Revert merges of r12531 and r12562 from 3.12 branch, going back to 3.12.19.12

src/x64/lithium-codegen-x64.cc

 // 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 3625 matching lines @@
       }
     } else {
       Register reg2 = ToRegister(instr->index());
       if (FLAG_debug_code &&
           !instr->hydrogen()->index()->representation().IsTagged()) {
         __ AbortIfNotZeroExtended(reg2);
       }
       __ cmpq(reg, reg2);
     }
   } else {
-    Operand length = ToOperand(instr->length());
     if (instr->index()->IsConstantOperand()) {
-      int constant_index =
-          ToInteger32(LConstantOperand::cast(instr->index()));
-      if (instr->hydrogen()->length()->representation().IsTagged()) {
-        __ Cmp(length, Smi::FromInt(constant_index));
-      } else {
-        __ cmpq(length, Immediate(constant_index));
-      }
+      __ cmpq(ToOperand(instr->length()),
+              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
     } else {
-      __ cmpq(length, ToRegister(instr->index()));
+      __ cmpq(ToOperand(instr->length()), ToRegister(instr->index()));
     }
   }
   DeoptimizeIf(below_equal, instr->environment());
 }
 
 
 void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
   Register value = ToRegister(instr->value());
   Register elements = ToRegister(instr->object());
   LOperand* key = instr->key();
@@ skipping 1439 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64