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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.
*/
#ifndef wasm_ir_drop_h
#define wasm_ir_drop_h
#include "ir/effects.h"
#include "ir/iteration.h"
#include "wasm-builder.h"
#include "wasm.h"
namespace wasm {
// Given an expression, returns a new expression that drops the given
// expression's children that cannot be removed outright due to their side
// effects. This is useful if we know the node is not needed but may need to
// keep the children around; this utility will automatically remove any children
// we do not actually need to keep, based on their effects.
//
// The caller must also pass in a last item to append to the output (which is
// typically what the original expression is replaced with).
Expression* getDroppedChildrenAndAppend(Expression* curr,
Module& wasm,
const PassOptions& options,
Expression* last) {
Builder builder(wasm);
std::vector<Expression*> contents;
for (auto* child : ChildIterator(curr)) {
if (!EffectAnalyzer(options, wasm, child).hasUnremovableSideEffects()) {
continue;
}
if (child->type.isConcrete()) {
contents.push_back(builder.makeDrop(child));
} else {
// The child is unreachable, or none (none is possible as a child of a
// block or loop, etc.); in both cases we do not need a drop.
contents.push_back(child);
}
}
contents.push_back(last);
if (contents.size() == 1) {
return contents[0];
}
return builder.makeBlock(contents);
}
} // namespace wasm
#endif // wasm_ir_drop_h
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