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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 sh
{
namespace
{
class PruneEmptyDeclarationsTraverser : private TIntermTraverser
{
public:
static void apply(TIntermNode *root);
private:
PruneEmptyDeclarationsTraverser();
bool visitDeclaration(Visit, TIntermDeclaration *node) override;
};
void PruneEmptyDeclarationsTraverser::apply(TIntermNode *root)
{
PruneEmptyDeclarationsTraverser prune;
root->traverse(&prune);
prune.updateTree();
}
PruneEmptyDeclarationsTraverser::PruneEmptyDeclarationsTraverser()
: TIntermTraverser(true, false, false)
{
}
bool PruneEmptyDeclarationsTraverser::visitDeclaration(Visit, TIntermDeclaration *node)
{
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;
TIntermBlock *parentAsBlock = getParentNode()->getAsBlock();
// The declaration may be inside a block or in a loop init expression.
ASSERT(parentAsBlock != nullptr || getParentNode()->getAsLoopNode() != nullptr);
if (parentAsBlock)
{
mMultiReplacements.push_back(
NodeReplaceWithMultipleEntry(parentAsBlock, node, emptyReplacement));
}
else
{
queueReplacement(node, nullptr, OriginalNode::IS_DROPPED);
}
}
else if (sym->getType().getQualifier() != EvqGlobal &&
sym->getType().getQualifier() != EvqTemporary)
{
// We've hit an empty struct declaration with a qualifier, for example like
// this:
// const struct a { int i; };
// NVIDIA GL driver version 367.27 doesn't accept this kind of declarations, so
// we convert the declaration to a regular struct declaration. This is okay,
// since ESSL 1.00 spec section 4.1.8 says about structs that "The optional
// qualifiers only apply to any declarators, and are not part of the type being
// defined for name."
if (mInGlobalScope)
{
sym->getTypePointer()->setQualifier(EvqGlobal);
}
else
{
sym->getTypePointer()->setQualifier(EvqTemporary);
}
}
}
}
return false;
}
} // namespace
void PruneEmptyDeclarations(TIntermNode *root)
{
PruneEmptyDeclarationsTraverser::apply(root);
}
} // namespace sh
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