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//
// 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/NodeSearch.h"
#include "compiler/translator/SymbolTable.h"
namespace sh
{
namespace
{
class ElseBlockRewriter : public TIntermTraverser
{
public:
ElseBlockRewriter();
protected:
bool visitAggregate(Visit visit, TIntermAggregate *aggregate);
private:
int mTemporaryIndex;
const TType *mFunctionType;
TIntermNode *rewriteSelection(TIntermSelection *selection);
};
TIntermSymbol *MakeNewTemporary(const TString &name, TBasicType type)
{
TType variableType(type, EbpHigh, EvqInternal);
return new TIntermSymbol(-1, name, variableType);
}
TIntermBinary *MakeNewBinary(TOperator op, TIntermTyped *left, TIntermTyped *right, const TType &resultType)
{
TIntermBinary *binary = new TIntermBinary(op);
binary->setLeft(left);
binary->setRight(right);
binary->setType(resultType);
return binary;
}
TIntermUnary *MakeNewUnary(TOperator op, TIntermTyped *operand)
{
TIntermUnary *unary = new TIntermUnary(op, operand->getType());
unary->setOperand(operand);
return unary;
}
ElseBlockRewriter::ElseBlockRewriter()
: TIntermTraverser(true, false, true, false),
mTemporaryIndex(0),
mFunctionType(NULL)
{}
bool ElseBlockRewriter::visitAggregate(Visit visit, TIntermAggregate *node)
{
switch (node->getOp())
{
case EOpSequence:
if (visit == PostVisit)
{
for (size_t statementIndex = 0; statementIndex != node->getSequence()->size(); statementIndex++)
{
TIntermNode *statement = (*node->getSequence())[statementIndex];
TIntermSelection *selection = statement->getAsSelectionNode();
if (selection && selection->getFalseBlock() != NULL)
{
// Check for if / else if
TIntermSelection *elseIfBranch = selection->getFalseBlock()->getAsSelectionNode();
if (elseIfBranch)
{
selection->replaceChildNode(elseIfBranch, rewriteSelection(elseIfBranch));
delete elseIfBranch;
}
(*node->getSequence())[statementIndex] = rewriteSelection(selection);
delete selection;
}
}
}
break;
case EOpFunction:
// Store the current function context (see comment below)
mFunctionType = ((visit == PreVisit) ? &node->getType() : NULL);
break;
default: break;
}
return true;
}
TIntermNode *ElseBlockRewriter::rewriteSelection(TIntermSelection *selection)
{
ASSERT(selection != NULL);
TString temporaryName = "cond_" + str(mTemporaryIndex++);
TIntermTyped *typedCondition = selection->getCondition()->getAsTyped();
TType resultType(EbtBool, EbpUndefined);
TIntermSymbol *conditionSymbolInit = MakeNewTemporary(temporaryName, EbtBool);
TIntermBinary *storeCondition = MakeNewBinary(EOpInitialize, conditionSymbolInit,
typedCondition, resultType);
TIntermNode *negatedElse = NULL;
TIntermSelection *falseBlock = NULL;
if (selection->getFalseBlock())
{
// 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)
{
TString typeString = mFunctionType->getStruct() ? mFunctionType->getStruct()->name() :
mFunctionType->getBasicString();
TString rawText = "return (" + typeString + ")0";
negatedElse = new TIntermRaw(*mFunctionType, rawText);
}
TIntermSymbol *conditionSymbolElse = MakeNewTemporary(temporaryName, EbtBool);
TIntermUnary *negatedCondition = MakeNewUnary(EOpLogicalNot, conditionSymbolElse);
falseBlock = new TIntermSelection(negatedCondition,
selection->getFalseBlock(), negatedElse);
}
TIntermSymbol *conditionSymbolSel = MakeNewTemporary(temporaryName, EbtBool);
TIntermSelection *newSelection = new TIntermSelection(conditionSymbolSel,
selection->getTrueBlock(), falseBlock);
TIntermAggregate *declaration = new TIntermAggregate(EOpDeclaration);
declaration->getSequence()->push_back(storeCondition);
TIntermAggregate *block = new TIntermAggregate(EOpSequence);
block->getSequence()->push_back(declaration);
block->getSequence()->push_back(newSelection);
return block;
}
}
void RewriteElseBlocks(TIntermNode *node)
{
ElseBlockRewriter rewriter;
node->traverse(&rewriter);
}
}
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