Simplify StringCharCodeAt in non-crankshaft codegen.

src/x64/full-codegen-x64.cc

 // Copyright 2011 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 2847 matching lines @@
 
 void FullCodeGenerator::EmitStringCharCodeAt(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT(args->length() == 2);
 
   VisitForStackValue(args->at(0));
   VisitForAccumulatorValue(args->at(1));
 
   Register object = rbx;
   Register index = rax;
-  Register scratch = rcx;
   Register result = rdx;
 
   __ pop(object);
 
   Label need_conversion;
   Label index_out_of_range;
   Label done;
   StringCharCodeAtGenerator generator(object,
                                       index,
-                                      scratch,
                                       result,
                                       &need_conversion,
                                       &need_conversion,
                                       &index_out_of_range,
                                       STRING_INDEX_IS_NUMBER);
   generator.GenerateFast(masm_);
   __ jmp(&done);
 
   __ bind(&index_out_of_range);
   // When the index is out of range, the spec requires us to return
@@ skipping 17 matching lines @@
 
 void FullCodeGenerator::EmitStringCharAt(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT(args->length() == 2);
 
   VisitForStackValue(args->at(0));
   VisitForAccumulatorValue(args->at(1));
 
   Register object = rbx;
   Register index = rax;
-  Register scratch1 = rcx;
-  Register scratch2 = rdx;
+  Register scratch = rdx;
   Register result = rax;
 
   __ pop(object);
 
   Label need_conversion;
   Label index_out_of_range;
   Label done;
   StringCharAtGenerator generator(object,
                                   index,
-                                  scratch1,
-                                  scratch2,
+                                  scratch,
                                   result,
                                   &need_conversion,
                                   &need_conversion,
                                   &index_out_of_range,
                                   STRING_INDEX_IS_NUMBER);
   generator.GenerateFast(masm_);
   __ jmp(&done);
 
   __ bind(&index_out_of_range);
   // When the index is out of range, the spec requires us to return
@@ skipping 1367 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64