Fix false x64 argument index assertion

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 2900 matching lines @@
 
 
 void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
   Register arguments = ToRegister(instr->arguments());
   Register result = ToRegister(instr->result());
 
   if (instr->length()->IsConstantOperand() &&
       instr->index()->IsConstantOperand()) {
     int32_t const_index = ToInteger32(LConstantOperand::cast(instr->index()));
     int32_t const_length = ToInteger32(LConstantOperand::cast(instr->length()));
-    StackArgumentsAccessor args(arguments, const_length,
-                                ARGUMENTS_DONT_CONTAIN_RECEIVER);
-    __ movp(result, args.GetArgumentOperand(const_index));
+    if (const_index < const_length) {
+      StackArgumentsAccessor args(arguments, const_length,
+                                  ARGUMENTS_DONT_CONTAIN_RECEIVER);
+      __ movp(result, args.GetArgumentOperand(const_index));
+    } else {
+      // This code should never be executed; just emit an abort here.
+      __ Abort(kInvalidArgumentIndex);

[Igor Sheludko, 2014/03/24 15:23:28]

Abort() calls runtime which requires context to be in rsi but this instruction
does not handle context. Most likely it will crash if ever hits the Abort()
case. I'm not fully sure but probably you should use int3() here.

[Jarin, 2014/03/24 16:36:05]

Done.

+    }
   } else {
     Register length = ToRegister(instr->length());
     // There are two words between the frame pointer and the last argument.
     // Subtracting from length accounts for one of them add one more.
     if (instr->index()->IsRegister()) {
       __ subl(length, ToRegister(instr->index()));
     } else {
       __ subl(length, ToOperand(instr->index()));
     }
     StackArgumentsAccessor args(arguments, length,
@@ skipping 2725 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64