kc3-lang/angle/src/common/mathutil.cpp

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• Hash : 31e36a63
  Author :
  Date : 2020-03-14T21:40:58
  

  Reland "Refactor BitCount"
  
  This is a reland of baecb7d55c692a93a29a46939029b8262174ca62
  
  Directly use NEON instructions on ARM/ARM64 on MSVC.
  
  Original change's description:
  > Refactor BitCount
  >
  > POPCNT intrinsics cannot be used without hardware support, so a CPUID
  > check and polyfills are required for some CPUs when using MSVC to
  > avoid runtime failure.
  >
  > Other changes include:
  > - Clang: use builtins on all platforms to provide exact intent to the
  > compiler;
  > - MSVC on ARM: use dedicated intrinsics;
  > - x86/x64 fallback is now branchless and works in constant time.
  >
  > Bug: angleproject:4462
  > Change-Id: I00fcabda1c842677d8cb4bfd280d932d0d10c0a5
  > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2102811
  > Reviewed-by: Jamie Madill <jmadill@chromium.org>
  > Reviewed-by: Geoff Lang <geofflang@chromium.org>
  > Commit-Queue: Geoff Lang <geofflang@chromium.org>
  
  Bug: angleproject:4462
  Change-Id: Ia58ae00fa4230f77d981d4ba393fa3481806c5b0
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2113570
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Commit-Queue: Jamie Madill <jmadill@chromium.org>
  

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• src/common/mathutil.cpp

• //
  // Copyright 2013 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  
  // mathutil.cpp: Math and bit manipulation functions.
  
  #include "common/mathutil.h"
  
  #include <math.h>
  #include <algorithm>
  
  namespace gl
  {
  
  namespace
  {
  
  struct RGB9E5Data
  {
      unsigned int R : 9;
      unsigned int G : 9;
      unsigned int B : 9;
      unsigned int E : 5;
  };
  
  // 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));
  
  }  // anonymous namespace
  
  unsigned int convertRGBFloatsTo999E5(float red, float green, float blue)
  {
      const float red_c   = std::max<float>(0, std::min(g_sharedexp_max, red));
      const float green_c = std::max<float>(0, std::min(g_sharedexp_max, green));
      const float blue_c  = std::max<float>(0, std::min(g_sharedexp_max, blue));
  
      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);
  
      RGB9E5Data output;
      output.R = static_cast<unsigned int>(
          floor((red_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
      output.G = static_cast<unsigned int>(
          floor((green_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
      output.B = static_cast<unsigned int>(
          floor((blue_c / (pow(2.0f, exp_s - g_sharedexp_bias - g_sharedexp_mantissabits))) + 0.5f));
      output.E = exp_s;
  
      return bitCast<unsigned int>(output);
  }
  
  void convert999E5toRGBFloats(unsigned int input, float *red, float *green, float *blue)
  {
      const RGB9E5Data *inputData = reinterpret_cast<const RGB9E5Data *>(&input);
  
      *red =
          inputData->R * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
      *green =
          inputData->G * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
      *blue =
          inputData->B * pow(2.0f, (int)inputData->E - g_sharedexp_bias - g_sharedexp_mantissabits);
  }
  
  }  // namespace gl
  

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