kc3-lang/angle/src/compiler/translator/BuiltInFunctionEmulatorGLSL.cpp

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• Author : Olli Etuaho
  Date : 2016-12-09 17:32:29
  Hash : da9fb093
  Message : Work around atan(y, x) bug on NVIDIA atan(y, x) is not always returning expected results on NVIDIA OpenGL drivers between versions 367 and 375. Work around this by emulating atan(y, x) using the regular atan(x) function. A fix to the driver is expected in a future release. It is most convenient to implement the vector atan(y, x) functions by using the scalar atan(y, x) function. Support for simple dependencies between emulated functions is added to BuiltInFunctionEmulator. In the current implementation one function is allowed to have at most one other function as its dependency. BUG=chromium:672380 TEST=angle_end2end_tests Change-Id: I9eba8b0b7979c7c7eaed353b264932e41830beb1 Reviewed-on: https://chromium-review.googlesource.com/419016 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>

• src/compiler/translator/BuiltInFunctionEmulatorGLSL.cpp

• //
  // Copyright (c) 2002-2011 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.
  //
  
  #include "angle_gl.h"
  #include "compiler/translator/BuiltInFunctionEmulator.h"
  #include "compiler/translator/BuiltInFunctionEmulatorGLSL.h"
  #include "compiler/translator/Cache.h"
  #include "compiler/translator/SymbolTable.h"
  #include "compiler/translator/VersionGLSL.h"
  
  namespace sh
  {
  
  void InitBuiltInAbsFunctionEmulatorForGLSLWorkarounds(BuiltInFunctionEmulator *emu,
                                                        sh::GLenum shaderType)
  {
      if (shaderType == GL_VERTEX_SHADER)
      {
          const TType *int1 = TCache::getType(EbtInt);
          emu->addEmulatedFunction(EOpAbs, int1, "int webgl_abs_emu(int x) { return x * sign(x); }");
      }
  }
  
  void InitBuiltInIsnanFunctionEmulatorForGLSLWorkarounds(BuiltInFunctionEmulator *emu,
                                                          int targetGLSLVersion)
  {
      // isnan() is supported since GLSL 1.3.
      if (targetGLSLVersion < GLSL_VERSION_130)
          return;
  
      const TType *float1 = TCache::getType(EbtFloat);
      const TType *float2 = TCache::getType(EbtFloat, 2);
      const TType *float3 = TCache::getType(EbtFloat, 3);
      const TType *float4 = TCache::getType(EbtFloat, 4);
  
      // !(x > 0.0 || x < 0.0 || x == 0.0) will be optimized and always equal to false.
      emu->addEmulatedFunction(
          EOpIsNan, float1,
          "bool webgl_isnan_emu(float x) { return (x > 0.0 || x < 0.0) ? false : x != 0.0; }");
      emu->addEmulatedFunction(
          EOpIsNan, float2,
          "bvec2 webgl_isnan_emu(vec2 x)\n"
          "{\n"
          "    bvec2 isnan;\n"
          "    for (int i = 0; i < 2; i++)\n"
          "    {\n"
          "        isnan[i] = (x[i] > 0.0 || x[i] < 0.0) ? false : x[i] != 0.0;\n"
          "    }\n"
          "    return isnan;\n"
          "}\n");
      emu->addEmulatedFunction(
          EOpIsNan, float3,
          "bvec3 webgl_isnan_emu(vec3 x)\n"
          "{\n"
          "    bvec3 isnan;\n"
          "    for (int i = 0; i < 3; i++)\n"
          "    {\n"
          "        isnan[i] = (x[i] > 0.0 || x[i] < 0.0) ? false : x[i] != 0.0;\n"
          "    }\n"
          "    return isnan;\n"
          "}\n");
      emu->addEmulatedFunction(
          EOpIsNan, float4,
          "bvec4 webgl_isnan_emu(vec4 x)\n"
          "{\n"
          "    bvec4 isnan;\n"
          "    for (int i = 0; i < 4; i++)\n"
          "    {\n"
          "        isnan[i] = (x[i] > 0.0 || x[i] < 0.0) ? false : x[i] != 0.0;\n"
          "    }\n"
          "    return isnan;\n"
          "}\n");
  }
  
  void InitBuiltInAtanFunctionEmulatorForGLSLWorkarounds(BuiltInFunctionEmulator *emu)
  {
      const TType *float1 = TCache::getType(EbtFloat);
      auto floatFuncId    = emu->addEmulatedFunction(
          EOpAtan, float1, float1,
          "webgl_emu_precision float webgl_atan_emu(webgl_emu_precision float y, webgl_emu_precision "
          "float x)\n"
          "{\n"
          "    if (x > 0.0) return atan(y / x);\n"
          "    else if (x < 0.0 && y >= 0.0) return atan(y / x) + 3.14159265;\n"
          "    else if (x < 0.0 && y < 0.0) return atan(y / x) - 3.14159265;\n"
          "    else return 1.57079632 * sign(y);\n"
          "}\n");
      for (int dim = 2; dim <= 4; ++dim)
      {
          const TType *floatVec = TCache::getType(EbtFloat, static_cast<unsigned char>(dim));
          std::stringstream ss;
          ss << "webgl_emu_precision vec" << dim << " webgl_atan_emu(webgl_emu_precision vec" << dim
             << " y, webgl_emu_precision vec" << dim << " x)\n"
                                                        "{\n"
                                                        "    return vec"
             << dim << "(";
          for (int i = 0; i < dim; ++i)
          {
              ss << "webgl_atan_emu(y[" << i << "], x[" << i << "])";
              if (i < dim - 1)
              {
                  ss << ", ";
              }
          }
          ss << ");\n"
                "}\n";
          emu->addEmulatedFunctionWithDependency(floatFuncId, EOpAtan, floatVec, floatVec,
                                                 ss.str().c_str());
      }
  }
  
  // Emulate built-in functions missing from GLSL 1.30 and higher
  void InitBuiltInFunctionEmulatorForGLSLMissingFunctions(BuiltInFunctionEmulator *emu,
                                                          sh::GLenum shaderType,
                                                          int targetGLSLVersion)
  {
      // Emulate packUnorm2x16 and unpackUnorm2x16 (GLSL 4.10)
      if (targetGLSLVersion < GLSL_VERSION_410)
      {
          const TType *float2 = TCache::getType(EbtFloat, 2);
          const TType *uint1  = TCache::getType(EbtUInt);
  
          // clang-format off
          emu->addEmulatedFunction(EOpPackUnorm2x16, float2,
              "uint webgl_packUnorm2x16_emu(vec2 v)\n"
              "{\n"
              "    int x = int(round(clamp(v.x, 0.0, 1.0) * 65535.0));\n"
              "    int y = int(round(clamp(v.y, 0.0, 1.0) * 65535.0));\n"
              "    return uint((y << 16) | (x & 0xFFFF));\n"
              "}\n");
  
          emu->addEmulatedFunction(EOpUnpackUnorm2x16, uint1,
              "vec2 webgl_unpackUnorm2x16_emu(uint u)\n"
              "{\n"
              "    float x = float(u & 0xFFFFu) / 65535.0;\n"
              "    float y = float(u >> 16) / 65535.0;\n"
              "    return vec2(x, y);\n"
              "}\n");
          // clang-format on
      }
  
      // Emulate packSnorm2x16, packHalf2x16, unpackSnorm2x16, and unpackHalf2x16 (GLSL 4.20)
      // by using floatBitsToInt, floatBitsToUint, intBitsToFloat, and uintBitsToFloat (GLSL 3.30).
      if (targetGLSLVersion >= GLSL_VERSION_330 && targetGLSLVersion < GLSL_VERSION_420)
      {
          const TType *float2 = TCache::getType(EbtFloat, 2);
          const TType *uint1  = TCache::getType(EbtUInt);
  
          // clang-format off
          emu->addEmulatedFunction(EOpPackSnorm2x16, float2,
              "uint webgl_packSnorm2x16_emu(vec2 v)\n"
              "{\n"
              "    #if defined(GL_ARB_shading_language_packing)\n"
              "        return packSnorm2x16(v);\n"
              "    #else\n"
              "        int x = int(round(clamp(v.x, -1.0, 1.0) * 32767.0));\n"
              "        int y = int(round(clamp(v.y, -1.0, 1.0) * 32767.0));\n"
              "        return uint((y << 16) | (x & 0xFFFF));\n"
              "    #endif\n"
              "}\n");
          emu->addEmulatedFunction(EOpUnpackSnorm2x16, uint1,
              "#if !defined(GL_ARB_shading_language_packing)\n"
              "    float webgl_fromSnorm(uint x)\n"
              "    {\n"
              "        int xi = (int(x) & 0x7FFF) - (int(x) & 0x8000);\n"
              "        return clamp(float(xi) / 32767.0, -1.0, 1.0);\n"
              "    }\n"
              "#endif\n"
              "\n"
              "vec2 webgl_unpackSnorm2x16_emu(uint u)\n"
              "{\n"
              "    #if defined(GL_ARB_shading_language_packing)\n"
              "        return unpackSnorm2x16(u);\n"
              "    #else\n"
              "        uint y = (u >> 16);\n"
              "        uint x = u;\n"
              "        return vec2(webgl_fromSnorm(x), webgl_fromSnorm(y));\n"
              "    #endif\n"
              "}\n");
          // Functions uint webgl_f32tof16(float val) and float webgl_f16tof32(uint val) are
          // based on the OpenGL redbook Appendix Session "Floating-Point Formats Used in OpenGL".
          emu->addEmulatedFunction(EOpPackHalf2x16, float2,
              "#if !defined(GL_ARB_shading_language_packing)\n"
              "    uint webgl_f32tof16(float val)\n"
              "    {\n"
              "        uint f32 = floatBitsToUint(val);\n"
              "        uint f16 = 0u;\n"
              "        uint sign = (f32 >> 16) & 0x8000u;\n"
              "        int exponent = int((f32 >> 23) & 0xFFu) - 127;\n"
              "        uint mantissa = f32 & 0x007FFFFFu;\n"
              "        if (exponent == 128)\n"
              "        {\n"
              "            // Infinity or NaN\n"
              "            // NaN bits that are masked out by 0x3FF get discarded.\n"
              "            // This can turn some NaNs to infinity, but this is allowed by the spec.\n"
              "            f16 = sign | (0x1Fu << 10);\n"
              "            f16 |= (mantissa & 0x3FFu);\n"
              "        }\n"
              "        else if (exponent > 15)\n"
              "        {\n"
              "            // Overflow - flush to Infinity\n"
              "            f16 = sign | (0x1Fu << 10);\n"
              "        }\n"
              "        else if (exponent > -15)\n"
              "        {\n"
              "            // Representable value\n"
              "            exponent += 15;\n"
              "            mantissa >>= 13;\n"
              "            f16 = sign | uint(exponent << 10) | mantissa;\n"
              "        }\n"
              "        else\n"
              "        {\n"
              "            f16 = sign;\n"
              "        }\n"
              "        return f16;\n"
              "    }\n"
              "#endif\n"
              "\n"
              "uint webgl_packHalf2x16_emu(vec2 v)\n"
              "{\n"
              "    #if defined(GL_ARB_shading_language_packing)\n"
              "        return packHalf2x16(v);\n"
              "    #else\n"
              "        uint x = webgl_f32tof16(v.x);\n"
              "        uint y = webgl_f32tof16(v.y);\n"
              "        return (y << 16) | x;\n"
              "    #endif\n"
              "}\n");
          emu->addEmulatedFunction(EOpUnpackHalf2x16, uint1,
              "#if !defined(GL_ARB_shading_language_packing)\n"
              "    float webgl_f16tof32(uint val)\n"
              "    {\n"
              "        uint sign = (val & 0x8000u) << 16;\n"
              "        int exponent = int((val & 0x7C00u) >> 10);\n"
              "        uint mantissa = val & 0x03FFu;\n"
              "        float f32 = 0.0;\n"
              "        if(exponent == 0)\n"
              "        {\n"
              "            if (mantissa != 0u)\n"
              "            {\n"
              "                const float scale = 1.0 / (1 << 24);\n"
              "                f32 = scale * mantissa;\n"
              "            }\n"
              "        }\n"
              "        else if (exponent == 31)\n"
              "        {\n"
              "            return uintBitsToFloat(sign | 0x7F800000u | mantissa);\n"
              "        }\n"
              "        else\n"
              "        {\n"
              "            exponent -= 15;\n"
              "            float scale;\n"
              "            if(exponent < 0)\n"
              "            {\n"
              "                // The negative unary operator is buggy on OSX.\n"
              "                // Work around this by using abs instead.\n"
              "                scale = 1.0 / (1 << abs(exponent));\n"
              "            }\n"
              "            else\n"
              "            {\n"
              "                scale = 1 << exponent;\n"
              "            }\n"
              "            float decimal = 1.0 + float(mantissa) / float(1 << 10);\n"
              "            f32 = scale * decimal;\n"
              "        }\n"
              "\n"
              "        if (sign != 0u)\n"
              "        {\n"
              "            f32 = -f32;\n"
              "        }\n"
              "\n"
              "        return f32;\n"
              "    }\n"
              "#endif\n"
              "\n"
              "vec2 webgl_unpackHalf2x16_emu(uint u)\n"
              "{\n"
              "    #if defined(GL_ARB_shading_language_packing)\n"
              "        return unpackHalf2x16(u);\n"
              "    #else\n"
              "        uint y = (u >> 16);\n"
              "        uint x = u & 0xFFFFu;\n"
              "        return vec2(webgl_f16tof32(x), webgl_f16tof32(y));\n"
              "    #endif\n"
              "}\n");
          // clang-format on
      }
  }
  
  }  // namespace sh