Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1066 insertions, 0 deletions

diff --git a/third_party/highway/hwy/base.h b/third_party/highway/hwy/base.h
new file mode 100644
index 0000000000..0ca755a8f8
--- /dev/null
+++ b/third_party/highway/hwy/base.h
@@ -0,0 +1,1066 @@
+// Copyright 2020 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef HIGHWAY_HWY_BASE_H_
+#define HIGHWAY_HWY_BASE_H_
+
+// For SIMD module implementations and their callers, target-independent.
+
+// IWYU pragma: begin_exports
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hwy/detect_compiler_arch.h"
+#include "hwy/highway_export.h"
+
+// "IWYU pragma: keep" does not work for this include, so hide it from the IDE.
+#if ((HWY_ARCH_X86 && !defined(HWY_NO_LIBCXX)) || HWY_COMPILER_MSVC) && !HWY_IDE
+#include <atomic>
+#endif
+// IWYU pragma: end_exports
+
+#if HWY_COMPILER_MSVC
+#include <string.h>  // memcpy
+#endif
+
+//------------------------------------------------------------------------------
+// Compiler-specific definitions
+
+#define HWY_STR_IMPL(macro) #macro
+#define HWY_STR(macro) HWY_STR_IMPL(macro)
+
+#if HWY_COMPILER_MSVC
+
+#include <intrin.h>
+
+#define HWY_RESTRICT __restrict
+#define HWY_INLINE __forceinline
+#define HWY_NOINLINE __declspec(noinline)
+#define HWY_FLATTEN
+#define HWY_NORETURN __declspec(noreturn)
+#define HWY_LIKELY(expr) (expr)
+#define HWY_UNLIKELY(expr) (expr)
+#define HWY_PRAGMA(tokens) __pragma(tokens)
+#define HWY_DIAGNOSTICS(tokens) HWY_PRAGMA(warning(tokens))
+#define HWY_DIAGNOSTICS_OFF(msc, gcc) HWY_DIAGNOSTICS(msc)
+#define HWY_MAYBE_UNUSED
+#define HWY_HAS_ASSUME_ALIGNED 0
+#if (_MSC_VER >= 1700)
+#define HWY_MUST_USE_RESULT _Check_return_
+#else
+#define HWY_MUST_USE_RESULT
+#endif
+
+#else
+
+#define HWY_RESTRICT __restrict__
+// force inlining without optimization enabled creates very inefficient code
+// that can cause compiler timeout
+#ifdef __OPTIMIZE__
+#define HWY_INLINE inline __attribute__((always_inline))
+#else
+#define HWY_INLINE inline
+#endif
+#define HWY_NOINLINE __attribute__((noinline))
+#define HWY_FLATTEN __attribute__((flatten))
+#define HWY_NORETURN __attribute__((noreturn))
+#define HWY_LIKELY(expr) __builtin_expect(!!(expr), 1)
+#define HWY_UNLIKELY(expr) __builtin_expect(!!(expr), 0)
+#define HWY_PRAGMA(tokens) _Pragma(#tokens)
+#define HWY_DIAGNOSTICS(tokens) HWY_PRAGMA(GCC diagnostic tokens)
+#define HWY_DIAGNOSTICS_OFF(msc, gcc) HWY_DIAGNOSTICS(gcc)
+// Encountered "attribute list cannot appear here" when using the C++17
+// [[maybe_unused]], so only use the old style attribute for now.
+#define HWY_MAYBE_UNUSED __attribute__((unused))
+#define HWY_MUST_USE_RESULT __attribute__((warn_unused_result))
+
+#endif  // !HWY_COMPILER_MSVC
+
+//------------------------------------------------------------------------------
+// Builtin/attributes
+
+// Enables error-checking of format strings.
+#if HWY_HAS_ATTRIBUTE(__format__)
+#define HWY_FORMAT(idx_fmt, idx_arg) \
+  __attribute__((__format__(__printf__, idx_fmt, idx_arg)))
+#else
+#define HWY_FORMAT(idx_fmt, idx_arg)
+#endif
+
+// Returns a void* pointer which the compiler then assumes is N-byte aligned.
+// Example: float* HWY_RESTRICT aligned = (float*)HWY_ASSUME_ALIGNED(in, 32);
+//
+// The assignment semantics are required by GCC/Clang. ICC provides an in-place
+// __assume_aligned, whereas MSVC's __assume appears unsuitable.
+#if HWY_HAS_BUILTIN(__builtin_assume_aligned)
+#define HWY_ASSUME_ALIGNED(ptr, align) __builtin_assume_aligned((ptr), (align))
+#else
+#define HWY_ASSUME_ALIGNED(ptr, align) (ptr) /* not supported */
+#endif
+
+// Clang and GCC require attributes on each function into which SIMD intrinsics
+// are inlined. Support both per-function annotation (HWY_ATTR) for lambdas and
+// automatic annotation via pragmas.
+#if HWY_COMPILER_CLANG
+#define HWY_PUSH_ATTRIBUTES(targets_str)                                \
+  HWY_PRAGMA(clang attribute push(__attribute__((target(targets_str))), \
+                                  apply_to = function))
+#define HWY_POP_ATTRIBUTES HWY_PRAGMA(clang attribute pop)
+#elif HWY_COMPILER_GCC
+#define HWY_PUSH_ATTRIBUTES(targets_str) \
+  HWY_PRAGMA(GCC push_options) HWY_PRAGMA(GCC target targets_str)
+#define HWY_POP_ATTRIBUTES HWY_PRAGMA(GCC pop_options)
+#else
+#define HWY_PUSH_ATTRIBUTES(targets_str)
+#define HWY_POP_ATTRIBUTES
+#endif
+
+//------------------------------------------------------------------------------
+// Macros
+
+#define HWY_API static HWY_INLINE HWY_FLATTEN HWY_MAYBE_UNUSED
+
+#define HWY_CONCAT_IMPL(a, b) a##b
+#define HWY_CONCAT(a, b) HWY_CONCAT_IMPL(a, b)
+
+#define HWY_MIN(a, b) ((a) < (b) ? (a) : (b))
+#define HWY_MAX(a, b) ((a) > (b) ? (a) : (b))
+
+#if HWY_COMPILER_GCC_ACTUAL
+// nielskm: GCC does not support '#pragma GCC unroll' without the factor.
+#define HWY_UNROLL(factor) HWY_PRAGMA(GCC unroll factor)
+#define HWY_DEFAULT_UNROLL HWY_UNROLL(4)
+#elif HWY_COMPILER_CLANG || HWY_COMPILER_ICC || HWY_COMPILER_ICX
+#define HWY_UNROLL(factor) HWY_PRAGMA(unroll factor)
+#define HWY_DEFAULT_UNROLL HWY_UNROLL()
+#else
+#define HWY_UNROLL(factor)
+#define HWY_DEFAULT_UNROLL
+#endif
+
+// Tell a compiler that the expression always evaluates to true.
+// The expression should be free from any side effects.
+// Some older compilers may have trouble with complex expressions, therefore
+// it is advisable to split multiple conditions into separate assume statements,
+// and manually check the generated code.
+// OK but could fail:
+//   HWY_ASSUME(x == 2 && y == 3);
+// Better:
+//   HWY_ASSUME(x == 2);
+//   HWY_ASSUME(y == 3);
+#if HWY_HAS_CPP_ATTRIBUTE(assume)
+#define HWY_ASSUME(expr) [[assume(expr)]]
+#elif HWY_COMPILER_MSVC || HWY_COMPILER_ICC
+#define HWY_ASSUME(expr) __assume(expr)
+// __builtin_assume() was added in clang 3.6.
+#elif HWY_COMPILER_CLANG && HWY_HAS_BUILTIN(__builtin_assume)
+#define HWY_ASSUME(expr) __builtin_assume(expr)
+// __builtin_unreachable() was added in GCC 4.5, but __has_builtin() was added
+// later, so check for the compiler version directly.
+#elif HWY_COMPILER_GCC_ACTUAL >= 405
+#define HWY_ASSUME(expr) \
+  ((expr) ? static_cast<void>(0) : __builtin_unreachable())
+#else
+#define HWY_ASSUME(expr) static_cast<void>(0)
+#endif
+
+// Compile-time fence to prevent undesirable code reordering. On Clang x86, the
+// typical asm volatile("" : : : "memory") has no effect, whereas atomic fence
+// does, without generating code.
+#if HWY_ARCH_X86 && !defined(HWY_NO_LIBCXX)
+#define HWY_FENCE std::atomic_thread_fence(std::memory_order_acq_rel)
+#else
+// TODO(janwas): investigate alternatives. On Arm, the above generates barriers.
+#define HWY_FENCE
+#endif
+
+// 4 instances of a given literal value, useful as input to LoadDup128.
+#define HWY_REP4(literal) literal, literal, literal, literal
+
+#define HWY_ABORT(format, ...) \
+  ::hwy::Abort(__FILE__, __LINE__, format, ##__VA_ARGS__)
+
+// Always enabled.
+#define HWY_ASSERT(condition)             \
+  do {                                    \
+    if (!(condition)) {                   \
+      HWY_ABORT("Assert %s", #condition); \
+    }                                     \
+  } while (0)
+
+#if HWY_HAS_FEATURE(memory_sanitizer) || defined(MEMORY_SANITIZER)
+#define HWY_IS_MSAN 1
+#else
+#define HWY_IS_MSAN 0
+#endif
+
+#if HWY_HAS_FEATURE(address_sanitizer) || defined(ADDRESS_SANITIZER)
+#define HWY_IS_ASAN 1
+#else
+#define HWY_IS_ASAN 0
+#endif
+
+#if HWY_HAS_FEATURE(thread_sanitizer) || defined(THREAD_SANITIZER)
+#define HWY_IS_TSAN 1
+#else
+#define HWY_IS_TSAN 0
+#endif
+
+// MSAN may cause lengthy build times or false positives e.g. in AVX3 DemoteTo.
+// You can disable MSAN by adding this attribute to the function that fails.
+#if HWY_IS_MSAN
+#define HWY_ATTR_NO_MSAN __attribute__((no_sanitize_memory))
+#else
+#define HWY_ATTR_NO_MSAN
+#endif
+
+// For enabling HWY_DASSERT and shortening tests in slower debug builds
+#if !defined(HWY_IS_DEBUG_BUILD)
+// Clang does not define NDEBUG, but it and GCC define __OPTIMIZE__, and recent
+// MSVC defines NDEBUG (if not, could instead check _DEBUG).
+#if (!defined(__OPTIMIZE__) && !defined(NDEBUG)) || HWY_IS_ASAN || \
+    HWY_IS_MSAN || HWY_IS_TSAN || defined(__clang_analyzer__)
+#define HWY_IS_DEBUG_BUILD 1
+#else
+#define HWY_IS_DEBUG_BUILD 0
+#endif
+#endif  // HWY_IS_DEBUG_BUILD
+
+#if HWY_IS_DEBUG_BUILD
+#define HWY_DASSERT(condition) HWY_ASSERT(condition)
+#else
+#define HWY_DASSERT(condition) \
+  do {                         \
+  } while (0)
+#endif
+
+namespace hwy {
+
+//------------------------------------------------------------------------------
+// kMaxVectorSize (undocumented, pending removal)
+
+#if HWY_ARCH_X86
+static constexpr HWY_MAYBE_UNUSED size_t kMaxVectorSize = 64;  // AVX-512
+#elif HWY_ARCH_RVV && defined(__riscv_v_intrinsic) && \
+    __riscv_v_intrinsic >= 11000
+// Not actually an upper bound on the size.
+static constexpr HWY_MAYBE_UNUSED size_t kMaxVectorSize = 4096;
+#else
+static constexpr HWY_MAYBE_UNUSED size_t kMaxVectorSize = 16;
+#endif
+
+//------------------------------------------------------------------------------
+// Alignment
+
+// Potentially useful for LoadDup128 and capped vectors. In other cases, arrays
+// should be allocated dynamically via aligned_allocator.h because Lanes() may
+// exceed the stack size.
+#if HWY_ARCH_X86
+#define HWY_ALIGN_MAX alignas(64)
+#elif HWY_ARCH_RVV && defined(__riscv_v_intrinsic) && \
+    __riscv_v_intrinsic >= 11000
+#define HWY_ALIGN_MAX alignas(8)  // only elements need be aligned
+#else
+#define HWY_ALIGN_MAX alignas(16)
+#endif
+
+//------------------------------------------------------------------------------
+// Lane types
+
+// Match [u]int##_t naming scheme so rvv-inl.h macros can obtain the type name
+// by concatenating base type and bits.
+
+#pragma pack(push, 1)
+
+// ACLE (https://gcc.gnu.org/onlinedocs/gcc/Half-Precision.html):
+// always supported on Armv8, for Armv7 only if -mfp16-format is given.
+#if ((HWY_ARCH_ARM_A64 || (__ARM_FP & 2)) && HWY_COMPILER_GCC)
+using float16_t = __fp16;
+// C11 extension ISO/IEC TS 18661-3:2015 but not supported on all targets.
+// Required for Clang RVV if the float16 extension is used.
+#elif HWY_ARCH_RVV && HWY_COMPILER_CLANG && defined(__riscv_zvfh)
+using float16_t = _Float16;
+// Otherwise emulate
+#else
+struct float16_t {
+  uint16_t bits;
+};
+#endif
+
+struct bfloat16_t {
+  uint16_t bits;
+};
+
+#pragma pack(pop)
+
+using float32_t = float;
+using float64_t = double;
+
+#pragma pack(push, 1)
+
+// Aligned 128-bit type. Cannot use __int128 because clang doesn't yet align it:
+// https://reviews.llvm.org/D86310
+struct alignas(16) uint128_t {
+  uint64_t lo;  // little-endian layout
+  uint64_t hi;
+};
+
+// 64 bit key plus 64 bit value. Faster than using uint128_t when only the key
+// field is to be compared (Lt128Upper instead of Lt128).
+struct alignas(16) K64V64 {
+  uint64_t value;  // little-endian layout
+  uint64_t key;
+};
+
+// 32 bit key plus 32 bit value. Allows vqsort recursions to terminate earlier
+// than when considering both to be a 64-bit key.
+struct alignas(8) K32V32 {
+  uint32_t value;  // little-endian layout
+  uint32_t key;
+};
+
+#pragma pack(pop)
+
+static inline HWY_MAYBE_UNUSED bool operator<(const uint128_t& a,
+                                              const uint128_t& b) {
+  return (a.hi == b.hi) ? a.lo < b.lo : a.hi < b.hi;
+}
+// Required for std::greater.
+static inline HWY_MAYBE_UNUSED bool operator>(const uint128_t& a,
+                                              const uint128_t& b) {
+  return b < a;
+}
+static inline HWY_MAYBE_UNUSED bool operator==(const uint128_t& a,
+                                               const uint128_t& b) {
+  return a.lo == b.lo && a.hi == b.hi;
+}
+
+static inline HWY_MAYBE_UNUSED bool operator<(const K64V64& a,
+                                              const K64V64& b) {
+  return a.key < b.key;
+}
+// Required for std::greater.
+static inline HWY_MAYBE_UNUSED bool operator>(const K64V64& a,
+                                              const K64V64& b) {
+  return b < a;
+}
+static inline HWY_MAYBE_UNUSED bool operator==(const K64V64& a,
+                                               const K64V64& b) {
+  return a.key == b.key;
+}
+
+static inline HWY_MAYBE_UNUSED bool operator<(const K32V32& a,
+                                              const K32V32& b) {
+  return a.key < b.key;
+}
+// Required for std::greater.
+static inline HWY_MAYBE_UNUSED bool operator>(const K32V32& a,
+                                              const K32V32& b) {
+  return b < a;
+}
+static inline HWY_MAYBE_UNUSED bool operator==(const K32V32& a,
+                                               const K32V32& b) {
+  return a.key == b.key;
+}
+
+//------------------------------------------------------------------------------
+// Controlling overload resolution (SFINAE)
+
+template <bool Condition>
+struct EnableIfT {};
+template <>
+struct EnableIfT<true> {
+  using type = void;
+};
+
+template <bool Condition>
+using EnableIf = typename EnableIfT<Condition>::type;
+
+template <typename T, typename U>
+struct IsSameT {
+  enum { value = 0 };
+};
+
+template <typename T>
+struct IsSameT<T, T> {
+  enum { value = 1 };
+};
+
+template <typename T, typename U>
+HWY_API constexpr bool IsSame() {
+  return IsSameT<T, U>::value;
+}
+
+template <bool Condition, typename Then, typename Else>
+struct IfT {
+  using type = Then;
+};
+
+template <class Then, class Else>
+struct IfT<false, Then, Else> {
+  using type = Else;
+};
+
+template <bool Condition, typename Then, typename Else>
+using If = typename IfT<Condition, Then, Else>::type;
+
+// Insert into template/function arguments to enable this overload only for
+// vectors of exactly, at most (LE), or more than (GT) this many bytes.
+//
+// As an example, checking for a total size of 16 bytes will match both
+// Simd<uint8_t, 16, 0> and Simd<uint8_t, 8, 1>.
+#define HWY_IF_V_SIZE(T, kN, bytes) \
+  hwy::EnableIf<kN * sizeof(T) == bytes>* = nullptr
+#define HWY_IF_V_SIZE_LE(T, kN, bytes) \
+  hwy::EnableIf<kN * sizeof(T) <= bytes>* = nullptr
+#define HWY_IF_V_SIZE_GT(T, kN, bytes) \
+  hwy::EnableIf<(kN * sizeof(T) > bytes)>* = nullptr
+
+#define HWY_IF_LANES(kN, lanes) hwy::EnableIf<(kN == lanes)>* = nullptr
+#define HWY_IF_LANES_LE(kN, lanes) hwy::EnableIf<(kN <= lanes)>* = nullptr
+#define HWY_IF_LANES_GT(kN, lanes) hwy::EnableIf<(kN > lanes)>* = nullptr
+
+#define HWY_IF_UNSIGNED(T) hwy::EnableIf<!IsSigned<T>()>* = nullptr
+#define HWY_IF_SIGNED(T)                                                   \
+  hwy::EnableIf<IsSigned<T>() && !IsFloat<T>() && !IsSpecialFloat<T>()>* = \
+      nullptr
+#define HWY_IF_FLOAT(T) hwy::EnableIf<hwy::IsFloat<T>()>* = nullptr
+#define HWY_IF_NOT_FLOAT(T) hwy::EnableIf<!hwy::IsFloat<T>()>* = nullptr
+#define HWY_IF_SPECIAL_FLOAT(T) \
+  hwy::EnableIf<hwy::IsSpecialFloat<T>()>* = nullptr
+#define HWY_IF_NOT_SPECIAL_FLOAT(T) \
+  hwy::EnableIf<!hwy::IsSpecialFloat<T>()>* = nullptr
+#define HWY_IF_NOT_FLOAT_NOR_SPECIAL(T) \
+  hwy::EnableIf<!hwy::IsFloat<T>() && !hwy::IsSpecialFloat<T>()>* = nullptr
+
+#define HWY_IF_T_SIZE(T, bytes) hwy::EnableIf<sizeof(T) == (bytes)>* = nullptr
+#define HWY_IF_NOT_T_SIZE(T, bytes) \
+  hwy::EnableIf<sizeof(T) != (bytes)>* = nullptr
+// bit_array = 0x102 means 1 or 8 bytes. There is no NONE_OF because it sounds
+// too similar. If you want the opposite of this (2 or 4 bytes), ask for those
+// bits explicitly (0x14) instead of attempting to 'negate' 0x102.
+#define HWY_IF_T_SIZE_ONE_OF(T, bit_array) \
+  hwy::EnableIf<((size_t{1} << sizeof(T)) & (bit_array)) != 0>* = nullptr
+
+// Use instead of HWY_IF_T_SIZE to avoid ambiguity with float/double
+// overloads.
+#define HWY_IF_UI32(T) \
+  hwy::EnableIf<IsSame<T, uint32_t>() || IsSame<T, int32_t>()>* = nullptr
+#define HWY_IF_UI64(T) \
+  hwy::EnableIf<IsSame<T, uint64_t>() || IsSame<T, int64_t>()>* = nullptr
+
+#define HWY_IF_LANES_PER_BLOCK(T, N, LANES) \
+  hwy::EnableIf<HWY_MIN(sizeof(T) * N, 16) / sizeof(T) == (LANES)>* = nullptr
+
+// Empty struct used as a size tag type.
+template <size_t N>
+struct SizeTag {};
+
+template <class T>
+struct RemoveConstT {
+  using type = T;
+};
+template <class T>
+struct RemoveConstT<const T> {
+  using type = T;
+};
+
+template <class T>
+using RemoveConst = typename RemoveConstT<T>::type;
+
+template <class T>
+struct RemoveRefT {
+  using type = T;
+};
+template <class T>
+struct RemoveRefT<T&> {
+  using type = T;
+};
+
+template <class T>
+using RemoveRef = typename RemoveRefT<T>::type;
+
+//------------------------------------------------------------------------------
+// Type relations
+
+namespace detail {
+
+template <typename T>
+struct Relations;
+template <>
+struct Relations<uint8_t> {
+  using Unsigned = uint8_t;
+  using Signed = int8_t;
+  using Wide = uint16_t;
+  enum { is_signed = 0, is_float = 0 };
+};
+template <>
+struct Relations<int8_t> {
+  using Unsigned = uint8_t;
+  using Signed = int8_t;
+  using Wide = int16_t;
+  enum { is_signed = 1, is_float = 0 };
+};
+template <>
+struct Relations<uint16_t> {
+  using Unsigned = uint16_t;
+  using Signed = int16_t;
+  using Wide = uint32_t;
+  using Narrow = uint8_t;
+  enum { is_signed = 0, is_float = 0 };
+};
+template <>
+struct Relations<int16_t> {
+  using Unsigned = uint16_t;
+  using Signed = int16_t;
+  using Wide = int32_t;
+  using Narrow = int8_t;
+  enum { is_signed = 1, is_float = 0 };
+};
+template <>
+struct Relations<uint32_t> {
+  using Unsigned = uint32_t;
+  using Signed = int32_t;
+  using Float = float;
+  using Wide = uint64_t;
+  using Narrow = uint16_t;
+  enum { is_signed = 0, is_float = 0 };
+};
+template <>
+struct Relations<int32_t> {
+  using Unsigned = uint32_t;
+  using Signed = int32_t;
+  using Float = float;
+  using Wide = int64_t;
+  using Narrow = int16_t;
+  enum { is_signed = 1, is_float = 0 };
+};
+template <>
+struct Relations<uint64_t> {
+  using Unsigned = uint64_t;
+  using Signed = int64_t;
+  using Float = double;
+  using Wide = uint128_t;
+  using Narrow = uint32_t;
+  enum { is_signed = 0, is_float = 0 };
+};
+template <>
+struct Relations<int64_t> {
+  using Unsigned = uint64_t;
+  using Signed = int64_t;
+  using Float = double;
+  using Narrow = int32_t;
+  enum { is_signed = 1, is_float = 0 };
+};
+template <>
+struct Relations<uint128_t> {
+  using Unsigned = uint128_t;
+  using Narrow = uint64_t;
+  enum { is_signed = 0, is_float = 0 };
+};
+template <>
+struct Relations<float16_t> {
+  using Unsigned = uint16_t;
+  using Signed = int16_t;
+  using Float = float16_t;
+  using Wide = float;
+  enum { is_signed = 1, is_float = 1 };
+};
+template <>
+struct Relations<bfloat16_t> {
+  using Unsigned = uint16_t;
+  using Signed = int16_t;
+  using Wide = float;
+  enum { is_signed = 1, is_float = 1 };
+};
+template <>
+struct Relations<float> {
+  using Unsigned = uint32_t;
+  using Signed = int32_t;
+  using Float = float;
+  using Wide = double;
+  using Narrow = float16_t;
+  enum { is_signed = 1, is_float = 1 };
+};
+template <>
+struct Relations<double> {
+  using Unsigned = uint64_t;
+  using Signed = int64_t;
+  using Float = double;
+  using Narrow = float;
+  enum { is_signed = 1, is_float = 1 };
+};
+
+template <size_t N>
+struct TypeFromSize;
+template <>
+struct TypeFromSize<1> {
+  using Unsigned = uint8_t;
+  using Signed = int8_t;
+};
+template <>
+struct TypeFromSize<2> {
+  using Unsigned = uint16_t;
+  using Signed = int16_t;
+};
+template <>
+struct TypeFromSize<4> {
+  using Unsigned = uint32_t;
+  using Signed = int32_t;
+  using Float = float;
+};
+template <>
+struct TypeFromSize<8> {
+  using Unsigned = uint64_t;
+  using Signed = int64_t;
+  using Float = double;
+};
+template <>
+struct TypeFromSize<16> {
+  using Unsigned = uint128_t;
+};
+
+}  // namespace detail
+
+// Aliases for types of a different category, but the same size.
+template <typename T>
+using MakeUnsigned = typename detail::Relations<T>::Unsigned;
+template <typename T>
+using MakeSigned = typename detail::Relations<T>::Signed;
+template <typename T>
+using MakeFloat = typename detail::Relations<T>::Float;
+
+// Aliases for types of the same category, but different size.
+template <typename T>
+using MakeWide = typename detail::Relations<T>::Wide;
+template <typename T>
+using MakeNarrow = typename detail::Relations<T>::Narrow;
+
+// Obtain type from its size [bytes].
+template <size_t N>
+using UnsignedFromSize = typename detail::TypeFromSize<N>::Unsigned;
+template <size_t N>
+using SignedFromSize = typename detail::TypeFromSize<N>::Signed;
+template <size_t N>
+using FloatFromSize = typename detail::TypeFromSize<N>::Float;
+
+// Avoid confusion with SizeTag where the parameter is a lane size.
+using UnsignedTag = SizeTag<0>;
+using SignedTag = SizeTag<0x100>;  // integer
+using FloatTag = SizeTag<0x200>;
+
+template <typename T, class R = detail::Relations<T>>
+constexpr auto TypeTag() -> hwy::SizeTag<((R::is_signed + R::is_float) << 8)> {
+  return hwy::SizeTag<((R::is_signed + R::is_float) << 8)>();
+}
+
+// For when we only want to distinguish FloatTag from everything else.
+using NonFloatTag = SizeTag<0x400>;
+
+template <typename T, class R = detail::Relations<T>>
+constexpr auto IsFloatTag() -> hwy::SizeTag<(R::is_float ? 0x200 : 0x400)> {
+  return hwy::SizeTag<(R::is_float ? 0x200 : 0x400)>();
+}
+
+//------------------------------------------------------------------------------
+// Type traits
+
+template <typename T>
+HWY_API constexpr bool IsFloat() {
+  // Cannot use T(1.25) != T(1) for float16_t, which can only be converted to or
+  // from a float, not compared.
+  return IsSame<T, float>() || IsSame<T, double>();
+}
+
+// These types are often special-cased and not supported in all ops.
+template <typename T>
+HWY_API constexpr bool IsSpecialFloat() {
+  return IsSame<T, float16_t>() || IsSame<T, bfloat16_t>();
+}
+
+template <typename T>
+HWY_API constexpr bool IsSigned() {
+  return T(0) > T(-1);
+}
+template <>
+constexpr bool IsSigned<float16_t>() {
+  return true;
+}
+template <>
+constexpr bool IsSigned<bfloat16_t>() {
+  return true;
+}
+
+// Largest/smallest representable integer values.
+template <typename T>
+HWY_API constexpr T LimitsMax() {
+  static_assert(!IsFloat<T>(), "Only for integer types");
+  using TU = MakeUnsigned<T>;
+  return static_cast<T>(IsSigned<T>() ? (static_cast<TU>(~0ull) >> 1)
+                                      : static_cast<TU>(~0ull));
+}
+template <typename T>
+HWY_API constexpr T LimitsMin() {
+  static_assert(!IsFloat<T>(), "Only for integer types");
+  return IsSigned<T>() ? T(-1) - LimitsMax<T>() : T(0);
+}
+
+// Largest/smallest representable value (integer or float). This naming avoids
+// confusion with numeric_limits<float>::min() (the smallest positive value).
+template <typename T>
+HWY_API constexpr T LowestValue() {
+  return LimitsMin<T>();
+}
+template <>
+constexpr float LowestValue<float>() {
+  return -3.402823466e+38F;
+}
+template <>
+constexpr double LowestValue<double>() {
+  return -1.7976931348623158e+308;
+}
+
+template <typename T>
+HWY_API constexpr T HighestValue() {
+  return LimitsMax<T>();
+}
+template <>
+constexpr float HighestValue<float>() {
+  return 3.402823466e+38F;
+}
+template <>
+constexpr double HighestValue<double>() {
+  return 1.7976931348623158e+308;
+}
+
+// Difference between 1.0 and the next representable value.
+template <typename T>
+HWY_API constexpr T Epsilon() {
+  return 1;
+}
+template <>
+constexpr float Epsilon<float>() {
+  return 1.192092896e-7f;
+}
+template <>
+constexpr double Epsilon<double>() {
+  return 2.2204460492503131e-16;
+}
+
+// Returns width in bits of the mantissa field in IEEE binary32/64.
+template <typename T>
+constexpr int MantissaBits() {
+  static_assert(sizeof(T) == 0, "Only instantiate the specializations");
+  return 0;
+}
+template <>
+constexpr int MantissaBits<float>() {
+  return 23;
+}
+template <>
+constexpr int MantissaBits<double>() {
+  return 52;
+}
+
+// Returns the (left-shifted by one bit) IEEE binary32/64 representation with
+// the largest possible (biased) exponent field. Used by IsInf.
+template <typename T>
+constexpr MakeSigned<T> MaxExponentTimes2() {
+  return -(MakeSigned<T>{1} << (MantissaBits<T>() + 1));
+}
+
+// Returns bitmask of the sign bit in IEEE binary32/64.
+template <typename T>
+constexpr MakeUnsigned<T> SignMask() {
+  return MakeUnsigned<T>{1} << (sizeof(T) * 8 - 1);
+}
+
+// Returns bitmask of the exponent field in IEEE binary32/64.
+template <typename T>
+constexpr MakeUnsigned<T> ExponentMask() {
+  return (~(MakeUnsigned<T>{1} << MantissaBits<T>()) + 1) & ~SignMask<T>();
+}
+
+// Returns bitmask of the mantissa field in IEEE binary32/64.
+template <typename T>
+constexpr MakeUnsigned<T> MantissaMask() {
+  return (MakeUnsigned<T>{1} << MantissaBits<T>()) - 1;
+}
+
+// Returns 1 << mantissa_bits as a floating-point number. All integers whose
+// absolute value are less than this can be represented exactly.
+template <typename T>
+constexpr T MantissaEnd() {
+  static_assert(sizeof(T) == 0, "Only instantiate the specializations");
+  return 0;
+}
+template <>
+constexpr float MantissaEnd<float>() {
+  return 8388608.0f;  // 1 << 23
+}
+template <>
+constexpr double MantissaEnd<double>() {
+  // floating point literal with p52 requires C++17.
+  return 4503599627370496.0;  // 1 << 52
+}
+
+// Returns width in bits of the exponent field in IEEE binary32/64.
+template <typename T>
+constexpr int ExponentBits() {
+  // Exponent := remaining bits after deducting sign and mantissa.
+  return 8 * sizeof(T) - 1 - MantissaBits<T>();
+}
+
+// Returns largest value of the biased exponent field in IEEE binary32/64,
+// right-shifted so that the LSB is bit zero. Example: 0xFF for float.
+// This is expressed as a signed integer for more efficient comparison.
+template <typename T>
+constexpr MakeSigned<T> MaxExponentField() {
+  return (MakeSigned<T>{1} << ExponentBits<T>()) - 1;
+}
+
+//------------------------------------------------------------------------------
+// Helper functions
+
+template <typename T1, typename T2>
+constexpr inline T1 DivCeil(T1 a, T2 b) {
+  return (a + b - 1) / b;
+}
+
+// Works for any `align`; if a power of two, compiler emits ADD+AND.
+constexpr inline size_t RoundUpTo(size_t what, size_t align) {
+  return DivCeil(what, align) * align;
+}
+
+// Undefined results for x == 0.
+HWY_API size_t Num0BitsBelowLS1Bit_Nonzero32(const uint32_t x) {
+#if HWY_COMPILER_MSVC
+  unsigned long index;  // NOLINT
+  _BitScanForward(&index, x);
+  return index;
+#else   // HWY_COMPILER_MSVC
+  return static_cast<size_t>(__builtin_ctz(x));
+#endif  // HWY_COMPILER_MSVC
+}
+
+HWY_API size_t Num0BitsBelowLS1Bit_Nonzero64(const uint64_t x) {
+#if HWY_COMPILER_MSVC
+#if HWY_ARCH_X86_64
+  unsigned long index;  // NOLINT
+  _BitScanForward64(&index, x);
+  return index;
+#else   // HWY_ARCH_X86_64
+  // _BitScanForward64 not available
+  uint32_t lsb = static_cast<uint32_t>(x & 0xFFFFFFFF);
+  unsigned long index;  // NOLINT
+  if (lsb == 0) {
+    uint32_t msb = static_cast<uint32_t>(x >> 32u);
+    _BitScanForward(&index, msb);
+    return 32 + index;
+  } else {
+    _BitScanForward(&index, lsb);
+    return index;
+  }
+#endif  // HWY_ARCH_X86_64
+#else   // HWY_COMPILER_MSVC
+  return static_cast<size_t>(__builtin_ctzll(x));
+#endif  // HWY_COMPILER_MSVC
+}
+
+// Undefined results for x == 0.
+HWY_API size_t Num0BitsAboveMS1Bit_Nonzero32(const uint32_t x) {
+#if HWY_COMPILER_MSVC
+  unsigned long index;  // NOLINT
+  _BitScanReverse(&index, x);
+  return 31 - index;
+#else   // HWY_COMPILER_MSVC
+  return static_cast<size_t>(__builtin_clz(x));
+#endif  // HWY_COMPILER_MSVC
+}
+
+HWY_API size_t Num0BitsAboveMS1Bit_Nonzero64(const uint64_t x) {
+#if HWY_COMPILER_MSVC
+#if HWY_ARCH_X86_64
+  unsigned long index;  // NOLINT
+  _BitScanReverse64(&index, x);
+  return 63 - index;
+#else   // HWY_ARCH_X86_64
+  // _BitScanReverse64 not available
+  const uint32_t msb = static_cast<uint32_t>(x >> 32u);
+  unsigned long index;  // NOLINT
+  if (msb == 0) {
+    const uint32_t lsb = static_cast<uint32_t>(x & 0xFFFFFFFF);
+    _BitScanReverse(&index, lsb);
+    return 63 - index;
+  } else {
+    _BitScanReverse(&index, msb);
+    return 31 - index;
+  }
+#endif  // HWY_ARCH_X86_64
+#else   // HWY_COMPILER_MSVC
+  return static_cast<size_t>(__builtin_clzll(x));
+#endif  // HWY_COMPILER_MSVC
+}
+
+HWY_API size_t PopCount(uint64_t x) {
+#if HWY_COMPILER_GCC  // includes clang
+  return static_cast<size_t>(__builtin_popcountll(x));
+  // This instruction has a separate feature flag, but is often called from
+  // non-SIMD code, so we don't want to require dynamic dispatch. It was first
+  // supported by Intel in Nehalem (SSE4.2), but MSVC only predefines a macro
+  // for AVX, so check for that.
+#elif HWY_COMPILER_MSVC && HWY_ARCH_X86_64 && defined(__AVX__)
+  return _mm_popcnt_u64(x);
+#elif HWY_COMPILER_MSVC && HWY_ARCH_X86_32 && defined(__AVX__)
+  return _mm_popcnt_u32(static_cast<uint32_t>(x & 0xFFFFFFFFu)) +
+         _mm_popcnt_u32(static_cast<uint32_t>(x >> 32));
+#else
+  x -= ((x >> 1) & 0x5555555555555555ULL);
+  x = (((x >> 2) & 0x3333333333333333ULL) + (x & 0x3333333333333333ULL));
+  x = (((x >> 4) + x) & 0x0F0F0F0F0F0F0F0FULL);
+  x += (x >> 8);
+  x += (x >> 16);
+  x += (x >> 32);
+  return static_cast<size_t>(x & 0x7Fu);
+#endif
+}
+
+// Skip HWY_API due to GCC "function not considered for inlining". Previously
+// such errors were caused by underlying type mismatches, but it's not clear
+// what is still mismatched despite all the casts.
+template <typename TI>
+/*HWY_API*/ constexpr size_t FloorLog2(TI x) {
+  return x == TI{1}
+             ? 0
+             : static_cast<size_t>(FloorLog2(static_cast<TI>(x >> 1)) + 1);
+}
+
+template <typename TI>
+/*HWY_API*/ constexpr size_t CeilLog2(TI x) {
+  return x == TI{1}
+             ? 0
+             : static_cast<size_t>(FloorLog2(static_cast<TI>(x - 1)) + 1);
+}
+
+template <typename T>
+HWY_INLINE constexpr T AddWithWraparound(hwy::FloatTag /*tag*/, T t, size_t n) {
+  return t + static_cast<T>(n);
+}
+
+template <typename T>
+HWY_INLINE constexpr T AddWithWraparound(hwy::NonFloatTag /*tag*/, T t,
+                                         size_t n) {
+  using TU = MakeUnsigned<T>;
+  return static_cast<T>(
+      static_cast<TU>(static_cast<TU>(t) + static_cast<TU>(n)) &
+      hwy::LimitsMax<TU>());
+}
+
+#if HWY_COMPILER_MSVC && HWY_ARCH_X86_64
+#pragma intrinsic(_umul128)
+#endif
+
+// 64 x 64 = 128 bit multiplication
+HWY_API uint64_t Mul128(uint64_t a, uint64_t b, uint64_t* HWY_RESTRICT upper) {
+#if defined(__SIZEOF_INT128__)
+  __uint128_t product = (__uint128_t)a * (__uint128_t)b;
+  *upper = (uint64_t)(product >> 64);
+  return (uint64_t)(product & 0xFFFFFFFFFFFFFFFFULL);
+#elif HWY_COMPILER_MSVC && HWY_ARCH_X86_64
+  return _umul128(a, b, upper);
+#else
+  constexpr uint64_t kLo32 = 0xFFFFFFFFU;
+  const uint64_t lo_lo = (a & kLo32) * (b & kLo32);
+  const uint64_t hi_lo = (a >> 32) * (b & kLo32);
+  const uint64_t lo_hi = (a & kLo32) * (b >> 32);
+  const uint64_t hi_hi = (a >> 32) * (b >> 32);
+  const uint64_t t = (lo_lo >> 32) + (hi_lo & kLo32) + lo_hi;
+  *upper = (hi_lo >> 32) + (t >> 32) + hi_hi;
+  return (t << 32) | (lo_lo & kLo32);
+#endif
+}
+
+#if HWY_COMPILER_MSVC
+#pragma intrinsic(memcpy)
+#pragma intrinsic(memset)
+#endif
+
+// The source/destination must not overlap/alias.
+template <size_t kBytes, typename From, typename To>
+HWY_API void CopyBytes(const From* from, To* to) {
+#if HWY_COMPILER_MSVC
+  memcpy(to, from, kBytes);
+#else
+  __builtin_memcpy(
+      static_cast<void*>(to), static_cast<const void*>(from), kBytes);
+#endif
+}
+
+// Same as CopyBytes, but for same-sized objects; avoids a size argument.
+template <typename From, typename To>
+HWY_API void CopySameSize(const From* HWY_RESTRICT from, To* HWY_RESTRICT to) {
+  static_assert(sizeof(From) == sizeof(To), "");
+  CopyBytes<sizeof(From)>(from, to);
+}
+
+template <size_t kBytes, typename To>
+HWY_API void ZeroBytes(To* to) {
+#if HWY_COMPILER_MSVC
+  memset(to, 0, kBytes);
+#else
+  __builtin_memset(to, 0, kBytes);
+#endif
+}
+
+HWY_API float F32FromBF16(bfloat16_t bf) {
+  uint32_t bits = bf.bits;
+  bits <<= 16;
+  float f;
+  CopySameSize(&bits, &f);
+  return f;
+}
+
+HWY_API bfloat16_t BF16FromF32(float f) {
+  uint32_t bits;
+  CopySameSize(&f, &bits);
+  bfloat16_t bf;
+  bf.bits = static_cast<uint16_t>(bits >> 16);
+  return bf;
+}
+
+HWY_DLLEXPORT HWY_NORETURN void HWY_FORMAT(3, 4)
+    Abort(const char* file, int line, const char* format, ...);
+
+// Prevents the compiler from eliding the computations that led to "output".
+template <class T>
+HWY_API void PreventElision(T&& output) {
+#if HWY_COMPILER_MSVC
+  // MSVC does not support inline assembly anymore (and never supported GCC's
+  // RTL constraints). Self-assignment with #pragma optimize("off") might be
+  // expected to prevent elision, but it does not with MSVC 2015. Type-punning
+  // with volatile pointers generates inefficient code on MSVC 2017.
+  static std::atomic<RemoveRef<T>> dummy;
+  dummy.store(output, std::memory_order_relaxed);
+#else
+  // Works by indicating to the compiler that "output" is being read and
+  // modified. The +r constraint avoids unnecessary writes to memory, but only
+  // works for built-in types (typically FuncOutput).
+  asm volatile("" : "+r"(output) : : "memory");
+#endif
+}
+
+}  // namespace hwy
+
+#endif  // HIGHWAY_HWY_BASE_H_