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

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• Author : Le Quyen
  Date : 2019-10-29 22:57:55
  Hash : a5a04ac0
  Message : Metal backend pt3: shader translator Implementation of GLSL to MSL translator Bug: angleproject:2634 Change-Id: I66e2374b461548fac46163ea79790a488515e6b0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1887251 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>

• src/compiler/translator/TranslatorMetal.cpp

• //
  // Copyright (c) 2019 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.
  //
  // TranslatorMetal:
  //   A GLSL-based translator that outputs shaders that fit GL_KHR_vulkan_glsl.
  //   It takes into account some considerations for Metal backend also.
  //   The shaders are then fed into glslang to spit out SPIR-V (libANGLE-side).
  //   See: https://www.khronos.org/registry/vulkan/specs/misc/GL_KHR_vulkan_glsl.txt
  //
  //   The SPIR-V will then be translated to Metal Shading Language later in Metal backend.
  //
  
  #include "compiler/translator/TranslatorMetal.h"
  
  #include "angle_gl.h"
  #include "common/utilities.h"
  #include "compiler/translator/OutputVulkanGLSLForMetal.h"
  #include "compiler/translator/StaticType.h"
  #include "compiler/translator/tree_util/BuiltIn.h"
  #include "compiler/translator/tree_util/RunAtTheEndOfShader.h"
  #include "compiler/translator/util.h"
  
  namespace sh
  {
  
  namespace
  {
  
  // Unlike Vulkan having auto viewport flipping extension, in Metal we have to flip gl_Position.y
  // manually.
  // This operation performs flipping the gl_Position.y using this expression:
  // gl_Position.y = gl_Position.y * negViewportScaleY
  ANGLE_NO_DISCARD bool AppendVertexShaderPositionYCorrectionToMain(TCompiler *compiler,
                                                                    TIntermBlock *root,
                                                                    TSymbolTable *symbolTable,
                                                                    TIntermBinary *negViewportYScale)
  {
      // Create a symbol reference to "gl_Position"
      const TVariable *position  = BuiltInVariable::gl_Position();
      TIntermSymbol *positionRef = new TIntermSymbol(position);
  
      // Create a swizzle to "gl_Position.y"
      TVector<int> swizzleOffsetY;
      swizzleOffsetY.push_back(1);
      TIntermSwizzle *positionY = new TIntermSwizzle(positionRef, swizzleOffsetY);
  
      // Create the expression "gl_Position.y * negViewportScaleY"
      TIntermBinary *inverseY = new TIntermBinary(EOpMul, positionY->deepCopy(), negViewportYScale);
  
      // Create the assignment "gl_Position.y = gl_Position.y * negViewportScaleY
      TIntermTyped *positionYLHS = positionY->deepCopy();
      TIntermBinary *assignment  = new TIntermBinary(TOperator::EOpAssign, positionYLHS, inverseY);
  
      // Append the assignment as a statement at the end of the shader.
      return RunAtTheEndOfShader(compiler, root, assignment, symbolTable);
  }
  
  }  // anonymous namespace
  
  TranslatorMetal::TranslatorMetal(sh::GLenum type, ShShaderSpec spec) : TranslatorVulkan(type, spec)
  {}
  
  bool TranslatorMetal::translate(TIntermBlock *root,
                                  ShCompileOptions compileOptions,
                                  PerformanceDiagnostics *perfDiagnostics)
  {
      TInfoSinkBase &sink = getInfoSink().obj;
      TOutputVulkanGLSL outputGLSL(sink, getArrayIndexClampingStrategy(), getHashFunction(),
                                   getNameMap(), &getSymbolTable(), getShaderType(),
                                   getShaderVersion(), getOutputType(), compileOptions);
  
      const TVariable *driverUniforms = nullptr;
      if (!TranslatorVulkan::translateImpl(root, compileOptions, perfDiagnostics, &driverUniforms,
                                           &outputGLSL))
      {
          return false;
      }
  
      if (getShaderType() == GL_VERTEX_SHADER)
      {
          auto negViewportYScale = getDriverUniformNegViewportYScaleRef(driverUniforms);
  
          // Append gl_Position.y correction to main
          if (!AppendVertexShaderPositionYCorrectionToMain(this, root, &getSymbolTable(),
                                                           negViewportYScale))
          {
              return false;
          }
      }
  
      // Write translated shader.
      root->traverse(&outputGLSL);
  
      return true;
  }
  
  }  // namespace sh