Fix false x64 argument index assertion

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 5849cf4ef910d6573c75dd7b4858a964e75192b9..5e7cc617bd93ca40149134baed86fa1456a3806f 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2918,9 +2918,14 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
       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.