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

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• Hash : 3272a6d3
  Author :
  Date : 2016-08-29T17:54:50
  

  Promote and fold indexing nodes similarly to other binary ops
  
  Indexing nodes now get their type set in TIntermBinary::promote, same
  as math and logic ops. They are also constant folded through
  TIntermBinary::fold() instead of having special functions for constant
  folding them in ParseContext.
  
  Index nodes for struct and interface block member access now always
  have integer type, instead of sometimes having the type of the field
  they were used to access.
  
  Usage of TIntermBinary constructor is cleaned up so only the
  constructor that takes in left and right operands is used. The type
  of TIntermBinary nodes is always determined automatically.
  
  Together these changes make the code considerably cleaner.
  
  Note that the code for constant folding for array indexing is actually
  never hit because constant folding array constructors is still
  intentionally disabled in the code.
  
  BUG=angleproject:1490
  TEST=angle_unittests
  
  Change-Id: Ifcec45257476cdb0d495c7d72e3cf2f83388e8c5
  Reviewed-on: https://chromium-review.googlesource.com/377961
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
  

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• src/compiler/translator/ExpandIntegerPowExpressions.cpp

• //
  // Copyright (c) 2016 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.
  //
  // Implementation of the integer pow expressions HLSL bug workaround.
  // See header for more info.
  
  #include "compiler/translator/ExpandIntegerPowExpressions.h"
  
  #include <cmath>
  #include <cstdlib>
  
  #include "compiler/translator/IntermNode.h"
  
  namespace sh
  {
  
  namespace
  {
  
  class Traverser : public TIntermTraverser
  {
    public:
      static void Apply(TIntermNode *root, unsigned int *tempIndex);
  
    private:
      Traverser();
      bool visitAggregate(Visit visit, TIntermAggregate *node) override;
      void nextIteration();
  
      bool mFound = false;
  };
  
  // static
  void Traverser::Apply(TIntermNode *root, unsigned int *tempIndex)
  {
      Traverser traverser;
      traverser.useTemporaryIndex(tempIndex);
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          if (traverser.mFound)
          {
              traverser.updateTree();
          }
      } while (traverser.mFound);
  }
  
  Traverser::Traverser() : TIntermTraverser(true, false, false)
  {
  }
  
  void Traverser::nextIteration()
  {
      mFound = false;
      nextTemporaryIndex();
  }
  
  bool Traverser::visitAggregate(Visit visit, TIntermAggregate *node)
  {
      if (mFound)
      {
          return false;
      }
  
      // Test 0: skip non-pow operators.
      if (node->getOp() != EOpPow)
      {
          return true;
      }
  
      const TIntermSequence *sequence = node->getSequence();
      ASSERT(sequence->size() == 2u);
      const TIntermConstantUnion *constantNode = sequence->at(1)->getAsConstantUnion();
  
      // Test 1: check for a single constant.
      if (!constantNode || constantNode->getNominalSize() != 1)
      {
          return true;
      }
  
      const TConstantUnion *constant = constantNode->getUnionArrayPointer();
  
      TConstantUnion asFloat;
      asFloat.cast(EbtFloat, *constant);
  
      float value = asFloat.getFConst();
  
      // Test 2: value is in the problematic range.
      if (value < -5.0f || value > 9.0f)
      {
          return true;
      }
  
      // Test 3: value is integer or pretty close to an integer.
      float absval = std::abs(value);
      float frac   = absval - std::round(absval);
      if (frac > 0.0001f)
      {
          return true;
      }
  
      // Test 4: skip -1, 0, and 1
      int exponent = static_cast<int>(value);
      int n        = std::abs(exponent);
      if (n < 2)
      {
          return true;
      }
  
      // Potential problem case detected, apply workaround.
      nextTemporaryIndex();
  
      TIntermTyped *lhs = sequence->at(0)->getAsTyped();
      ASSERT(lhs);
  
      TIntermAggregate *init = createTempInitDeclaration(lhs);
      TIntermTyped *current  = createTempSymbol(lhs->getType());
  
      insertStatementInParentBlock(init);
  
      // Create a chain of n-1 multiples.
      for (int i = 1; i < n; ++i)
      {
          TIntermBinary *mul = new TIntermBinary(EOpMul, current, createTempSymbol(lhs->getType()));
          mul->setLine(node->getLine());
          current = mul;
      }
  
      // For negative pow, compute the reciprocal of the positive pow.
      if (exponent < 0)
      {
          TConstantUnion *oneVal = new TConstantUnion();
          oneVal->setFConst(1.0f);
          TIntermConstantUnion *oneNode = new TIntermConstantUnion(oneVal, node->getType());
          TIntermBinary *div            = new TIntermBinary(EOpDiv, oneNode, current);
          current = div;
      }
  
      queueReplacement(node, current, OriginalNode::IS_DROPPED);
      mFound = true;
      return false;
  }
  
  }  // anonymous namespace
  
  void ExpandIntegerPowExpressions(TIntermNode *root, unsigned int *tempIndex)
  {
      Traverser::Apply(root, tempIndex);
  }
  
  }  // namespace sh
  

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