[compiler] Replace BigInt with direct reads

Bug: v8:7790
Change-Id: Ib0c95f27d21e4aea09dcc9804a800b16440a2fe2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2403254Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69835}

src/compiler/heap-refs.h

@@ -64,6 +64,7 @@ enum class OddballType : uint8_t {
   /* Subtypes of HeapObject */                      \
   V(AccessorInfo)                                   \
   V(ArrayBoilerplateDescription)                    \
+  V(BigInt)                                         \
   V(HeapNumber)
 
 // This list is sorted such that subtypes appear before their supertypes.
@@ -94,7 +95,6 @@ enum class OddballType : uint8_t {
   V(JSObject)                                 \
   /* Subtypes of HeapObject */                \
   V(AllocationSite)                           \
-  V(BigInt)                                   \
   V(CallHandlerInfo)                          \
   V(Cell)                                     \
   V(Code)                                     \

src/compiler/js-heap-broker.cc

@@ -1019,7 +1019,9 @@ class BigIntData : public HeapObjectData {
  public:
   BigIntData(JSHeapBroker* broker, ObjectData** storage, Handle<BigInt> object)
       : HeapObjectData(broker, storage, object),
-        as_uint64_(object->AsUint64(nullptr)) {}
+        as_uint64_(object->AsUint64(nullptr)) {
+    DCHECK(!FLAG_turbo_direct_heap_access);
+  }
 
   uint64_t AsUint64() const { return as_uint64_; }
 
@@ -3336,6 +3338,8 @@ BIMODAL_ACCESSOR_C(AllocationSite, bool, PointsToLiteral)
 BIMODAL_ACCESSOR_C(AllocationSite, ElementsKind, GetElementsKind)
 BIMODAL_ACCESSOR_C(AllocationSite, AllocationType, GetAllocationType)
 
+BIMODAL_ACCESSOR_C(BigInt, uint64_t, AsUint64)
+
 BIMODAL_ACCESSOR_C(BytecodeArray, int, register_count)
 BIMODAL_ACCESSOR_C(BytecodeArray, int, parameter_count)
 BIMODAL_ACCESSOR_C(BytecodeArray, interpreter::Register,
@@ -3879,11 +3883,6 @@ base::Optional<ObjectRef> JSArrayRef::GetOwnCowElement(
   return ObjectRef(broker(), element);
 }
 
-uint64_t BigIntRef::AsUint64() const {
-  IF_ACCESS_FROM_HEAP_C(AsUint64);
-  return data()->AsBigInt()->AsUint64();
-}
-
 base::Optional<CellRef> SourceTextModuleRef::GetCell(int cell_index) const {
   if (data_->should_access_heap()) {
     AllowHandleAllocationIfNeeded allow_handle_allocation(data()->kind(),

src/compiler/pipeline.cc

@@ -1684,6 +1684,9 @@ struct SimplifiedLoweringPhase {
                                 data->source_positions(), data->node_origins(),
                                 data->info()->GetPoisoningMitigationLevel(),
                                 &data->info()->tick_counter());
+
+    // RepresentationChanger needs the LocalHeap unparked.
+    UnparkedScopeIfNeeded scope(data->broker());
     lowering.LowerAllNodes();
   }
 };