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//
// 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.
//
// The PruneEmptyDeclarations function prunes unnecessary empty declarations and declarators from the AST.
#include "compiler/translator/PruneEmptyDeclarations.h"
#include "compiler/translator/IntermNode.h"
namespace
{
class PruneEmptyDeclarationsTraverser : private TIntermTraverser
{
public:
static void apply(TIntermNode *root);
private:
PruneEmptyDeclarationsTraverser();
bool visitAggregate(Visit, TIntermAggregate *node) override;
};
void PruneEmptyDeclarationsTraverser::apply(TIntermNode *root)
{
PruneEmptyDeclarationsTraverser prune;
root->traverse(&prune);
prune.updateTree();
}
PruneEmptyDeclarationsTraverser::PruneEmptyDeclarationsTraverser()
: TIntermTraverser(true, false, false)
{
}
bool PruneEmptyDeclarationsTraverser::visitAggregate(Visit, TIntermAggregate *node)
{
if (node->getOp() == EOpDeclaration)
{
TIntermSequence *sequence = node->getSequence();
if (sequence->size() >= 1)
{
TIntermSymbol *sym = sequence->front()->getAsSymbolNode();
// Prune declarations without a variable name, unless it's an interface block declaration.
if (sym != nullptr && sym->getSymbol() == "" && !sym->isInterfaceBlock())
{
if (sequence->size() > 1)
{
// Generate a replacement that will remove the empty declarator in the beginning of a declarator
// list. Example of a declaration that will be changed:
// float, a;
// will be changed to
// float a;
// This applies also to struct declarations.
TIntermSequence emptyReplacement;
mMultiReplacements.push_back(NodeReplaceWithMultipleEntry(node, sym, emptyReplacement));
}
else if (sym->getBasicType() != EbtStruct)
{
// Single struct declarations may just declare the struct type and no variables, so they should
// not be pruned. All other single empty declarations can be pruned entirely. Example of an empty
// declaration that will be pruned:
// float;
TIntermSequence emptyReplacement;
TIntermAggregate *parentAgg = getParentNode()->getAsAggregate();
ASSERT(parentAgg != nullptr);
mMultiReplacements.push_back(NodeReplaceWithMultipleEntry(parentAgg, node, emptyReplacement));
}
}
}
return false;
}
return true;
}
} // namespace
void PruneEmptyDeclarations(TIntermNode *root)
{
PruneEmptyDeclarationsTraverser::apply(root);
}
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