Allocation space decisions are precisely made in hydrogen.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 54b53db5940d723ba0ccd58f2293688b553824c5..793d3f1a91cc9157ac468df3c9902c9466c80933 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -3766,8 +3766,8 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
   HValue* current_size = size();
   // We can just fold allocations that are guaranteed in new space.
   // TODO(hpayer): Add support for non-constant allocation in dominator.
-  if (!GuaranteedInNewSpace() || !current_size->IsInteger32Constant() ||
-      !dominator_allocate_instr->GuaranteedInNewSpace() ||
+  if (!AllocateInNewSpace() || !current_size->IsInteger32Constant() ||
+      !dominator_allocate_instr->AllocateInNewSpace() ||
       !dominator_size->IsInteger32Constant()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s)\n",
@@ -3830,7 +3830,7 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
 
 void HAllocate::PrintDataTo(StringStream* stream) {
   size()->PrintNameTo(stream);
-  if (!GuaranteedInNewSpace()) stream->Add(" (pretenure)");
+  if (!AllocateInNewSpace()) stream->Add(" (pretenure)");
 }