[Tremor] Tremor code optimisations [fwd]

[Segher Boessenkool]

> Dave Taylor asked me to forward this on to the list. It's a patch
> against
> Tremor-lowmem, and increases performance by around 10% (obviously,
> this'll be
> platform dependant), while cleaning up the code a little.

The bitwise.diff change creates incorrect C code (aliasing
problem); furthermore, it is very likely a performance loss
on most (modern) architectures (didn't actually test, though).

These routines are excellent candidates to code in assembler
for your target platform, if you are going to do machine-
specific micro-optimizations anyway...  GCC tends not to
be too smart on this kind of code (not as smart as a human
programmer that can do all kinds of interesting bit-fiddling
tricks, that is).

Didn't look at the other patch, sorry.


Segher