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

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• Hash : 195be942
  Author :
  Date : 2017-12-04T23:40:14
  

  Always create TVariables for TIntermSymbol nodes
  
  TIntermSymbol nodes are now constructed based on a specific TVariable.
  This makes sure that all TIntermSymbol nodes that are created to refer
  to a specific temporary in an AST transform will have consistent data.
  The TVariable objects are not necessarily added to the symbol table
  levels - just those variables that can be referred to by their name
  during parsing need to be reachable through there.
  
  In the future this can be taken a step further so that TIntermSymbol
  nodes just to point to a TVariable instead of duplicating the
  information.
  
  BUG=angleproject:2267
  TEST=angle_unittests
  
  Change-Id: I4e7bcdb0637cd3b588d3c202ef02f4b7bd7954a1
  Reviewed-on: https://chromium-review.googlesource.com/811925
  Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
  Reviewed-by: Corentin Wallez <cwallez@chromium.org>
  

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• src/compiler/translator/RewriteElseBlocks.cpp

• //
  // Copyright (c) 2014 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.
  //
  // RewriteElseBlocks.cpp: Implementation for tree transform to change
  //   all if-else blocks to if-if blocks.
  //
  
  #include "compiler/translator/RewriteElseBlocks.h"
  
  #include "compiler/translator/IntermNode.h"
  #include "compiler/translator/IntermNode_util.h"
  #include "compiler/translator/NodeSearch.h"
  #include "compiler/translator/SymbolTable.h"
  
  namespace sh
  {
  
  namespace
  {
  
  class ElseBlockRewriter : public TIntermTraverser
  {
    public:
      ElseBlockRewriter(TSymbolTable *symbolTable);
  
    protected:
      bool visitFunctionDefinition(Visit visit, TIntermFunctionDefinition *aggregate) override;
      bool visitBlock(Visit visit, TIntermBlock *block) override;
  
    private:
      TIntermNode *rewriteIfElse(TIntermIfElse *ifElse);
  
      const TType *mFunctionType;
  };
  
  ElseBlockRewriter::ElseBlockRewriter(TSymbolTable *symbolTable)
      : TIntermTraverser(true, false, true, symbolTable), mFunctionType(nullptr)
  {
  }
  
  bool ElseBlockRewriter::visitFunctionDefinition(Visit visit, TIntermFunctionDefinition *node)
  {
      // Store the current function context (see comment below)
      mFunctionType = ((visit == PreVisit) ? &node->getFunctionPrototype()->getType() : nullptr);
      return true;
  }
  
  bool ElseBlockRewriter::visitBlock(Visit visit, TIntermBlock *node)
  {
      if (visit == PostVisit)
      {
          for (size_t statementIndex = 0; statementIndex != node->getSequence()->size();
               statementIndex++)
          {
              TIntermNode *statement = (*node->getSequence())[statementIndex];
              TIntermIfElse *ifElse  = statement->getAsIfElseNode();
              if (ifElse && ifElse->getFalseBlock() != nullptr)
              {
                  (*node->getSequence())[statementIndex] = rewriteIfElse(ifElse);
              }
          }
      }
      return true;
  }
  
  TIntermNode *ElseBlockRewriter::rewriteIfElse(TIntermIfElse *ifElse)
  {
      ASSERT(ifElse != nullptr);
  
      TIntermDeclaration *storeCondition = nullptr;
      TVariable *conditionVariable =
          DeclareTempVariable(mSymbolTable, ifElse->getCondition(), EvqTemporary, &storeCondition);
  
      TIntermBlock *falseBlock = nullptr;
  
      TType boolType(EbtBool, EbpUndefined, EvqTemporary);
  
      if (ifElse->getFalseBlock())
      {
          TIntermBlock *negatedElse = nullptr;
          // crbug.com/346463
          // D3D generates error messages claiming a function has no return value, when rewriting
          // an if-else clause that returns something non-void in a function. By appending dummy
          // returns (that are unreachable) we can silence this compile error.
          if (mFunctionType && mFunctionType->getBasicType() != EbtVoid)
          {
              TIntermNode *returnNode = new TIntermBranch(EOpReturn, CreateZeroNode(*mFunctionType));
              negatedElse = new TIntermBlock();
              negatedElse->appendStatement(returnNode);
          }
  
          TIntermSymbol *conditionSymbolElse = CreateTempSymbolNode(conditionVariable);
          TIntermUnary *negatedCondition     = new TIntermUnary(EOpLogicalNot, conditionSymbolElse);
          TIntermIfElse *falseIfElse =
              new TIntermIfElse(negatedCondition, ifElse->getFalseBlock(), negatedElse);
          falseBlock = EnsureBlock(falseIfElse);
      }
  
      TIntermSymbol *conditionSymbolSel = CreateTempSymbolNode(conditionVariable);
      TIntermIfElse *newIfElse =
          new TIntermIfElse(conditionSymbolSel, ifElse->getTrueBlock(), falseBlock);
  
      TIntermBlock *block = new TIntermBlock();
      block->getSequence()->push_back(storeCondition);
      block->getSequence()->push_back(newIfElse);
  
      return block;
  }
  
  }  // anonymous namespace
  
  void RewriteElseBlocks(TIntermNode *node, TSymbolTable *symbolTable)
  {
      ElseBlockRewriter rewriter(symbolTable);
      node->traverse(&rewriter);
  }
  
  }  // namespace sh
  

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