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

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• Hash : 3c9eeb97
  Author :
  Date : 2013-11-04T11:09:26
  

  Disable optimizations for shaders with conditional discard in D3D9, and
  only use expanded short-circuiting conditionals for expressions with
  potential side-effects.
  
  Conservatively assume aggreate and selection operators have side effects for now.
  
  BUG=
  ANGLEBUG=486
  R=geofflang@chromium.org, kbr@chromium.org, nicolas@transgaming.com, shannonwoods@chromium.org
  
  Review URL: https://codereview.appspot.com/14441075
  
  Conflicts:
  	src/common/version.h
  	src/compiler/translator.vcxproj
  	src/compiler/translator.vcxproj.filters
  	src/compiler/translator/OutputHLSL.cpp
  	src/libGLESv2/ProgramBinary.cpp
  	src/libGLESv2/Shader.cpp
  	src/libGLESv2/Shader.h
  
  Change-Id: Iaf9f10b5de7b33c927ef032f3c4fe9d5095f64dd
  

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• src/compiler/translator/UnfoldShortCircuit.cpp

• //
  // Copyright (c) 2002-2013 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.
  //
  // UnfoldShortCircuit is an AST traverser to output short-circuiting operators as if-else statements.
  // The results are assigned to s# temporaries, which are used by the main translator instead of
  // the original expression.
  //
  
  #include "compiler/translator/UnfoldShortCircuit.h"
  
  #include "compiler/translator/InfoSink.h"
  #include "compiler/translator/OutputHLSL.h"
  
  namespace sh
  {
  UnfoldShortCircuit::UnfoldShortCircuit(TParseContext &context, OutputHLSL *outputHLSL) : mContext(context), mOutputHLSL(outputHLSL)
  {
      mTemporaryIndex = 0;
  }
  
  void UnfoldShortCircuit::traverse(TIntermNode *node)
  {
      int rewindIndex = mTemporaryIndex;
      node->traverse(this);
      mTemporaryIndex = rewindIndex;
  }
  
  bool UnfoldShortCircuit::visitBinary(Visit visit, TIntermBinary *node)
  {
      TInfoSinkBase &out = mOutputHLSL->getBodyStream();
  
      // If our right node doesn't have side effects, we know we don't need to unfold this
      // expression: there will be no short-circuiting side effects to avoid
      // (note: unfolding doesn't depend on the left node -- it will always be evaluated)
      if (!node->getRight()->hasSideEffects())
      {
          return true;
      }
  
      switch (node->getOp())
      {
        case EOpLogicalOr:
          // "x || y" is equivalent to "x ? true : y", which unfolds to "bool s; if(x) s = true; else s = y;",
          // and then further simplifies down to "bool s = x; if(!s) s = y;".
          {
              int i = mTemporaryIndex;
  
              out << "bool s" << i << ";\n";
  
              out << "{\n";
  
              mTemporaryIndex = i + 1;
              node->getLeft()->traverse(this);
              out << "s" << i << " = ";
              mTemporaryIndex = i + 1;
              node->getLeft()->traverse(mOutputHLSL);
              out << ";\n";
              out << "if (!s" << i << ")\n"
                     "{\n";
              mTemporaryIndex = i + 1;
              node->getRight()->traverse(this);
              out << "    s" << i << " = ";
              mTemporaryIndex = i + 1;
              node->getRight()->traverse(mOutputHLSL);
              out << ";\n"
                     "}\n";
  
              out << "}\n";
  
              mTemporaryIndex = i + 1;
          }
          return false;
        case EOpLogicalAnd:
          // "x && y" is equivalent to "x ? y : false", which unfolds to "bool s; if(x) s = y; else s = false;",
          // and then further simplifies down to "bool s = x; if(s) s = y;".
          {
              int i = mTemporaryIndex;
  
              out << "bool s" << i << ";\n";
  
              out << "{\n";
  
              mTemporaryIndex = i + 1;
              node->getLeft()->traverse(this);
              out << "s" << i << " = ";
              mTemporaryIndex = i + 1;
              node->getLeft()->traverse(mOutputHLSL);
              out << ";\n";
              out << "if (s" << i << ")\n"
                     "{\n";
              mTemporaryIndex = i + 1;
              node->getRight()->traverse(this);
              out << "    s" << i << " = ";
              mTemporaryIndex = i + 1;
              node->getRight()->traverse(mOutputHLSL);
              out << ";\n"
                     "}\n";
  
              out << "}\n";
  
              mTemporaryIndex = i + 1;
          }
          return false;
        default:
          return true;
      }
  }
  
  bool UnfoldShortCircuit::visitSelection(Visit visit, TIntermSelection *node)
  {
      TInfoSinkBase &out = mOutputHLSL->getBodyStream();
  
      // Unfold "b ? x : y" into "type s; if(b) s = x; else s = y;"
      if (node->usesTernaryOperator())
      {
          int i = mTemporaryIndex;
  
          out << mOutputHLSL->typeString(node->getType()) << " s" << i << ";\n";
  
          out << "{\n";
  
          mTemporaryIndex = i + 1;
          node->getCondition()->traverse(this);
          out << "if (";
          mTemporaryIndex = i + 1;
          node->getCondition()->traverse(mOutputHLSL);
          out << ")\n"
                 "{\n";
          mTemporaryIndex = i + 1;
          node->getTrueBlock()->traverse(this);
          out << "    s" << i << " = ";
          mTemporaryIndex = i + 1;
          node->getTrueBlock()->traverse(mOutputHLSL);
          out << ";\n"
                 "}\n"
                 "else\n"
                 "{\n";
          mTemporaryIndex = i + 1;
          node->getFalseBlock()->traverse(this);
          out << "    s" << i << " = ";
          mTemporaryIndex = i + 1;
          node->getFalseBlock()->traverse(mOutputHLSL);
          out << ";\n"
                 "}\n";
  
          out << "}\n";
  
          mTemporaryIndex = i + 1;
      }
  
      return false;
  }
  
  bool UnfoldShortCircuit::visitLoop(Visit visit, TIntermLoop *node)
  {
      int rewindIndex = mTemporaryIndex;
  
      if (node->getInit())
      {
          node->getInit()->traverse(this);
      }
      
      if (node->getCondition())
      {
          node->getCondition()->traverse(this);
      }
  
      if (node->getExpression())
      {
          node->getExpression()->traverse(this);
      }
  
      mTemporaryIndex = rewindIndex;
  
      return false;
  }
  
  int UnfoldShortCircuit::getNextTemporaryIndex()
  {
      return mTemporaryIndex++;
  }
  }
  

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