// Copyright 2016 The SwiftShader Authors. All Rights Reserved.
//
// 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 sw_Half_hpp
#define sw_Half_hpp
#include <algorithm>
#include <cmath>
namespace sw
{
class half
{
public:
half() = default;
explicit half(float f);
operator float() const;
half &operator=(half h);
half &operator=(float f);
private:
unsigned short fp16i;
};
inline half shortAsHalf(short s)
{
union
{
half h;
short s;
} hs;
hs.s = s;
return hs.h;
}
class RGB9E5
{
unsigned int R : 9;
unsigned int G : 9;
unsigned int B : 9;
unsigned int E : 5;
public:
RGB9E5(float rgb[3])
{
// B is the exponent bias (15)
constexpr int g_sharedexp_bias = 15;
// N is the number of mantissa bits per component (9)
constexpr int g_sharedexp_mantissabits = 9;
// Emax is the maximum allowed biased exponent value (31)
constexpr int g_sharedexp_maxexponent = 31;
constexpr float g_sharedexp_max =
((static_cast<float>(1 << g_sharedexp_mantissabits) - 1) /
static_cast<float>(1 << g_sharedexp_mantissabits)) *
static_cast<float>(1 << (g_sharedexp_maxexponent - g_sharedexp_bias));
const float red_c = std::max<float>(0, std::min(g_sharedexp_max, rgb[0]));
const float green_c = std::max<float>(0, std::min(g_sharedexp_max, rgb[1]));
const float blue_c = std::max<float>(0, std::min(g_sharedexp_max, rgb[2]));
const float max_c = std::max<float>(std::max<float>(red_c, green_c), blue_c);
const float exp_p =
std::max<float>(-g_sharedexp_bias - 1, floor(log(max_c))) + 1 + g_sharedexp_bias;
const int max_s = static_cast<int>(
floor((max_c / (pow(2.0f, exp_p - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
const int exp_s =
static_cast<int>((max_s < pow(2.0f, g_sharedexp_mantissabits)) ? exp_p : exp_p + 1);
R = static_cast<unsigned int>(
floor((red_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
G = static_cast<unsigned int>(
floor((green_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
B = static_cast<unsigned int>(
floor((blue_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
E = exp_s;
}
operator unsigned int() const
{
return *reinterpret_cast<const unsigned int*>(this);
}
void toRGB16F(half rgb[3]) const
{
constexpr int offset = 24; // Exponent bias (15) + number of mantissa bits per component (9) = 24
const float factor = (1u << E) * (1.0f / (1 << offset));
rgb[0] = half(R * factor);
rgb[1] = half(G * factor);
rgb[2] = half(B * factor);
}
};
class R11G11B10F
{
unsigned int R : 11;
unsigned int G : 11;
unsigned int B : 10;
static inline half float11ToFloat16(unsigned short fp11)
{
return shortAsHalf(fp11 << 4); // Sign bit 0
}
static inline half float10ToFloat16(unsigned short fp10)
{
return shortAsHalf(fp10 << 5); // Sign bit 0
}
inline unsigned short float32ToFloat11(float fp32)
{
const unsigned int float32MantissaMask = 0x7FFFFF;
const unsigned int float32ExponentMask = 0x7F800000;
const unsigned int float32SignMask = 0x80000000;
const unsigned int float32ValueMask = ~float32SignMask;
const unsigned int float32ExponentFirstBit = 23;
const unsigned int float32ExponentBias = 127;
const unsigned short float11Max = 0x7BF;
const unsigned short float11MantissaMask = 0x3F;
const unsigned short float11ExponentMask = 0x7C0;
const unsigned short float11BitMask = 0x7FF;
const unsigned int float11ExponentBias = 14;
const unsigned int float32Maxfloat11 = 0x477E0000;
const unsigned int float32Minfloat11 = 0x38800000;
const unsigned int float32Bits = *reinterpret_cast<unsigned int*>(&fp32);
const bool float32Sign = (float32Bits & float32SignMask) == float32SignMask;
unsigned int float32Val = float32Bits & float32ValueMask;
if((float32Val & float32ExponentMask) == float32ExponentMask)
{
// INF or NAN
if((float32Val & float32MantissaMask) != 0)
{
return float11ExponentMask |
(((float32Val >> 17) | (float32Val >> 11) | (float32Val >> 6) | (float32Val)) &
float11MantissaMask);
}
else if(float32Sign)
{
// -INF is clamped to 0 since float11 is positive only
return 0;
}
else
{
return float11ExponentMask;
}
}
else if(float32Sign)
{
// float11 is positive only, so clamp to zero
return 0;
}
else if(float32Val > float32Maxfloat11)
{
// The number is too large to be represented as a float11, set to max
return float11Max;
}
else
{
if(float32Val < float32Minfloat11)
{
// The number is too small to be represented as a normalized float11
// Convert it to a denormalized value.
const unsigned int shift = (float32ExponentBias - float11ExponentBias) -
(float32Val >> float32ExponentFirstBit);
float32Val =
((1 << float32ExponentFirstBit) | (float32Val & float32MantissaMask)) >> shift;
}
else
{
// Rebias the exponent to represent the value as a normalized float11
float32Val += 0xC8000000;
}
return ((float32Val + 0xFFFF + ((float32Val >> 17) & 1)) >> 17) & float11BitMask;
}
}
inline unsigned short float32ToFloat10(float fp32)
{
const unsigned int float32MantissaMask = 0x7FFFFF;
const unsigned int float32ExponentMask = 0x7F800000;
const unsigned int float32SignMask = 0x80000000;
const unsigned int float32ValueMask = ~float32SignMask;
const unsigned int float32ExponentFirstBit = 23;
const unsigned int float32ExponentBias = 127;
const unsigned short float10Max = 0x3DF;
const unsigned short float10MantissaMask = 0x1F;
const unsigned short float10ExponentMask = 0x3E0;
const unsigned short float10BitMask = 0x3FF;
const unsigned int float10ExponentBias = 14;
const unsigned int float32Maxfloat10 = 0x477C0000;
const unsigned int float32Minfloat10 = 0x38800000;
const unsigned int float32Bits = *reinterpret_cast<unsigned int*>(&fp32);
const bool float32Sign = (float32Bits & float32SignMask) == float32SignMask;
unsigned int float32Val = float32Bits & float32ValueMask;
if((float32Val & float32ExponentMask) == float32ExponentMask)
{
// INF or NAN
if((float32Val & float32MantissaMask) != 0)
{
return float10ExponentMask |
(((float32Val >> 18) | (float32Val >> 13) | (float32Val >> 3) | (float32Val)) &
float10MantissaMask);
}
else if(float32Sign)
{
// -INF is clamped to 0 since float11 is positive only
return 0;
}
else
{
return float10ExponentMask;
}
}
else if(float32Sign)
{
// float10 is positive only, so clamp to zero
return 0;
}
else if(float32Val > float32Maxfloat10)
{
// The number is too large to be represented as a float11, set to max
return float10Max;
}
else
{
if(float32Val < float32Minfloat10)
{
// The number is too small to be represented as a normalized float11
// Convert it to a denormalized value.
const unsigned int shift = (float32ExponentBias - float10ExponentBias) -
(float32Val >> float32ExponentFirstBit);
float32Val =
((1 << float32ExponentFirstBit) | (float32Val & float32MantissaMask)) >> shift;
}
else
{
// Rebias the exponent to represent the value as a normalized float11
float32Val += 0xC8000000;
}
return ((float32Val + 0x1FFFF + ((float32Val >> 18) & 1)) >> 18) & float10BitMask;
}
}
public:
R11G11B10F(float rgb[3])
{
R = float32ToFloat11(rgb[0]);
G = float32ToFloat11(rgb[1]);
B = float32ToFloat10(rgb[2]);
}
operator unsigned int() const
{
return *reinterpret_cast<const unsigned int*>(this);
}
void toRGB16F(half rgb[3]) const
{
rgb[0] = float11ToFloat16(R);
rgb[1] = float11ToFloat16(G);
rgb[2] = float10ToFloat16(B);
}
};
}
#endif // sw_Half_hpp