Reapply "Shuffle around deopt id allocation...

runtime/vm/simulator_dbc.cc

Index: runtime/vm/simulator_dbc.cc
diff --git a/runtime/vm/simulator_dbc.cc b/runtime/vm/simulator_dbc.cc
index 75b94dd9236a77ce62d06c7b8c67fdcb81cbf762..3a9b2d8414b70a5574ac244ed85d12e38565671c 100644
--- a/runtime/vm/simulator_dbc.cc
+++ b/runtime/vm/simulator_dbc.cc
@@ -2955,33 +2955,36 @@ RawObject* Simulator::Call(const Code& code,
 
   {
     BYTECODE(CreateArrayOpt, A_B_C);
-    const intptr_t length = Smi::Value(RAW_CAST(Smi, FP[rB]));
-    if (LIKELY(static_cast<uintptr_t>(length) <= Array::kMaxElements)) {
-      const intptr_t fixed_size_plus_alignment_padding =
-          sizeof(RawArray) + kObjectAlignment - 1;
-      const intptr_t instance_size =
-          (fixed_size_plus_alignment_padding + length * kWordSize) &
-          ~(kObjectAlignment - 1);
-      const uword start =
-          thread->heap()->new_space()->TryAllocate(instance_size);
-      if (LIKELY(start != 0)) {
-        const intptr_t cid = kArrayCid;
-        uword tags = 0;
-        if (LIKELY(instance_size <= RawObject::SizeTag::kMaxSizeTag)) {
-          tags = RawObject::SizeTag::update(instance_size, tags);
-        }
-        tags = RawObject::ClassIdTag::update(cid, tags);
-        *reinterpret_cast<uword*>(start + Instance::tags_offset()) = tags;
-        *reinterpret_cast<RawObject**>(start + Array::length_offset()) = FP[rB];
-        *reinterpret_cast<RawObject**>(start + Array::type_arguments_offset()) =
-            FP[rC];
-        RawObject** data =
-            reinterpret_cast<RawObject**>(start + Array::data_offset());
-        for (intptr_t i = 0; i < length; i++) {
-          data[i] = null_value;
+    if (LIKELY(!FP[rB]->IsHeapObject())) {
+      const intptr_t length = Smi::Value(RAW_CAST(Smi, FP[rB]));
+      if (LIKELY(static_cast<uintptr_t>(length) <= Array::kMaxElements)) {
+        const intptr_t fixed_size_plus_alignment_padding =
+            sizeof(RawArray) + kObjectAlignment - 1;
+        const intptr_t instance_size =
+            (fixed_size_plus_alignment_padding + length * kWordSize) &
+            ~(kObjectAlignment - 1);
+        const uword start =
+            thread->heap()->new_space()->TryAllocate(instance_size);
+        if (LIKELY(start != 0)) {
+          const intptr_t cid = kArrayCid;
+          uword tags = 0;
+          if (LIKELY(instance_size <= RawObject::SizeTag::kMaxSizeTag)) {
+            tags = RawObject::SizeTag::update(instance_size, tags);
+          }
+          tags = RawObject::ClassIdTag::update(cid, tags);
+          *reinterpret_cast<uword*>(start + Instance::tags_offset()) = tags;
+          *reinterpret_cast<RawObject**>(start + Array::length_offset()) =
+              FP[rB];
+          *reinterpret_cast<RawObject**>(
+              start + Array::type_arguments_offset()) = FP[rC];
+          RawObject** data =
+              reinterpret_cast<RawObject**>(start + Array::data_offset());
+          for (intptr_t i = 0; i < length; i++) {
+            data[i] = null_value;
+          }
+          FP[rA] = reinterpret_cast<RawObject*>(start + kHeapObjectTag);
+          pc += 4;
         }
-        FP[rA] = reinterpret_cast<RawObject*>(start + kHeapObjectTag);
-        pc += 4;
       }
     }
     DISPATCH();