Adapt Danno's Track Allocation Info idea to fast literals. When allocating a literal array,

src/arm/macro-assembler-arm.h

 // 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 1291 matching lines @@
   }
 
   // Activation support.
   void EnterFrame(StackFrame::Type type);
   void LeaveFrame(StackFrame::Type type);
 
   // Expects object in r0 and returns map with validated enum cache
   // in r0.  Assumes that any other register can be used as a scratch.
   void CheckEnumCache(Register null_value, Label* call_runtime);
 
+  // AllocationSiteInfo support. Arrays may have an associated
+  // AllocationSiteInfo object that can be checked for in order to pretransition
+  // to another type.
+  // On entry, r2 should point to the array object. r4 gets clobbered.
+  // If allocation info is present, jump to allocation_info_present
+  void PerformAllocationSiteInfoCheck(Label* allocation_info_present);

[danno, 2013/01/04 08:50:55]

Pass the two registers that are used into this function like in other functions
in the macro assembler (for example, take a look at InitializeNewString). Then
specify r2 and r4 at the calling site. Same on other platforms, too.

You might want to make the name here and on other platforms mention arrays, too,
since this routine only works for JSArrays. For example,
TestJSArrayForAllocationSiteInfo

[mvstanton, 2013/01/04 12:07:52]

Done.

+
  private:
   void CallCFunctionHelper(Register function,
                            int num_reg_arguments,
                            int num_double_arguments);
 
   void Jump(intptr_t target, RelocInfo::Mode rmode, Condition cond = al);
 
   // Helper functions for generating invokes.
   void InvokePrologue(const ParameterCount& expected,
                       const ParameterCount& actual,
@@ skipping 95 matching lines @@
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_MACRO_ASSEMBLER_ARM_H_