src/dawn/common/Math.h

// Copyright 2017 The Dawn & Tint Authors
//
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// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
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//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
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#ifndef SRC_DAWN_COMMON_MATH_H_
#define SRC_DAWN_COMMON_MATH_H_

#include <cstddef>
#include <cstdint>
#include <cstring>

#include <limits>
#include <optional>
#include <type_traits>

#include "dawn/common/Assert.h"
#include "partition_alloc/pointers/raw_ptr.h"

namespace dawn {

// The following are not valid for 0
uint32_t ScanForward(uint32_t bits);
uint32_t Log2(uint32_t value);
uint32_t Log2(uint64_t value);
bool IsPowerOfTwo(uint64_t n);
uint64_t RoundUp(uint64_t n, uint64_t m);

constexpr uint32_t ConstexprLog2(uint64_t v) {
    return v <= 1 ? 0 : 1 + ConstexprLog2(v / 2);
}

constexpr uint32_t ConstexprLog2Ceil(uint64_t v) {
    return v <= 1 ? 0 : ConstexprLog2(v - 1) + 1;
}

inline uint32_t Log2Ceil(uint32_t v) {
    return v <= 1 ? 0 : Log2(v - 1) + 1;
}

inline uint32_t Log2Ceil(uint64_t v) {
    return v <= 1 ? 0 : Log2(v - 1) + 1;
}

uint64_t NextPowerOfTwo(uint64_t n);
bool IsPtrAligned(const void* ptr, size_t alignment);
void* AlignVoidPtr(void* ptr, size_t alignment);
bool IsAligned(uint32_t value, size_t alignment);

template <typename T>
T Align(T value, size_t alignment) {
    DAWN_ASSERT(value <= std::numeric_limits<T>::max() - (alignment - 1));
    DAWN_ASSERT(IsPowerOfTwo(alignment));
    DAWN_ASSERT(alignment != 0);
    T alignmentT = static_cast<T>(alignment);
    return (value + (alignmentT - 1)) & ~(alignmentT - 1);
}

template <typename T, size_t Alignment>
constexpr size_t AlignSizeof() {
    static_assert(Alignment != 0 && (Alignment & (Alignment - 1)) == 0,
                  "Alignment must be a valid power of 2.");
    static_assert(sizeof(T) <= std::numeric_limits<size_t>::max() - (Alignment - 1));
    return (sizeof(T) + (Alignment - 1)) & ~(Alignment - 1);
}

// Returns an aligned size for an n-sized array of T elements. If the size would overflow, returns
// nullopt instead.
template <typename T, size_t Alignment>
std::optional<size_t> AlignSizeofN(uint64_t n) {
    constexpr uint64_t kMaxCountWithoutOverflows =
        (std::numeric_limits<size_t>::max() - Alignment + 1) / sizeof(T);
    if (n > kMaxCountWithoutOverflows) {
        return std::nullopt;
    }
    return Align(sizeof(T) * n, Alignment);
}

template <typename T>
DAWN_FORCE_INLINE T* AlignPtr(T* ptr, size_t alignment) {
    DAWN_ASSERT(IsPowerOfTwo(alignment));
    DAWN_ASSERT(alignment != 0);
    return reinterpret_cast<T*>((reinterpret_cast<size_t>(ptr) + (alignment - 1)) &
                                ~(alignment - 1));
}

template <typename T, partition_alloc::internal::RawPtrTraits Traits>
DAWN_FORCE_INLINE T* AlignPtr(raw_ptr<T, Traits> ptr, size_t alignment) {
    return AlignPtr(ptr.get(), alignment);
}

template <typename T>
DAWN_FORCE_INLINE const T* AlignPtr(const T* ptr, size_t alignment) {
    DAWN_ASSERT(IsPowerOfTwo(alignment));
    DAWN_ASSERT(alignment != 0);
    return reinterpret_cast<const T*>((reinterpret_cast<size_t>(ptr) + (alignment - 1)) &
                                      ~(alignment - 1));
}

template <typename destType, typename sourceType>
destType BitCast(const sourceType& source) {
    static_assert(sizeof(destType) == sizeof(sourceType), "BitCast: cannot lose precision.");
    destType output;
    std::memcpy(&output, &source, sizeof(destType));
    return output;
}

uint16_t Float32ToFloat16(float fp32);
float Float16ToFloat32(uint16_t fp16);
bool IsFloat16NaN(uint16_t fp16);

template <typename T>
T FloatToUnorm(float value) {
    return static_cast<T>(value * static_cast<float>(std::numeric_limits<T>::max()));
}

float SRGBToLinear(float srgb);

template <typename T1,
          typename T2,
          typename Enable = typename std::enable_if<sizeof(T1) == sizeof(T2)>::type>
constexpr bool IsSubset(T1 subset, T2 set) {
    T2 bitsAlsoInSet = subset & set;
    return bitsAlsoInSet == subset;
}

}  // namespace dawn

#endif  // SRC_DAWN_COMMON_MATH_H_