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/*
* Copyright 2017 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_ast_block_h
#define wasm_ast_block_h
#include "literal.h"
#include "wasm.h"
#include "ast_utils.h"
namespace wasm {
namespace BlockUtils {
// if a block has just one element, it can often be replaced
// with that content
template<typename T>
inline Expression* simplifyToContents(Block* block, T* parent, bool allowTypeChange = false) {
auto& list = block->list;
if (list.size() == 1 && !BreakSeeker::has(list[0], block->name)) {
// just one element. try to replace the block
auto* singleton = list[0];
auto sideEffects = EffectAnalyzer(parent->getPassOptions(), singleton).hasSideEffects();
if (!sideEffects && !isConcreteWasmType(singleton->type)) {
// no side effects, and singleton is not returning a value, so we can throw away
// the block and its contents, basically
return Builder(*parent->getModule()).replaceWithIdenticalType(block);
} else if (block->type == singleton->type || allowTypeChange) {
return singleton;
} else {
// (side effects +) type change, must be block with declared value but inside is unreachable
// (if both concrete, must match, and since no name on block, we can't be
// branched to, so if singleton is unreachable, so is the block)
assert(isConcreteWasmType(block->type) && singleton->type == unreachable);
// we could replace with unreachable, but would need to update all
// the parent's types
}
} else if (list.size() == 0) {
ExpressionManipulator::nop(block);
}
return block;
}
// similar, but when we allow the type to change while doing so
template<typename T>
inline Expression* simplifyToContentsWithPossibleTypeChange(Block* block, T* parent) {
return simplifyToContents(block, parent, true);
}
};
} // namespace wasm
#endif // wasm_ast_block_h
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