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// Copyright 2021 The Tint Authors.
//
// 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 SRC_TINT_NUMBER_H_
#define SRC_TINT_NUMBER_H_
#include <stdint.h>
#include <cmath>
#include <functional>
#include <limits>
#include <optional>
#include <ostream>
#include "src/tint/utils/compiler_macros.h"
#include "src/tint/utils/result.h"
// Forward declaration
namespace tint {
/// Number wraps a integer or floating point number, enforcing explicit casting.
template <typename T>
struct Number;
} // namespace tint
namespace tint::detail {
/// An empty structure used as a unique template type for Number when
/// specializing for the f16 type.
struct NumberKindF16 {};
/// Helper for obtaining the underlying type for a Number.
template <typename T>
struct NumberUnwrapper {
/// When T is not a Number, then type defined to be T.
using type = T;
};
/// NumberUnwrapper specialization for Number<T>.
template <typename T>
struct NumberUnwrapper<Number<T>> {
/// The Number's underlying type.
using type = typename Number<T>::type;
};
} // namespace tint::detail
namespace tint {
/// Evaluates to true iff T is a floating-point type or is NumberKindF16.
template <typename T>
constexpr bool IsFloatingPoint =
std::is_floating_point_v<T> || std::is_same_v<T, detail::NumberKindF16>;
/// Evaluates to true iff T is an integer type.
template <typename T>
constexpr bool IsInteger = std::is_integral_v<T>;
/// Evaluates to true iff T is an integer type, floating-point type or is NumberKindF16.
template <typename T>
constexpr bool IsNumeric = IsInteger<T> || IsFloatingPoint<T>;
/// Number wraps a integer or floating point number, enforcing explicit casting.
template <typename T>
struct Number {
static_assert(IsNumeric<T>, "Number<T> constructed with non-numeric type");
/// type is the underlying type of the Number
using type = T;
/// Highest finite representable value of this type.
static constexpr type kHighest = std::numeric_limits<type>::max();
/// Lowest finite representable value of this type.
static constexpr type kLowest = std::numeric_limits<type>::lowest();
/// Smallest positive normal value of this type.
static constexpr type kSmallest =
std::is_integral_v<type> ? 0 : std::numeric_limits<type>::min();
/// Smallest positive subnormal value of this type, 0 for integral type.
static constexpr type kSmallestSubnormal =
std::is_integral_v<type> ? 0 : std::numeric_limits<type>::denorm_min();
/// Constructor. The value is zero-initialized.
Number() = default;
/// Constructor.
/// @param v the value to initialize this Number to
template <typename U>
explicit Number(U v) : value(static_cast<T>(v)) {}
/// Constructor.
/// @param v the value to initialize this Number to
template <typename U>
explicit Number(Number<U> v) : value(static_cast<T>(v.value)) {}
/// Conversion operator
/// @returns the value as T
operator T() const { return value; }
/// Negation operator
/// @returns the negative value of the number
Number operator-() const { return Number(-value); }
/// Assignment operator
/// @param v the new value
/// @returns this Number so calls can be chained
Number& operator=(T v) {
value = v;
return *this;
}
/// The number value
type value = {};
};
/// Resolves to the underlying type for a Number.
template <typename T>
using UnwrapNumber = typename detail::NumberUnwrapper<T>::type;
/// Writes the number to the ostream.
/// @param out the std::ostream to write to
/// @param num the Number
/// @return the std::ostream so calls can be chained
template <typename T>
inline std::ostream& operator<<(std::ostream& out, Number<T> num) {
return out << num.value;
}
/// The partial specification of Number for f16 type, storing the f16 value as float,
/// and enforcing proper explicit casting.
template <>
struct Number<detail::NumberKindF16> {
/// C++ does not have a native float16 type, so we use a 32-bit float instead.
using type = float;
/// Highest finite representable value of this type.
static constexpr type kHighest = 65504.0f; // 2¹⁵ × (1 + 1023/1024)
/// Lowest finite representable value of this type.
static constexpr type kLowest = -65504.0f;
/// Smallest positive normal value of this type.
/// binary16 0_00001_0000000000, value is 2⁻¹⁴.
static constexpr type kSmallest = 0x1p-14f;
/// Smallest positive subnormal value of this type.
/// binary16 0_00000_0000000001, value is 2⁻¹⁴ * 2⁻¹⁰ = 2⁻²⁴.
static constexpr type kSmallestSubnormal = 0x1p-24f;
/// Constructor. The value is zero-initialized.
Number() = default;
/// Constructor.
/// @param v the value to initialize this Number to
template <typename U>
explicit Number(U v) : value(Quantize(static_cast<type>(v))) {}
/// Constructor.
/// @param v the value to initialize this Number to
template <typename U>
explicit Number(Number<U> v) : value(Quantize(static_cast<type>(v.value))) {}
/// Conversion operator
/// @returns the value as the internal representation type of F16
operator float() const { return value; }
/// Negation operator
/// @returns the negative value of the number
Number operator-() const { return Number<detail::NumberKindF16>(-value); }
/// Assignment operator with parameter as native floating point type
/// @param v the new value
/// @returns this Number so calls can be chained
Number& operator=(type v) {
value = Quantize(v);
return *this;
}
/// Get the binary16 bit pattern in type uint16_t of this value.
/// @returns the binary16 bit pattern, in type uint16_t, of the stored quantized f16 value. If
/// the value is NaN, the returned value will be 0x7e00u. If the value is positive infinity, the
/// returned value will be 0x7c00u. If the input value is negative infinity, the returned value
/// will be 0xfc00u.
uint16_t BitsRepresentation() const;
/// @param value the input float32 value
/// @returns the float32 value quantized to the smaller float16 value, through truncation of the
/// mantissa bits (no rounding). If the float32 value is too large (positive or negative) to be
/// represented by a float16 value, then the returned value will be positive or negative
/// infinity.
static type Quantize(type value);
/// The number value, stored as float
type value = {};
};
/// `AInt` is a type alias to `Number<int64_t>`.
using AInt = Number<int64_t>;
/// `AFloat` is a type alias to `Number<double>`.
using AFloat = Number<double>;
/// `i32` is a type alias to `Number<int32_t>`.
using i32 = Number<int32_t>;
/// `u32` is a type alias to `Number<uint32_t>`.
using u32 = Number<uint32_t>;
/// `f32` is a type alias to `Number<float>`
using f32 = Number<float>;
/// `f16` is a type alias to `Number<detail::NumberKindF16>`, which should be IEEE 754 binary16.
/// However since C++ don't have native binary16 type, the value is stored as float.
using f16 = Number<detail::NumberKindF16>;
/// Enumerator of failure reasons when converting from one number to another.
enum class ConversionFailure {
kExceedsPositiveLimit, // The value was too big (+'ve) to fit in the target type
kExceedsNegativeLimit, // The value was too big (-'ve) to fit in the target type
};
/// Writes the conversion failure message to the ostream.
/// @param out the std::ostream to write to
/// @param failure the ConversionFailure
/// @return the std::ostream so calls can be chained
std::ostream& operator<<(std::ostream& out, ConversionFailure failure);
/// Converts a number from one type to another, checking that the value fits in the target type.
/// @returns the resulting value of the conversion, or a failure reason.
template <typename TO, typename FROM>
utils::Result<TO, ConversionFailure> CheckedConvert(Number<FROM> num) {
// Use the highest-precision integer or floating-point type to perform the comparisons.
using T = std::conditional_t<IsFloatingPoint<UnwrapNumber<TO>> || IsFloatingPoint<FROM>,
AFloat::type, AInt::type>;
const auto value = static_cast<T>(num.value);
if (value > static_cast<T>(TO::kHighest)) {
return ConversionFailure::kExceedsPositiveLimit;
}
if (value < static_cast<T>(TO::kLowest)) {
return ConversionFailure::kExceedsNegativeLimit;
}
return TO(value); // Success
}
/// Equality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly equal. Also considers sign bit.
template <typename A, typename B>
bool operator==(Number<A> a, Number<B> b) {
// Use the highest-precision integer or floating-point type to perform the comparisons.
using T =
std::conditional_t<IsFloatingPoint<A> || IsFloatingPoint<B>, AFloat::type, AInt::type>;
auto va = static_cast<T>(a.value);
auto vb = static_cast<T>(b.value);
if constexpr (IsFloatingPoint<T>) {
if (std::signbit(va) != std::signbit(vb)) {
return false;
}
}
return std::equal_to<T>()(va, vb);
}
/// Inequality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly unequal. Also considers sign bit.
template <typename A, typename B>
bool operator!=(Number<A> a, Number<B> b) {
return !(a == b);
}
/// Equality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly equal.
template <typename A, typename B>
std::enable_if_t<IsNumeric<B>, bool> operator==(Number<A> a, B b) {
return a == Number<B>(b);
}
/// Inequality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly unequal.
template <typename A, typename B>
std::enable_if_t<IsNumeric<B>, bool> operator!=(Number<A> a, B b) {
return !(a == b);
}
/// Equality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly equal.
template <typename A, typename B>
std::enable_if_t<IsNumeric<A>, bool> operator==(A a, Number<B> b) {
return Number<A>(a) == b;
}
/// Inequality operator.
/// @param a the LHS number
/// @param b the RHS number
/// @returns true if the numbers `a` and `b` are exactly unequal.
template <typename A, typename B>
std::enable_if_t<IsNumeric<A>, bool> operator!=(A a, Number<B> b) {
return !(a == b);
}
/// Define 'TINT_HAS_OVERFLOW_BUILTINS' if the compiler provide overflow checking builtins.
/// If the compiler does not support these builtins, then these are emulated with algorithms
/// described in:
/// https://wiki.sei.cmu.edu/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow
#if defined(__GNUC__) && __GNUC__ >= 5
#define TINT_HAS_OVERFLOW_BUILTINS
#elif defined(__clang__)
#if __has_builtin(__builtin_add_overflow) && __has_builtin(__builtin_mul_overflow)
#define TINT_HAS_OVERFLOW_BUILTINS
#endif
#endif
/// @returns a + b, or an empty optional if the resulting value overflowed the AInt
inline std::optional<AInt> CheckedAdd(AInt a, AInt b) {
int64_t result;
#ifdef TINT_HAS_OVERFLOW_BUILTINS
if (__builtin_add_overflow(a.value, b.value, &result)) {
return {};
}
#else // TINT_HAS_OVERFLOW_BUILTINS
if (a.value >= 0) {
if (AInt::kHighest - a.value < b.value) {
return {};
}
} else {
if (b.value < AInt::kLowest - a.value) {
return {};
}
}
result = a.value + b.value;
#endif // TINT_HAS_OVERFLOW_BUILTINS
return AInt(result);
}
/// @returns a * b, or an empty optional if the resulting value overflowed the AInt
inline std::optional<AInt> CheckedMul(AInt a, AInt b) {
int64_t result;
#ifdef TINT_HAS_OVERFLOW_BUILTINS
if (__builtin_mul_overflow(a.value, b.value, &result)) {
return {};
}
#else // TINT_HAS_OVERFLOW_BUILTINS
if (a > 0) {
if (b > 0) {
if (a > (AInt::kHighest / b)) {
return {};
}
} else {
if (b < (AInt::kLowest / a)) {
return {};
}
}
} else {
if (b > 0) {
if (a < (AInt::kLowest / b)) {
return {};
}
} else {
if ((a != 0) && (b < (AInt::kHighest / a))) {
return {};
}
}
}
result = a.value * b.value;
#endif // TINT_HAS_OVERFLOW_BUILTINS
return AInt(result);
}
/// @returns a * b + c, or an empty optional if the value overflowed the AInt
inline std::optional<AInt> CheckedMadd(AInt a, AInt b, AInt c) {
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635
TINT_BEGIN_DISABLE_WARNING(MAYBE_UNINITIALIZED);
if (auto mul = CheckedMul(a, b)) {
return CheckedAdd(mul.value(), c);
}
return {};
TINT_END_DISABLE_WARNING(MAYBE_UNINITIALIZED);
}
} // namespace tint
namespace tint::number_suffixes {
/// Literal suffix for abstract integer literals
inline AInt operator""_a(unsigned long long int value) { // NOLINT
return AInt(static_cast<int64_t>(value));
}
/// Literal suffix for abstract float literals
inline AFloat operator""_a(long double value) { // NOLINT
return AFloat(static_cast<double>(value));
}
/// Literal suffix for i32 literals
inline i32 operator""_i(unsigned long long int value) { // NOLINT
return i32(static_cast<int32_t>(value));
}
/// Literal suffix for u32 literals
inline u32 operator""_u(unsigned long long int value) { // NOLINT
return u32(static_cast<uint32_t>(value));
}
/// Literal suffix for f32 literals
inline f32 operator""_f(long double value) { // NOLINT
return f32(static_cast<double>(value));
}
/// Literal suffix for f32 literals
inline f32 operator""_f(unsigned long long int value) { // NOLINT
return f32(static_cast<double>(value));
}
/// Literal suffix for f16 literals
inline f16 operator""_h(long double value) { // NOLINT
return f16(static_cast<double>(value));
}
/// Literal suffix for f16 literals
inline f16 operator""_h(unsigned long long int value) { // NOLINT
return f16(static_cast<double>(value));
}
} // namespace tint::number_suffixes
#endif // SRC_TINT_NUMBER_H_