Bookkeeping for allocation site pretenuring

src/arm/full-codegen-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1762 matching lines @@
   ZoneList<Expression*>* subexprs = expr->values();
   int length = subexprs->length();
   Handle<FixedArray> constant_elements = expr->constant_elements();
   ASSERT_EQ(2, constant_elements->length());
   ElementsKind constant_elements_kind =
       static_cast<ElementsKind>(Smi::cast(constant_elements->get(0))->value());
   bool has_fast_elements = IsFastObjectElementsKind(constant_elements_kind);
   Handle<FixedArrayBase> constant_elements_values(
       FixedArrayBase::cast(constant_elements->get(1)));
 
+  AllocationSiteMode allocation_site_mode = FLAG_track_allocation_sites
+      ? TRACK_ALLOCATION_SITE : DONT_TRACK_ALLOCATION_SITE;
+  if (has_constant_fast_elements && !FLAG_allocation_site_pretenuring) {
+    // If the only customer of allocation sites is transitioning, then
+    // we can turn it off if we don't have anywhere else to transition to.
+    allocation_site_mode = DONT_TRACK_ALLOCATION_SITE;
+  }
+
   __ ldr(r3, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
   __ ldr(r3, FieldMemOperand(r3, JSFunction::kLiteralsOffset));
   __ mov(r2, Operand(Smi::FromInt(expr->literal_index())));
   __ mov(r1, Operand(constant_elements));
   if (has_fast_elements && constant_elements_values->map() ==
       isolate()->heap()->fixed_cow_array_map()) {
     FastCloneShallowArrayStub stub(
         FastCloneShallowArrayStub::COPY_ON_WRITE_ELEMENTS,
-        DONT_TRACK_ALLOCATION_SITE,
+        allocation_site_mode,
         length);
     __ CallStub(&stub);
     __ IncrementCounter(
         isolate()->counters()->cow_arrays_created_stub(), 1, r1, r2);
   } else if (expr->depth() > 1 || Serializer::enabled() ||
              length > FastCloneShallowArrayStub::kMaximumClonedLength) {
     __ Push(r3, r2, r1);
     __ CallRuntime(Runtime::kCreateArrayLiteral, 3);
   } else {
     ASSERT(IsFastSmiOrObjectElementsKind(constant_elements_kind) ||
            FLAG_smi_only_arrays);
     FastCloneShallowArrayStub::Mode mode =
         FastCloneShallowArrayStub::CLONE_ANY_ELEMENTS;
-    AllocationSiteMode allocation_site_mode = FLAG_track_allocation_sites
-        ? TRACK_ALLOCATION_SITE : DONT_TRACK_ALLOCATION_SITE;
 
     if (has_fast_elements) {
       mode = FastCloneShallowArrayStub::CLONE_ELEMENTS;
-      allocation_site_mode = DONT_TRACK_ALLOCATION_SITE;
     }
 
     FastCloneShallowArrayStub stub(mode, allocation_site_mode, length);
     __ CallStub(&stub);
   }
 
   bool result_saved = false;  // Is the result saved to the stack?
 
   // Emit code to evaluate all the non-constant subexpressions and to store
   // them into the newly cloned array.
@@ skipping 3142 matching lines @@
   ASSERT(Memory::uint32_at(interrupt_address_pointer) ==
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM