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/*
* Copyright 2022 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.
*/
//
// Remove unused types from private rec groups. This is done implicitly by other
// type optimizations as well, but only if they find anything else they want to
// optimize.
//
#include "ir/module-utils.h"
#include "ir/type-updating.h"
#include "pass.h"
namespace wasm {
namespace {
struct RemoveUnusedTypes : Pass {
void run(Module* module) override {
if (!module->features.hasGC()) {
// This pass only does anything with GC types.
return;
}
// Consider (rec $A $unused), where anyrefs received from the outside are
// cast to `$A`. In an open world we cannot remove $unused because that
// would change the identity of $A. Currently we would incorrectly remove
// $unused. To fix that, we need to fix our collection of public types to
// consider $A (and $unused) public in an open world.
if (!getPassOptions().closedWorld) {
Fatal() << "RemoveUnusedTypes requires --closed-world";
}
// We're not changing the contents of any of the types, so we just round
// trip them through GlobalTypeRewriter which will put all the private types
// in a single new rec group and leave out all the unused types.
GlobalTypeRewriter(*module).update();
}
};
} // anonymous namespace
Pass* createRemoveUnusedTypesPass() { return new RemoveUnusedTypes(); }
} // namespace wasm
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