chromium/third_party/angle/src/compiler/translator/tree_util/ReplaceShadowingVariables.cpp

//
// Copyright 2019 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.
//
// ReplaceShadowingVariables.cpp: Replace all references to any variable in the AST that is
// a redefinition of a variable in a nested scope. This is a useful for ESSL 1.00 shaders
// where the spec section "4.2.3. Redeclaring Variables" states "However, a nested scope can
// override an outer scope's declaration of a particular variable name." This is changed in
// later spec versions, such as ESSL 3.20 spec which states "If [a variable] is declared as
// a parameter in a function definition, it is scoped until the end of that function
// definition. A function's parameter declarations and body together form a single scope."
//
// So this class is useful when translating from ESSL 1.00 shaders, where function body var
// redefinition is allowed, to later shader versions where it's not allowed.
//

#include "compiler/translator/tree_util/ReplaceShadowingVariables.h"
#include "compiler/translator/tree_util/ReplaceVariable.h"

#include "compiler/translator/Compiler.h"
#include "compiler/translator/IntermNode.h"
#include "compiler/translator/Symbol.h"
#include "compiler/translator/SymbolTable.h"
#include "compiler/translator/tree_util/IntermNode_util.h"
#include "compiler/translator/tree_util/IntermTraverse.h"

#include <unordered_set>

namespace sh
{

namespace
{

// Custom struct to queue up any replacements until after AST traversal
struct DeferredReplacementBlock
{ … };

class ReplaceShadowingVariablesTraverser : public TIntermTraverser
{ … };

}  // anonymous namespace

// Replaces every occurrence of a variable with another variable.
[[nodiscard]] bool ReplaceShadowingVariables(TCompiler *compiler,
                                             TIntermBlock *root,
                                             TSymbolTable *symbolTable)
{ … }

}  // namespace sh