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/*
* Copyright 2021 WebAssembly Community Group participants
*
* 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.
*/
#ifndef wasm_ir_numberings_h
#define wasm_ir_numberings_h
#include "ir/properties.h"
#include "wasm.h"
namespace wasm {
// General value numbering: Returns a number for an expression. Expressions with
// the same number must be identical in value; expressions with different values
// might happen to be identical at runtime.
class ValueNumbering {
public:
// Get the value numbering of an arbitrary expression.
Index getValue(Expression* expr) {
if (Properties::isConstantExpression(expr)) {
return getValue(Properties::getLiterals(expr));
} else {
auto iter = expressionValues.find(expr);
if (iter != expressionValues.end()) {
return iter->second;
}
// TODO: full GVN to check for different expressions with the same value.
return expressionValues[expr] = getUniqueValue();
}
}
// Get the value numbering of an arbitrary set of constants.
Index getValue(Literals lit) {
auto iter = literalValues.find(lit);
if (iter != literalValues.end()) {
return iter->second;
}
return literalValues[lit] = getUniqueValue();
}
// Return a new unique value. Normally this is called internally, but there
// are also use cases for the user of the class to call this, when they want
// to get a new value that will not collide with any others.
Index getUniqueValue() { return nextValue++; }
private:
Index nextValue = 0;
// Cache the value numbers of literals and expressions.
std::unordered_map<Literals, Index> literalValues;
std::unordered_map<Expression*, Index> expressionValues;
};
} // namespace wasm
#endif // wasm_ir_numberings_h
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