[heap] Add --trace-pending-allocations

Traces calls to Heap::IsAllocationPending that return true. This is
useful when debugging concurrent Turbofan.

Bug: v8:7790
Change-Id: If10e6f40c3bf03c768ad8b74403007fe86f860fe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3060488Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76012}

src/flags/flag-definitions.h

@@ -720,6 +720,7 @@ DEFINE_BOOL(trace_heap_broker, false,
             "trace the heap broker (reports on missing data only)")
 DEFINE_IMPLICATION(trace_heap_broker_verbose, trace_heap_broker)
 DEFINE_IMPLICATION(trace_heap_broker_memory, trace_heap_broker)
+DEFINE_IMPLICATION(trace_heap_broker, trace_pending_allocations)
 
 // Flags for stress-testing the compiler.
 DEFINE_INT(stress_runs, 0, "number of stress runs")
@@ -1130,6 +1131,8 @@ DEFINE_BOOL(
     trace_allocations_origins, false,
     "Show statistics about the origins of allocations. "
     "Combine with --no-inline-new to track allocations from generated code")
+DEFINE_BOOL(trace_pending_allocations, false,
+            "trace calls to Heap::IsAllocationPending that return true")
 
 DEFINE_INT(trace_allocation_stack_interval, -1,
            "print stack trace after <n> free-list allocations")

src/heap/heap-inl.h

@@ -45,6 +45,7 @@
 #include "src/objects/struct-inl.h"
 #include "src/profiler/heap-profiler.h"
 #include "src/strings/string-hasher.h"
+#include "src/utils/ostreams.h"
 #include "src/zone/zone-list-inl.h"
 
 namespace v8 {
@@ -615,7 +616,7 @@ void Heap::UpdateAllocationSite(Map map, HeapObject object,
   (*pretenuring_feedback)[AllocationSite::unchecked_cast(Object(key))]++;
 }
 
-bool Heap::IsPendingAllocation(HeapObject object) {
+bool Heap::IsPendingAllocationInternal(HeapObject object) {
   DCHECK(deserialization_complete());
 
   if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
@@ -667,6 +668,15 @@ bool Heap::IsPendingAllocation(HeapObject object) {
   UNREACHABLE();
 }
 
+bool Heap::IsPendingAllocation(HeapObject object) {
+  bool result = IsPendingAllocationInternal(object);
+  if (FLAG_trace_pending_allocations && result) {
+    StdoutStream{} << "Pending allocation: " << std::hex << "0x" << object.ptr()
+                   << "\n";
+  }
+  return result;
+}
+
 bool Heap::IsPendingAllocation(Object object) {
   return object.IsHeapObject() && IsPendingAllocation(HeapObject::cast(object));
 }

src/heap/heap.h

@@ -2149,6 +2149,9 @@ class Heap {
     force_gc_on_next_allocation_ = true;
   }
 
+  // Helper for IsPendingAllocation.
+  inline bool IsPendingAllocationInternal(HeapObject object);
+
   // ===========================================================================
   // Retaining path tracing ====================================================
   // ===========================================================================