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

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• Author : Jamie Madill
  Date : 2016-12-12 14:42:19
  Hash : d7b1ab58
  Message : Fix up translator style. Using git cl format. BUG=angleproject:650 Change-Id: I7d3f98d2b0dcfb0a8de6c35327db74e55c28d761 Reviewed-on: https://chromium-review.googlesource.com/419059 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>

• src/compiler/translator/UnfoldShortCircuitToIf.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.
  //
  // UnfoldShortCircuitToIf is an AST traverser to convert short-circuiting operators to 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/UnfoldShortCircuitToIf.h"
  
  #include "compiler/translator/IntermNode.h"
  #include "compiler/translator/IntermNodePatternMatcher.h"
  
  namespace sh
  {
  
  namespace
  {
  
  // Traverser that unfolds one short-circuiting operation at a time.
  class UnfoldShortCircuitTraverser : public TIntermTraverser
  {
    public:
      UnfoldShortCircuitTraverser();
  
      bool visitBinary(Visit visit, TIntermBinary *node) override;
      bool visitTernary(Visit visit, TIntermTernary *node) override;
  
      void nextIteration();
      bool foundShortCircuit() const { return mFoundShortCircuit; }
  
    protected:
      // Marked to true once an operation that needs to be unfolded has been found.
      // After that, no more unfolding is performed on that traversal.
      bool mFoundShortCircuit;
  
      IntermNodePatternMatcher mPatternToUnfoldMatcher;
  };
  
  UnfoldShortCircuitTraverser::UnfoldShortCircuitTraverser()
      : TIntermTraverser(true, false, true),
        mFoundShortCircuit(false),
        mPatternToUnfoldMatcher(IntermNodePatternMatcher::kUnfoldedShortCircuitExpression)
  {
  }
  
  bool UnfoldShortCircuitTraverser::visitBinary(Visit visit, TIntermBinary *node)
  {
      if (mFoundShortCircuit)
          return false;
  
      if (visit != PreVisit)
          return true;
  
      if (!mPatternToUnfoldMatcher.match(node, getParentNode()))
          return true;
  
      // 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)
      ASSERT(node->getRight()->hasSideEffects());
  
      mFoundShortCircuit = 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;".
  
              TIntermSequence insertions;
              TType boolType(EbtBool, EbpUndefined, EvqTemporary);
  
              ASSERT(node->getLeft()->getType() == boolType);
              insertions.push_back(createTempInitDeclaration(node->getLeft()));
  
              TIntermBlock *assignRightBlock = new TIntermBlock();
              ASSERT(node->getRight()->getType() == boolType);
              assignRightBlock->getSequence()->push_back(createTempAssignment(node->getRight()));
  
              TIntermUnary *notTempSymbol =
                  new TIntermUnary(EOpLogicalNot, createTempSymbol(boolType));
              TIntermIfElse *ifNode = new TIntermIfElse(notTempSymbol, assignRightBlock, nullptr);
              insertions.push_back(ifNode);
  
              insertStatementsInParentBlock(insertions);
  
              queueReplacement(node, createTempSymbol(boolType), OriginalNode::IS_DROPPED);
              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;".
              TIntermSequence insertions;
              TType boolType(EbtBool, EbpUndefined, EvqTemporary);
  
              ASSERT(node->getLeft()->getType() == boolType);
              insertions.push_back(createTempInitDeclaration(node->getLeft()));
  
              TIntermBlock *assignRightBlock = new TIntermBlock();
              ASSERT(node->getRight()->getType() == boolType);
              assignRightBlock->getSequence()->push_back(createTempAssignment(node->getRight()));
  
              TIntermIfElse *ifNode =
                  new TIntermIfElse(createTempSymbol(boolType), assignRightBlock, nullptr);
              insertions.push_back(ifNode);
  
              insertStatementsInParentBlock(insertions);
  
              queueReplacement(node, createTempSymbol(boolType), OriginalNode::IS_DROPPED);
              return false;
          }
          default:
              UNREACHABLE();
              return true;
      }
  }
  
  bool UnfoldShortCircuitTraverser::visitTernary(Visit visit, TIntermTernary *node)
  {
      if (mFoundShortCircuit)
          return false;
  
      if (visit != PreVisit)
          return true;
  
      if (!mPatternToUnfoldMatcher.match(node))
          return true;
  
      mFoundShortCircuit = true;
  
      // Unfold "b ? x : y" into "type s; if(b) s = x; else s = y;"
      TIntermSequence insertions;
  
      TIntermDeclaration *tempDeclaration = createTempDeclaration(node->getType());
      insertions.push_back(tempDeclaration);
  
      TIntermBlock *trueBlock       = new TIntermBlock();
      TIntermBinary *trueAssignment = createTempAssignment(node->getTrueExpression());
      trueBlock->getSequence()->push_back(trueAssignment);
  
      TIntermBlock *falseBlock       = new TIntermBlock();
      TIntermBinary *falseAssignment = createTempAssignment(node->getFalseExpression());
      falseBlock->getSequence()->push_back(falseAssignment);
  
      TIntermIfElse *ifNode =
          new TIntermIfElse(node->getCondition()->getAsTyped(), trueBlock, falseBlock);
      insertions.push_back(ifNode);
  
      insertStatementsInParentBlock(insertions);
  
      TIntermSymbol *ternaryResult = createTempSymbol(node->getType());
      queueReplacement(node, ternaryResult, OriginalNode::IS_DROPPED);
  
      return false;
  }
  
  void UnfoldShortCircuitTraverser::nextIteration()
  {
      mFoundShortCircuit = false;
      nextTemporaryIndex();
  }
  
  }  // namespace
  
  void UnfoldShortCircuitToIf(TIntermNode *root, unsigned int *temporaryIndex)
  {
      UnfoldShortCircuitTraverser traverser;
      ASSERT(temporaryIndex != nullptr);
      traverser.useTemporaryIndex(temporaryIndex);
      // Unfold one operator at a time, and reset the traverser between iterations.
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          if (traverser.foundShortCircuit())
              traverser.updateTree();
      } while (traverser.foundShortCircuit());
  }
  
  }  // namespace sh