Support immediate operands for array bounds checks.

runtime/vm/locations.h

Index: runtime/vm/locations.h
===================================================================
--- runtime/vm/locations.h	(revision 11818)
+++ runtime/vm/locations.h	(working copy)
@@ -12,6 +12,7 @@
 namespace dart {
 
 class BufferFormatter;
+class Value;
 
 // Location objects are used to connect register allocator and code generator.
 // Instruction templates used by code generator have a corresponding
@@ -229,6 +230,10 @@
     return payload() - kStackIndexBias;
   }
 
+  // Constants.
+  static Location RegisterOrConstant(Value* value);
+  static Location FixedRegisterOrConstant(Value* value, Register reg);
+
   const char* Name() const;
   void PrintTo(BufferFormatter* f) const;
   void Print() const;