Small Buffer Optimization for string and friends

[Andrei Alexandrescu]

Walter and I discussed today about using the small string optimization 
in string and other arrays of immutable small objects.

On 64 bit machines, string occupies 16 bytes. We could use the first 
byte as discriminator, which means that all strings under 16 chars need 
no memory allocation at all.

It turns out statistically a lot of strings are small. According to a 
variety of systems we use at Facebook, the small buffer optimization is 
king - it just works great in all cases. In D that means better speed, 
better locality, and less garbage.

For this to happen, we need to start an effort of migrating built-in 
arrays into runtime, essentially making them templates that the compiler 
lowers to. So I have two questions:

1. What happened to the new hash project? We need to take that to 
completion.

2. Is anyone willing to start the effort of migrating built-in slices 
into templates?


Thanks,

Andrei