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/*
* Copyright 2016 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.
*/
//
// Removes obviously unneeded code
//
#include <wasm.h>
#include <pass.h>
#include <ast_utils.h>
#include <wasm-builder.h>
namespace wasm {
struct Vacuum : public WalkerPass<PostWalker<Vacuum, Visitor<Vacuum>>> {
bool isFunctionParallel() { return true; }
void visitBlock(Block *curr) {
// compress out nops
int skip = 0;
auto& list = curr->list;
size_t size = list.size();
bool needResize = false;
for (size_t z = 0; z < size; z++) {
if (list[z]->is<Nop>()) {
skip++;
needResize = true;
} else {
if (skip > 0) {
list[z - skip] = list[z];
}
// if this is an unconditional br, the rest is dead code
Break* br = list[z - skip]->dynCast<Break>();
Switch* sw = list[z - skip]->dynCast<Switch>();
if ((br && !br->condition) || sw) {
list.resize(z - skip + 1);
needResize = false;
break;
}
}
}
if (needResize) {
list.resize(size - skip);
}
if (!curr->name.is()) {
if (list.size() == 1) {
replaceCurrent(list[0]);
} else if (list.size() == 0) {
ExpressionManipulator::nop(curr);
}
}
}
void visitIf(If* curr) {
if (curr->ifFalse) {
if (curr->ifFalse->is<Nop>()) {
curr->ifFalse = nullptr;
} else if (curr->ifTrue->is<Nop>()) {
curr->ifTrue = curr->ifFalse;
curr->ifFalse = nullptr;
curr->condition = Builder(*getModule()).makeUnary(EqZ, curr->condition);
}
}
if (!curr->ifFalse) {
// no else
if (curr->ifTrue->is<Nop>()) {
// no nothing
replaceCurrent(curr->condition);
}
}
}
};
static RegisterPass<Vacuum> registerPass("vacuum", "removes obviously unneeded code");
} // namespace wasm
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