[compiler] AssumeMemoryFence in FeedbackCellRef::value

Drive-by: simplifications and avoid a repeated concurrent read.

Bug: v8:7790,v8:12157
Change-Id: I460c44853a78bcd9a1427e62a92994ff8602dbed
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3133148
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76640}

src/compiler/bytecode-graph-builder.cc

@@ -1052,7 +1052,7 @@ BytecodeGraphBuilder::BytecodeGraphBuilder(
       shared_info_(shared_info),
       bytecode_array_(shared_info.GetBytecodeArray()),
       feedback_cell_(feedback_cell),
-      feedback_vector_(feedback_cell.value()->AsFeedbackVector()),
+      feedback_vector_(feedback_cell.value().value()),
       invocation_frequency_(invocation_frequency),
       type_hint_lowering_(
           broker, jsgraph, feedback_vector_,

src/compiler/heap-refs.cc

@@ -2176,7 +2176,7 @@ base::Optional<FeedbackVectorRef> FeedbackCellRef::value() const {
   DCHECK(data_->should_access_heap());
   Object value = object()->value(kAcquireLoad);
   if (!value.IsFeedbackVector()) return base::nullopt;
-  return TryMakeRef(broker(), FeedbackVector::cast(value));
+  return MakeRefAssumeMemoryFence(broker(), FeedbackVector::cast(value));
 }
 
 base::Optional<ObjectRef> MapRef::GetStrongValue(
@@ -2659,10 +2659,9 @@ base::Optional<ObjectRef> DescriptorArrayRef::GetStrongValue(
 
 base::Optional<SharedFunctionInfoRef> FeedbackCellRef::shared_function_info()
     const {
-  if (value()) {
-    return value()->shared_function_info();
-  }
-  return base::nullopt;
+  base::Optional<FeedbackVectorRef> feedback_vector = value();
+  if (!feedback_vector.has_value()) return {};
+  return feedback_vector->shared_function_info();
 }
 
 SharedFunctionInfoRef FeedbackVectorRef::shared_function_info() const {

src/compiler/js-typed-lowering.cc

@@ -1707,10 +1707,7 @@ Reduction JSTypedLowering::ReduceJSCall(Node* node) {
     shared = ccp.shared_info(broker());
   } else if (target->opcode() == IrOpcode::kCheckClosure) {
     FeedbackCellRef cell = MakeRef(broker(), FeedbackCellOf(target->op()));
-    base::Optional<FeedbackVectorRef> feedback_vector = cell.value();
-    if (feedback_vector.has_value()) {
-      shared = feedback_vector->shared_function_info();
-    }
+    shared = cell.shared_function_info();
   }
 
   if (shared.has_value()) {