Allocation space decisions are precisely made in hydrogen.

src/ia32/lithium-codegen-ia32.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 6030 matching lines @@
       new(zone()) DeferredAllocate(this, instr);
 
   Register result = ToRegister(instr->result());
   Register temp = ToRegister(instr->temp());
 
   // Allocate memory for the object.
   AllocationFlags flags = TAG_OBJECT;
   if (instr->hydrogen()->MustAllocateDoubleAligned()) {
     flags = static_cast<AllocationFlags>(flags | DOUBLE_ALIGNMENT);
   }
-  if (instr->hydrogen()->CanAllocateInOldPointerSpace()) {
-    ASSERT(!instr->hydrogen()->CanAllocateInOldDataSpace());
+  if (instr->hydrogen()->IsOldPointerSpaceAllocation()) {
+    ASSERT(!instr->hydrogen()->IsOldDataSpaceAllocation());
+    ASSERT(!instr->hydrogen()->IsNewSpaceAllocation());
     flags = static_cast<AllocationFlags>(flags | PRETENURE_OLD_POINTER_SPACE);
-  } else if (instr->hydrogen()->CanAllocateInOldDataSpace()) {
+  } else if (instr->hydrogen()->IsOldDataSpaceAllocation()) {
+    ASSERT(!instr->hydrogen()->IsNewSpaceAllocation());
     flags = static_cast<AllocationFlags>(flags | PRETENURE_OLD_DATA_SPACE);
   }
 
   if (instr->size()->IsConstantOperand()) {
     int32_t size = ToInteger32(LConstantOperand::cast(instr->size()));
     __ Allocate(size, result, temp, no_reg, deferred->entry(), flags);
   } else {
     Register size = ToRegister(instr->size());
     __ Allocate(size, result, temp, no_reg, deferred->entry(), flags);
   }
@@ skipping 31 matching lines @@
   if (instr->size()->IsRegister()) {
     Register size = ToRegister(instr->size());
     ASSERT(!size.is(result));
     __ SmiTag(ToRegister(instr->size()));
     __ push(size);
   } else {
     int32_t size = ToInteger32(LConstantOperand::cast(instr->size()));
     __ push(Immediate(Smi::FromInt(size)));
   }
 
-  if (instr->hydrogen()->CanAllocateInOldPointerSpace()) {
-    ASSERT(!instr->hydrogen()->CanAllocateInOldDataSpace());
+  if (instr->hydrogen()->IsOldPointerSpaceAllocation()) {
+    ASSERT(!instr->hydrogen()->IsOldDataSpaceAllocation());
+    ASSERT(!instr->hydrogen()->IsNewSpaceAllocation());
     CallRuntimeFromDeferred(
         Runtime::kAllocateInOldPointerSpace, 1, instr, instr->context());
-  } else if (instr->hydrogen()->CanAllocateInOldDataSpace()) {
+  } else if (instr->hydrogen()->IsOldDataSpaceAllocation()) {
+    ASSERT(!instr->hydrogen()->IsNewSpaceAllocation());
     CallRuntimeFromDeferred(
         Runtime::kAllocateInOldDataSpace, 1, instr, instr->context());
   } else {
     CallRuntimeFromDeferred(
         Runtime::kAllocateInNewSpace, 1, instr, instr->context());
   }
   __ StoreToSafepointRegisterSlot(result, eax);
 }
 
 
@@ skipping 402 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32