Shorter TryAllocate instruction sequence on ARM/ARM64/MIPS.

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 413 matching lines @@
 
   // Debugging and bringup support.
   void Stop(const char* message);
   void Unimplemented(const char* message);
   void Untested(const char* message);
   void Unreachable(const char* message);
 
   static void InitializeMemoryWithBreakpoints(uword data, intptr_t length);
 
   void Comment(const char* format, ...) PRINTF_ATTRIBUTE(2, 3);
+  static bool EmittingComments();
 
   const Code::Comments& GetCodeComments() const;
 
   static const char* RegisterName(Register reg);
 
   static const char* FpuRegisterName(FpuRegister reg);
 
   void SetPrologueOffset() {
     if (prologue_offset_ == -1) {
       prologue_offset_ = CodeSize();
@@ skipping 766 matching lines @@
                                      Register pp,
                                      Heap::Space space = Heap::kNew);
 
   // 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'.
   // Only the tags field of the object is initialized.
   void TryAllocate(const Class& cls,
                    Label* failure,
                    Register instance_reg,
+                   Register temp_reg,

[regis, 2014/07/23 22:29:33]

Not required. We have 2 temp registers on ARM64: TMP and TMP2.

                    Register pp);
 
   Address ElementAddressForIntIndex(bool is_external,
                                     intptr_t cid,
                                     intptr_t index_scale,
                                     Register array,
                                     intptr_t index) const;
   Address ElementAddressForRegIndex(bool is_load,
                                     bool is_external,
                                     intptr_t cid,
@@ skipping 455 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM64_H_