Pretenure ASCII cons string in high promotion mode.

src/arm/macro-assembler-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 1915 matching lines @@
                       scratch1,
                       scratch2);
 }
 
 
 void MacroAssembler::AllocateAsciiConsString(Register result,
                                              Register length,
                                              Register scratch1,
                                              Register scratch2,
                                              Label* gc_required) {
-  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());
+  mov(scratch1, Operand(high_promotion_mode));
+  ldr(scratch1, MemOperand(r4, 0));
+  cmp(scratch1, Operand::Zero());
+  b(eq, &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);
 
   InitializeNewString(result,
                       length,
                       Heap::kConsAsciiStringMapRootIndex,
                       scratch1,
                       scratch2);
 }
 
 
 void MacroAssembler::AllocateTwoByteSlicedString(Register result,
@@ skipping 1884 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM