dawn-cmake/src/symbol_table.cc

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// Copyright 2020 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "src/symbol_table.h"
namespace tint {
SymbolTable::SymbolTable() = default;
SymbolTable::SymbolTable(const SymbolTable&) = default;
SymbolTable::SymbolTable(SymbolTable&&) = default;
SymbolTable::~SymbolTable() = default;
SymbolTable& SymbolTable::operator=(const SymbolTable& other) = default;
SymbolTable& SymbolTable::operator=(SymbolTable&&) = default;
Symbol SymbolTable::Register(const std::string& name) {
if (name == "")
return Symbol();
auto it = name_to_symbol_.find(name);
if (it != name_to_symbol_.end())
return it->second;
Symbol sym(next_symbol_);
++next_symbol_;
name_to_symbol_[name] = sym;
symbol_to_name_[sym] = name;
return sym;
}
Symbol SymbolTable::Get(const std::string& name) const {
auto it = name_to_symbol_.find(name);
return it != name_to_symbol_.end() ? it->second : Symbol();
}
std::string SymbolTable::NameFor(const Symbol symbol) const {
auto it = symbol_to_name_.find(symbol);
if (it == symbol_to_name_.end()) {
return symbol.to_str();
}
return it->second;
}
SymbolTable: Change behavior of anonymous symbols SymbolTable::New() used to build and return a symbol without a registered name. When you asked for the name of the symbol it would return tint_symbol_N, where N is the numerical identifier for the symbol. This approach was a major tripping hazzard for transforms that liked to fetch the source program name, and register it in the new program (in this situation, you should always use `CloneContext::Clone(Symbol)`). Without special casing for unnamed symbols, you could end up promoting the unnamed symbol to a named symbol, and then colliding against a new unnamed symbol. This is exactly what happened in tint:711. Instead, with this change: * The concept of unnamed symbols has been removed. All symbols now have a name. * The signature of `SymbolTable::New()` has been changed to take a name parameter (which defaults to 'tint_symbol'). This can be used to create a new, unique named symbol (possibly with a suffix), which will not collide with any existing symbols. Note these symbols may still collide if `SymbolTable::Register()` is called with the same name. All Transforms that currently use `SymbolTable::Register()` will be fixed in another change. * The CloneContext has been updated to use `SymbolTable::New()` instead of `Register()`. This means that any symbols defined before a clone will not collide. * `CloneContext::CloneSymbols()` has been added which allows a transform to pre-clone all the symbols from the source program. This can be used to avoid the authored identifiers being suffixed with a number, in the case a transform calls New() before the symbol is cloned. * `Symbol::to_str()` has been changed to return `$<id>` instead of `tint_symbol_N`. This is to avoid any confusion between the actual name and the symbol ID. Bug: tint:711 Bug: tint:712 Change-Id: I526e4b49b7027545613859de487e6a275686107a Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47631 Commit-Queue: Ben Clayton <bclayton@google.com> Reviewed-by: Antonio Maiorano <amaiorano@google.com>
2021-04-13 20:07:57 +00:00
Symbol SymbolTable::New(std::string prefix /* = "tint_symbol" */) {
auto it = name_to_symbol_.find(prefix);
if (it == name_to_symbol_.end()) {
return Register(prefix);
}
std::string name;
size_t i = 1;
do {
name = prefix + "_" + std::to_string(i++);
} while (name_to_symbol_.count(name));
return Register(name);
}
} // namespace tint