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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.
*/
//
// Computes code at compile time where possible.
//
#include <wasm.h>
#include <pass.h>
#include <wasm-builder.h>
#include <wasm-interpreter.h>
#include <ast_utils.h>
#include "ast/manipulation.h"
namespace wasm {
static const Name NONSTANDALONE_FLOW("Binaryen|nonstandalone");
// Execute an expression by itself. Errors if we hit anything we need anything not in the expression itself standalone.
class StandaloneExpressionRunner : public ExpressionRunner<StandaloneExpressionRunner> {
public:
struct NonstandaloneException {}; // TODO: use a flow with a special name, as this is likely very slow
Flow visitLoop(Loop* curr) {
// loops might be infinite, so must be careful
// but we can't tell if non-infinite, since we don't have state, so loops are just impossible to optimize for now
return Flow(NONSTANDALONE_FLOW);
}
Flow visitCall(Call* curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitCallImport(CallImport* curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitCallIndirect(CallIndirect* curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitGetLocal(GetLocal *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitSetLocal(SetLocal *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitGetGlobal(GetGlobal *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitSetGlobal(SetGlobal *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitLoad(Load *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitStore(Store *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitAtomicRMW(AtomicRMW *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitAtomicCmpxchg(AtomicCmpxchg *curr) {
return Flow(NONSTANDALONE_FLOW);
}
Flow visitHost(Host *curr) {
return Flow(NONSTANDALONE_FLOW);
}
void trap(const char* why) override {
throw NonstandaloneException();
}
};
struct Precompute : public WalkerPass<PostWalker<Precompute, UnifiedExpressionVisitor<Precompute>>> {
bool isFunctionParallel() override { return true; }
Pass* create() override { return new Precompute; }
void visitExpression(Expression* curr) {
if (curr->is<Const>() || curr->is<Nop>()) return;
// try to evaluate this into a const
Flow flow;
try {
flow = StandaloneExpressionRunner().visit(curr);
} catch (StandaloneExpressionRunner::NonstandaloneException& e) {
return;
}
if (flow.breaking()) {
if (flow.breakTo == NONSTANDALONE_FLOW) return;
if (flow.breakTo == RETURN_FLOW) {
// this expression causes a return. if it's already a return, reuse the node
if (auto* ret = curr->dynCast<Return>()) {
if (flow.value.type != none) {
// reuse a const value if there is one
if (ret->value) {
if (auto* value = ret->value->dynCast<Const>()) {
value->value = flow.value;
value->finalize();
return;
}
}
ret->value = Builder(*getModule()).makeConst(flow.value);
} else {
ret->value = nullptr;
}
} else {
Builder builder(*getModule());
replaceCurrent(builder.makeReturn(flow.value.type != none ? builder.makeConst(flow.value) : nullptr));
}
return;
}
// this expression causes a break, emit it directly. if it's already a br, reuse the node.
if (auto* br = curr->dynCast<Break>()) {
br->name = flow.breakTo;
br->condition = nullptr;
if (flow.value.type != none) {
// reuse a const value if there is one
if (br->value) {
if (auto* value = br->value->dynCast<Const>()) {
value->value = flow.value;
value->finalize();
br->finalize();
return;
}
}
br->value = Builder(*getModule()).makeConst(flow.value);
} else {
br->value = nullptr;
}
br->finalize();
} else {
Builder builder(*getModule());
replaceCurrent(builder.makeBreak(flow.breakTo, flow.value.type != none ? builder.makeConst(flow.value) : nullptr));
}
return;
}
// this was precomputed
if (isConcreteWasmType(flow.value.type)) {
replaceCurrent(Builder(*getModule()).makeConst(flow.value));
} else {
ExpressionManipulator::nop(curr);
}
}
void visitFunction(Function* curr) {
// removing breaks can alter types
ReFinalize().walkFunctionInModule(curr, getModule());
}
};
Pass *createPrecomputePass() {
return new Precompute();
}
} // namespace wasm
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