Current File : /home/vacivi36/vittasync.vacivitta.com.br/vittasync/node/deps/v8/src/wasm/wasm-engine.cc
// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/wasm/wasm-engine.h"
#include "src/base/functional.h"
#include "src/base/platform/time.h"
#include "src/base/small-vector.h"
#include "src/common/assert-scope.h"
#include "src/common/globals.h"
#include "src/debug/debug.h"
#include "src/diagnostics/code-tracer.h"
#include "src/diagnostics/compilation-statistics.h"
#include "src/execution/frames.h"
#include "src/execution/v8threads.h"
#include "src/handles/global-handles-inl.h"
#include "src/logging/counters.h"
#include "src/logging/metrics.h"
#include "src/objects/heap-number.h"
#include "src/objects/managed-inl.h"
#include "src/objects/objects-inl.h"
#include "src/objects/objects.h"
#include "src/objects/primitive-heap-object.h"
#include "src/utils/ostreams.h"
#include "src/wasm/function-compiler.h"
#include "src/wasm/module-compiler.h"
#include "src/wasm/module-decoder.h"
#include "src/wasm/module-instantiate.h"
#include "src/wasm/pgo.h"
#include "src/wasm/stacks.h"
#include "src/wasm/std-object-sizes.h"
#include "src/wasm/streaming-decoder.h"
#include "src/wasm/wasm-debug.h"
#include "src/wasm/wasm-limits.h"
#include "src/wasm/wasm-objects-inl.h"
#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
#include "src/debug/wasm/gdb-server/gdb-server.h"
#endif // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
namespace v8::internal::wasm {
#define TRACE_CODE_GC(...) \
do { \
if (v8_flags.trace_wasm_code_gc) PrintF("[wasm-gc] " __VA_ARGS__); \
} while (false)
namespace {
// A task to log a set of {WasmCode} objects in an isolate. It does not own any
// data itself, since it is owned by the platform, so lifetime is not really
// bound to the wasm engine.
class LogCodesTask : public Task {
public:
LogCodesTask(base::Mutex* mutex, LogCodesTask** task_slot, Isolate* isolate,
WasmEngine* engine)
: mutex_(mutex),
task_slot_(task_slot),
isolate_(isolate),
engine_(engine) {
DCHECK_NOT_NULL(task_slot);
DCHECK_NOT_NULL(isolate);
}
~LogCodesTask() override {
// If the platform deletes this task before executing it, we also deregister
// it to avoid use-after-free from still-running background threads.
if (!cancelled()) DeregisterTask();
}
void Run() override {
if (cancelled()) return;
DeregisterTask();
engine_->LogOutstandingCodesForIsolate(isolate_);
}
void Cancel() {
// Cancel will only be called on Isolate shutdown, which happens on the
// Isolate's foreground thread. Thus no synchronization needed.
isolate_ = nullptr;
}
bool cancelled() const { return isolate_ == nullptr; }
void DeregisterTask() {
// The task will only be deregistered from the foreground thread (executing
// this task or calling its destructor), thus we do not need synchronization
// on this field access.
if (task_slot_ == nullptr) return; // already deregistered.
// Remove this task from the {IsolateInfo} in the engine. The next
// logging request will allocate and schedule a new task.
base::MutexGuard guard(mutex_);
DCHECK_EQ(this, *task_slot_);
*task_slot_ = nullptr;
task_slot_ = nullptr;
}
private:
// The mutex of the WasmEngine.
base::Mutex* const mutex_;
// The slot in the WasmEngine where this LogCodesTask is stored. This is
// cleared by this task before execution or on task destruction.
LogCodesTask** task_slot_;
Isolate* isolate_;
WasmEngine* const engine_;
};
void CheckNoArchivedThreads(Isolate* isolate) {
class ArchivedThreadsVisitor : public ThreadVisitor {
void VisitThread(Isolate* isolate, ThreadLocalTop* top) override {
// Archived threads are rarely used, and not combined with Wasm at the
// moment. Implement this and test it properly once we have a use case for
// that.
FATAL("archived threads in combination with wasm not supported");
}
} archived_threads_visitor;
isolate->thread_manager()->IterateArchivedThreads(&archived_threads_visitor);
}
class WasmGCForegroundTask : public CancelableTask {
public:
explicit WasmGCForegroundTask(Isolate* isolate)
: CancelableTask(isolate->cancelable_task_manager()), isolate_(isolate) {}
void RunInternal() final {
// The stack can contain live frames, for instance when this is invoked
// during a pause or a breakpoint.
GetWasmEngine()->ReportLiveCodeFromStackForGC(isolate_);
}
private:
Isolate* isolate_;
};
class WeakScriptHandle {
public:
explicit WeakScriptHandle(Handle<Script> script) : script_id_(script->id()) {
DCHECK(IsString(script->name()) || IsUndefined(script->name()));
if (IsString(script->name())) {
std::unique_ptr<char[]> source_url =
String::cast(script->name())->ToCString();
// Convert from {unique_ptr} to {shared_ptr}.
source_url_ = {source_url.release(), source_url.get_deleter()};
}
auto global_handle =
script->GetIsolate()->global_handles()->Create(*script);
location_ = std::make_unique<Address*>(global_handle.location());
GlobalHandles::MakeWeak(location_.get());
}
// Usually the destructor of this class should always be called after the weak
// callback because the Script keeps the NativeModule alive. So we expect the
// handle to be destroyed and the location to be reset already.
// We cannot check this because of one exception. When the native module is
// freed during isolate shutdown, the destructor will be called
// first, and the callback will never be called.
~WeakScriptHandle() = default;
WeakScriptHandle(WeakScriptHandle&&) V8_NOEXCEPT = default;
Handle<Script> handle() const { return Handle<Script>(*location_); }
int script_id() const { return script_id_; }
const std::shared_ptr<const char>& source_url() const { return source_url_; }
private:
// Store the location in a unique_ptr so that its address stays the same even
// when this object is moved/copied.
std::unique_ptr<Address*> location_;
// Store the script ID independent of the weak handle, such that it's always
// available.
int script_id_;
// Similar for the source URL. We cannot dereference the Handle from arbitrary
// threads, but we need the URL available for code logging.
// The shared pointer is kept alive by unlogged code, even if this entry is
// collected in the meantime.
// TODO(chromium:1132260): Revisit this for huge URLs.
std::shared_ptr<const char> source_url_;
};
// If PGO data is being collected, keep all native modules alive, so repeated
// runs of a benchmark (with different configuration) all use the same module.
// This vector is protected by the global WasmEngine's mutex, but not defined in
// the header because it's a private implementation detail.
std::vector<std::shared_ptr<NativeModule>>* native_modules_kept_alive_for_pgo;
} // namespace
std::shared_ptr<NativeModule> NativeModuleCache::MaybeGetNativeModule(
ModuleOrigin origin, base::Vector<const uint8_t> wire_bytes) {
if (!v8_flags.wasm_native_module_cache_enabled) return nullptr;
if (origin != kWasmOrigin) return nullptr;
base::MutexGuard lock(&mutex_);
size_t prefix_hash = PrefixHash(wire_bytes);
NativeModuleCache::Key key{prefix_hash, wire_bytes};
while (true) {
auto it = map_.find(key);
if (it == map_.end()) {
// Even though this exact key is not in the cache, there might be a
// matching prefix hash indicating that a streaming compilation is
// currently compiling a module with the same prefix. {OnFinishedStream}
// happens on the main thread too, so waiting for streaming compilation to
// finish would create a deadlock. Instead, compile the module twice and
// handle the conflict in {UpdateNativeModuleCache}.
// Insert a {nullopt} entry to let other threads know that this
// {NativeModule} is already being created on another thread.
auto p = map_.emplace(key, base::nullopt);
USE(p);
DCHECK(p.second);
return nullptr;
}
if (it->second.has_value()) {
if (auto shared_native_module = it->second.value().lock()) {
DCHECK_EQ(shared_native_module->wire_bytes(), wire_bytes);
return shared_native_module;
}
}
// TODO(11858): This deadlocks in predictable mode, because there is only a
// single thread.
cache_cv_.Wait(&mutex_);
}
}
bool NativeModuleCache::GetStreamingCompilationOwnership(size_t prefix_hash) {
base::MutexGuard lock(&mutex_);
auto it = map_.lower_bound(Key{prefix_hash, {}});
if (it != map_.end() && it->first.prefix_hash == prefix_hash) {
DCHECK_IMPLIES(!it->first.bytes.empty(),
PrefixHash(it->first.bytes) == prefix_hash);
return false;
}
Key key{prefix_hash, {}};
DCHECK_EQ(0, map_.count(key));
map_.emplace(key, base::nullopt);
return true;
}
void NativeModuleCache::StreamingCompilationFailed(size_t prefix_hash) {
base::MutexGuard lock(&mutex_);
Key key{prefix_hash, {}};
map_.erase(key);
cache_cv_.NotifyAll();
}
std::shared_ptr<NativeModule> NativeModuleCache::Update(
std::shared_ptr<NativeModule> native_module, bool error) {
DCHECK_NOT_NULL(native_module);
if (!v8_flags.wasm_native_module_cache_enabled) return native_module;
if (native_module->module()->origin != kWasmOrigin) return native_module;
base::Vector<const uint8_t> wire_bytes = native_module->wire_bytes();
DCHECK(!wire_bytes.empty());
size_t prefix_hash = PrefixHash(native_module->wire_bytes());
base::MutexGuard lock(&mutex_);
map_.erase(Key{prefix_hash, {}});
const Key key{prefix_hash, wire_bytes};
auto it = map_.find(key);
if (it != map_.end()) {
if (it->second.has_value()) {
auto conflicting_module = it->second.value().lock();
if (conflicting_module != nullptr) {
DCHECK_EQ(conflicting_module->wire_bytes(), wire_bytes);
// This return might delete {native_module} if we were the last holder.
// That in turn can call {NativeModuleCache::Erase}, which takes the
// mutex. This is not a problem though, since the {MutexGuard} above is
// released before the {native_module}, per the definition order.
return conflicting_module;
}
}
map_.erase(it);
}
if (!error) {
// The key now points to the new native module's owned copy of the bytes,
// so that it stays valid until the native module is freed and erased from
// the map.
auto p = map_.emplace(
key, base::Optional<std::weak_ptr<NativeModule>>(native_module));
USE(p);
DCHECK(p.second);
}
cache_cv_.NotifyAll();
return native_module;
}
void NativeModuleCache::Erase(NativeModule* native_module) {
if (!v8_flags.wasm_native_module_cache_enabled) return;
if (native_module->module()->origin != kWasmOrigin) return;
// Happens in some tests where bytes are set directly.
if (native_module->wire_bytes().empty()) return;
base::MutexGuard lock(&mutex_);
size_t prefix_hash = PrefixHash(native_module->wire_bytes());
map_.erase(Key{prefix_hash, native_module->wire_bytes()});
cache_cv_.NotifyAll();
}
// static
size_t NativeModuleCache::PrefixHash(base::Vector<const uint8_t> wire_bytes) {
// Compute the hash as a combined hash of the sections up to the code section
// header, to mirror the way streaming compilation does it.
Decoder decoder(wire_bytes.begin(), wire_bytes.end());
decoder.consume_bytes(8, "module header");
size_t hash = GetWireBytesHash(wire_bytes.SubVector(0, 8));
SectionCode section_id = SectionCode::kUnknownSectionCode;
while (decoder.ok() && decoder.more()) {
section_id = static_cast<SectionCode>(decoder.consume_u8());
uint32_t section_size = decoder.consume_u32v("section size");
if (section_id == SectionCode::kCodeSectionCode) {
hash = base::hash_combine(hash, section_size);
break;
}
const uint8_t* payload_start = decoder.pc();
decoder.consume_bytes(section_size, "section payload");
size_t section_hash =
GetWireBytesHash(base::VectorOf(payload_start, section_size));
hash = base::hash_combine(hash, section_hash);
}
return hash;
}
struct WasmEngine::CurrentGCInfo {
explicit CurrentGCInfo(int8_t gc_sequence_index)
: gc_sequence_index(gc_sequence_index) {
DCHECK_NE(0, gc_sequence_index);
}
// Set of isolates that did not scan their stack yet for used WasmCode, and
// their scheduled foreground task.
std::unordered_map<Isolate*, WasmGCForegroundTask*> outstanding_isolates;
// Set of dead code. Filled with all potentially dead code on initialization.
// Code that is still in-use is removed by the individual isolates.
std::unordered_set<WasmCode*> dead_code;
// The number of GCs triggered in the native module that triggered this GC.
// This is stored in the histogram for each participating isolate during
// execution of that isolate's foreground task.
const int8_t gc_sequence_index;
// If during this GC, another GC was requested, we skipped that other GC (we
// only run one GC at a time). Remember though to trigger another one once
// this one finishes. {next_gc_sequence_index} is 0 if no next GC is needed,
// and >0 otherwise. It stores the {num_code_gcs_triggered} of the native
// module which triggered the next GC.
int8_t next_gc_sequence_index = 0;
// The start time of this GC; used for tracing and sampled via {Counters}.
// Can be null ({TimeTicks::IsNull()}) if timer is not high resolution.
base::TimeTicks start_time;
};
struct WasmEngine::IsolateInfo {
explicit IsolateInfo(Isolate* isolate)
: log_codes(WasmCode::ShouldBeLogged(isolate)),
async_counters(isolate->async_counters()),
wrapper_compilation_barrier_(std::make_shared<OperationsBarrier>()) {
v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate);
v8::Platform* platform = V8::GetCurrentPlatform();
foreground_task_runner = platform->GetForegroundTaskRunner(v8_isolate);
}
#ifdef DEBUG
~IsolateInfo() {
// Before destructing, the {WasmEngine} must have cleared outstanding code
// to log.
DCHECK_EQ(0, code_to_log.size());
}
#endif
// All native modules that are being used by this Isolate.
std::unordered_set<NativeModule*> native_modules;
// Scripts created for each native module in this isolate.
std::unordered_map<NativeModule*, WeakScriptHandle> scripts;
// Caches whether code needs to be logged on this isolate.
bool log_codes;
// The currently scheduled LogCodesTask.
LogCodesTask* log_codes_task = nullptr;
// Maps script ID to vector of code objects that still need to be logged, and
// the respective source URL.
struct CodeToLogPerScript {
std::vector<WasmCode*> code;
std::shared_ptr<const char> source_url;
};
std::unordered_map<int, CodeToLogPerScript> code_to_log;
// The foreground task runner of the isolate (can be called from background).
std::shared_ptr<v8::TaskRunner> foreground_task_runner;
const std::shared_ptr<Counters> async_counters;
// Keep new modules in debug state.
bool keep_in_debug_state = false;
// Keep track whether we already added a sample for PKU support (we only want
// one sample per Isolate).
bool pku_support_sampled = false;
// Elapsed time since last throw/rethrow/catch event.
base::ElapsedTimer throw_timer;
base::ElapsedTimer rethrow_timer;
base::ElapsedTimer catch_timer;
// Total number of exception events in this isolate.
int throw_count = 0;
int rethrow_count = 0;
int catch_count = 0;
// Operations barrier to synchronize on wrapper compilation on isolate
// shutdown.
// TODO(wasm): Remove this once we can use the generic js-to-wasm wrapper
// everywhere.
std::shared_ptr<OperationsBarrier> wrapper_compilation_barrier_;
};
struct WasmEngine::NativeModuleInfo {
explicit NativeModuleInfo(std::weak_ptr<NativeModule> native_module)
: weak_ptr(std::move(native_module)) {}
// Weak pointer, to gain back a shared_ptr if needed.
std::weak_ptr<NativeModule> weak_ptr;
// Set of isolates using this NativeModule.
std::unordered_set<Isolate*> isolates;
// Set of potentially dead code. This set holds one ref for each code object,
// until code is detected to be really dead. At that point, the ref count is
// decremented and code is move to the {dead_code} set. If the code is finally
// deleted, it is also removed from {dead_code}.
std::unordered_set<WasmCode*> potentially_dead_code;
// Code that is not being executed in any isolate any more, but the ref count
// did not drop to zero yet.
std::unordered_set<WasmCode*> dead_code;
// Number of code GCs triggered because code in this native module became
// potentially dead.
int8_t num_code_gcs_triggered = 0;
};
WasmEngine::WasmEngine() : call_descriptors_(&allocator_) {}
WasmEngine::~WasmEngine() {
#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
// Synchronize on the GDB-remote thread, if running.
gdb_server_.reset();
#endif // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
// Free all modules that were kept alive for collecting PGO. This is to avoid
// memory leaks.
if (V8_UNLIKELY(native_modules_kept_alive_for_pgo)) {
delete native_modules_kept_alive_for_pgo;
}
operations_barrier_->CancelAndWait();
// All AsyncCompileJobs have been canceled.
DCHECK(async_compile_jobs_.empty());
// All Isolates have been deregistered.
DCHECK(isolates_.empty());
// All NativeModules did die.
DCHECK(native_modules_.empty());
// Native module cache does not leak.
DCHECK(native_module_cache_.empty());
}
bool WasmEngine::SyncValidate(Isolate* isolate, WasmFeatures enabled,
ModuleWireBytes bytes) {
TRACE_EVENT0("v8.wasm", "wasm.SyncValidate");
if (bytes.length() == 0) return false;
auto result = DecodeWasmModule(
enabled, bytes.module_bytes(), true, kWasmOrigin, isolate->counters(),
isolate->metrics_recorder(),
isolate->GetOrRegisterRecorderContextId(isolate->native_context()),
DecodingMethod::kSync);
return result.ok();
}
MaybeHandle<AsmWasmData> WasmEngine::SyncCompileTranslatedAsmJs(
Isolate* isolate, ErrorThrower* thrower, ModuleWireBytes bytes,
base::Vector<const uint8_t> asm_js_offset_table_bytes,
Handle<HeapNumber> uses_bitset, LanguageMode language_mode) {
int compilation_id = next_compilation_id_.fetch_add(1);
TRACE_EVENT1("v8.wasm", "wasm.SyncCompileTranslatedAsmJs", "id",
compilation_id);
ModuleOrigin origin = language_mode == LanguageMode::kSloppy
? kAsmJsSloppyOrigin
: kAsmJsStrictOrigin;
// TODO(leszeks): If we want asm.js in UKM, we should figure out a way to pass
// the context id in here.
v8::metrics::Recorder::ContextId context_id =
v8::metrics::Recorder::ContextId::Empty();
ModuleResult result =
DecodeWasmModule(WasmFeatures::ForAsmjs(), bytes.module_bytes(), false,
origin, isolate->counters(), isolate->metrics_recorder(),
context_id, DecodingMethod::kSync);
if (result.failed()) {
// This happens once in a while when we have missed some limit check
// in the asm parser. Output an error message to help diagnose, but crash.
std::cout << result.error().message();
UNREACHABLE();
}
result.value()->asm_js_offset_information =
std::make_unique<AsmJsOffsetInformation>(asm_js_offset_table_bytes);
// Transfer ownership of the WasmModule to the {Managed<WasmModule>} generated
// in {CompileToNativeModule}.
constexpr ProfileInformation* kNoProfileInformation = nullptr;
std::shared_ptr<NativeModule> native_module = CompileToNativeModule(
isolate, WasmFeatures::ForAsmjs(), thrower, std::move(result).value(),
bytes, compilation_id, context_id, kNoProfileInformation);
if (!native_module) return {};
return AsmWasmData::New(isolate, std::move(native_module), uses_bitset);
}
Handle<WasmModuleObject> WasmEngine::FinalizeTranslatedAsmJs(
Isolate* isolate, Handle<AsmWasmData> asm_wasm_data,
Handle<Script> script) {
std::shared_ptr<NativeModule> native_module =
asm_wasm_data->managed_native_module()->get();
Handle<WasmModuleObject> module_object =
WasmModuleObject::New(isolate, std::move(native_module), script);
return module_object;
}
MaybeHandle<WasmModuleObject> WasmEngine::SyncCompile(Isolate* isolate,
WasmFeatures enabled,
ErrorThrower* thrower,
ModuleWireBytes bytes) {
int compilation_id = next_compilation_id_.fetch_add(1);
TRACE_EVENT1("v8.wasm", "wasm.SyncCompile", "id", compilation_id);
v8::metrics::Recorder::ContextId context_id =
isolate->GetOrRegisterRecorderContextId(isolate->native_context());
std::shared_ptr<WasmModule> module;
{
ModuleResult result = DecodeWasmModule(
enabled, bytes.module_bytes(), false, kWasmOrigin, isolate->counters(),
isolate->metrics_recorder(), context_id, DecodingMethod::kSync);
if (result.failed()) {
thrower->CompileFailed(result.error());
return {};
}
module = std::move(result).value();
}
// If experimental PGO via files is enabled, load profile information now.
std::unique_ptr<ProfileInformation> pgo_info;
if (V8_UNLIKELY(v8_flags.experimental_wasm_pgo_from_file)) {
pgo_info = LoadProfileFromFile(module.get(), bytes.module_bytes());
}
// Transfer ownership of the WasmModule to the {Managed<WasmModule>} generated
// in {CompileToNativeModule}.
std::shared_ptr<NativeModule> native_module =
CompileToNativeModule(isolate, enabled, thrower, std::move(module), bytes,
compilation_id, context_id, pgo_info.get());
if (!native_module) return {};
#ifdef DEBUG
// Ensure that code GC will check this isolate for live code.
{
base::MutexGuard lock(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
DCHECK_EQ(1, isolates_[isolate]->native_modules.count(native_module.get()));
DCHECK_EQ(1, native_modules_.count(native_module.get()));
DCHECK_EQ(1, native_modules_[native_module.get()]->isolates.count(isolate));
}
#endif
constexpr base::Vector<const char> kNoSourceUrl;
Handle<Script> script =
GetOrCreateScript(isolate, native_module, kNoSourceUrl);
native_module->LogWasmCodes(isolate, *script);
// Create the compiled module object and populate with compiled functions
// and information needed at instantiation time. This object needs to be
// serializable. Instantiation may occur off a deserialized version of this
// object.
Handle<WasmModuleObject> module_object =
WasmModuleObject::New(isolate, std::move(native_module), script);
// Finish the Wasm script now and make it public to the debugger.
isolate->debug()->OnAfterCompile(script);
return module_object;
}
MaybeHandle<WasmInstanceObject> WasmEngine::SyncInstantiate(
Isolate* isolate, ErrorThrower* thrower,
Handle<WasmModuleObject> module_object, MaybeHandle<JSReceiver> imports,
MaybeHandle<JSArrayBuffer> memory) {
TRACE_EVENT0("v8.wasm", "wasm.SyncInstantiate");
return InstantiateToInstanceObject(isolate, thrower, module_object, imports,
memory);
}
void WasmEngine::AsyncInstantiate(
Isolate* isolate, std::unique_ptr<InstantiationResultResolver> resolver,
Handle<WasmModuleObject> module_object, MaybeHandle<JSReceiver> imports) {
ErrorThrower thrower(isolate, "WebAssembly.instantiate()");
TRACE_EVENT0("v8.wasm", "wasm.AsyncInstantiate");
// Instantiate a TryCatch so that caught exceptions won't progagate out.
// They will still be set as pending exceptions on the isolate.
// TODO(clemensb): Avoid TryCatch, use Execution::TryCall internally to invoke
// start function and report thrown exception explicitly via out argument.
v8::TryCatch catcher(reinterpret_cast<v8::Isolate*>(isolate));
catcher.SetVerbose(false);
catcher.SetCaptureMessage(false);
MaybeHandle<WasmInstanceObject> instance_object = SyncInstantiate(
isolate, &thrower, module_object, imports, Handle<JSArrayBuffer>::null());
if (!instance_object.is_null()) {
resolver->OnInstantiationSucceeded(instance_object.ToHandleChecked());
return;
}
if (isolate->has_pending_exception()) {
// The JS code executed during instantiation has thrown an exception.
// We have to move the exception to the promise chain.
Handle<Object> exception(isolate->pending_exception(), isolate);
isolate->clear_pending_exception();
*isolate->external_caught_exception_address() = false;
resolver->OnInstantiationFailed(exception);
thrower.Reset();
} else {
DCHECK(thrower.error());
resolver->OnInstantiationFailed(thrower.Reify());
}
}
void WasmEngine::AsyncCompile(
Isolate* isolate, WasmFeatures enabled,
std::shared_ptr<CompilationResultResolver> resolver, ModuleWireBytes bytes,
bool is_shared, const char* api_method_name_for_errors) {
int compilation_id = next_compilation_id_.fetch_add(1);
TRACE_EVENT1("v8.wasm", "wasm.AsyncCompile", "id", compilation_id);
if (!v8_flags.wasm_async_compilation) {
// Asynchronous compilation disabled; fall back on synchronous compilation.
ErrorThrower thrower(isolate, api_method_name_for_errors);
MaybeHandle<WasmModuleObject> module_object;
if (is_shared) {
// Make a copy of the wire bytes to avoid concurrent modification.
std::unique_ptr<uint8_t[]> copy(new uint8_t[bytes.length()]);
memcpy(copy.get(), bytes.start(), bytes.length());
ModuleWireBytes bytes_copy(copy.get(), copy.get() + bytes.length());
module_object = SyncCompile(isolate, enabled, &thrower, bytes_copy);
} else {
// The wire bytes are not shared, OK to use them directly.
module_object = SyncCompile(isolate, enabled, &thrower, bytes);
}
if (thrower.error()) {
resolver->OnCompilationFailed(thrower.Reify());
return;
}
Handle<WasmModuleObject> module = module_object.ToHandleChecked();
resolver->OnCompilationSucceeded(module);
return;
}
if (v8_flags.wasm_test_streaming) {
std::shared_ptr<StreamingDecoder> streaming_decoder =
StartStreamingCompilation(
isolate, enabled, handle(isolate->context(), isolate),
api_method_name_for_errors, std::move(resolver));
auto* rng = isolate->random_number_generator();
base::SmallVector<base::Vector<const uint8_t>, 16> ranges;
if (!bytes.module_bytes().empty()) ranges.push_back(bytes.module_bytes());
// Split into up to 16 ranges (2^4).
for (int round = 0; round < 4; ++round) {
for (auto it = ranges.begin(); it != ranges.end(); ++it) {
auto range = *it;
if (range.size() < 2 || !rng->NextBool()) continue; // Do not split.
// Choose split point within [1, range.size() - 1].
static_assert(kV8MaxWasmModuleSize <= kMaxInt);
size_t split_point =
1 + rng->NextInt(static_cast<int>(range.size() - 1));
// Insert first sub-range *before* {it} and make {it} point after it.
it = ranges.insert(it, range.SubVector(0, split_point)) + 1;
*it = range.SubVectorFrom(split_point);
}
}
for (auto range : ranges) {
streaming_decoder->OnBytesReceived(range);
}
streaming_decoder->Finish();
return;
}
// Make a copy of the wire bytes in case the user program changes them
// during asynchronous compilation.
base::OwnedVector<const uint8_t> copy =
base::OwnedVector<const uint8_t>::Of(bytes.module_bytes());
AsyncCompileJob* job = CreateAsyncCompileJob(
isolate, enabled, std::move(copy), isolate->native_context(),
api_method_name_for_errors, std::move(resolver), compilation_id);
job->Start();
}
std::shared_ptr<StreamingDecoder> WasmEngine::StartStreamingCompilation(
Isolate* isolate, WasmFeatures enabled, Handle<Context> context,
const char* api_method_name,
std::shared_ptr<CompilationResultResolver> resolver) {
int compilation_id = next_compilation_id_.fetch_add(1);
TRACE_EVENT1("v8.wasm", "wasm.StartStreamingCompilation", "id",
compilation_id);
if (v8_flags.wasm_async_compilation) {
AsyncCompileJob* job =
CreateAsyncCompileJob(isolate, enabled, {}, context, api_method_name,
std::move(resolver), compilation_id);
return job->CreateStreamingDecoder();
}
return StreamingDecoder::CreateSyncStreamingDecoder(
isolate, enabled, context, api_method_name, std::move(resolver));
}
void WasmEngine::CompileFunction(Counters* counters,
NativeModule* native_module,
uint32_t function_index, ExecutionTier tier) {
// Note we assume that "one-off" compilations can discard detected features.
WasmFeatures detected = WasmFeatures::None();
WasmCompilationUnit::CompileWasmFunction(
counters, native_module, &detected,
&native_module->module()->functions[function_index], tier);
}
void WasmEngine::EnterDebuggingForIsolate(Isolate* isolate) {
std::vector<std::shared_ptr<NativeModule>> native_modules;
// {mutex_} gets taken both here and in {RemoveCompiledCode} in
// {AddPotentiallyDeadCode}. Therefore {RemoveCompiledCode} has to be
// called outside the lock.
{
base::MutexGuard lock(&mutex_);
if (isolates_[isolate]->keep_in_debug_state) return;
isolates_[isolate]->keep_in_debug_state = true;
for (auto* native_module : isolates_[isolate]->native_modules) {
DCHECK_EQ(1, native_modules_.count(native_module));
if (auto shared_ptr = native_modules_[native_module]->weak_ptr.lock()) {
native_modules.emplace_back(std::move(shared_ptr));
}
native_module->SetDebugState(kDebugging);
}
}
for (auto& native_module : native_modules) {
native_module->RemoveCompiledCode(
NativeModule::RemoveFilter::kRemoveNonDebugCode);
}
}
void WasmEngine::LeaveDebuggingForIsolate(Isolate* isolate) {
// Only trigger recompilation after releasing the mutex, otherwise we risk
// deadlocks because of lock inversion. The bool tells whether the module
// needs recompilation for tier up.
std::vector<std::pair<std::shared_ptr<NativeModule>, bool>> native_modules;
{
base::MutexGuard lock(&mutex_);
isolates_[isolate]->keep_in_debug_state = false;
auto can_remove_debug_code = [this](NativeModule* native_module) {
DCHECK_EQ(1, native_modules_.count(native_module));
for (auto* isolate : native_modules_[native_module]->isolates) {
DCHECK_EQ(1, isolates_.count(isolate));
if (isolates_[isolate]->keep_in_debug_state) return false;
}
return true;
};
for (auto* native_module : isolates_[isolate]->native_modules) {
DCHECK_EQ(1, native_modules_.count(native_module));
auto shared_ptr = native_modules_[native_module]->weak_ptr.lock();
if (!shared_ptr) continue; // The module is not used any more.
if (!native_module->IsInDebugState()) continue;
// Only start tier-up if no other isolate needs this module in tiered
// down state.
bool remove_debug_code = can_remove_debug_code(native_module);
if (remove_debug_code) native_module->SetDebugState(kNotDebugging);
native_modules.emplace_back(std::move(shared_ptr), remove_debug_code);
}
}
for (auto& entry : native_modules) {
auto& native_module = entry.first;
bool remove_debug_code = entry.second;
// Remove all breakpoints set by this isolate.
if (native_module->HasDebugInfo()) {
native_module->GetDebugInfo()->RemoveIsolate(isolate);
}
if (remove_debug_code) {
native_module->RemoveCompiledCode(
NativeModule::RemoveFilter::kRemoveDebugCode);
}
}
}
std::shared_ptr<NativeModule> WasmEngine::ExportNativeModule(
Handle<WasmModuleObject> module_object) {
return module_object->shared_native_module();
}
namespace {
Handle<Script> CreateWasmScript(Isolate* isolate,
std::shared_ptr<NativeModule> native_module,
base::Vector<const char> source_url) {
base::Vector<const uint8_t> wire_bytes = native_module->wire_bytes();
// The source URL of the script is
// - the original source URL if available (from the streaming API),
// - wasm://wasm/<module name>-<hash> if a module name has been set, or
// - wasm://wasm/<hash> otherwise.
const WasmModule* module = native_module->module();
Handle<String> url_str;
if (!source_url.empty()) {
url_str = isolate->factory()
->NewStringFromUtf8(source_url, AllocationType::kOld)
.ToHandleChecked();
} else {
// Limit the printed hash to 8 characters.
uint32_t hash = static_cast<uint32_t>(GetWireBytesHash(wire_bytes));
base::EmbeddedVector<char, 32> buffer;
if (module->name.is_empty()) {
// Build the URL in the form "wasm://wasm/<hash>".
int url_len = SNPrintF(buffer, "wasm://wasm/%08x", hash);
DCHECK(url_len >= 0 && url_len < buffer.length());
url_str = isolate->factory()
->NewStringFromUtf8(buffer.SubVector(0, url_len),
AllocationType::kOld)
.ToHandleChecked();
} else {
// Build the URL in the form "wasm://wasm/<module name>-<hash>".
int hash_len = SNPrintF(buffer, "-%08x", hash);
DCHECK(hash_len >= 0 && hash_len < buffer.length());
Handle<String> prefix =
isolate->factory()->NewStringFromStaticChars("wasm://wasm/");
Handle<String> module_name =
WasmModuleObject::ExtractUtf8StringFromModuleBytes(
isolate, wire_bytes, module->name, kNoInternalize);
Handle<String> hash_str =
isolate->factory()
->NewStringFromUtf8(buffer.SubVector(0, hash_len))
.ToHandleChecked();
// Concatenate the three parts.
url_str = isolate->factory()
->NewConsString(prefix, module_name)
.ToHandleChecked();
url_str = isolate->factory()
->NewConsString(url_str, hash_str)
.ToHandleChecked();
}
}
Handle<PrimitiveHeapObject> source_map_url =
isolate->factory()->undefined_value();
const WasmDebugSymbols& debug_symbols = module->debug_symbols;
if (debug_symbols.type == WasmDebugSymbols::Type::SourceMap &&
!debug_symbols.external_url.is_empty()) {
base::Vector<const char> external_url =
ModuleWireBytes(wire_bytes).GetNameOrNull(debug_symbols.external_url);
MaybeHandle<String> src_map_str = isolate->factory()->NewStringFromUtf8(
external_url, AllocationType::kOld);
source_map_url = src_map_str.ToHandleChecked();
}
// Use the given shared {NativeModule}, but increase its reference count by
// allocating a new {Managed<T>} that the {Script} references.
size_t code_size_estimate = native_module->committed_code_space();
size_t memory_estimate =
code_size_estimate +
wasm::WasmCodeManager::EstimateNativeModuleMetaDataSize(module);
Handle<Managed<wasm::NativeModule>> managed_native_module =
Managed<wasm::NativeModule>::FromSharedPtr(isolate, memory_estimate,
std::move(native_module));
Handle<Script> script =
isolate->factory()->NewScript(isolate->factory()->undefined_value());
{
DisallowGarbageCollection no_gc;
Tagged<Script> raw_script = *script;
raw_script->set_compilation_state(Script::CompilationState::kCompiled);
raw_script->set_context_data(isolate->native_context()->debug_context_id());
raw_script->set_name(*url_str);
raw_script->set_type(Script::Type::kWasm);
raw_script->set_source_mapping_url(*source_map_url);
raw_script->set_line_ends(ReadOnlyRoots(isolate).empty_fixed_array(),
SKIP_WRITE_BARRIER);
raw_script->set_wasm_managed_native_module(*managed_native_module);
raw_script->set_wasm_breakpoint_infos(
ReadOnlyRoots(isolate).empty_fixed_array(), SKIP_WRITE_BARRIER);
raw_script->set_wasm_weak_instance_list(
ReadOnlyRoots(isolate).empty_weak_array_list(), SKIP_WRITE_BARRIER);
}
return script;
}
} // namespace
Handle<WasmModuleObject> WasmEngine::ImportNativeModule(
Isolate* isolate, std::shared_ptr<NativeModule> shared_native_module,
base::Vector<const char> source_url) {
NativeModule* native_module = shared_native_module.get();
ModuleWireBytes wire_bytes(native_module->wire_bytes());
Handle<Script> script =
GetOrCreateScript(isolate, shared_native_module, source_url);
native_module->LogWasmCodes(isolate, *script);
Handle<WasmModuleObject> module_object =
WasmModuleObject::New(isolate, std::move(shared_native_module), script);
{
base::MutexGuard lock(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
IsolateInfo* isolate_info = isolates_.find(isolate)->second.get();
isolate_info->native_modules.insert(native_module);
DCHECK_EQ(1, native_modules_.count(native_module));
native_modules_[native_module]->isolates.insert(isolate);
if (isolate_info->log_codes) native_module->EnableCodeLogging();
}
// Finish the Wasm script now and make it public to the debugger.
isolate->debug()->OnAfterCompile(script);
return module_object;
}
void WasmEngine::FlushCode() {
for (auto& entry : native_modules_) {
NativeModule* native_module = entry.first;
native_module->RemoveCompiledCode(
NativeModule::RemoveFilter::kRemoveLiftoffCode);
}
}
std::shared_ptr<CompilationStatistics>
WasmEngine::GetOrCreateTurboStatistics() {
base::MutexGuard guard(&mutex_);
if (compilation_stats_ == nullptr) {
compilation_stats_.reset(new CompilationStatistics());
}
return compilation_stats_;
}
void WasmEngine::DumpAndResetTurboStatistics() {
base::MutexGuard guard(&mutex_);
if (compilation_stats_ != nullptr) {
StdoutStream os;
os << AsPrintableStatistics{"Turbofan Wasm", *compilation_stats_.get(),
false}
<< std::endl;
}
compilation_stats_.reset();
}
void WasmEngine::DumpTurboStatistics() {
base::MutexGuard guard(&mutex_);
if (compilation_stats_ != nullptr) {
StdoutStream os;
os << AsPrintableStatistics{"Turbofan Wasm", *compilation_stats_.get(),
false}
<< std::endl;
}
}
CodeTracer* WasmEngine::GetCodeTracer() {
base::MutexGuard guard(&mutex_);
if (code_tracer_ == nullptr) code_tracer_.reset(new CodeTracer(-1));
return code_tracer_.get();
}
AsyncCompileJob* WasmEngine::CreateAsyncCompileJob(
Isolate* isolate, WasmFeatures enabled,
base::OwnedVector<const uint8_t> bytes, Handle<Context> context,
const char* api_method_name,
std::shared_ptr<CompilationResultResolver> resolver, int compilation_id) {
Handle<NativeContext> incumbent_context = isolate->GetIncumbentContext();
AsyncCompileJob* job = new AsyncCompileJob(
isolate, enabled, std::move(bytes), context, incumbent_context,
api_method_name, std::move(resolver), compilation_id);
// Pass ownership to the unique_ptr in {async_compile_jobs_}.
base::MutexGuard guard(&mutex_);
async_compile_jobs_[job] = std::unique_ptr<AsyncCompileJob>(job);
return job;
}
std::unique_ptr<AsyncCompileJob> WasmEngine::RemoveCompileJob(
AsyncCompileJob* job) {
base::MutexGuard guard(&mutex_);
auto item = async_compile_jobs_.find(job);
DCHECK(item != async_compile_jobs_.end());
std::unique_ptr<AsyncCompileJob> result = std::move(item->second);
async_compile_jobs_.erase(item);
return result;
}
bool WasmEngine::HasRunningCompileJob(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
for (auto& entry : async_compile_jobs_) {
if (entry.first->isolate() == isolate) return true;
}
return false;
}
void WasmEngine::DeleteCompileJobsOnContext(Handle<Context> context) {
// Under the mutex get all jobs to delete. Then delete them without holding
// the mutex, such that deletion can reenter the WasmEngine.
std::vector<std::unique_ptr<AsyncCompileJob>> jobs_to_delete;
{
base::MutexGuard guard(&mutex_);
for (auto it = async_compile_jobs_.begin();
it != async_compile_jobs_.end();) {
if (!it->first->context().is_identical_to(context)) {
++it;
continue;
}
jobs_to_delete.push_back(std::move(it->second));
it = async_compile_jobs_.erase(it);
}
}
}
void WasmEngine::DeleteCompileJobsOnIsolate(Isolate* isolate) {
// Under the mutex get all jobs to delete. Then delete them without holding
// the mutex, such that deletion can reenter the WasmEngine.
std::vector<std::unique_ptr<AsyncCompileJob>> jobs_to_delete;
std::vector<std::weak_ptr<NativeModule>> modules_in_isolate;
std::shared_ptr<OperationsBarrier> wrapper_compilation_barrier;
{
base::MutexGuard guard(&mutex_);
for (auto it = async_compile_jobs_.begin();
it != async_compile_jobs_.end();) {
if (it->first->isolate() != isolate) {
++it;
continue;
}
jobs_to_delete.push_back(std::move(it->second));
it = async_compile_jobs_.erase(it);
}
DCHECK_EQ(1, isolates_.count(isolate));
auto* isolate_info = isolates_[isolate].get();
wrapper_compilation_barrier = isolate_info->wrapper_compilation_barrier_;
for (auto* native_module : isolate_info->native_modules) {
DCHECK_EQ(1, native_modules_.count(native_module));
modules_in_isolate.emplace_back(native_modules_[native_module]->weak_ptr);
}
}
// All modules that have not finished initial compilation yet cannot be
// shared with other isolates. Hence we cancel their compilation. In
// particular, this will cancel wrapper compilation which is bound to this
// isolate (this would be a UAF otherwise).
for (auto& weak_module : modules_in_isolate) {
if (auto shared_module = weak_module.lock()) {
shared_module->compilation_state()->CancelInitialCompilation();
}
}
// After cancelling, wait for all current wrapper compilation to actually
// finish.
wrapper_compilation_barrier->CancelAndWait();
}
OperationsBarrier::Token WasmEngine::StartWrapperCompilation(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
auto isolate_info_it = isolates_.find(isolate);
if (isolate_info_it == isolates_.end()) return {};
return isolate_info_it->second->wrapper_compilation_barrier_->TryLock();
}
void WasmEngine::AddIsolate(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
DCHECK_EQ(0, isolates_.count(isolate));
isolates_.emplace(isolate, std::make_unique<IsolateInfo>(isolate));
#if defined(V8_COMPRESS_POINTERS)
// The null value is not accessible on mksnapshot runs.
if (isolate->snapshot_available()) {
wasm_null_tagged_compressed_ = V8HeapCompressionScheme::CompressObject(
isolate->factory()->wasm_null()->ptr());
}
#endif
// Install sampling GC callback.
// TODO(v8:7424): For now we sample module sizes in a GC callback. This will
// bias samples towards apps with high memory pressure. We should switch to
// using sampling based on regular intervals independent of the GC.
auto callback = [](v8::Isolate* v8_isolate, v8::GCType type,
v8::GCCallbackFlags flags, void* data) {
Isolate* isolate = reinterpret_cast<Isolate*>(v8_isolate);
Counters* counters = isolate->counters();
WasmEngine* engine = GetWasmEngine();
base::MutexGuard lock(&engine->mutex_);
DCHECK_EQ(1, engine->isolates_.count(isolate));
for (auto* native_module : engine->isolates_[isolate]->native_modules) {
native_module->SampleCodeSize(counters);
}
};
isolate->heap()->AddGCEpilogueCallback(callback, v8::kGCTypeMarkSweepCompact,
nullptr);
#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
if (gdb_server_) {
gdb_server_->AddIsolate(isolate);
}
#endif // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
}
void WasmEngine::RemoveIsolate(Isolate* isolate) {
#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
if (gdb_server_) {
gdb_server_->RemoveIsolate(isolate);
}
#endif // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
// Keep a WasmCodeRefScope which dies after the {mutex_} is released, to avoid
// deadlock when code actually dies, as that requires taking the {mutex_}.
WasmCodeRefScope code_ref_scope_for_dead_code;
base::MutexGuard guard(&mutex_);
// Lookup the IsolateInfo; do not remove it yet (that happens below).
auto isolates_it = isolates_.find(isolate);
DCHECK_NE(isolates_.end(), isolates_it);
IsolateInfo* isolate_info = isolates_it->second.get();
// Remove the isolate from the per-native-module info, and other cleanup.
for (auto* native_module : isolate_info->native_modules) {
DCHECK_EQ(1, native_modules_.count(native_module));
NativeModuleInfo* native_module_info =
native_modules_.find(native_module)->second.get();
// Check that the {NativeModule::log_code_} field has the expected value,
// and update if the dying isolate was the last one with code logging
// enabled.
auto has_isolate_with_code_logging = [this, native_module_info] {
return std::any_of(native_module_info->isolates.begin(),
native_module_info->isolates.end(),
[this](Isolate* isolate) {
return isolates_.find(isolate)->second->log_codes;
});
};
DCHECK_EQ(native_module->log_code(), has_isolate_with_code_logging());
DCHECK_EQ(1, native_module_info->isolates.count(isolate));
native_module_info->isolates.erase(isolate);
if (!has_isolate_with_code_logging()) {
native_module->DisableCodeLogging();
}
// Remove any debug code and other info for this isolate.
if (native_module->HasDebugInfo()) {
native_module->GetDebugInfo()->RemoveIsolate(isolate);
}
}
// Abort any outstanding GC.
if (current_gc_info_) {
if (RemoveIsolateFromCurrentGC(isolate)) PotentiallyFinishCurrentGC();
}
// Cancel outstanding code logging and clear the {code_to_log} vector.
if (auto* task = isolate_info->log_codes_task) {
task->Cancel();
for (auto& [script_id, code_to_log] : isolate_info->code_to_log) {
for (WasmCode* code : code_to_log.code) {
// Keep a reference in the {code_ref_scope_for_dead_code} such that the
// code cannot become dead immediately.
WasmCodeRefScope::AddRef(code);
code->DecRefOnLiveCode();
}
}
isolate_info->code_to_log.clear();
}
DCHECK(isolate_info->code_to_log.empty());
// Finally remove the {IsolateInfo} for this isolate.
isolates_.erase(isolates_it);
}
void WasmEngine::LogCode(base::Vector<WasmCode*> code_vec) {
if (code_vec.empty()) return;
NativeModule* native_module = code_vec[0]->native_module();
if (!native_module->log_code()) return;
using TaskToSchedule =
std::pair<std::shared_ptr<v8::TaskRunner>, std::unique_ptr<LogCodesTask>>;
std::vector<TaskToSchedule> to_schedule;
{
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, native_modules_.count(native_module));
NativeModuleInfo* native_module_info =
native_modules_.find(native_module)->second.get();
for (Isolate* isolate : native_module_info->isolates) {
DCHECK_EQ(1, isolates_.count(isolate));
IsolateInfo* info = isolates_[isolate].get();
if (info->log_codes == false) continue;
auto script_it = info->scripts.find(native_module);
// If the script does not yet exist, logging will happen later. If the
// weak handle is cleared already, we also don't need to log any more.
if (script_it == info->scripts.end()) continue;
// If this is the first code to log in that isolate, request an interrupt
// to log the newly added code as soon as possible.
if (info->code_to_log.empty()) {
isolate->stack_guard()->RequestLogWasmCode();
}
WeakScriptHandle& weak_script_handle = script_it->second;
auto& log_entry = info->code_to_log[weak_script_handle.script_id()];
if (!log_entry.source_url) {
log_entry.source_url = weak_script_handle.source_url();
}
log_entry.code.insert(log_entry.code.end(), code_vec.begin(),
code_vec.end());
// Increment the reference count for the added {log_entry.code} entries.
for (WasmCode* code : code_vec) {
DCHECK_EQ(native_module, code->native_module());
code->IncRef();
}
if (info->log_codes_task == nullptr) {
auto new_task = std::make_unique<LogCodesTask>(
&mutex_, &info->log_codes_task, isolate, this);
info->log_codes_task = new_task.get();
// Store the LogCodeTasks to post them outside the WasmEngine::mutex_.
// Posting the task in the mutex can cause the following deadlock (only
// in d8): When d8 shuts down, it sets a terminate to the task runner.
// When the terminate flag in the taskrunner is set, all newly posted
// tasks get destroyed immediately. When the LogCodesTask gets
// destroyed, it takes the WasmEngine::mutex_ lock to deregister itself
// from the IsolateInfo. Therefore, as the LogCodesTask may get
// destroyed immediately when it gets posted, it cannot get posted when
// the WasmEngine::mutex_ lock is held.
to_schedule.emplace_back(info->foreground_task_runner,
std::move(new_task));
}
}
}
for (auto& [runner, task] : to_schedule) {
runner->PostTask(std::move(task));
}
}
void WasmEngine::EnableCodeLogging(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
auto it = isolates_.find(isolate);
DCHECK_NE(isolates_.end(), it);
IsolateInfo* info = it->second.get();
info->log_codes = true;
// Also set {NativeModule::log_code_} for all native modules currently used by
// this isolate.
for (NativeModule* native_module : info->native_modules) {
native_module->EnableCodeLogging();
}
}
void WasmEngine::LogOutstandingCodesForIsolate(Isolate* isolate) {
// Under the mutex, get the vector of wasm code to log. Then log and decrement
// the ref count without holding the mutex.
std::unordered_map<int, IsolateInfo::CodeToLogPerScript> code_to_log;
{
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
code_to_log.swap(isolates_[isolate]->code_to_log);
}
// Check again whether we still need to log code.
bool should_log = WasmCode::ShouldBeLogged(isolate);
TRACE_EVENT0("v8.wasm", "wasm.LogCode");
for (auto& [script_id, code_to_log] : code_to_log) {
for (WasmCode* code : code_to_log.code) {
if (should_log) {
code->LogCode(isolate, code_to_log.source_url.get(), script_id);
}
}
WasmCode::DecrementRefCount(base::VectorOf(code_to_log.code));
}
}
std::shared_ptr<NativeModule> WasmEngine::NewNativeModule(
Isolate* isolate, WasmFeatures enabled,
std::shared_ptr<const WasmModule> module, size_t code_size_estimate) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.wasm.detailed"),
"wasm.NewNativeModule");
#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
if (v8_flags.wasm_gdb_remote && !gdb_server_) {
gdb_server_ = gdb_server::GdbServer::Create();
gdb_server_->AddIsolate(isolate);
}
#endif // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
std::shared_ptr<NativeModule> native_module =
GetWasmCodeManager()->NewNativeModule(
isolate, enabled, code_size_estimate, std::move(module));
base::MutexGuard lock(&mutex_);
if (V8_UNLIKELY(v8_flags.experimental_wasm_pgo_to_file)) {
if (!native_modules_kept_alive_for_pgo) {
native_modules_kept_alive_for_pgo =
new std::vector<std::shared_ptr<NativeModule>>;
}
native_modules_kept_alive_for_pgo->emplace_back(native_module);
}
auto [iterator, inserted] = native_modules_.insert(std::make_pair(
native_module.get(), std::make_unique<NativeModuleInfo>(native_module)));
DCHECK(inserted);
NativeModuleInfo* native_module_info = iterator->second.get();
native_module_info->isolates.insert(isolate);
DCHECK_EQ(1, isolates_.count(isolate));
IsolateInfo* isolate_info = isolates_.find(isolate)->second.get();
isolate_info->native_modules.insert(native_module.get());
if (isolate_info->keep_in_debug_state) {
native_module->SetDebugState(kDebugging);
}
if (isolate_info->log_codes) {
native_module->EnableCodeLogging();
}
// Record memory protection key support.
if (!isolate_info->pku_support_sampled) {
isolate_info->pku_support_sampled = true;
auto* histogram =
isolate->counters()->wasm_memory_protection_keys_support();
bool has_mpk = WasmCodeManager::HasMemoryProtectionKeySupport();
histogram->AddSample(has_mpk ? 1 : 0);
}
isolate->counters()->wasm_modules_per_isolate()->AddSample(
static_cast<int>(isolate_info->native_modules.size()));
isolate->counters()->wasm_modules_per_engine()->AddSample(
static_cast<int>(native_modules_.size()));
return native_module;
}
std::shared_ptr<NativeModule> WasmEngine::MaybeGetNativeModule(
ModuleOrigin origin, base::Vector<const uint8_t> wire_bytes,
Isolate* isolate) {
TRACE_EVENT1("v8.wasm", "wasm.GetNativeModuleFromCache", "wire_bytes",
wire_bytes.size());
std::shared_ptr<NativeModule> native_module =
native_module_cache_.MaybeGetNativeModule(origin, wire_bytes);
bool remove_all_code = false;
if (native_module) {
TRACE_EVENT0("v8.wasm", "CacheHit");
base::MutexGuard guard(&mutex_);
auto& native_module_info = native_modules_[native_module.get()];
if (!native_module_info) {
native_module_info = std::make_unique<NativeModuleInfo>(native_module);
}
native_module_info->isolates.insert(isolate);
auto* isolate_data = isolates_[isolate].get();
isolate_data->native_modules.insert(native_module.get());
if (isolate_data->keep_in_debug_state && !native_module->IsInDebugState()) {
remove_all_code = true;
native_module->SetDebugState(kDebugging);
}
if (isolate_data->log_codes && !native_module->log_code()) {
native_module->EnableCodeLogging();
}
}
if (remove_all_code) {
native_module->RemoveCompiledCode(
NativeModule::RemoveFilter::kRemoveNonDebugCode);
}
return native_module;
}
std::shared_ptr<NativeModule> WasmEngine::UpdateNativeModuleCache(
bool has_error, std::shared_ptr<NativeModule> native_module,
Isolate* isolate) {
// Keep the previous pointer, but as a `void*`, because we only want to use it
// later to compare pointers, and never need to dereference it.
void* prev = native_module.get();
native_module =
native_module_cache_.Update(std::move(native_module), has_error);
if (prev == native_module.get()) return native_module;
bool remove_all_code = false;
{
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, native_modules_.count(native_module.get()));
native_modules_[native_module.get()]->isolates.insert(isolate);
DCHECK_EQ(1, isolates_.count(isolate));
auto* isolate_data = isolates_[isolate].get();
isolate_data->native_modules.insert(native_module.get());
if (isolate_data->keep_in_debug_state && !native_module->IsInDebugState()) {
remove_all_code = true;
native_module->SetDebugState(kDebugging);
}
if (isolate_data->log_codes && !native_module->log_code()) {
native_module->EnableCodeLogging();
}
}
if (remove_all_code) {
native_module->RemoveCompiledCode(
NativeModule::RemoveFilter::kRemoveNonDebugCode);
}
return native_module;
}
bool WasmEngine::GetStreamingCompilationOwnership(size_t prefix_hash) {
TRACE_EVENT0("v8.wasm", "wasm.GetStreamingCompilationOwnership");
if (native_module_cache_.GetStreamingCompilationOwnership(prefix_hash)) {
return true;
}
// This is only a marker, not for tracing execution time. There should be a
// later "wasm.GetNativeModuleFromCache" event for trying to get the module
// from the cache.
TRACE_EVENT0("v8.wasm", "CacheHit");
return false;
}
void WasmEngine::StreamingCompilationFailed(size_t prefix_hash) {
native_module_cache_.StreamingCompilationFailed(prefix_hash);
}
void WasmEngine::FreeNativeModule(NativeModule* native_module) {
base::MutexGuard guard(&mutex_);
auto module = native_modules_.find(native_module);
DCHECK_NE(native_modules_.end(), module);
for (Isolate* isolate : module->second->isolates) {
DCHECK_EQ(1, isolates_.count(isolate));
IsolateInfo* info = isolates_[isolate].get();
DCHECK_EQ(1, info->native_modules.count(native_module));
info->native_modules.erase(native_module);
info->scripts.erase(native_module);
// If there are {WasmCode} objects of the deleted {NativeModule}
// outstanding to be logged in this isolate, remove them. Decrementing the
// ref count is not needed, since the {NativeModule} dies anyway.
for (auto& log_entry : info->code_to_log) {
auto part_of_native_module = [native_module](WasmCode* code) {
return code->native_module() == native_module;
};
std::vector<WasmCode*>& code = log_entry.second.code;
auto new_end =
std::remove_if(code.begin(), code.end(), part_of_native_module);
code.erase(new_end, code.end());
}
// Now remove empty entries in {code_to_log}.
for (auto it = info->code_to_log.begin(), end = info->code_to_log.end();
it != end;) {
if (it->second.code.empty()) {
it = info->code_to_log.erase(it);
} else {
++it;
}
}
}
// If there is a GC running which has references to code contained in the
// deleted {NativeModule}, remove those references.
if (current_gc_info_) {
for (auto it = current_gc_info_->dead_code.begin(),
end = current_gc_info_->dead_code.end();
it != end;) {
if ((*it)->native_module() == native_module) {
it = current_gc_info_->dead_code.erase(it);
} else {
++it;
}
}
TRACE_CODE_GC("Native module %p died, reducing dead code objects to %zu.\n",
native_module, current_gc_info_->dead_code.size());
}
native_module_cache_.Erase(native_module);
native_modules_.erase(module);
}
void WasmEngine::ReportLiveCodeForGC(Isolate* isolate,
base::Vector<WasmCode*> live_code) {
TRACE_EVENT0("v8.wasm", "wasm.ReportLiveCodeForGC");
TRACE_CODE_GC("Isolate %d reporting %zu live code objects.\n", isolate->id(),
live_code.size());
base::MutexGuard guard(&mutex_);
// This report might come in late (note that we trigger both a stack guard and
// a foreground task). In that case, ignore it.
if (current_gc_info_ == nullptr) return;
if (!RemoveIsolateFromCurrentGC(isolate)) return;
isolate->counters()->wasm_module_num_triggered_code_gcs()->AddSample(
current_gc_info_->gc_sequence_index);
for (WasmCode* code : live_code) current_gc_info_->dead_code.erase(code);
PotentiallyFinishCurrentGC();
}
namespace {
void ReportLiveCodeFromFrameForGC(
StackFrame* frame, std::unordered_set<wasm::WasmCode*>& live_wasm_code) {
if (frame->type() != StackFrame::WASM) return;
live_wasm_code.insert(WasmFrame::cast(frame)->wasm_code());
#if V8_TARGET_ARCH_X64
if (WasmFrame::cast(frame)->wasm_code()->for_debugging()) {
Address osr_target = base::Memory<Address>(WasmFrame::cast(frame)->fp() -
kOSRTargetOffset);
if (osr_target) {
WasmCode* osr_code = GetWasmCodeManager()->LookupCode(osr_target);
DCHECK_NOT_NULL(osr_code);
live_wasm_code.insert(osr_code);
}
}
#endif
}
} // namespace
void WasmEngine::ReportLiveCodeFromStackForGC(Isolate* isolate) {
wasm::WasmCodeRefScope code_ref_scope;
std::unordered_set<wasm::WasmCode*> live_wasm_code;
if (v8_flags.experimental_wasm_stack_switching) {
wasm::StackMemory* current = isolate->wasm_stacks();
DCHECK_NOT_NULL(current);
do {
if (current->IsActive()) {
// The active stack's jump buffer does not match the current state, use
// the thread info below instead.
current = current->next();
continue;
}
for (StackFrameIterator it(isolate, current); !it.done(); it.Advance()) {
StackFrame* const frame = it.frame();
ReportLiveCodeFromFrameForGC(frame, live_wasm_code);
}
current = current->next();
} while (current != isolate->wasm_stacks());
}
for (StackFrameIterator it(isolate); !it.done(); it.Advance()) {
StackFrame* const frame = it.frame();
ReportLiveCodeFromFrameForGC(frame, live_wasm_code);
}
CheckNoArchivedThreads(isolate);
ReportLiveCodeForGC(
isolate, base::OwnedVector<WasmCode*>::Of(live_wasm_code).as_vector());
}
bool WasmEngine::AddPotentiallyDeadCode(WasmCode* code) {
base::MutexGuard guard(&mutex_);
auto it = native_modules_.find(code->native_module());
DCHECK_NE(native_modules_.end(), it);
NativeModuleInfo* info = it->second.get();
if (info->dead_code.count(code)) return false; // Code is already dead.
auto added = info->potentially_dead_code.insert(code);
if (!added.second) return false; // An entry already existed.
new_potentially_dead_code_size_ += code->instructions().size();
if (v8_flags.wasm_code_gc) {
// Trigger a GC if 64kB plus 10% of committed code are potentially dead.
size_t dead_code_limit =
v8_flags.stress_wasm_code_gc
? 0
: 64 * KB + GetWasmCodeManager()->committed_code_space() / 10;
if (new_potentially_dead_code_size_ > dead_code_limit) {
bool inc_gc_count =
info->num_code_gcs_triggered < std::numeric_limits<int8_t>::max();
if (current_gc_info_ == nullptr) {
if (inc_gc_count) ++info->num_code_gcs_triggered;
TRACE_CODE_GC(
"Triggering GC (potentially dead: %zu bytes; limit: %zu bytes).\n",
new_potentially_dead_code_size_, dead_code_limit);
TriggerGC(info->num_code_gcs_triggered);
} else if (current_gc_info_->next_gc_sequence_index == 0) {
if (inc_gc_count) ++info->num_code_gcs_triggered;
TRACE_CODE_GC(
"Scheduling another GC after the current one (potentially dead: "
"%zu bytes; limit: %zu bytes).\n",
new_potentially_dead_code_size_, dead_code_limit);
current_gc_info_->next_gc_sequence_index = info->num_code_gcs_triggered;
DCHECK_NE(0, current_gc_info_->next_gc_sequence_index);
}
}
}
return true;
}
void WasmEngine::FreeDeadCode(const DeadCodeMap& dead_code) {
base::MutexGuard guard(&mutex_);
FreeDeadCodeLocked(dead_code);
}
void WasmEngine::FreeDeadCodeLocked(const DeadCodeMap& dead_code) {
TRACE_EVENT0("v8.wasm", "wasm.FreeDeadCode");
DCHECK(!mutex_.TryLock());
for (auto& dead_code_entry : dead_code) {
NativeModule* native_module = dead_code_entry.first;
const std::vector<WasmCode*>& code_vec = dead_code_entry.second;
DCHECK_EQ(1, native_modules_.count(native_module));
auto* info = native_modules_[native_module].get();
TRACE_CODE_GC("Freeing %zu code object%s of module %p.\n", code_vec.size(),
code_vec.size() == 1 ? "" : "s", native_module);
for (WasmCode* code : code_vec) {
DCHECK_EQ(1, info->dead_code.count(code));
info->dead_code.erase(code);
}
native_module->FreeCode(base::VectorOf(code_vec));
}
}
Handle<Script> WasmEngine::GetOrCreateScript(
Isolate* isolate, const std::shared_ptr<NativeModule>& native_module,
base::Vector<const char> source_url) {
{
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
auto& scripts = isolates_[isolate]->scripts;
auto it = scripts.find(native_module.get());
if (it != scripts.end()) {
Handle<Script> weak_global_handle = it->second.handle();
if (weak_global_handle.is_null()) {
scripts.erase(it);
} else {
return Handle<Script>::New(*weak_global_handle, isolate);
}
}
}
// Temporarily release the mutex to let the GC collect native modules.
auto script = CreateWasmScript(isolate, native_module, source_url);
{
base::MutexGuard guard(&mutex_);
DCHECK_EQ(1, isolates_.count(isolate));
auto& scripts = isolates_[isolate]->scripts;
DCHECK_EQ(0, scripts.count(native_module.get()));
scripts.emplace(native_module.get(), WeakScriptHandle(script));
return script;
}
}
std::shared_ptr<OperationsBarrier>
WasmEngine::GetBarrierForBackgroundCompile() {
return operations_barrier_;
}
namespace {
void SampleExceptionEvent(base::ElapsedTimer* timer, TimedHistogram* counter) {
if (!timer->IsStarted()) {
timer->Start();
return;
}
counter->AddSample(static_cast<int>(timer->Elapsed().InMilliseconds()));
timer->Restart();
}
} // namespace
void WasmEngine::SampleThrowEvent(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
IsolateInfo* isolate_info = isolates_[isolate].get();
int& throw_count = isolate_info->throw_count;
// To avoid an int overflow, clip the count to the histogram's max value.
throw_count =
std::min(throw_count + 1, isolate->counters()->wasm_throw_count()->max());
isolate->counters()->wasm_throw_count()->AddSample(throw_count);
SampleExceptionEvent(&isolate_info->throw_timer,
isolate->counters()->wasm_time_between_throws());
}
void WasmEngine::SampleRethrowEvent(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
IsolateInfo* isolate_info = isolates_[isolate].get();
int& rethrow_count = isolate_info->rethrow_count;
// To avoid an int overflow, clip the count to the histogram's max value.
rethrow_count = std::min(rethrow_count + 1,
isolate->counters()->wasm_rethrow_count()->max());
isolate->counters()->wasm_rethrow_count()->AddSample(rethrow_count);
SampleExceptionEvent(&isolate_info->rethrow_timer,
isolate->counters()->wasm_time_between_rethrows());
}
void WasmEngine::SampleCatchEvent(Isolate* isolate) {
base::MutexGuard guard(&mutex_);
IsolateInfo* isolate_info = isolates_[isolate].get();
int& catch_count = isolate_info->catch_count;
// To avoid an int overflow, clip the count to the histogram's max value.
catch_count =
std::min(catch_count + 1, isolate->counters()->wasm_catch_count()->max());
isolate->counters()->wasm_catch_count()->AddSample(catch_count);
SampleExceptionEvent(&isolate_info->catch_timer,
isolate->counters()->wasm_time_between_catch());
}
void WasmEngine::TriggerGC(int8_t gc_sequence_index) {
DCHECK(!mutex_.TryLock());
DCHECK_NULL(current_gc_info_);
DCHECK(v8_flags.wasm_code_gc);
new_potentially_dead_code_size_ = 0;
current_gc_info_.reset(new CurrentGCInfo(gc_sequence_index));
// Add all potentially dead code to this GC, and trigger a GC task in each
// isolate.
for (auto& entry : native_modules_) {
NativeModuleInfo* info = entry.second.get();
if (info->potentially_dead_code.empty()) continue;
for (auto* isolate : native_modules_[entry.first]->isolates) {
auto& gc_task = current_gc_info_->outstanding_isolates[isolate];
if (!gc_task) {
auto new_task = std::make_unique<WasmGCForegroundTask>(isolate);
gc_task = new_task.get();
DCHECK_EQ(1, isolates_.count(isolate));
isolates_[isolate]->foreground_task_runner->PostTask(
std::move(new_task));
}
isolate->stack_guard()->RequestWasmCodeGC();
}
for (WasmCode* code : info->potentially_dead_code) {
current_gc_info_->dead_code.insert(code);
}
}
TRACE_CODE_GC(
"Starting GC (nr %d). Number of potentially dead code objects: %zu\n",
current_gc_info_->gc_sequence_index, current_gc_info_->dead_code.size());
// Ensure that there are outstanding isolates that will eventually finish this
// GC. If there are no outstanding isolates, we finish the GC immediately.
PotentiallyFinishCurrentGC();
DCHECK(current_gc_info_ == nullptr ||
!current_gc_info_->outstanding_isolates.empty());
}
bool WasmEngine::RemoveIsolateFromCurrentGC(Isolate* isolate) {
DCHECK(!mutex_.TryLock());
DCHECK_NOT_NULL(current_gc_info_);
return current_gc_info_->outstanding_isolates.erase(isolate) != 0;
}
void WasmEngine::PotentiallyFinishCurrentGC() {
DCHECK(!mutex_.TryLock());
TRACE_CODE_GC(
"Remaining dead code objects: %zu; outstanding isolates: %zu.\n",
current_gc_info_->dead_code.size(),
current_gc_info_->outstanding_isolates.size());
// If there are more outstanding isolates, return immediately.
if (!current_gc_info_->outstanding_isolates.empty()) return;
// All remaining code in {current_gc_info->dead_code} is really dead.
// Move it from the set of potentially dead code to the set of dead code,
// and decrement its ref count.
size_t num_freed = 0;
DeadCodeMap dead_code;
for (WasmCode* code : current_gc_info_->dead_code) {
DCHECK_EQ(1, native_modules_.count(code->native_module()));
auto* native_module_info = native_modules_[code->native_module()].get();
DCHECK_EQ(1, native_module_info->potentially_dead_code.count(code));
native_module_info->potentially_dead_code.erase(code);
DCHECK_EQ(0, native_module_info->dead_code.count(code));
native_module_info->dead_code.insert(code);
if (code->DecRefOnDeadCode()) {
dead_code[code->native_module()].push_back(code);
++num_freed;
}
}
FreeDeadCodeLocked(dead_code);
TRACE_CODE_GC("Found %zu dead code objects, freed %zu.\n",
current_gc_info_->dead_code.size(), num_freed);
USE(num_freed);
int8_t next_gc_sequence_index = current_gc_info_->next_gc_sequence_index;
current_gc_info_.reset();
if (next_gc_sequence_index != 0) TriggerGC(next_gc_sequence_index);
}
size_t WasmEngine::EstimateCurrentMemoryConsumption() const {
UPDATE_WHEN_CLASS_CHANGES(WasmEngine, 680);
UPDATE_WHEN_CLASS_CHANGES(IsolateInfo, 256);
UPDATE_WHEN_CLASS_CHANGES(NativeModuleInfo, 144);
UPDATE_WHEN_CLASS_CHANGES(CurrentGCInfo, 96);
size_t result = sizeof(WasmEngine);
result += type_canonicalizer_.EstimateCurrentMemoryConsumption();
{
base::MutexGuard lock(&mutex_);
result += ContentSize(async_compile_jobs_);
result += async_compile_jobs_.size() * sizeof(AsyncCompileJob);
// TODO(14106): Do we care about {compilation_stats_}?
// TODO(14106): Do we care about {code_tracer_}?
result += ContentSize(isolates_);
result += isolates_.size() * sizeof(IsolateInfo);
for (const auto& [isolate, isolate_info] : isolates_) {
result += ContentSize(isolate_info->native_modules);
result += ContentSize(isolate_info->scripts);
result += ContentSize(isolate_info->code_to_log);
}
result += ContentSize(native_modules_);
result += native_modules_.size() * sizeof(NativeModuleInfo);
for (const auto& [native_module, native_module_info] : native_modules_) {
result += native_module->EstimateCurrentMemoryConsumption();
result += ContentSize(native_module_info->isolates);
result += ContentSize(native_module_info->potentially_dead_code);
result += ContentSize(native_module_info->dead_code);
}
if (current_gc_info_) {
result += sizeof(CurrentGCInfo);
result += ContentSize(current_gc_info_->outstanding_isolates);
result += ContentSize(current_gc_info_->dead_code);
}
}
if (v8_flags.trace_wasm_offheap_memory) {
PrintF("WasmEngine: %zu\n", result);
}
return result;
}
namespace {
struct GlobalWasmState {
// Note: The order of fields is important here, as the WasmEngine's destructor
// must run first. It contains a barrier which ensures that background threads
// finished, and that has to happen before the WasmCodeManager gets destroyed.
WasmCodeManager code_manager;
WasmEngine engine;
};
GlobalWasmState* global_wasm_state = nullptr;
} // namespace
// static
void WasmEngine::InitializeOncePerProcess() {
DCHECK_NULL(global_wasm_state);
global_wasm_state = new GlobalWasmState();
}
// static
void WasmEngine::GlobalTearDown() {
// Note: This can be called multiple times in a row (see
// test-api/InitializeAndDisposeMultiple). This is fine, as
// {global_wasm_engine} will be nullptr then.
delete global_wasm_state;
global_wasm_state = nullptr;
}
WasmEngine* GetWasmEngine() {
DCHECK_NOT_NULL(global_wasm_state);
return &global_wasm_state->engine;
}
WasmCodeManager* GetWasmCodeManager() {
DCHECK_NOT_NULL(global_wasm_state);
return &global_wasm_state->code_manager;
}
// {max_mem_pages} is declared in wasm-limits.h.
uint32_t max_mem32_pages() {
static_assert(
kV8MaxWasmMemory32Pages * kWasmPageSize <= JSArrayBuffer::kMaxByteLength,
"Wasm memories must not be bigger than JSArrayBuffers");
static_assert(kV8MaxWasmMemory32Pages <= kMaxUInt32);
return std::min(uint32_t{kV8MaxWasmMemory32Pages},
v8_flags.wasm_max_mem_pages.value());
}
uint32_t max_mem64_pages() {
static_assert(
kV8MaxWasmMemory64Pages * kWasmPageSize <= JSArrayBuffer::kMaxByteLength,
"Wasm memories must not be bigger than JSArrayBuffers");
static_assert(kV8MaxWasmMemory64Pages <= kMaxUInt32);
return std::min(uint32_t{kV8MaxWasmMemory64Pages},
v8_flags.wasm_max_mem_pages.value());
}
// {max_table_init_entries} is declared in wasm-limits.h.
uint32_t max_table_init_entries() {
return std::min(uint32_t{kV8MaxWasmTableInitEntries},
v8_flags.wasm_max_table_size.value());
}
// {max_module_size} is declared in wasm-limits.h.
size_t max_module_size() {
// Clamp the value of --wasm-max-module-size between 16 and just below 2GB.
constexpr size_t kMin = 16;
constexpr size_t kMax = RoundDown<kSystemPointerSize>(size_t{kMaxInt});
static_assert(kMin <= kV8MaxWasmModuleSize && kV8MaxWasmModuleSize <= kMax);
return std::clamp(v8_flags.wasm_max_module_size.value(), kMin, kMax);
}
#undef TRACE_CODE_GC
} // namespace v8::internal::wasm
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