On MIPS, uses more branch delay slots.

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 153 matching lines @@
   }
   const GrowableObjectArray& object_pool() const { return object_pool_; }
   void FinalizeInstructions(const MemoryRegion& region) {
     buffer_.FinalizeInstructions(region);
   }
 
   // Set up a stub frame so that the stack traversal code can easily identify
   // a stub frame.
   void EnterStubFrame(bool uses_pp = false);
   void LeaveStubFrame(bool uses_pp = false);
+  // A separate macro for restoring the SP that we can put in the delay slot
+  // of jumps that often follow LeaveStubFrame.
+  void LeaveStubFrameSPRestore(bool uses_pp = false);

[regis, 2013/05/01 01:21:46]

I think it would be clearer to leave LeaveStubFrame untouched (it would restore
sp as before) and add instead a LeaveStubFrameAndRet that would make use of the
delay slot.

[zra, 2013/05/01 16:53:17]

Done.

 
   // Instruction pattern from entrypoint is used in dart frame prologs
   // to set up the frame and save a PC which can be used to figure out the
   // RawInstruction object corresponding to the code running in the frame.
   // See EnterDartFrame. There are 6 instructions before we know the PC.
   static const intptr_t kOffsetOfSavedPCfromEntrypoint = 6 * Instr::kInstrSize;
 
   // Inlined allocation of an instance of class 'cls', code has no runtime
   // calls. Jump to 'failure' if the instance cannot be allocated here.
   // Allocated instance is returned in 'instance_reg'.
@@ skipping 817 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_MIPS_H_