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/*
* Copyright 2023 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_analysis_lattices_valtype_h
#define wasm_analysis_lattices_valtype_h
#include "../lattice.h"
#include "wasm-type.h"
namespace wasm::analysis {
// Thin wrapper around `wasm::Type` giving it the interface of a lattice. As
// usual, `Type::unreachable` is the bottom element, but unlike in the
// underlying API, we uniformly treat `Type::none` as the top type so that we
// have a proper lattice.
struct ValType {
using Element = Type;
Element getBottom() const noexcept { return Type::unreachable; }
Element getTop() const noexcept { return Type::none; }
LatticeComparison compare(Element a, Element b) const noexcept {
if (a == b) {
return EQUAL;
}
if (b == Type::none || Type::isSubType(a, b)) {
return LESS;
}
if (a == Type::none || Type::isSubType(b, a)) {
return GREATER;
}
return NO_RELATION;
}
bool join(Element& joinee, Element joiner) const noexcept {
// `getLeastUpperBound` already treats `Type::none` as top.
auto lub = Type::getLeastUpperBound(joinee, joiner);
if (lub != joinee) {
joinee = lub;
return true;
}
return false;
}
bool meet(Element& meetee, Element meeter) const noexcept {
if (meetee == meeter || meeter == Type::none) {
return false;
}
if (meetee == Type::none) {
meetee = meeter;
return true;
}
auto glb = Type::getGreatestLowerBound(meetee, meeter);
if (glb != meetee) {
meetee = glb;
return true;
}
return false;
}
};
#if __cplusplus >= 202002L
static_assert(FullLattice<ValType>);
#endif
} // namespace wasm::analysis
#endif // wasm_analysis_lattices_valtype_h
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