Pretenure ASCII cons string in high promotion mode.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index da29ce7cdd28726be2ac0636427981dc75caf8d7..175b1ca1d2fecb2c0d921283e64719c83e95e7cc 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1603,10 +1603,32 @@ void MacroAssembler::AllocateAsciiConsString(Register result,
                                              Register scratch1,
                                              Register scratch2,
                                              Label* gc_required) {
-  // Allocate heap number in new space.
-  Allocate(ConsString::kSize, result, scratch1, scratch2, gc_required,
-           TAG_OBJECT);
+  Label allocate_new_space, install_map;
+  AllocationFlags flags = TAG_OBJECT;
+
+  ExternalReference high_promotion_mode = ExternalReference::
+      new_space_high_promotion_mode_active_address(isolate());
+
+  test(Operand::StaticVariable(high_promotion_mode), Immediate(1));
+  j(zero, &allocate_new_space);
+
+  Allocate(ConsString::kSize,
+           result,
+           scratch1,
+           scratch2,
+           gc_required,
+           static_cast<AllocationFlags>(flags | PRETENURE_OLD_POINTER_SPACE));
+  jmp(&install_map);
+
+  bind(&allocate_new_space);
+  Allocate(ConsString::kSize,
+           result,
+           scratch1,
+           scratch2,
+           gc_required,
+           flags);
 
+  bind(&install_map);
   // Set the map. The other fields are left uninitialized.
   mov(FieldOperand(result, HeapObject::kMapOffset),
       Immediate(isolate()->factory()->cons_ascii_string_map()));