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

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• Hash : bb5a7e29
  Author :
  Date : 2017-08-30T13:03:12
  

  Allow length() on arbitrary array expressions
  
  This is required to pass some dEQP GLES 3.1 tests for arrays of
  arrays, and WebGL conformance tests were also recently fixed to
  require this behavior. The intent of the GLSL ES spec was not to
  restrict usage of length().
  
  In practice GL drivers don't implement array length() on expressions
  with side effects correctly in all cases. HLSL doesn't have an array
  length operator either. Because of this we always remove array length
  ops from the AST before output.
  
  BUG=angleproject:2142
  TEST=angle_unittests, angle_end2end_tests, WebGL conformance tests
  
  Change-Id: I863a92e83ac5315b013af9a5626348482bad72b3
  Reviewed-on: https://chromium-review.googlesource.com/643190
  Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  

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• src/compiler/translator/RemoveArrayLengthMethod.cpp

• //
  // Copyright (c) 2017 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.
  //
  // RemoveArrayLengthMethod.cpp:
  //   Fold array length expressions, including cases where the "this" node has side effects.
  //   Example:
  //     int i = (a = b).length();
  //     int j = (func()).length();
  //   becomes:
  //     (a = b);
  //     int i = <constant array length>;
  //     func();
  //     int j = <constant array length>;
  //
  //   Must be run after SplitSequenceOperator, SimplifyLoopConditions and SeparateDeclarations steps
  //   have been done to expressions containing calls of the array length method.
  
  #include "compiler/translator/RemoveArrayLengthMethod.h"
  
  #include "compiler/translator/IntermNode.h"
  #include "compiler/translator/IntermTraverse.h"
  
  namespace sh
  {
  
  namespace
  {
  
  class RemoveArrayLengthTraverser : public TIntermTraverser
  {
    public:
      RemoveArrayLengthTraverser() : TIntermTraverser(true, false, false), mFoundArrayLength(false) {}
  
      bool visitUnary(Visit visit, TIntermUnary *node) override;
  
      void nextIteration() { mFoundArrayLength = false; }
  
      bool foundArrayLength() const { return mFoundArrayLength; }
  
    private:
      bool mFoundArrayLength;
  };
  
  bool RemoveArrayLengthTraverser::visitUnary(Visit visit, TIntermUnary *node)
  {
      if (node->getOp() == EOpArrayLength)
      {
          mFoundArrayLength = true;
          if (!node->getOperand()->hasSideEffects())
          {
              queueReplacement(node->fold(nullptr), OriginalNode::IS_DROPPED);
              return false;
          }
          insertStatementInParentBlock(node->getOperand()->deepCopy());
          TConstantUnion *constArray = new TConstantUnion[1];
          constArray->setIConst(node->getOperand()->getOutermostArraySize());
          queueReplacement(new TIntermConstantUnion(constArray, node->getType()),
                           OriginalNode::IS_DROPPED);
          return false;
      }
      return true;
  }
  
  }  // anonymous namespace
  
  void RemoveArrayLengthMethod(TIntermBlock *root)
  {
      RemoveArrayLengthTraverser traverser;
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          if (traverser.foundArrayLength())
              traverser.updateTree();
      } while (traverser.foundArrayLength());
  }
  
  }  // namespace sh
  

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