Fix debug printing of pointers, and a keyed store with smi index error, in X6...

src/x64/ic-x64.cc

Index: src/x64/ic-x64.cc
===================================================================
--- src/x64/ic-x64.cc	(revision 2604)
+++ src/x64/ic-x64.cc	(working copy)
@@ -424,6 +424,9 @@
   // Check that the key is a smi.
   __ testl(rbx, Immediate(kSmiTagMask));
   __ j(not_zero, &slow);
+  // If it is a smi, make sure it is zero-extended, so it can be
+  // used as an index in a memory operand.
+  __ movl(rbx, rbx);  // Clear the high bits of rbx.
 
   __ CmpInstanceType(rcx, JS_ARRAY_TYPE);
   __ j(equal, &array);
@@ -434,7 +437,7 @@
   // Object case: Check key against length in the elements array.
   // rax: value
   // rdx: JSObject
-  // rbx: index (as a smi)
+  // rbx: index (as a smi), zero-extended.
   __ movq(rcx, FieldOperand(rdx, JSObject::kElementsOffset));
   // Check that the object is in fast mode (not dictionary).
   __ Cmp(FieldOperand(rcx, HeapObject::kMapOffset), Factory::fixed_array_map());