I changed ```tbaa_arrayptr``` to ```tbaa_const```.  LLVM's documentation on [TBBA's support for constant memory](http://llvm.org/docs/AliasAnalysis.html#the-pointstoconstantmemory-method) is not rigorous about defining what constant memory really is.  The examples seem less constant than a ROM.  I'm taking it to mean that a memory location is constant by the time LLVM can see it.  In this case, LLVM can't get at the location until ```jl_array_to_string``` allocates it (and assigns to it), so I think I'm on safe ground.