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Commit 5c09b6a7 by Nicolas Capens Committed by Nicolas Capens
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Implement faster E5B9G9R9 conversion

We can avoid calling transcendental functions by manipulating the IEEE-754 representation of the single-precision floating point values. This implementation produces results identical to the reference code. Bug: b/138944025 Change-Id: I95faf7e80d0604be115dd1b8dfec72f3b8ece841 Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34748 Presubmit-Ready: Nicolas Capens <nicolascapens@google.com> Kokoro-Presubmit: kokoro <noreply+kokoro@google.com> Tested-by: 's avatarNicolas Capens <nicolascapens@google.com> Reviewed-by: 's avatarBen Clayton <bclayton@google.com>
parent 02cbe8ec
Showing with 388 additions and 14 deletions
CMakeLists.txt
......@@ -2127,6 +2127,32 @@ if(BUILD_TESTS)
endif()
endif()
if(BUILD_TESTS)
set(MATH_UNITTESTS_LIST
${CMAKE_CURRENT_SOURCE_DIR}/tests/MathUnitTests/main.cpp
${CMAKE_CURRENT_SOURCE_DIR}/tests/MathUnitTests/unittests.cpp
${CMAKE_CURRENT_SOURCE_DIR}/third_party/googletest/googletest/src/gtest-all.cc
)
set(MATH_UNITTESTS_INCLUDE_DIR
${CMAKE_CURRENT_SOURCE_DIR}/third_party/googletest/googletest/include/
${CMAKE_CURRENT_SOURCE_DIR}/third_party/googletest/googlemock/include/
${CMAKE_CURRENT_SOURCE_DIR}/third_party/googletest/googletest/
${CMAKE_CURRENT_SOURCE_DIR}/src/
)
add_executable(math-unittests ${MATH_UNITTESTS_LIST})
set_target_properties(math-unittests PROPERTIES
INCLUDE_DIRECTORIES "${MATH_UNITTESTS_INCLUDE_DIR}"
FOLDER "Tests"
COMPILE_OPTIONS "${SWIFTSHADER_COMPILE_OPTIONS}"
)
if(NOT WIN32)
target_link_libraries(math-unittests pthread)
endif()
endif()
if(BUILD_TESTS AND BUILD_VULKAN)
set(VK_UNITTESTS_LIST
${CMAKE_CURRENT_SOURCE_DIR}/tests/VulkanUnitTests/Device.cpp
......
SwiftShader.sln
......@@ -120,6 +120,8 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "spv-tools-spv-amd-sevp", "b
EndProject
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "spv-tools-spv-amd-stm", "build\Visual Studio 15 2017 Win64\third_party\SPIRV-Tools\source\spv-tools-spv-amd-stm.vcxproj", "{9E8623BF-3469-3104-9674-DED25861C7CF}"
EndProject
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "MathUnitTests", "tests\MathUnitTests\MathUnitTests.vcxproj", "{B4FDF21A-D945-40B2-B459-2A8707879980}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|x64 = Debug|x64
......@@ -518,6 +520,18 @@ Global
{9E8623BF-3469-3104-9674-DED25861C7CF}.Release|x64.ActiveCfg = Release|x64
{9E8623BF-3469-3104-9674-DED25861C7CF}.Release|x64.Build.0 = Release|x64
{9E8623BF-3469-3104-9674-DED25861C7CF}.Release|x86.ActiveCfg = Release|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Debug|x64.ActiveCfg = Debug|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Debug|x64.Build.0 = Debug|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Debug|x86.ActiveCfg = Debug|Win32
{B4FDF21A-D945-40B2-B459-2A8707879980}.Debug|x86.Build.0 = Debug|Win32
{B4FDF21A-D945-40B2-B459-2A8707879980}.Profile|x64.ActiveCfg = Release|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Profile|x64.Build.0 = Release|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Profile|x86.ActiveCfg = Release|Win32
{B4FDF21A-D945-40B2-B459-2A8707879980}.Profile|x86.Build.0 = Release|Win32
{B4FDF21A-D945-40B2-B459-2A8707879980}.Release|x64.ActiveCfg = Release|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Release|x64.Build.0 = Release|x64
{B4FDF21A-D945-40B2-B459-2A8707879980}.Release|x86.ActiveCfg = Release|Win32
{B4FDF21A-D945-40B2-B459-2A8707879980}.Release|x86.Build.0 = Release|Win32
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
......@@ -552,6 +566,7 @@ Global
{1262CB67-3BC7-35D5-9036-3D3B3A9DC3CE} = {ABF69E39-C15E-4DAC-A27E-3480DE2C0CF0}
{32C0DDEA-EC24-3465-B0F9-9DA187D45ED3} = {ABF69E39-C15E-4DAC-A27E-3480DE2C0CF0}
{9E8623BF-3469-3104-9674-DED25861C7CF} = {ABF69E39-C15E-4DAC-A27E-3480DE2C0CF0}
{B4FDF21A-D945-40B2-B459-2A8707879980} = {ED25C308-5BDB-43A7-BED6-C2C059FC2D7D}
EndGlobalSection
GlobalSection(ExtensibilityGlobals) = postSolution
SolutionGuid = {4DF423D2-8425-48A7-9CEC-835C4C3CA957}
......
src/System/Half.hpp
......@@ -15,6 +15,8 @@
#ifndef sw_Half_hpp
#define sw_Half_hpp
#include "Math.hpp"
#include <algorithm>
#include <cmath>
......@@ -56,8 +58,14 @@ namespace sw
unsigned int E : 5;
public:
RGB9E5(float rgb[3])
RGB9E5(float rgb[3]) : RGB9E5(rgb[0], rgb[1], rgb[2])
{
}
RGB9E5(float r, float g, float b)
{
// Vulkan 1.1.117 section 15.2.1 RGB to Shared Exponent Conversion
// B is the exponent bias (15)
constexpr int g_sharedexp_bias = 15;
......@@ -72,19 +80,33 @@ namespace sw
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(log2(max_c))) + 1 + g_sharedexp_bias;
const int max_s = static_cast<int>(floor((max_c / exp2(exp_p - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
const int exp_s = static_cast<int>((max_s < exp2(g_sharedexp_mantissabits)) ? exp_p : exp_p + 1);
R = static_cast<unsigned int>(floor((red_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
G = static_cast<unsigned int>(floor((green_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
B = static_cast<unsigned int>(floor((blue_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
E = exp_s;
// Clamp components to valid range.
const float red_c = std::max<float>(0, std::min(g_sharedexp_max, r));
const float green_c = std::max<float>(0, std::min(g_sharedexp_max, g));
const float blue_c = std::max<float>(0, std::min(g_sharedexp_max, b));
// We're reducing the mantissa to 9 bits, so we must round up if the next
// bit is 1. In other words add 0.5 to the new mantissa's position and
// allow overflow into the exponent so we can scale correctly.
constexpr int half = 1 << (23 - g_sharedexp_mantissabits);
const float red_r = bit_cast<float>(bit_cast<int>(red_c) + half);
const float green_r = bit_cast<float>(bit_cast<int>(green_c) + half);
const float blue_r = bit_cast<float>(bit_cast<int>(blue_c) + half);
// The largest component determines the shared exponent. It can't be lower
// than 0 (after bias subtraction) so also limit to the mimimum representable.
constexpr float min_s = 0.5f / (1 << g_sharedexp_bias);
float max_s = std::max(std::max(red_r, green_r), std::max(blue_r, min_s));
// Obtain the reciprocal of the shared exponent by inverting the bits,
// and scale by the new mantissa's size. Note that the IEEE-754 single-precision
// format has an implicit leading 1, but this shared component format does not.
float scale = bit_cast<float>((bit_cast<int>(max_s) & 0x7F800000) ^ 0x7F800000) * (1 << (g_sharedexp_mantissabits - 2));
R = static_cast<unsigned int>(round(red_c * scale));
G = static_cast<unsigned int>(round(green_c * scale));
B = static_cast<unsigned int>(round(blue_c * scale));
E = (bit_cast<unsigned int>(max_s) >> 23) - 127 + 15 + 1;
}
operator unsigned int() const
......
tests/MathUnitTests/MathUnitTests.vcxproj 0 → 100644
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<VCProjectVersion>15.0</VCProjectVersion>
<ProjectGuid>{B4FDF21A-D945-40B2-B459-2A8707879980}</ProjectGuid>
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tests/MathUnitTests/MathUnitTests.vcxproj.filters 0 → 100644
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tests/MathUnitTests/main.cpp 0 → 100644
// Copyright 2017 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.
#include "gtest/gtest.h"
int main(int argc, char **argv)
{
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
tests/MathUnitTests/unittests.cpp 0 → 100644
// Copyright 2019 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.
#include "System/Half.hpp"
#include <gtest/gtest.h>
#include <gmock/gmock.h>
#include <cstdlib>
using namespace sw;
unsigned int RGB9E5_reference(float r, float g, float b)
{
// Vulkan 1.1.117 section 15.2.1 RGB to Shared Exponent Conversion
// 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, r));
const float green_c = std::max<float>(0, std::min(g_sharedexp_max, g));
const float blue_c = std::max<float>(0, std::min(g_sharedexp_max, b));
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(log2(max_c))) + 1 + g_sharedexp_bias;
const int max_s = static_cast<int>(floor((max_c / exp2(exp_p - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
const int exp_s = static_cast<int>((max_s < exp2(g_sharedexp_mantissabits)) ? exp_p : exp_p + 1);
unsigned int R = static_cast<unsigned int>(floor((red_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
unsigned int G = static_cast<unsigned int>(floor((green_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
unsigned int B = static_cast<unsigned int>(floor((blue_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f));
unsigned int E = exp_s;
return (E << 27) | (B << 18) | (G << 9) | R;
}
TEST(MathTest, SharedExponentSparse)
{
for(uint64_t i = 0; i < 0x0000000100000000; i += 0x400)
{
float f = bit_cast<float>(i);
unsigned int ref = RGB9E5_reference(f, 0.0f, 0.0f);
unsigned int val = RGB9E5(f, 0.0f, 0.0f);
EXPECT_EQ(ref, val);
}
}
TEST(MathTest, SharedExponentRandom)
{
srand(0);
unsigned int x = 0;
unsigned int y = 0;
unsigned int z = 0;
for(int i = 0; i < 10000000; i++)
{
float r = bit_cast<float>(x);
float g = bit_cast<float>(y);
float b = bit_cast<float>(z);
unsigned int ref = RGB9E5_reference(r, g, b);
unsigned int val = RGB9E5(r, g, b);
EXPECT_EQ(ref, val);
x += rand();
y += rand();
z += rand();
}
}
TEST(MathTest, SharedExponentExhaustive)
{
for(uint64_t i = 0; i < 0x0000000100000000; i += 1)
{
float f = bit_cast<float>(i);
unsigned int ref = RGB9E5_reference(f, 0.0f, 0.0f);
unsigned int val = RGB9E5(f, 0.0f, 0.0f);
EXPECT_EQ(ref, val);
}
}
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