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

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• Hash : 7cab38b5
  Author :
  Date : 2013-10-15T12:59:30
  

  Add an option to unfold short circuiting in AST.
  
  We replace "a || b" with "a ? true : b",
  "a && b" with "a ? b : false".
  
  This is to work around short circuiting bug in Mac drivers.
  
  ANGLEBUG=482
  TEST=webgl conformance tests
  R=alokp@chromium.org, kbr@chromium.org
  
  Review URL: https://codereview.appspot.com/14529048
  
  Conflicts:
  
  	src/build_angle.gypi
  	src/compiler/translator/Compiler.cpp
  
  Change-Id: Ic2384a97d58f54294efcb3a012deb2007a9fc658
  Reviewed-on: https://chromium-review.googlesource.com/178996
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Commit-Queue: Jamie Madill <jmadill@chromium.org>
  Tested-by: Shannon Woods <shannonwoods@chromium.org>
  

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• src/compiler/translator/UnfoldShortCircuitAST.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.
  //
  
  #include "compiler/translator/UnfoldShortCircuitAST.h"
  
  namespace
  {
  
  // "x || y" is equivalent to "x ? true : y".
  TIntermSelection *UnfoldOR(TIntermTyped *x, TIntermTyped *y)
  {
      const TType boolType(EbtBool, EbpUndefined);
      ConstantUnion *u = new ConstantUnion;
      u->setBConst(true);
      TIntermConstantUnion *trueNode = new TIntermConstantUnion(
          u, TType(EbtBool, EbpUndefined, EvqConst, 1));
      return new TIntermSelection(x, trueNode, y, boolType);
  }
  
  // "x && y" is equivalent to "x ? y : false".
  TIntermSelection *UnfoldAND(TIntermTyped *x, TIntermTyped *y)
  {
      const TType boolType(EbtBool, EbpUndefined);
      ConstantUnion *u = new ConstantUnion;
      u->setBConst(false);
      TIntermConstantUnion *falseNode = new TIntermConstantUnion(
          u, TType(EbtBool, EbpUndefined, EvqConst, 1));
      return new TIntermSelection(x, y, falseNode, boolType);
  }
  
  }  // namespace anonymous
  
  bool UnfoldShortCircuitAST::visitBinary(Visit visit, TIntermBinary *node)
  {
      TIntermSelection *replacement = NULL;
  
      switch (node->getOp())
      {
        case EOpLogicalOr:
          replacement = UnfoldOR(node->getLeft(), node->getRight());
          break;
        case EOpLogicalAnd:
          replacement = UnfoldAND(node->getLeft(), node->getRight());
          break;
        default:
          break;
      }
      if (replacement)
      {
          replacements.push_back(
              NodeUpdateEntry(getParentNode(), node, replacement));
      }
      return true;
  }
  
  void UnfoldShortCircuitAST::updateTree()
  {
      for (size_t ii = 0; ii < replacements.size(); ++ii)
      {
          const NodeUpdateEntry& entry = replacements[ii];
          ASSERT(entry.parent);
          bool replaced = entry.parent->replaceChildNode(
              entry.original, entry.replacement);
          ASSERT(replaced);
  
          // In AST traversing, a parent is visited before its children.
          // After we replace a node, if an immediate child is to
          // be replaced, we need to make sure we don't update the replaced
  	// node; instead, we update the replacement node.
          for (size_t jj = ii + 1; jj < replacements.size(); ++jj)
          {
              NodeUpdateEntry& entry2 = replacements[jj];
              if (entry2.parent == entry.original)
                  entry2.parent = entry.replacement;
          }
      }
  }
  
  

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