Fix an undetected Smi overflow on ARM.

runtime/vm/assembler_arm64.h

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_ASSEMBLER_ARM64_H_
 #define VM_ASSEMBLER_ARM64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_arm64.h directly; use assembler.h instead.
 #endif
@@ skipping 808 matching lines @@
     blr(TMP);
   }
 
   // Macros accepting a pp Register argument may attempt to load values from
   // the object pool when possible. Unless you are sure that the untagged object
   // pool pointer is in another register, or that it is not available at all,
   // PP should be passed for pp.
   void AddImmediate(Register dest, Register rn, int64_t imm, Register pp);
   void AddImmediateSetFlags(
       Register dest, Register rn, int64_t imm, Register pp);
+  void SubImmediateSetFlags(
+      Register dest, Register rn, int64_t imm, Register pp);
   void AndImmediate(Register rd, Register rn, int64_t imm, Register pp);
   void OrImmediate(Register rd, Register rn, int64_t imm, Register pp);
   void XorImmediate(Register rd, Register rn, int64_t imm, Register pp);
   void TestImmediate(Register rn, int64_t imm, Register pp);
   void CompareImmediate(Register rn, int64_t imm, Register pp);
 
   void LoadFromOffset(Register dest, Register base, int32_t offset,
                       Register pp, OperandSize sz = kDoubleWord);
   void LoadFieldFromOffset(
       Register dest, Register base, int32_t offset, Register pp) {
@@ skipping 558 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM64_H_