Allocation space decisions are precisely made in hydrogen.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index e9210a9eed693843f20246ac7fd9c6ca9424b516..0f72e2944ad293b544dd735d20ee37e223b10ee6 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -5091,10 +5091,12 @@ void LCodeGen::DoAllocate(LAllocate* instr) {
   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);
   }
 
@@ -5146,10 +5148,12 @@ void LCodeGen::DoDeferredAllocate(LAllocate* instr) {
     __ Push(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);
-  } else if (instr->hydrogen()->CanAllocateInOldDataSpace()) {
+  } else if (instr->hydrogen()->IsOldDataSpaceAllocation()) {
+    ASSERT(!instr->hydrogen()->IsNewSpaceAllocation());
     CallRuntimeFromDeferred(Runtime::kAllocateInOldDataSpace, 1, instr);
   } else {
     CallRuntimeFromDeferred(Runtime::kAllocateInNewSpace, 1, instr);