle_t<T0>{x},
+             detail::simplify_if_swizzle_t<T0>{y},
+             detail::simplify_if_swizzle_t<T0>{z});
+}
+
+BUILTIN_COMMON(TWO_ARGS, step, __spirv_ocl_step)
+template <typename T>
+detail::builtin_enable_common_non_scalar_t<T> step(detail::get_elem_type_t<T> x,
+                                                   T y) {
+  return step(detail::simplify_if_swizzle_t<T>{x},
+              detail::simplify_if_swizzle_t<T>{y});
+}
+
+BUILTIN_COMMON(THREE_ARGS, smoothstep, __spirv_ocl_smoothstep)
+template <typename T>
+detail::builtin_enable_common_non_scalar_t<T>
+smoothstep(detail::get_elem_type_t<T> x, detail::get_elem_type_t<T> y, T z) {
+  return smoothstep(detail::simplify_if_swizzle_t<T>{x},
+                    detail::simplify_if_swizzle_t<T>{y},
+                    detail::simplify_if_swizzle_t<T>{z});
+}
+
+BUILTIN_COMMON(TWO_ARGS, max, __spirv_ocl_fmax_common)
+template <typename T>
+detail::builtin_enable_common_non_scalar_t<T>
+max(T x, detail::get_elem_type_t<T> y) {
+  return max(detail::simplify_if_swizzle_t<T>{x},
+             detail::simplify_if_swizzle_t<T>{y});
+}
+
+BUILTIN_COMMON(TWO_ARGS, min, __spirv_ocl_fmin_common)
+template <typename T>
+detail::builtin_enable_common_non_scalar_t<T>
+min(T x, detail::get_elem_type_t<T> y) {
+  return min(detail::simplify_if_swizzle_t<T>{x},
+             detail::simplify_if_swizzle_t<T>{y});
+}
+
+#undef BUILTIN_COMMON
+
+#ifdef __SYCL_DEVICE_ONLY__
+DEVICE_IMPL_TEMPLATE(THREE_ARGS, clamp, builtin_enable_generic_t,
+                     [](auto... xs) {
+                       using ElemTy = detail::get_elem_type_t<T0>;
+                       if constexpr (std::is_integral_v<ElemTy>) {
+                         if constexpr (std::is_signed_v<ElemTy>) {
+                           return __spirv_ocl_s_clamp(xs...);
+                         } else {
+                           return __spirv_ocl_u_clamp(xs...);
+                         }
+                       } else {
+                         return __spirv_ocl_fclamp(xs...);
+                       }
+                     })
+#else
+HOST_IMPL_TEMPLATE(THREE_ARGS, clamp, builtin_enable_generic_t, common,
+                   default_ret_type)
+#endif
+template <typename T>
+detail::builtin_enable_generic_non_scalar_t<T>
+clamp(T x, detail::get_elem_type_t<T> y, detail::get_elem_type_t<T> z) {
+  return clamp(detail::simplify_if_swizzle_t<T>{x},
+               detail::simplify_if_swizzle_t<T>{y},
+               detail::simplify_if_swizzle_t<T>{z});
+}
+} // namespace _V1
+} // namespace sycl