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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/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);
nextTemporaryId();
TIntermDeclaration *storeCondition = createTempInitDeclaration(ifElse->getCondition());
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 = createTempSymbol(boolType);
TIntermUnary *negatedCondition = new TIntermUnary(EOpLogicalNot, conditionSymbolElse);
TIntermIfElse *falseIfElse =
new TIntermIfElse(negatedCondition, ifElse->getFalseBlock(), negatedElse);
falseBlock = EnsureBlock(falseIfElse);
}
TIntermSymbol *conditionSymbolSel = createTempSymbol(boolType);
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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