MIPS: Add negative lookups to polymorphic loads in Crankshaft.

src/mips/macro-assembler-mips.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 974 matching lines @@
   // "branch_to" if the result of the comparison is "cond". If multiple map
   // compares are required, the compare sequences branches to early_success.
   void CompareMapAndBranch(Register obj,
                            Register scratch,
                            Handle<Map> map,
                            Label* early_success,
                            Condition cond,
                            Label* branch_to,
                            CompareMapMode mode = REQUIRE_EXACT_MAP);
 
+  // As above, but the map of the object is already loaded into the register
+  // which is preserved by the code generated.
+  void CompareMapAndBranch(Register obj_map,
+                           Handle<Map> map,
+                           Label* early_success,
+                           Condition cond,
+                           Label* branch_to,
+                           CompareMapMode mode = REQUIRE_EXACT_MAP);
+
   // Check if the map of an object is equal to a specified map and branch to
   // label if not. Skip the smi check if not required (object is known to be a
   // heap object). If mode is ALLOW_ELEMENT_TRANSITION_MAPS, then also match
   // against maps that are ElementsKind transition maps of the specificed map.
   void CheckMap(Register obj,
                 Register scratch,
                 Handle<Map> map,
                 Label* fail,
                 SmiCheckType smi_check_type,
                 CompareMapMode mode = REQUIRE_EXACT_MAP);
@@ skipping 519 matching lines @@
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #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_MIPS_MACRO_ASSEMBLER_MIPS_H_