> Also, the only situations where 64-bit code is beneficial are 1- large
> integer arithmetic (bignums, crypto), and 2- exploiting more than 4 Gb
> of RAM.

3 - some floating point intensive code if unaligned accesses are slow

On 32 bit machines heap values are only 32 bit aligned and loads and
stores of 64 bit floats may be slower due to misalignment.  The
performance impact varies by CPU.