Update Assembler::TryAllocate to support inline allocation tracing

runtime/vm/assembler_arm64.cc

Index: runtime/vm/assembler_arm64.cc
diff --git a/runtime/vm/assembler_arm64.cc b/runtime/vm/assembler_arm64.cc
index 7b002148648b4e3e22396b13030158e6d7ced3c7..9452315cd5e201bee661c71b37732bde1de4d378 100644
--- a/runtime/vm/assembler_arm64.cc
+++ b/runtime/vm/assembler_arm64.cc
@@ -1322,6 +1322,31 @@ void Assembler::UpdateAllocationStatsWithSize(intptr_t cid,
 }
 
 
+void Assembler::MaybeTraceAllocation(intptr_t cid,
+                                     Register temp_reg,
+                                     Register pp,
+                                     Label* trace) {
+  ASSERT(cid > 0);
+  Isolate* isolate = Isolate::Current();
+  ClassTable* class_table = isolate->class_table();
+  const uword class_offset = cid * sizeof(ClassHeapStats);  // NOLINT
+  if (cid < kNumPredefinedCids) {
+    const uword class_heap_stats_table_address =
+        class_table->PredefinedClassHeapStatsTableAddress();
+    LoadImmediate(temp_reg, class_heap_stats_table_address + class_offset, pp);
+  } else {
+    LoadImmediate(temp_reg, class_table->ClassStatsTableAddress(), pp);
+    ldr(temp_reg, Address(temp_reg, 0));
+    AddImmediate(temp_reg, temp_reg, class_offset, pp);
+  }
+  const uword state_offset = ClassHeapStats::state_offset();
+  const Address& state_address = Address(temp_reg, state_offset);
+  ldr(temp_reg, state_address);
+  tsti(temp_reg, Immediate(ClassHeapStats::TraceAllocationMask()));
+  b(trace, NE);
+}
+
+
 void Assembler::TryAllocate(const Class& cls,
                             Label* failure,
                             Register instance_reg,
@@ -1329,6 +1354,10 @@ void Assembler::TryAllocate(const Class& cls,
                             Register pp) {
   ASSERT(failure != NULL);
   if (FLAG_inline_alloc) {
+    // If this allocation is traced, program will jump to failure path
+    // (i.e. the allocation stub) which will allocate the object and trace the
+    // allocation call site.
+    MaybeTraceAllocation(cls.id(), temp_reg, pp, failure);
     const intptr_t instance_size = cls.instance_size();
     Heap* heap = Isolate::Current()->heap();
     Heap::Space space = heap->SpaceForAllocation(cls.id());