deps: backport v8 f19142e6

[top-level-await] Implement the new post-order requirement for
async subgraphs

Refs: v8/v8@f19142e
PR-URL: #37864
Backport-PR-URL: #37985
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

deps/v8/src/common/globals.h

@@ -349,6 +349,9 @@ constexpr int kUC16Size = sizeof(uc16);  // NOLINT
 // 128 bit SIMD value size.
 constexpr int kSimd128Size = 16;
 
+// Maximum ordinal used for tracking asynchronous module evaluation order.
+constexpr unsigned kMaxModuleAsyncEvaluatingOrdinal = (1 << 30) - 1;
+
 // FUNCTION_ADDR(f) gets the address of a C function f.
 #define FUNCTION_ADDR(f) (reinterpret_cast<v8::internal::Address>(f))
 

deps/v8/src/diagnostics/objects-debug.cc

@@ -1390,7 +1390,8 @@ void SourceTextModule::SourceTextModuleVerify(Isolate* isolate) {
           (status() == kPreInstantiating && code().IsSharedFunctionInfo()) ||
           (status() == kUninstantiated && code().IsSharedFunctionInfo()));
     CHECK(top_level_capability().IsUndefined() && !AsyncParentModuleCount() &&
-          !pending_async_dependencies() && !async_evaluating());
+          !pending_async_dependencies());
+    CHECK(!IsAsyncEvaluating());
   }
 
   CHECK_EQ(requested_modules().length(), info().module_requests().length());

deps/v8/src/diagnostics/objects-printer.cc

@@ -1602,6 +1602,7 @@ void SourceTextModule::SourceTextModulePrint(std::ostream& os) {  // NOLINT
   os << "\n - script: " << Brief(script());
   os << "\n - import_meta: " << Brief(import_meta());
   os << "\n - cycle_root: " << Brief(cycle_root());
+  os << "\n - async_evaluating_ordinal: " << async_evaluating_ordinal();
   os << "\n";
 }
 

deps/v8/src/execution/isolate-inl.h

@@ -13,6 +13,7 @@
 #include "src/objects/property-cell.h"
 #include "src/objects/regexp-match-info.h"
 #include "src/objects/shared-function-info.h"
+#include "src/objects/source-text-module.h"
 
 namespace v8 {
 namespace internal {
@@ -118,6 +119,36 @@ Isolate::ExceptionScope::~ExceptionScope() {
   isolate_->set_pending_exception(*pending_exception_);
 }
 
+void Isolate::DidFinishModuleAsyncEvaluation(unsigned ordinal) {
+  // To address overflow, the ordinal is reset when the async module with the
+  // largest vended ordinal finishes evaluating. Modules are evaluated in
+  // ascending order of their async_evaluating_ordinal.
+  //
+  // While the specification imposes a global total ordering, the intention is
+  // that for each async module, all its parents are totally ordered by when
+  // they first had their [[AsyncEvaluating]] bit set.
+  //
+  // The module with largest vended ordinal finishes evaluating implies that the
+  // async dependency as well as all other modules in that module's graph
+  // depending on async dependencies are finished evaluating.
+  //
+  // If the async dependency participates in other module graphs (e.g. via
+  // dynamic import, or other <script type=module> tags), those module graphs
+  // must have been evaluated either before or after the async dependency is
+  // settled, as the concrete Evaluate() method on cyclic module records is
+  // neither reentrant nor performs microtask checkpoints during its
+  // evaluation. If before, then all modules that depend on the async
+  // dependencies were given an ordinal that ensure they are relatively ordered,
+  // before the global ordinal was reset. If after, then the async evaluating
+  // ordering does not apply, as the dependency is no longer asynchronous.
+  //
+  // https://tc39.es/ecma262/#sec-moduleevaluation
+  if (ordinal + 1 == next_module_async_evaluating_ordinal_) {
+    next_module_async_evaluating_ordinal_ =
+        SourceTextModule::kFirstAsyncEvaluatingOrdinal;
+  }
+}
+
 #define NATIVE_CONTEXT_FIELD_ACCESSOR(index, type, name)    \
   Handle<type> Isolate::name() {                            \
     return Handle<type>(raw_native_context().name(), this); \

deps/v8/src/execution/isolate.cc

@@ -69,6 +69,7 @@
 #include "src/objects/prototype.h"
 #include "src/objects/slots.h"
 #include "src/objects/smi.h"
+#include "src/objects/source-text-module.h"
 #include "src/objects/stack-frame-info-inl.h"
 #include "src/objects/visitors.h"
 #include "src/profiler/heap-profiler.h"
@@ -2929,6 +2930,8 @@ Isolate::Isolate(std::unique_ptr<i::IsolateAllocator> isolate_allocator)
 #if V8_SFI_HAS_UNIQUE_ID
       next_unique_sfi_id_(0),
 #endif
+      next_module_async_evaluating_ordinal_(
+          SourceTextModule::kFirstAsyncEvaluatingOrdinal),
       cancelable_task_manager_(new CancelableTaskManager()) {
   TRACE_ISOLATE(constructor);
   CheckIsolateLayout();

deps/v8/src/execution/isolate.h

@@ -1284,6 +1284,22 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
     return id;
   }
 
+  // https://github.com/tc39/proposal-top-level-await/pull/159
+  // TODO(syg): Update to actual spec link once merged.
+  //
+  // According to the spec, modules that depend on async modules (i.e. modules
+  // with top-level await) must be evaluated in order in which their
+  // [[AsyncEvaluating]] flags were set to true. V8 tracks this global total
+  // order with next_module_async_evaluating_ordinal_. Each module that sets its
+  // [[AsyncEvaluating]] to true grabs the next ordinal.
+  unsigned NextModuleAsyncEvaluatingOrdinal() {
+    unsigned ordinal = next_module_async_evaluating_ordinal_++;
+    CHECK_LT(ordinal, kMaxModuleAsyncEvaluatingOrdinal);
+    return ordinal;
+  }
+
+  inline void DidFinishModuleAsyncEvaluation(unsigned ordinal);
+
   void AddNearHeapLimitCallback(v8::NearHeapLimitCallback, void* data);
   void RemoveNearHeapLimitCallback(v8::NearHeapLimitCallback callback,
                                    size_t heap_limit);
@@ -1815,6 +1831,8 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
   std::atomic<int> next_unique_sfi_id_;
 #endif
 
+  unsigned next_module_async_evaluating_ordinal_;
+
   // Vector of callbacks before a Call starts execution.
   std::vector<BeforeCallEnteredCallback> before_call_entered_callbacks_;
 

deps/v8/src/heap/factory.cc

@@ -2504,7 +2504,7 @@ Handle<SourceTextModule> Factory::NewSourceTextModule(
   module->set_top_level_capability(roots.undefined_value());
   module->set_flags(0);
   module->set_async(IsAsyncModule(code->kind()));
-  module->set_async_evaluating(false);
+  module->set_async_evaluating_ordinal(SourceTextModule::kNotAsyncEvaluated);
   module->set_cycle_root(roots.the_hole_value());
   module->set_async_parent_modules(*async_parent_modules);
   module->set_pending_async_dependencies(0);

deps/v8/src/objects/module-inl.h

@@ -37,8 +37,8 @@ SMI_ACCESSORS(Module, status, kStatusOffset)
 SMI_ACCESSORS(Module, hash, kHashOffset)
 
 BOOL_ACCESSORS(SourceTextModule, flags, async, AsyncBit::kShift)
-BOOL_ACCESSORS(SourceTextModule, flags, async_evaluating,
-               AsyncEvaluatingBit::kShift)
+BIT_FIELD_ACCESSORS(SourceTextModule, flags, async_evaluating_ordinal,
+                    SourceTextModule::AsyncEvaluatingOrdinalBits)
 ACCESSORS(SourceTextModule, async_parent_modules, ArrayList,
           kAsyncParentModulesOffset)
 ACCESSORS(SourceTextModule, top_level_capability, HeapObject,
@@ -141,6 +141,10 @@ int SourceTextModule::AsyncParentModuleCount() {
   return async_parent_modules().Length();
 }
 
+bool SourceTextModule::IsAsyncEvaluating() const {
+  return async_evaluating_ordinal() >= kFirstAsyncEvaluatingOrdinal;
+}
+
 bool SourceTextModule::HasPendingAsyncDependencies() {
   DCHECK_GE(pending_async_dependencies(), 0);
   return pending_async_dependencies() > 0;