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

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• Author : Olli Etuaho
  Date : 2015-02-27 13:57:32
  Hash : 2cd7a0ed
  Message : Remove switch fall-through on HLSL Remove fall-through from non-empty labels in switch statements. Tested with dEQP-GLES3.functional.shaders.*switch*. All pass except for tests that require dFdx/dFdy, which fail for an unrelated reason. Additional test coverage could still be useful for cases where a label is terminated by a continue or return statement. BUG=angle:921 Change-Id: I4741867789a9308d66d0adeabdaf83907106e2d2 Reviewed-on: https://chromium-review.googlesource.com/254550 Tested-by: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Zhenyao Mo <zmo@chromium.org>

• src/compiler/translator/RemoveSwitchFallThrough.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.
  //
  
  #include "compiler/translator/RemoveSwitchFallThrough.h"
  
  TIntermAggregate *RemoveSwitchFallThrough::removeFallThrough(TIntermAggregate *statementList)
  {
      RemoveSwitchFallThrough rm(statementList);
      ASSERT(statementList);
      statementList->traverse(&rm);
      bool lastStatementWasBreak = rm.mLastStatementWasBreak;
      rm.mLastStatementWasBreak = true;
      rm.handlePreviousCase();
      if (!lastStatementWasBreak)
      {
          TIntermBranch *finalBreak = new TIntermBranch(EOpBreak, nullptr);
          rm.mStatementListOut->getSequence()->push_back(finalBreak);
      }
      return rm.mStatementListOut;
  }
  
  RemoveSwitchFallThrough::RemoveSwitchFallThrough(TIntermAggregate *statementList)
      : TIntermTraverser(true, false, false),
        mStatementList(statementList),
        mLastStatementWasBreak(false),
        mPreviousCase(nullptr)
  {
      mStatementListOut = new TIntermAggregate();
      mStatementListOut->setOp(EOpSequence);
  }
  
  void RemoveSwitchFallThrough::visitSymbol(TIntermSymbol *node)
  {
      // Note that this assumes that switch statements which don't begin by a case statement
      // have already been weeded out in validation.
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
  }
  
  void RemoveSwitchFallThrough::visitConstantUnion(TIntermConstantUnion *node)
  {
      // Conditions of case labels are not traversed, so this is some other constant
      // Could be just a statement like "0;"
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
  }
  
  bool RemoveSwitchFallThrough::visitBinary(Visit, TIntermBinary *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
      return false;
  }
  
  bool RemoveSwitchFallThrough::visitUnary(Visit, TIntermUnary *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
      return false;
  }
  
  bool RemoveSwitchFallThrough::visitSelection(Visit, TIntermSelection *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
      return false;
  }
  
  bool RemoveSwitchFallThrough::visitSwitch(Visit, TIntermSwitch *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
      // Don't go into nested switch statements
      return false;
  }
  
  void RemoveSwitchFallThrough::outputSequence(TIntermSequence *sequence, size_t startIndex)
  {
      for (size_t i = startIndex; i < sequence->size(); ++i)
      {
          mStatementListOut->getSequence()->push_back(sequence->at(i));
      }
  }
  
  void RemoveSwitchFallThrough::handlePreviousCase()
  {
      if (mPreviousCase)
          mCasesSharingBreak.push_back(mPreviousCase);
      if (mLastStatementWasBreak)
      {
          bool labelsWithNoStatements = true;
          for (size_t i = 0; i < mCasesSharingBreak.size(); ++i)
          {
              if (mCasesSharingBreak.at(i)->getSequence()->size() > 1)
              {
                  labelsWithNoStatements = false;
              }
              if (labelsWithNoStatements)
              {
                  // Fall-through is allowed in case the label has no statements.
                  outputSequence(mCasesSharingBreak.at(i)->getSequence(), 0);
              }
              else
              {
                  // Include all the statements that this case can fall through under the same label.
                  for (size_t j = i; j < mCasesSharingBreak.size(); ++j)
                  {
                      size_t startIndex = j > i ? 1 : 0; // Add the label only from the first sequence.
                      outputSequence(mCasesSharingBreak.at(j)->getSequence(), startIndex);
  
                  }
              }
          }
          mCasesSharingBreak.clear();
      }
      mLastStatementWasBreak = false;
      mPreviousCase = nullptr;
  }
  
  bool RemoveSwitchFallThrough::visitCase(Visit, TIntermCase *node)
  {
      handlePreviousCase();
      mPreviousCase = new TIntermAggregate();
      mPreviousCase->setOp(EOpSequence);
      mPreviousCase->getSequence()->push_back(node);
      // Don't traverse the condition of the case statement
      return false;
  }
  
  bool RemoveSwitchFallThrough::visitAggregate(Visit, TIntermAggregate *node)
  {
      if (node != mStatementList)
      {
          mPreviousCase->getSequence()->push_back(node);
          mLastStatementWasBreak = false;
          return false;
      }
      return true;
  }
  
  bool RemoveSwitchFallThrough::visitLoop(Visit, TIntermLoop *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      mLastStatementWasBreak = false;
      return false;
  }
  
  bool RemoveSwitchFallThrough::visitBranch(Visit, TIntermBranch *node)
  {
      mPreviousCase->getSequence()->push_back(node);
      // TODO: Verify that accepting return or continue statements here doesn't cause problems.
      mLastStatementWasBreak = true;
      return false;
  }