Reduce register pressure on ARM, ARM64, and MIPS.

runtime/vm/assembler_mips.h

 // Copyright (c) 2013, 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_MIPS_H_
 #define VM_ASSEMBLER_MIPS_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_mips.h directly; use assembler.h instead.
 #endif
@@ skipping 1098 matching lines @@
   }
 
   void SmiTag(Register reg) {
     sll(reg, reg, kSmiTagSize);
   }
 
   void SmiUntag(Register reg) {
     sra(reg, reg, kSmiTagSize);
   }
 
+  void SmiUntag(Register dst, Register src) {
+    sra(dst, src, kSmiTagSize);
+  }
+
   void LoadFromOffset(Register reg, Register base, int32_t offset) {
     ASSERT(!in_delay_slot_);
     if (Utils::IsInt(kImmBits, offset)) {
       lw(reg, Address(base, offset));
     } else {
       LoadImmediate(TMP, offset);
       addu(TMP, base, TMP);
       lw(reg, Address(TMP, 0));
     }
   }
@@ skipping 210 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_MIPS_H_