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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.
*/
#include "ir/function-utils.h"
#include "ir/local-graph.h"
#include "ir/type-updating.h"
#include "support/sorted_vector.h"
#include "wasm.h"
namespace wasm::ParamUtils {
std::unordered_set<Index> getUsedParams(Function* func) {
LocalGraph localGraph(func);
std::unordered_set<Index> usedParams;
for (auto& [get, sets] : localGraph.getSetses) {
if (!func->isParam(get->index)) {
continue;
}
for (auto* set : sets) {
// A nullptr value indicates there is no LocalSet* that sets the value,
// so it must be the parameter value.
if (!set) {
usedParams.insert(get->index);
}
}
}
return usedParams;
}
bool removeParameter(const std::vector<Function*> funcs,
Index index,
const std::vector<Call*>& calls,
const std::vector<CallRef*>& callRefs,
Module* module,
PassRunner* runner) {
assert(funcs.size() > 0);
auto* first = funcs[0];
#ifndef NDEBUG
for (auto* func : funcs) {
assert(func->type == first->type);
}
#endif
// Check if none of the calls has a param with side effects that we cannot
// remove (as if we can remove them, we will simply do that when we remove the
// parameter). Note: flattening the IR beforehand can help here.
bool callParamsAreValid =
std::none_of(calls.begin(), calls.end(), [&](Call* call) {
auto* operand = call->operands[index];
return EffectAnalyzer(runner->options, *module, operand)
.hasUnremovableSideEffects();
});
if (!callParamsAreValid) {
return false;
}
// The type must be valid for us to handle as a local (since we
// replace the parameter with a local).
// TODO: if there are no references at all, we can avoid creating a
// local
bool typeIsValid = TypeUpdating::canHandleAsLocal(first->getLocalType(index));
if (!typeIsValid) {
return false;
}
// We can do it!
// Remove the parameter from the function. We must add a new local
// for uses of the parameter, but cannot make it use the same index
// (in general).
auto paramsType = first->getParams();
std::vector<Type> params(paramsType.begin(), paramsType.end());
auto type = params[index];
params.erase(params.begin() + index);
// TODO: parallelize some of these loops?
for (auto* func : funcs) {
func->setParams(Type(params));
// It's cumbersome to adjust local names - TODO don't clear them?
Builder::clearLocalNames(func);
}
std::vector<Index> newIndexes;
for (auto* func : funcs) {
newIndexes.push_back(Builder::addVar(func, type));
}
// Update local operations.
struct LocalUpdater : public PostWalker<LocalUpdater> {
Index removedIndex;
Index newIndex;
LocalUpdater(Function* func, Index removedIndex, Index newIndex)
: removedIndex(removedIndex), newIndex(newIndex) {
walk(func->body);
}
void visitLocalGet(LocalGet* curr) { updateIndex(curr->index); }
void visitLocalSet(LocalSet* curr) { updateIndex(curr->index); }
void updateIndex(Index& index) {
if (index == removedIndex) {
index = newIndex;
} else if (index > removedIndex) {
index--;
}
}
};
for (Index i = 0; i < funcs.size(); i++) {
auto* func = funcs[i];
if (!func->imported()) {
LocalUpdater(funcs[i], index, newIndexes[i]);
TypeUpdating::handleNonDefaultableLocals(func, *module);
}
}
// Remove the arguments from the calls.
for (auto* call : calls) {
call->operands.erase(call->operands.begin() + index);
}
for (auto* call : callRefs) {
call->operands.erase(call->operands.begin() + index);
}
return true;
}
SortedVector removeParameters(const std::vector<Function*> funcs,
SortedVector indexes,
const std::vector<Call*>& calls,
const std::vector<CallRef*>& callRefs,
Module* module,
PassRunner* runner) {
if (indexes.empty()) {
return {};
}
assert(funcs.size() > 0);
auto* first = funcs[0];
#ifndef NDEBUG
for (auto* func : funcs) {
assert(func->type == first->type);
}
#endif
// Iterate downwards, as we may remove more than one, and going forwards would
// alter the indexes after us.
Index i = first->getNumParams() - 1;
SortedVector removed;
while (1) {
if (indexes.has(i)) {
if (removeParameter(funcs, i, calls, callRefs, module, runner)) {
// Success!
removed.insert(i);
}
}
if (i == 0) {
break;
}
i--;
}
return removed;
}
} // namespace wasm::ParamUtils
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