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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.
//
// PruneNoOps.cpp: The PruneNoOps function prunes:
// 1. Empty declarations "int;". Empty declarators will be pruned as well, so for example:
// int , a;
// is turned into
// int a;
// 2. Literal statements: "1.0;". The ESSL output doesn't define a default precision for float,
// so float literal statements would end up with no precision which is invalid ESSL.
#include "compiler/translator/PruneNoOps.h"
#include "compiler/translator/IntermTraverse.h"
namespace sh
{
namespace
{
bool IsNoOp(TIntermNode *node)
{
if (node->getAsConstantUnion() != nullptr)
{
return true;
}
bool isEmptyDeclaration = node->getAsDeclarationNode() != nullptr &&
node->getAsDeclarationNode()->getSequence()->empty();
if (isEmptyDeclaration)
{
return true;
}
return false;
}
class PruneNoOpsTraverser : private TIntermTraverser
{
public:
static void apply(TIntermBlock *root);
private:
PruneNoOpsTraverser();
bool visitDeclaration(Visit, TIntermDeclaration *node) override;
bool visitBlock(Visit visit, TIntermBlock *node) override;
bool visitLoop(Visit visit, TIntermLoop *loop) override;
};
void PruneNoOpsTraverser::apply(TIntermBlock *root)
{
PruneNoOpsTraverser prune;
root->traverse(&prune);
prune.updateTree();
}
PruneNoOpsTraverser::PruneNoOpsTraverser() : TIntermTraverser(true, false, false)
{
}
bool PruneNoOpsTraverser::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)
{
// If there are entirely empty non-struct declarations, they result in
// TIntermDeclaration nodes without any children in the parsing stage. These are
// handled in visitBlock and visitLoop.
UNREACHABLE();
}
else if (sym->getType().getQualifier() != EvqGlobal &&
sym->getType().getQualifier() != EvqTemporary)
{
// Single struct declarations may just declare the struct type and no variables, so
// they should not be pruned. Here we handle 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;
}
bool PruneNoOpsTraverser::visitBlock(Visit visit, TIntermBlock *node)
{
TIntermSequence *statements = node->getSequence();
for (TIntermNode *statement : *statements)
{
if (IsNoOp(statement))
{
TIntermSequence emptyReplacement;
mMultiReplacements.push_back(
NodeReplaceWithMultipleEntry(node, statement, emptyReplacement));
}
}
return true;
}
bool PruneNoOpsTraverser::visitLoop(Visit visit, TIntermLoop *loop)
{
TIntermTyped *expr = loop->getExpression();
if (expr != nullptr && IsNoOp(expr))
{
loop->setExpression(nullptr);
}
TIntermNode *init = loop->getInit();
if (init != nullptr && IsNoOp(init))
{
loop->setInit(nullptr);
}
return true;
}
} // namespace
void PruneNoOps(TIntermBlock *root)
{
PruneNoOpsTraverser::apply(root);
}
} // namespace sh
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