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/*
* Copyright 2021 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/properties.h"
#include "wasm-traversal.h"
namespace wasm::Properties {
bool isGenerative(Expression* curr, FeatureSet features) {
// Practically no wasm instructions are generative. Exceptions occur only in
// GC atm.
if (!features.hasGC()) {
return false;
}
struct Scanner : public PostWalker<Scanner> {
bool generative = false;
void visitStructNew(StructNew* curr) { generative = true; }
void visitArrayNew(ArrayNew* curr) { generative = true; }
void visitArrayNewFixed(ArrayNewFixed* curr) { generative = true; }
} scanner;
scanner.walk(curr);
return scanner.generative;
}
// Checks an expression in a shallow manner (i.e., does not check children) as
// to whether it is valid in a wasm constant expression.
static bool isValidInConstantExpression(Module& wasm, Expression* expr) {
if (isSingleConstantExpression(expr) || expr->is<StructNew>() ||
expr->is<ArrayNew>() || expr->is<ArrayNewFixed>() || expr->is<I31New>() ||
expr->is<StringConst>()) {
return true;
}
if (auto* refAs = expr->dynCast<RefAs>()) {
if (refAs->op == ExternExternalize || refAs->op == ExternInternalize) {
return true;
}
}
if (auto* get = expr->dynCast<GlobalGet>()) {
auto* g = wasm.getGlobalOrNull(get->name);
// This is called from the validator, so we have to handle non-existent
// globals gracefully.
if (!g) {
return false;
}
// Only gets of immutable globals are constant.
if (g->mutable_) {
return false;
}
// Only imported globals are available in constant expressions unless GC is
// enabled.
return g->imported() || wasm.features.hasGC();
// TODO: Check that there are no cycles between globals.
}
if (wasm.features.hasExtendedConst()) {
if (auto* bin = expr->dynCast<Binary>()) {
if (bin->op == AddInt64 || bin->op == SubInt64 || bin->op == MulInt64 ||
bin->op == AddInt32 || bin->op == SubInt32 || bin->op == MulInt32) {
return true;
}
}
}
return false;
}
bool isValidConstantExpression(Module& wasm, Expression* expr) {
struct Walker : public PostWalker<Walker, UnifiedExpressionVisitor<Walker>> {
bool valid = true;
void visitExpression(Expression* curr) {
if (!isValidInConstantExpression(*getModule(), curr)) {
valid = false;
}
}
} walker;
walker.setModule(&wasm);
walker.walk(expr);
return walker.valid;
}
} // namespace wasm::Properties
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