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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_lubs_h
#define wasm_ir_lubs_h
#include "ir/module-utils.h"
#include "wasm.h"
namespace wasm {
//
// Helper to find a LUB of a series of expressions. This works incrementally so
// that if we see we are not improving on an existing type then we can stop
// early.
//
struct LUBFinder {
LUBFinder() {}
LUBFinder(Type initialType) { note(initialType); }
// Note another type to take into account in the lub.
void note(Type type) { lub = Type::getLeastUpperBound(lub, type); }
// Returns whether we noted any (reachable) value.
bool noted() { return lub != Type::unreachable; }
// Returns the lub.
Type getLUB() { return lub; }
// Combines the information in another LUBFinder into this one, and returns
// whether we changed anything.
bool combine(const LUBFinder& other) {
// Check if the lub was changed.
auto old = lub;
note(other.lub);
return old != lub;
}
private:
// The least upper bound. As we go this always contains the latest value based
// on everything we've seen so far, except for nulls.
Type lub = Type::unreachable;
};
namespace LUB {
// Given a function, computes a LUB for its results. The caller can then decide
// to apply a refined type if we found one.
//
// This modifies the called function even if it fails to find a refined type as
// it does a refinalize in order to be able to compute the new types. We could
// roll back that change, but it's not harmful and can help, so we keep it
// regardless.
LUBFinder getResultsLUB(Function* func, Module& wasm);
} // namespace LUB
} // namespace wasm
#endif // wasm_ir_lubs_h
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