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

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• Hash : a223430c
  Author :
  Date : 2016-08-31T12:05:39
  

  Promote unary nodes automatically
  
  Unary nodes now get their type set automatically based on the
  operation and operand. The operand should only be changed to another
  of the same type after the node is constructed. The operation can't
  be changed on unary and binary nodes after they've been constructed.
  
  BUG=angleproject:1490
  TEST=angle_unittests
  
  Change-Id: Ib1ea3dcb1162261966c02d5f03d8091cf647fac1
  Reviewed-on: https://chromium-review.googlesource.com/378935
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
  

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• src/compiler/translator/RemovePow.cpp

• //
  // Copyright (c) 2002-2015 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.
  //
  // RemovePow is an AST traverser to convert pow(x, y) built-in calls where y is a
  // constant to exp2(y * log2(x)). This works around an issue in NVIDIA 311 series
  // OpenGL drivers.
  //
  
  #include "compiler/translator/RemovePow.h"
  
  #include "compiler/translator/InfoSink.h"
  #include "compiler/translator/IntermNode.h"
  
  namespace
  {
  
  bool IsProblematicPow(TIntermTyped *node)
  {
      TIntermAggregate *agg = node->getAsAggregate();
      if (agg != nullptr && agg->getOp() == EOpPow)
      {
          ASSERT(agg->getSequence()->size() == 2);
          return agg->getSequence()->at(1)->getAsConstantUnion() != nullptr;
      }
      return false;
  }
  
  // Traverser that converts all pow operations simultaneously.
  class RemovePowTraverser : public TIntermTraverser
  {
    public:
      RemovePowTraverser();
  
      bool visitAggregate(Visit visit, TIntermAggregate *node) override;
  
      void nextIteration() { mNeedAnotherIteration = false; }
      bool needAnotherIteration() const { return mNeedAnotherIteration; }
  
    protected:
      bool mNeedAnotherIteration;
  };
  
  RemovePowTraverser::RemovePowTraverser()
      : TIntermTraverser(true, false, false),
        mNeedAnotherIteration(false)
  {
  }
  
  bool RemovePowTraverser::visitAggregate(Visit visit, TIntermAggregate *node)
  {
      if (IsProblematicPow(node))
      {
          TIntermTyped *x = node->getSequence()->at(0)->getAsTyped();
          TIntermTyped *y = node->getSequence()->at(1)->getAsTyped();
  
          TIntermUnary *log = new TIntermUnary(EOpLog2, x);
          log->setLine(node->getLine());
  
          TOperator op       = TIntermBinary::GetMulOpBasedOnOperands(y->getType(), log->getType());
          TIntermBinary *mul = new TIntermBinary(op, y, log);
          mul->setLine(node->getLine());
  
          TIntermUnary *exp = new TIntermUnary(EOpExp2, mul);
          exp->setLine(node->getLine());
  
          queueReplacement(node, exp, OriginalNode::IS_DROPPED);
  
          // If the x parameter also needs to be replaced, we need to do that in another traversal,
          // since it's parent node will change in a way that's not handled correctly by updateTree().
          if (IsProblematicPow(x))
          {
              mNeedAnotherIteration = true;
              return false;
          }
      }
      return true;
  }
  
  } // namespace
  
  void RemovePow(TIntermNode *root)
  {
      RemovePowTraverser traverser;
      // Iterate as necessary, and reset the traverser between iterations.
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          traverser.updateTree();
      }
      while (traverser.needAnotherIteration());
  }
  

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