kc3-lang/angle/src/compiler/translator/tree_ops/UnfoldShortCircuitToIf.cpp

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• Hash : 472c74c6
  Author :
  Date : 2019-08-19T16:32:13
  

  Translator: Allow tree validation in children of TCompiler
  
  This is to be able to perform validation inside TranslatorVulkan, even
  if it's through ASSERTs.
  
  Additionally, every transformation is changed such that they do their
  validation themselves.  TIntermTraverser::updateTree() performs the
  validation, which indirectly validates many of three tree
  transformations.  Some of the more ancient transformations that don't
  use this function directly call TCompiler::validateAST.
  
  Bug: angleproject:2733
  Change-Id: Ie4af029d34e053c5ad1dc8c2c2568eecd625d344
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1761149
  Reviewed-by: Geoff Lang <geofflang@chromium.org>
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
  

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• src/compiler/translator/tree_ops/UnfoldShortCircuitToIf.cpp

• //
  // Copyright 2002 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.
  //
  // UnfoldShortCircuitToIf is an AST traverser to convert short-circuiting operators to if-else
  // statements.
  // The results are assigned to s# temporaries, which are used by the main translator instead of
  // the original expression.
  //
  
  #include "compiler/translator/tree_ops/UnfoldShortCircuitToIf.h"
  
  #include "compiler/translator/StaticType.h"
  #include "compiler/translator/tree_util/IntermNodePatternMatcher.h"
  #include "compiler/translator/tree_util/IntermNode_util.h"
  #include "compiler/translator/tree_util/IntermTraverse.h"
  
  namespace sh
  {
  
  namespace
  {
  
  // Traverser that unfolds one short-circuiting operation at a time.
  class UnfoldShortCircuitTraverser : public TIntermTraverser
  {
    public:
      UnfoldShortCircuitTraverser(TSymbolTable *symbolTable);
  
      bool visitBinary(Visit visit, TIntermBinary *node) override;
      bool visitTernary(Visit visit, TIntermTernary *node) override;
  
      void nextIteration();
      bool foundShortCircuit() const { return mFoundShortCircuit; }
  
    protected:
      // Marked to true once an operation that needs to be unfolded has been found.
      // After that, no more unfolding is performed on that traversal.
      bool mFoundShortCircuit;
  
      IntermNodePatternMatcher mPatternToUnfoldMatcher;
  };
  
  UnfoldShortCircuitTraverser::UnfoldShortCircuitTraverser(TSymbolTable *symbolTable)
      : TIntermTraverser(true, false, true, symbolTable),
        mFoundShortCircuit(false),
        mPatternToUnfoldMatcher(IntermNodePatternMatcher::kUnfoldedShortCircuitExpression)
  {}
  
  bool UnfoldShortCircuitTraverser::visitBinary(Visit visit, TIntermBinary *node)
  {
      if (mFoundShortCircuit)
          return false;
  
      if (visit != PreVisit)
          return true;
  
      if (!mPatternToUnfoldMatcher.match(node, getParentNode()))
          return true;
  
      // If our right node doesn't have side effects, we know we don't need to unfold this
      // expression: there will be no short-circuiting side effects to avoid
      // (note: unfolding doesn't depend on the left node -- it will always be evaluated)
      ASSERT(node->getRight()->hasSideEffects());
  
      mFoundShortCircuit = true;
  
      switch (node->getOp())
      {
          case EOpLogicalOr:
          {
              // "x || y" is equivalent to "x ? true : y", which unfolds to "bool s; if(x) s = true;
              // else s = y;",
              // and then further simplifies down to "bool s = x; if(!s) s = y;".
  
              TIntermSequence insertions;
              const TType *boolType = StaticType::Get<EbtBool, EbpUndefined, EvqTemporary, 1, 1>();
              TVariable *resultVariable = CreateTempVariable(mSymbolTable, boolType);
  
              ASSERT(node->getLeft()->getType() == *boolType);
              insertions.push_back(CreateTempInitDeclarationNode(resultVariable, node->getLeft()));
  
              TIntermBlock *assignRightBlock = new TIntermBlock();
              ASSERT(node->getRight()->getType() == *boolType);
              assignRightBlock->getSequence()->push_back(
                  CreateTempAssignmentNode(resultVariable, node->getRight()));
  
              TIntermUnary *notTempSymbol =
                  new TIntermUnary(EOpLogicalNot, CreateTempSymbolNode(resultVariable), nullptr);
              TIntermIfElse *ifNode = new TIntermIfElse(notTempSymbol, assignRightBlock, nullptr);
              insertions.push_back(ifNode);
  
              insertStatementsInParentBlock(insertions);
  
              queueReplacement(CreateTempSymbolNode(resultVariable), OriginalNode::IS_DROPPED);
              return false;
          }
          case EOpLogicalAnd:
          {
              // "x && y" is equivalent to "x ? y : false", which unfolds to "bool s; if(x) s = y;
              // else s = false;",
              // and then further simplifies down to "bool s = x; if(s) s = y;".
              TIntermSequence insertions;
              const TType *boolType = StaticType::Get<EbtBool, EbpUndefined, EvqTemporary, 1, 1>();
              TVariable *resultVariable = CreateTempVariable(mSymbolTable, boolType);
  
              ASSERT(node->getLeft()->getType() == *boolType);
              insertions.push_back(CreateTempInitDeclarationNode(resultVariable, node->getLeft()));
  
              TIntermBlock *assignRightBlock = new TIntermBlock();
              ASSERT(node->getRight()->getType() == *boolType);
              assignRightBlock->getSequence()->push_back(
                  CreateTempAssignmentNode(resultVariable, node->getRight()));
  
              TIntermIfElse *ifNode =
                  new TIntermIfElse(CreateTempSymbolNode(resultVariable), assignRightBlock, nullptr);
              insertions.push_back(ifNode);
  
              insertStatementsInParentBlock(insertions);
  
              queueReplacement(CreateTempSymbolNode(resultVariable), OriginalNode::IS_DROPPED);
              return false;
          }
          default:
              UNREACHABLE();
              return true;
      }
  }
  
  bool UnfoldShortCircuitTraverser::visitTernary(Visit visit, TIntermTernary *node)
  {
      if (mFoundShortCircuit)
          return false;
  
      if (visit != PreVisit)
          return true;
  
      if (!mPatternToUnfoldMatcher.match(node))
          return true;
  
      mFoundShortCircuit = true;
  
      // Unfold "b ? x : y" into "type s; if(b) s = x; else s = y;"
      TIntermSequence insertions;
      TIntermDeclaration *tempDeclaration = nullptr;
      TVariable *resultVariable = DeclareTempVariable(mSymbolTable, new TType(node->getType()),
                                                      EvqTemporary, &tempDeclaration);
      insertions.push_back(tempDeclaration);
  
      TIntermBlock *trueBlock = new TIntermBlock();
      TIntermBinary *trueAssignment =
          CreateTempAssignmentNode(resultVariable, node->getTrueExpression());
      trueBlock->getSequence()->push_back(trueAssignment);
  
      TIntermBlock *falseBlock = new TIntermBlock();
      TIntermBinary *falseAssignment =
          CreateTempAssignmentNode(resultVariable, node->getFalseExpression());
      falseBlock->getSequence()->push_back(falseAssignment);
  
      TIntermIfElse *ifNode =
          new TIntermIfElse(node->getCondition()->getAsTyped(), trueBlock, falseBlock);
      insertions.push_back(ifNode);
  
      insertStatementsInParentBlock(insertions);
  
      TIntermSymbol *ternaryResult = CreateTempSymbolNode(resultVariable);
      queueReplacement(ternaryResult, OriginalNode::IS_DROPPED);
  
      return false;
  }
  
  void UnfoldShortCircuitTraverser::nextIteration()
  {
      mFoundShortCircuit = false;
  }
  
  }  // namespace
  
  bool UnfoldShortCircuitToIf(TCompiler *compiler, TIntermNode *root, TSymbolTable *symbolTable)
  {
      UnfoldShortCircuitTraverser traverser(symbolTable);
      // Unfold one operator at a time, and reset the traverser between iterations.
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          if (traverser.foundShortCircuit())
          {
              if (!traverser.updateTree(compiler, root))
              {
                  return false;
              }
          }
      } while (traverser.foundShortCircuit());
  
      return true;
  }
  
  }  // namespace sh
  

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