deps: add LookupAlsValue to V8 heap profiler

Expose a public API to look up ALS values from the CPED map, so the
allocator can resolve labels without duplicating V8 internal logic.

Signed-off-by: Rudolf Meijering <[email protected]>

Author: rudolf

deps/v8/include/v8-profiler.h

@@ -1330,6 +1330,16 @@ class V8_EXPORT HeapProfiler {
    * Pass an empty handle to clear.
    */
   void SetHeapProfileSampleLabelsKey(Local<Value> key);
+
+  /**
+   * Extracts the ALS value from a CPED (ContinuationPreservedEmbedderData)
+   * Map using the stored ALS key (set via SetHeapProfileSampleLabelsKey).
+   *
+   * Uses OrderedHashMap::FindEntry internally — zero-allocation, GC-safe.
+   * Returns an empty MaybeLocal if the CPED is not a Map, no ALS key is set,
+   * or the key is not found in the Map.
+   */
+  MaybeLocal<Value> LookupAlsValue(Local<Value> cped);
 #endif  // V8_HEAP_PROFILER_SAMPLE_LABELS
 
   /**

deps/v8/src/api/api.cc

@@ -11840,6 +11840,10 @@ void HeapProfiler::SetHeapProfileSampleLabelsKey(Local<Value> key) {
   reinterpret_cast<i::HeapProfiler*>(this)
       ->SetHeapProfileSampleLabelsKey(key);
 }
+
+MaybeLocal<Value> HeapProfiler::LookupAlsValue(Local<Value> cped) {
+  return reinterpret_cast<i::HeapProfiler*>(this)->LookupAlsValue(cped);
+}
 #endif  // V8_HEAP_PROFILER_SAMPLE_LABELS
 
 bool HeapProfiler::IsTakingSnapshot() {

deps/v8/src/profiler/heap-profiler.cc

@@ -18,6 +18,8 @@
 #include "src/heap/heap.h"
 #include "src/objects/cpp-heap-object-wrapper-inl.h"
 #include "src/objects/js-array-buffer-inl.h"
+#include "src/objects/js-collection-inl.h"
+#include "src/objects/ordered-hash-table.h"
 #include "src/profiler/allocation-tracker.h"
 #include "src/profiler/heap-snapshot-generator-inl.h"
 #include "src/profiler/sampling-heap-profiler.h"
@@ -405,4 +407,27 @@ void HeapProfiler::QueryObjects(DirectHandle<Context> context,
   });
 }
 
+#ifdef V8_HEAP_PROFILER_SAMPLE_LABELS
+v8::MaybeLocal<v8::Value> HeapProfiler::LookupAlsValue(
+    v8::Local<v8::Value> cped) {
+  if (sample_labels_als_key_.IsEmpty() || cped.IsEmpty()) {
+    return v8::MaybeLocal<v8::Value>();
+  }
+  Tagged<Object> cped_obj = *Utils::OpenDirectHandle(*cped);
+  if (!IsJSMap(cped_obj)) return v8::MaybeLocal<v8::Value>();
+
+  Tagged<JSMap> js_map = Cast<JSMap>(cped_obj);
+  Tagged<OrderedHashMap> table = Cast<OrderedHashMap>(js_map->table());
+
+  v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate());
+  v8::Local<v8::Value> als_key_local = sample_labels_als_key_.Get(v8_isolate);
+  Tagged<Object> key_obj = *Utils::OpenDirectHandle(*als_key_local);
+  InternalIndex entry = table->FindEntry(isolate(), key_obj);
+  if (!entry.is_found()) return v8::MaybeLocal<v8::Value>();
+
+  Tagged<Object> value = table->ValueAt(entry);
+  return Utils::ToLocal(direct_handle(value, isolate()));
+}
+#endif  // V8_HEAP_PROFILER_SAMPLE_LABELS
+
 }  // namespace v8::internal

deps/v8/src/profiler/heap-profiler.h

@@ -105,6 +105,10 @@ class HeapProfiler : public HeapObjectAllocationTracker {
   const v8::Global<v8::Value>& sample_labels_als_key() const {
     return sample_labels_als_key_;
   }
+
+  // Extracts the ALS value from a CPED Map using the stored ALS key.
+  // Uses OrderedHashMap::FindEntry — zero-allocation, GC-safe.
+  v8::MaybeLocal<v8::Value> LookupAlsValue(v8::Local<v8::Value> cped);
 #endif  // V8_HEAP_PROFILER_SAMPLE_LABELS
 
   void StartHeapObjectsTracking(bool track_allocations);