S390: Used RISBG in MacroAssembler::IndexToArrayOffset to improve performance.

src/crankshaft/s390/lithium-codegen-s390.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CRANKSHAFT_S390_LITHIUM_CODEGEN_S390_H_
 #define V8_CRANKSHAFT_S390_LITHIUM_CODEGEN_S390_H_
 
 #include "src/ast/scopes.h"
 #include "src/crankshaft/lithium-codegen.h"
 #include "src/crankshaft/s390/lithium-gap-resolver-s390.h"
@@ skipping 98 matching lines @@
   void DoDeferredLoadMutableDouble(LLoadFieldByIndex* instr, Register result,
                                    Register object, Register index);
 
   // Parallel move support.
   void DoParallelMove(LParallelMove* move);
   void DoGap(LGap* instr);
 
   MemOperand PrepareKeyedOperand(Register key, Register base,
                                  bool key_is_constant, bool key_is_tagged,
                                  int constant_key, int element_size_shift,
-                                 int base_offset);
+                                 int base_offset,
+                                 bool keyMaybeNegative = true);
 
   // Emit frame translation commands for an environment.
   void WriteTranslation(LEnvironment* environment, Translation* translation);
 
 // Declare methods that deal with the individual node types.
 #define DECLARE_DO(type) void Do##type(L##type* node);
   LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_DO)
 #undef DECLARE_DO
 
  private:
@@ skipping 218 matching lines @@
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
   int instruction_index_;
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CRANKSHAFT_S390_LITHIUM_CODEGEN_S390_H_